View Full Version : 85R Top End Rebuild and Upgrades
Samjp22
12-07-2014, 09:53 PM
So at the title states my R has barely any compression. Was going on her pretty hard today in about a foot of fresh snow. Was ripping up this one hill when it overheated and shut off. Motor didn't seize (thank god) and i didn't try starting it. Brought it home and hooked up the compression tester and it only made about 50PSI. The cylinder looks pretty good (little bit of scoring by the exhaust port), head isn't warped and head gasket looks good. Going to head out right now and pull the jug off and look at the rings. 205665205666205667
Ill post some more picks in a couple hours after I'm done in the shop. I guess my question is if it is the rings should i replace the piston, rings and head gasket since its all apart and what kind of piston and ring sets do you guys recommend?
3wheelrider
12-07-2014, 10:48 PM
Doesnt look like the rings came apart? -Check that rod/bearings carefully when you get the jug off. You got plenty of bores left there. Stick with Wiesco piston/rings(85/86 style)- which is what you have in there now. Use OEM ATC/TRX gaskets.
Samjp22
12-08-2014, 12:16 AM
The rings are imbedded and melted into the piston and theres a little bit of scoring on the exhaust side of the cylinder, not too bad though. The current piston is a Wiesco 66.50mm piston, would you recommend boring it or running a hone through it and is there a nickel coating on these cylinders? Rod/bearings seem good and okay thanks for the tip on the gaskets. 205683205684205685205686205687205688
3wheelrider
12-08-2014, 06:54 AM
OK-I see that now... Looks possibly like insufficient piston to wall clearance/end gaps?? That piston wasnt in there very long -right? Are you letting it warm up well before you rip on it hard?....No nikasil plating there. You would want to bore it/hone only to next size 66.75 (it should be enough to clean up any scaring) Clearance is very important!-get a new piston/rings(matching) first- then take the cyl./ new piston to someone with exp. to check it/bore /hone & set clearances correctly if you want it to run long.
oscarmayer
12-08-2014, 10:52 AM
me, i would actually go 2 sizes up with that wall scoring jsut to be 100% sure it will get all the scoring out and allow the rings to seat. as mentioned piston to wall clearances were not right. the piston got warm, swelled up and grabbed the side of ghe cylinder walls. also that head gasket seems to be off on the holes. make sure you use only honda factory headgaskets. the holds should align up perfectly. i am wiondering if water flow was limited due to the holes beign off-set not matchign up properly and it caused the over heating. something to consider looking at next time you put it together. but again if you use factory honda, it will be fine.
Samjp22
12-08-2014, 03:36 PM
Okay thanks for the input guys and yeah it's always warm before I go ride, stays in a heated shop. The motor was rebuilt before I bought it so I'm not 100% sure if the clearances were correct but I have a feeling as soon as she over heated the jug got way too hot, swelled and that's when the rings became imbedded. As for boring it I'll probably get it done one size over at the local Honda shop as there's very little scoring on the exhaust port size.
Should I stick with a similar style wiseco piston (same style on top) or something different like a high comp piston or something along those lines
Dirtcrasher
12-08-2014, 04:46 PM
Stick with Wiseco.
Samjp22
12-08-2014, 04:49 PM
http://www.ebay.ca/itm/361024687191?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2648 ?
oscarmayer
12-08-2014, 04:49 PM
^ agreed.
hi comp is fine as lon as you have an aftermarket reed cage and pipe and carb upgrade. if not it can pose a few minor challanges.
Samjp22
12-08-2014, 04:51 PM
Okay I will stick with one similar to stock like the link I posted
RoscoW
12-08-2014, 08:41 PM
Before ordering your piston get your cylinder checked for size. Looking at your 2nd pic there seems to be a lot of gap on the intake side just above the #'s on the piston. Verify that the piston in there is the correct size for the bore, if you didn't rebuild it anything is possible. Have someone mic it, top and bottom, front to back and side to side, get the piston size that will clean up any oval-ing or taper. Get the piston and have the machine shop match the bore and clearance to the actual piston your using. I would also bump your main jet up one size, the plug is a little light for me. Head gasket is typical for 250R, more coolant flow on the exhaust side and less flow on the intake side.
Ross..
Samjp22
12-09-2014, 12:28 AM
I think why you're seeing a bit of a gap on the intake side of the piston is because the rings got pushed to that side of the piston causing a bit of spacing. Before I go ahead and order a piston I will have someone mic it and if they say it was the proper bore for that piston I will end up boring it up once, thanks
Samjp22
12-09-2014, 12:29 AM
And the head is actually a darker brown then the picture looks, flash probably caused that
crackshot
12-09-2014, 10:44 AM
Yeah ditto on having a machine shop do the bore, hone and fit the piston. I had a snowmobile/atv machine shop do my 85r back in 2007 and still runs hard.
Make SURE! who ever sets that up relives that exhaust bridge, and set the bore to wiseco spec if you go that rout, if that was set tight i can see why it stuck after watching your riding video...a screaming hot cylinder will cool off FAST when you bust though a snow bank and cover it and the radiators in snow. Might want to put a temp gauge on there and possibly some covers over the rads to keep a more consistent engine temp.
Samjp22
12-09-2014, 07:43 PM
Went and talked with the mechanic at the honda dealership today and he was also saying I should be covering my radiators some.. the thing I don't understand is if it were to cover them wouldn't that cause it to run hotter? The trike overheated (I don't think from the cold, probably from being wide open for about half hour cause if I got out of the power band I would've been stuck) and thats what I think lead to the failure. If they were covered wouldn't it overheat even quicker? And the mechanic is going to bore it to wiesco specs once the piston arrives.
Samjp22
12-10-2014, 05:26 PM
Do you guys also think I should replace the small connecting rob bearing at the top where the wrist pin goes through?
RoscoW
12-10-2014, 05:43 PM
Yes I would replace it.
Samjp22
12-10-2014, 05:59 PM
any special tricks to getting it out? Or just support the con rod and tap it out with a socket?
3wheelrider
12-10-2014, 06:25 PM
It slides out with no effort....
Get a temp guage on it, the cardbord on the rads is for more high speed riding in cold weather to retain engine heat. Did you notice your overflow tube spitting antifreez out? I think ya just riped on it too hard too long with too tight of piston/ wall clearence...once you got off the throttle it lost enough inertia to stick it...lucky for you it didnt stick at wot. And the pin bearing should pop right out , check the bearing surface in the rod for any pitting or bad scoring also.
Samjp22
12-10-2014, 07:01 PM
Thanks for all the help guys appreciate it as this is my first two stroke and first time going into a two stroke motor.
atc300r- I run BelRay H1-R synthetic oil at 40:1. (recommended to me by Honda dealership) I find i get great power and color on the plug with this.
MTS- Where would one get a temp gauge and install it? I did some looking around on ebay and was unsuccessful. As for coolant it was coming out the rad cap, spitting out the overflow tube, filled up my overflow bottle, bubbled out my overflow cap and came out my overflow bottle tube LOL basically everywhere it could.
I got a little trail tech deal with a lcd display i mounted on my bars at a local 4x4 shop, buuut im guessing the next time you see your overflow puking its guts out you will stop ..* cough* *cough* :beer
Samjp22
12-13-2014, 06:02 PM
progress update: new wiseco 66.75mm piston on order and local honda shop is going to bore it to wiseco's specs.
I'm going to take your guy's advice and go up a couple jet sizes, question is where would I purchase jets and how do I tell what size is in there right now?
And I've read all around on breaking it in just havent really seen if i should mix my gas with like a 32:1 ratio instead of 40:1 for the break in period, thoughts?
SUPERBEAST
12-13-2014, 07:01 PM
you can get jets are jetsrus.com
Samjp22
12-13-2014, 07:30 PM
thanks, itd be the main jet id go up in size correct? 300r whats the reasoning for non-synthetic break in?
Dirtcrasher
12-14-2014, 12:34 AM
Some wristpins have a tight fit in the piston.
Never EVER put force on the con rod pin. Use sockets/tubing and threaded rod to "pull it out".
Piston to cylinder wall clearances depending on the person doing the work can vary. Even how the cutting tool is sharpened matters.
Wiseco puts a green paper in the box with it regarding ring end gap and P to W clearances.
High RPM's and cold temperatures in the snow overheat pretty easy; Unless you have 4SNOWS!! :D
Whats the plug look like, was it jetted for cooler weather??
Samjp22
12-14-2014, 02:03 AM
Thanks guys and I didn't re-jet it for the colder weather and I'm still confused why multiple people say to go up in size. I know colder air is denser therefore more air into the carb but the plug was super brown. Is the summer it runs pretty rich, fouls plugs now and again but the plug looked great!
Samjp22
12-24-2014, 06:27 PM
Well after waiting two long weeks to receive my piston I open it up to find this.... 206707 there's a small knick in the top of the piston. Should I ask for a refund? Or is there no worries and just run it?
did it come from the machine shop like that or just out of the box? you could clean it up with a stone and run it likely with no issues, as long as the ring land isnt pushed in.
Dirtcrasher
12-25-2014, 12:47 AM
^ Bingo.....
Samjp22
12-25-2014, 01:47 AM
Came outta the box like that
El Camexican
12-25-2014, 02:04 AM
Okay thanks for the input guys and yeah it's always warm before I go ride, stays in a heated shop. That isn’t the kind of warm they mean. Your engine should be warm enough to open a thermostat before you rip on it, say 160F. That’s called operating temperature.
The motor was rebuilt before I bought it so I'm not 100% sure if the clearances were correct but I have a feeling as soon as she over heated the jug got way too hot, swelled and that's when the rings became imbedded. The cylinder actually gets larger when it’s hot. The problem is that the piston gets even larger. When an engine has the proper tolerances and is run hard the piston gets so big it doesn’t need the rings to seal. The problem with yours as many have pointed out is that the piston and rings were too big for the bore of your cylinder to start with, so when it got hot the ring gaps closed and the piston became bigger than the bore. When that happened there was no space for oil and metal to metal contact occurred and that is why your engine seized.
As MTS pointed out you want uniform heat in your cylinder. If you suddenly subject one part of your cylinder to a temperature change, be it due to crashing into a creek, or charging up to 100km in minus 40C weather with open rads the cylinder bore will distort, but the piston wont. Again a seizure can occur.
Non-synthetic oil creates a little more friction for seating in the rings better. I believe that only applies to 4 strokes. His engine is a two stroke.
Thanks guys and I didn't re-jet it for the colder weather and I'm still confused why multiple people say to go up in size. I know colder air is denser therefore more air into the carb but the plug was super brown. Is the summer it runs pretty rich, fouls plugs now and again but the plug looked great! Better safe than sorry. You can always go down later. At -20C air density is way below sea level. Unless you’re racing for money you want to be jetted rich when you take off across a frozen lake.
Also make sure your water pump is working before you run the new engine too long.
Samjp22
12-25-2014, 03:29 AM
The engine gets warmed up good before I go riding it, and I pulled the water pump cover off and it's good, not stripped or anything. I don't know what to say about the riding in the cold part, basically seems like if I ride in the cold and snow just going to hurt the motor
El Camexican
12-25-2014, 11:35 AM
The engine gets warmed up good before I go riding it, and I pulled the water pump cover off and it's good, not stripped or anything. I don't know what to say about the riding in the cold part, basically seems like if I ride in the cold and snow just going to hurt the motor
Look at it this way. You've seen the diesel trucks running down the roads with a cover snapped onto the grill right? Same idea. You don't want -40 air rushing directly through your rad fins at 100kph as the wind chill in those conditions is about -90F. At that temperature even pure antifreeze can congeal or even solidify. I think most new sleds now use heat exchangers rather than rads to solve this problem.
The problem with open rads like yours is that long before the antifreeze stops flowing it becomes so cold its entering the cylinder at sub-freezing temps. The effect is the same as if you fired the engine up stone cold and pinned the throttle. The piston is hot and the cylinder is cold and metal starts smearing. Putting a cardboard cut out in front of the rads stops the wind-chill effect and keeps the coolant warm. At -40 you could likely run your trike with no fluid in it and be fine all day like an air cooled engine (don't try it!)
The next issue is your intake. The carb is subject to wind-chill effects as well. In a sled the carbs are inside the shroud and getting some ambient heat, as are the cases, but your trike was never designed for use in the extremes of northern Canada. Everything is exposed to the wind. Being jetted a little rich is good insurance, but not a guarantee. If it was me I'd avoid top end runs in -20C conditions. Also if you've perforated your air box you may want to duct tape the holes shut for winter riding. You can ride your trike all winter, just be smart about it.
Jason125m
12-25-2014, 11:44 AM
I don't know what to say about the riding in the cold part, basically seems like if I ride in the cold and snow just going to hurt the motor
I disagree, I have been riding in -30 weather for years, i have never hurt any of my engines. Aslong as the engine is warm'd to operating pressure before riding, you will not have an issue. I've heard lots about covering a rad, but I never have, and it has always been fine. I run ice studs in the winter and play around all day out on the ice, lots of WOT. No issues. Just make sure you are jetted properly.
Samjp22
12-25-2014, 07:38 PM
I'm definitely going to jet up for winter riding as there's more WOT trying to get through the snow, just gotta figure out what size I have in there right now.. And I think I might make a "winter front" for my rads. Mostly concerned about this piston as of right now. Anyone else think I should just run it or if the seller says he'll refund it wait another two weeks fora new one?
Bren_downe
12-25-2014, 08:33 PM
I'm definitely going to jet up for winter riding as there's more WOT trying to get through the snow, just gotta figure out what size I have in there right now.. And I think I might make a "winter front" for my rads. Mostly concerned about this piston as of right now. Anyone else think I should just run it or if the seller says he'll refund it wait another two weeks fora new one?
How anxious are you to ride your R? As others said you could clean it up and probably fine. If your the type of person that will be bothered by it and always wondering, then I would wait for a new one.
Ultimately it's your decision.
Personally I would get a new one. If I pay for a new piston I would want it in NEW condition.
3wheelrider
12-25-2014, 08:34 PM
That dent should be fine- as stated before. I wouldnt worry about it as it is if it was mine. Rub it just a little with scotchbrite or stone to get the high spots off the dented edges & run it. That dent wont cause you no issues really....IMO
Samjp22
12-25-2014, 09:13 PM
Pretty anxious lol, going to wait for the seller to message me back first then I'll go from there, just looking for some opinions in case he tells me to jam it.
El Camexican
12-25-2014, 10:23 PM
Pretty anxious lol, going to wait for the seller to message me back first then I'll go from there, just looking for some opinions in case he tells me to jam it.
Sucks, but should not be an issue. I've received worse and lived with it.
Samjp22
12-26-2014, 08:41 PM
Camexican I was just thinking about the "winter front" for the rads and that'll just cause it to overheat quicker, I say this because it did overheat and I had coolant coming out everywhere basically lol
El Camexican
12-26-2014, 10:37 PM
Camexican I was just thinking about the "winter front" for the rads and that'll just cause it to overheat quicker, I say this because it did overheat and I had coolant coming out everywhere basically lol
If they are solid and stuck tight to the rads then yes it will overheat. If you leave an inch or two of space, or better yet pop some holes in the cardboard and stick em tight then no. If you wanted to just reduce the air flow by say 50% it's just a matter of making some holes. The likely reason it over heated last time is that you were either jetted too lean, or your rads froze up. Have you been in a car or truck that the rad or hoses was frozen on, or owned a winter beater that didn't blow good heat? Your tag says Alberta, but I'm starting to wonder:lol:
Samjp22
12-27-2014, 12:42 AM
Never owned a winter beater lol, drive my truck all year round and have a change of plans possibly for this rebuild.. Stay tuned :cool:
Samjp22
12-27-2014, 01:49 AM
Just got this from my girlfriends brother as a late christmas gift! Its for an 86trx250r but I'm assuming it'll work for an 85atc250r. Fully ported and polished by "A", MTS maybe you know of this company/person as were from the same area? Going to measure it tomorrow and he may even have a spare piston for it!206750206751206752206753
now thats a christmas gift!!! sorry i cant say i'm familiar with the ""A" but it looks like someone spent some time on it. wont really know what you have without taking a close look at the port angles and port timing along with the squish clearence and combustion chamber cc. :D
Samjp22
12-27-2014, 10:20 PM
Gets even better! That ported cylinder is .50mm over and could use a bore so my new .75mm over piston will work perfect! I still have what I think is stock reeds (they're metal) should I upgrade to some boysen reeds or is stock fine? And would using the stock reed cage be okay?
90guy
12-27-2014, 10:47 PM
Nice score there! Sounds like you still have stock reeds. I would atleast upgrade to Boysen on stock cage. Personally Being the cylinder already has work done to it I would buy Mossbarger reeds and cage for Vforce or ESR or the whole boysen setup. But thats just me.
Samjp22
12-27-2014, 11:17 PM
I'll look into it! Thanks Todd
Samjp22
12-28-2014, 03:08 PM
http://pages.ebay.com/link/?nav=item.view&alt=web&id=391012141039 These vforce3s with a spacer or
http://pages.ebay.com/link/?nav=item.view&alt=web&id=271529512692 Or these boyesen?
90guy
12-28-2014, 03:13 PM
Dunno how much I bieleve in torque spacers. On paper they look good. I would run the vforce. But that my opinion I've always ran vforce in my sleds and it's always improved throttle response. My water pumper has vforce on it and you can tell the diffrence between with and without. But I've heard good things about boysen as well.
Samjp22
12-28-2014, 03:28 PM
Yeah it seems that a lot of people go with vforce, and coming with that torque spacer lets me kinda "play around" with how it will react and run with this ported cylinder. I'm leaning more towards the vforce as well but I'll give it a day here to see if anyone has any reasoning why to choose boyesen over vforce. Not much luck finding mossbarger
El Camexican
12-28-2014, 05:47 PM
I'll give it a day here to see if anyone has any reasoning why to choose boyesen over vforce.
According to what you'll see on some sites V-Force is a better torque reed and Boyesen is a little stronger up top. I always use Boyesen because A) I have been using them for 35 years with out issue and B) because the V-Force reeds that came on one of my bikes were eroded and distorted, both the carbon reeds and plastic cage. V-Force reeds do look cool though. I'm sure you'll be happy with either.
Samjp22
12-28-2014, 07:11 PM
Ill do a bit more digging around before I spend $200 plus on reeds and a cage, thanks guys
90guy
12-28-2014, 07:17 PM
With vforce reeds can you not just replace the reeds? That's what it looks like in the picture.
Some have screws. Most have plastic clip like setup that hold them in place. Easy to replace.
Samjp22
12-29-2014, 07:49 AM
So went just with the vforce reeds and cage, didn't bother with that torque spacer plate, they wanted like an extra $60 for it and if I want it can buy one later. Next order of business is buying jets for this new cylinder and winter riding, currently have a 140 in it, was thinking about ordering 142 up to 152, should I go more/less?
El Camexican
12-29-2014, 09:38 AM
So went just with the vforce reeds and cage, didn't bother with that torque spacer plate, they wanted like an extra $60 for it and if I want it can buy one later. Next order of business is buying jets for this new cylinder and winter riding, currently have a 140 in it, was thinking about ordering 142 up to 152, should I go more/less?
I don't own a 250R, but I would think you would want to start at no less than a 175 main if you are using a 36 to 39mm Keihin carb and that would be for summer riding. What's your slow jet # and clip notch at?
If you have access to a weather station (sled/bike or car drag guys) find out what your air density is the day you think you have it jetted right and make a note. It the future you can use that base setting to make changes for hot or cold weather riding. Rule of thumb after that is one main size every 1,000ft of change and a slow jet size every 2,000 to 3,000ft. You can use the air screw to compensate between slow jet changes.
Samjp22
12-29-2014, 10:33 AM
34mm keihin and thanks for that info, ill look into the carb more to find everything else out. It's going to suck dialing this thing in, hopefully some warmer weather once shes back together or else ill be making lake runs and swapping jets out there at -20/25C
El Camexican
12-29-2014, 07:30 PM
34mm keihin and thanks for that info, ill look into the carb more to find everything else out. It's going to suck dialing this thing in, hopefully some warmer weather once shes back together or else ill be making lake runs and swapping jets out there at -20/25C
I suspect you'll want something a little bigger if you plan to run that fancy jug.
Samjp22
12-29-2014, 10:03 PM
Like a 38mm keihin pwk? http://pages.ebay.com/link/?nav=item.view&alt=web&id=400822321112
El Camexican
12-29-2014, 10:50 PM
Like a 38mm keihin pwk? http://pages.ebay.com/link/?nav=item.view&alt=web&id=400822321112
Exactly!!!
oscarmayer
12-29-2014, 11:07 PM
wished I would have spoken to you sooner.
we race 2strokers smaller but still same principles. under racing conditions the v-force setups always wear out 2-3 times faster than the Boyesen as well as yes the Boyesen does provide better top end support and with that setup you have, you may want to reconsider if you have the opportunity. I have seen at the track a v-force shatter sending shards of CF into the cylinder ruining a good motor. I have not seen that with a Boyesen setup at the tracks.
just wanted to offer my $0.02 worth if it matters.
also with a larger than stocker setup you can call Boyesen and get thicker CF reed setup and ensure you will never have problems. we had to do that every time we go up past .25mm piston size on our race motors. If you call them you can order it to handle exactly what your doing right out of the box. they even did a custom mod to a cage for us when we were running an Athena setup as the Athena inlet came deeper into the intake and was also a slightly longer intake run than stocker. Honestly it's that type of stuff is the reason why we are sponsored with them instead of V-Force. V-Force would not do anything custom or help us when we asked about stuff that needed modifying.
good luck. looks like a very fun setup for sure!!!
Samjp22
12-29-2014, 11:08 PM
I really need to get some swing arm stickers made that say "Money Pit" that's all my dad (coolpool) calls her and she sure is living up to her name! Lol
oscarmayer
12-29-2014, 11:13 PM
LOL yea, performance bikes, trikes, quads are expensive. But if you build it for reliability, you spend FAR less than if you cheeped out and redid stuff multiple times in a short period.
Old saying I live by.
Fast
Reliable
Cheap
You get to only pick 2 of the options......
Samjp22
12-30-2014, 01:33 AM
Just read your longer reply, I'll give the vforces a try! Appreciate all the input, if they don't work out boyesen is next in line
Samjp22
12-30-2014, 01:53 AM
38mm and 39mm keihin are basically the same price, probably be better in the long run to go with the 39? From reading around it seems more people go with the 39. Will using the stock air box (not drilled) and uni filter restrict too much airflow to this carb? Is an airbox delete needed?
oscarmayer
12-30-2014, 11:29 AM
I recommend you get with twin-air and order you some filters for air box lids. The reason why is with that much of an upgrade the stock air box cannot flow what you need. so you have limited options
1. remove lid and run w/o it
2. drill holes and leave it
3. drill hole and sue Twin-air's lid filters
4. run a filter that connects directly tot he carb open style and remove the air box all together. (done for racing purposes). This is how we run my son's quads. We have a round filter hanging off the carb and open to everything. Then I put on an outterware net cover and call it a day. We race MX so we typically are not submerging or getting into that much water.
Samjp22
12-30-2014, 11:37 AM
this looks pretty fancy :naughty: http://www.ebay.ca/itm/EHS-Racing-atc250r-air-box-atc-250r-airbox-Outerwears-/360119476509?pt=Motors_ATV_Parts_Accessories&hash=item53d8cb211d&vxp=mtr
probably be the best thing to use if I go with the 39mm pwk
oscarmayer
12-30-2014, 11:48 AM
perfect! looks like it is similar to the twin air stuff except rectangular instead of circles to be drilled out.
Samjp22
12-30-2014, 07:13 PM
going to get a better idea on how this cylinder will run this weekend thanks to MTS! At least hes only three hours away
oscarmayer
12-31-2014, 06:44 PM
cool! GJ gents!
Red Rider
12-31-2014, 09:58 PM
If your new piston doesn't have the holes pre-drilled in it, to lubricate the exhaust bridge, I would follow Wiseco's instructions, which should have come with the piston, and drill your piston before you run it.
Samjp22
12-31-2014, 10:18 PM
New piston has pre drilled lubrication holes thank God, wouldn't want to have to drill those lol
Red Rider
01-01-2015, 01:06 AM
New piston has pre drilled lubrication holes thank God, wouldn't want to have to drill those lolThat's what I thought the first time I had to do it, but it's really pretty easy.
Samjp22
01-01-2015, 10:31 AM
yeah their instructions seem pretty straight forward, just weird how they wouldn't do that from manufacture
onformula1
01-02-2015, 12:19 AM
Yeah it seems that a lot of people go with vforce, and coming with that torque spacer lets me kinda "play around" with how it will react and run with this ported cylinder. I'm leaning more towards the vforce as well but I'll give it a day here to see if anyone has any reasoning why to choose boyesen over vforce. Not much luck finding mossbarger
Here is there website-
http://mossbargerracing.com/
I have been using them since 1983.
250rmanfmf
01-02-2015, 12:46 PM
38mm and 39mm keihin are basically the same price, probably be better in the long run to go with the 39? From reading around it seems more people go with the 39. Will using the stock air box (not drilled) and uni filter restrict too much airflow to this carb? Is an airbox delete needed?
They are basically the same carb. You can bore 38mm carbs to about 39.5mm. Same thing with 39mm carbs, you can bore them to 40-40.5mm. 38mm is probably the best unless you plan on running a big bore. The larger carb you have you will loose bottemend power if the carb is too large for the motor. 38's are the perfect size for overall performance for 250-295cc 250r motors from what I have seen, IMO.
250rmanfmf
01-02-2015, 12:49 PM
What are you running for an exhaust system? You wont get full potential out of the intake mods (larger carb, v-force reeds, ported cylinder) if you don't have a good exhaust system
Samjp22
01-02-2015, 05:00 PM
Fmf expansion chamber and dg silencer and thanks for the tip on carbs, once we find out how this cylinder will react I'll go from there on size
Samjp22
01-05-2015, 06:59 PM
Well thanks to MTS got everything ordered and at the shop for this to finally get done! New throttle cable, 39mm PWK ordered, bunch of jets, cylinder dropped off at Honda and found out this cylinder should run good! :w00t: should be back together in a couple weeks, in the mean time ill make a leak down tester
Went with the 39mm because MTS and I think it'll be just fine for this set up and this will most likely just keep getting a bigger and bigger bore as the years go on lol
Samjp22
01-09-2015, 07:21 PM
Got the cylinder all bolted up and double checked my ring gap before putting it together. Almost had to split the bottom end..... while putting a cir clip on the piston it went ping and made its way past my rags and into the crank housing. I was about ready to start unbolting the motor when I got a glimpse of the cir clip in the bottom end. Made it a mission to get it out. I had a little screwdriver with a magnet on the end of it that was just a little to big to fit down into the crank housing. Took a file to the handle and made it fit. I was able to get the magnet to grab the cir clip and rotated it to the front of the housing, however it still wasn't coming out. Then I went and grabbed some long dental/surgical pliers that can grab and lock onto stuff. I was able to fit these down there and just grab the cir clip. With some fancy manoeuvres I was able to pull it out. THANK GOD!
Anyways, reeds will be here early next week so in the meantime ill make a leak down tester, definitely don't want this blowing up as soon as it fires up. Also have a water temp meter on it's way to splice in. Hopefully she'll be running soon.
El Camexican
01-09-2015, 07:40 PM
That would have sucked:lol: I'd flip the trike over, or pull the engine and shake before I'd split the cases on a 2 stroke for a clip. Next time (God forbid and there's not room for a magnet) you can try takin a piece of thin wire, like say a coat hanger and put a reverse wrap of duct tape on it, then slide it down and pick it up like that.
Did you install the open ends of the clips either straight up or straight down?
Samjp22
01-09-2015, 09:41 PM
yeah never thought of the duct tape one!
Installed the clip openings facing up
Samjp22
01-13-2015, 01:39 AM
Well making a 20$ leak down tester was well worth it. Just had to clean up my reed cage opening on the cylinder a bit. 207743 used an expandable plug for the exhaust then just some pipe/fittings for the rest of it.
Decided to put the stock carb on cause I was just itching to start it! Fired right up after a few kicks. No leaks and everything seems to be good. Gonna put around on it for a bit tomorrow to start breaking it in and the sound of a ported and polished cylinder is so much nicer than stock! A lot more snappy sounding than stock
Samjp22
01-13-2015, 06:01 PM
Well took her out on the lake today. She's running nice and rich for this break in period on the stock carb. Once the new carb is in and the motor is nicely broken in I'll get that set up. Just wanna say thanks to everyone who's helped me along in this rebuild, learned a lot! Ride on
Samjp22
01-13-2015, 06:03 PM
And my pictures sideways, don't know why it always does that lol
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