250R crapping out on topend

[Fox250R]

installed my 38 stryker and a rad valve a few days ago with a 182 main..it was spuddering at the topend so i dropped to a 178 and its still crapping out..Whats going on do i need to drop another size? Low and mid is AMAZING....Should i put my stock 34 back in?? lol
:)

[TrikerR]

may just be the needle setting...try adjusting that.

[wanta86r]

topend misfiring would be a rich main jet. I am running the same setup on my R. You basically have to keep dropping main jet sizes until it revs out clean. Do plug chops to be sure.

[Dammit!]

I'm running a 175 main with a similar setup.

[88 Turbo Coupe]

Swap the rad valve out

[jenndnn3]

What does the spark plug show?

[Fox250R]

Swap the rad valve out
Are you crazy? you know how much of a pain the butt that was installing those dam things? lol

[Fox250R]

What does the spark plug show?
Dark dark brown

[AZ250R]

You never tried that old round 38mm Kuni did ya... I was hoping you would so that when you upgraded to the stryker you could tell me the diff!?!?! Oh well, seems you gots some tune'n to do now. :mad:

[Yamahondaman]

I Agree with 88 Turbo .... Low-End Set Up ....Been There Done That ...
You Could Keep Jetting it till it's right but..... still slow .. Let Me Guess .... ?
You Have A FMF Pipe ? :-)

[Fox250R]

PT highrev/fatboy

[Fox250R]

You never tried that old round 38mm Kuni did ya... I was hoping you would so that when you upgraded to the stryker you could tell me the diff!?!?! Oh well, seems you gots some tune'n to do now. :mad:
Actually i was going to but i heard from many people thats its a real pain to tune....Then i found this A/s so i never used the kuni..Still have it tho :)

[Fox250R]

How many turns should my air screw be turned? could that be the problem?

[1984kxtTECATE]

Throw it down to a 172 main and see if there is a difference. What oil ratio are you at? Also a 38mm carb will give you top end along with the paul turner pipe, do you have any port work what so ever, or any other types of motor mods that you have left out you could have 2 performance parts that arnt working good together. Last but not least are you running the correct spark plug for it, I know I fouled a plug one time and had to put a colder plug in it and it totally crapped out for my top-end, or you may want to try several different plugs and see if you cant get better results. Just a few things to consider......

[3leggeddog]

your air screw will have nothing to do with top end.your rich on the main drop to a 170-172.if your gonna jet go atleast 1 size at a time.thats two jets lower,would equal i size,the others are half sizes.it's breaking up at full throttle right?

[Fox250R]

38 a/s ,radvalve,ported,no airbox bored .10 40-1 hp2 with 110 racing fuel,eunning a br9es...pilot is 55,mail is 178 needle is 2 slot.

[Fox250R]

your air screw will have nothing to do with top end.your rich on the main drop to a 170-172.if your gonna jet go atleast 1 size at a time.thats two jets lower,would equal i size,the others are half sizes.it's breaking up at full throttle right?
Yes when i pin the thottle its crapping out..

[cr500=3wheeler]

Any compression mods ie thinner head jasket,cut cylinder head. etc i realize this is not the direction you where going but im wondering about the 110 octane to me it sounds like wasted money but hey, as far as the other question id keep going down in jet size, sounds like its fat to me, what altitude are you at. The other question is was it running good with the other carb might be an ignition problem but id bet its just fat.

[deathman53]

well, low end reeds and a top end pipe are gonna be part of the problem, but not enough to make that much of a difference, it sounds as it has port work done to it. A low end pipe would help, if thats what you want.

[OldManDM]

sounds like the same thing mine does,and i`m clueless,lol......don`t know squat about messin with jets and all

[Dammit!]

This ain't that complicated. It's too rich. Dark brown is too rich. Sputtering at WOT is too rich. It isn't the rad valve or anything else. Go down to about a 172 and if the problem isn't gone it's gonna be much better and you'll have a better idea of what's going on. Check the plug and go from there.

Edit: that 55 pilot is probably richer than it needs to be too. If it's not snapping off idle real good lean that out as well. Is the needle in the 2nd position from the top or the bottom?

[Fox250R]

This ain't that complicated. It's too rich. Dark brown is too rich. Sputtering at WOT is too rich. It isn't the rad valve or anything else. Go down to about a 172 and if the problem isn't gone it's gonna be much better and you'll have a better idea of what's going on. Check the plug and go from there.

Edit: that 55 pilot is probably richer than it needs to be too. If it's not snapping off idle real good lean that out as well. Is the needle in the 2nd position from the top or the bottom?
From the top............I just went to honda and got a 172 main and a 52 slow...Lets see what happens now : :rolleyes:

[wanta86r]

make sure you only change one jet at a time. dont do both changes at once

[Fox250R]

yeah ill make sure i do that....THanks man :)

[3leggeddog]

jet er down bud and things will be fine.drop a 172 in there and do the plug chop like i told ya.report back after that.

[Fox250R]

Well, i put a 172 in and 2 turns out on the air screw and running a br8es...My plugs are coming out light tan and its stopped spuddering on the topend..i rode a wheelie from 1st to 5th down my street till i ran out of room, otherwise i could of hit 6th lol..So i guess its running good now..The only prob is when i pull the choke it still runs the same...Im not sure if this is a big deal but it starts 2nd kick everytime and when i let off the gas it comes down to a perfect idle..I think its running a litte rich but that ok with me....Thanks for all the feedback on this! you guys really helped me out.................

[OldManDM]

yea,i was running the stock 142 in mine and went and picked up a 140 and a 138 today at Honda....put the 140 in and it seems to be running better now....i just wouldn`t know how to tune this thing right if my life depended on it,LOL

[Fox250R]

well its not to tough if you read your plugs...I was having probs trying to get this stryker tuned..I listened to the guys at honda witch proved to be a HUGE mistake..Just post what your trying to do to your R and these guys out here will get you on the right track...They did me!! :)

[3leggeddog]

glad we could help bro,shoot me your carb troubles anytime,sometimes i may help,other times i may not.

[Fox250R]

glad we could help bro,shoot me your carb troubles anytime,sometimes i may help,other times i may not.
Well i finally got to take my R to a wide open space and open it up..Low and behold its still doing the sput sput sput at the topend..Its running much much better then what it was ,but i was wondering could i drop another size to a 170? or just leave it as it is and see if it might clear out after a few runs...THANKS!!

[x.system]

Well i finally got to take my R to a wide open space and open it up..Low and behold its still doing the sput sput sput at the topend..Its running much much better then what it was ,but i was wondering could i drop another size to a 170? or just leave it as it is and see if it might clear out after a few runs...THANKS!!

You should be doing plug chops every time you change a jet if you want your motor to last. If you had done a plug chop you would probably already know the answer to your question. Learn what a plug is suposed to look like and you will be able to tune your motor to really rip and you won't have to worry about grenading it. I'm not trying to come off as being mean but I've seen alot of people get these bikes and they know nothing about tuning them, 2 weeks later they are blown up and then I swoop in for the cheap sale. :D

[3leggeddog]

thats what i was tellin you about fox,wide open for 5-8 seconds in 4th gear andimmeditaly shut down and pull in the clutch.this will tell you lean or rich.gurantee it is still fat up top.try a 168,AFTER a plug chop with the 172.if your gonna jet go i full size at a time till it's real close,then use your half sizes to dial it in

[Rex Karz]

What's up with mikuni vs keihin jets? My Keihin has a 162 (sounds all wrong) in it but I went and bought mikuni jets. The mikuni 200 jet is about the same size (hole) at the Keihin 162 !! Are they interchangeable? The Keihin jet is longer....

[3leggeddog]

i don't belive they will interchange

[1984kxtTECATE]

You might also consider just trying your stock reed cage with the cr250 reeds in it, im not too sure how much of a differance it would make it it might be worth a shot, you should have a top end power motor with your mods listed so I find it suprising its still doin it too you. Although it sounds like you almost are there.

[Fox250R]

You should be doing plug chops every time you change a jet if you want your motor to last. If you had done a plug chop you would probably already know the answer to your question. Learn what a plug is suposed to look like and you will be able to tune your motor to really rip and you won't have to worry about grenading it. I'm not trying to come off as being mean but I've seen alot of people get these bikes and they know nothing about tuning them, 2 weeks later they are blown up and then I swoop in for the cheap sale. :D
Well like i said, my plugs are coming out tan but its still feels rich on the topend...Im just not sure if i should drop another size or not....The bike says yes but the plug says no...Thats the problem im trying to figure out!

[Dammit!]

How are you doing the plug chops? If you're not running it wide open for a few seconds, pulling in the clutch and killing it in one motion, you're not going to get an accurate result. If you really want to put a hard load on it, do that going uphill.

I was getting weird plug chops when I was jetting mine with some new parts. The dude at a local shop warned me that not running an airbox at all could cause me some weirdness like that due to wind turbulence (not sure how true that is but just thought I'd throw it out there) so I just jetted it rich to the point that it was sputtering like that and leaned it out until the sputter went away.

Do you run an airbox and a lid? An easy way to check something is to pop the lid off and see if the sputter improves. That lets in more air so it has the result off going down a size in the main jet (more or less).

Just out of curiousity, what is your elevation?

[Fox250R]

no box at all...But i do run an air filter out of a honda civic :) Anyway i did a few more plug chops today and its coming out dark tan now...Im just going to ride it as is and see how i like it...I dont have much room around my house to really open it up but the room i do have all it does is wheelie :) Anyway thanks for all the help!!!!!!!!

[jenndnn3]

Hey xsystem, or 3leggeddog could he simply be running out of gas?

[Trike Dude]

That would cause it to rev out like it was way lean, not sputter on the top end. Top end is controlled by the main jet.

[cr500=3wheeler]

When you say dark tan is that at the tip or down inside the plug, sounds like your on the right track just keep going and youll get it right one other thing to throw on the fire are you doing your checks at similar times of day,in the dunes if you tune in the cool of the morning it can cause problems in the hot afternoon and vise versa but that might be getting a little critical
.

[Fox250R]

Dark tan at the tip...Any i do plugschecks mostly in the afternoon ....

[x.system]

Dark tan at the tip...Any i do plugschecks mostly in the afternoon ....

You read a plug down inside at the base, not at the tip of the electrode. If you feel confident drop another jet size and do another plug chop or post a pic of it.

[86250RZ]

You read a plug down inside at the base, not at the tip of the electrode. If you feel confident drop another jet size and do another plug chop or post a pic of it.


x.system is correct, get a magnifying glass if you have to, look deep inside the plug all the way down to the base. You should see a brownish paper bag color if its jetted correctly.

[Fox250R]

well my clutch just went out so can't do any plug chops till tomorrow lol ..... thanks for the help!!

[1984kxtTECATE]

See what happens when you buy a Honda lol.............j/k

[Fox250R]

lol yea!!! ITs been acting up for a while so i was too suprized...I just pulled my pressure plates out and all of them were warped LOL!! WTF?

[Fox250R]

I installed a new clutch today and holy crap its like a new bike...My motor pulls twice has hard from low to top..My clutch must of been really messed up..But i've run into another problem tho..I did a few plug chops and my bike is geting really hot. I pulled the plug and it was red hot..My plug was very light tan and dry..Im running a bR8 but i was thinking a Br9 might do the trick..This is my first time doing a clutch so im not sure if this would make my motor lean out?? In 6th gear it revs to the moon and it wants to wheelie! It has to be running lean..Is it normal for my motor to be getting this hot? Maybe i'll put a 175 back in and see what it does.........

[3leggeddog]

depends how hot is hot.it should not be over heating or ssurging during the plug chop.
if it surges during the chop it is lean,go up a half size.if is not surging or over heating i would say you found the sweet spot!!!post a pic of the plug,light tan is where you want it.

[atc86r]

Keep jetting. I've went as low as 162main and high as 178main. Your lucky if only 1 size will fit all conditions.

[Dammit!]

Take all those BR8's you have and throw them away. No reason to use those in your climate. Get some BR9's and it should be fine. Remember with jap plugs the lower the number, the hotter the plug.

[Fox250R]

Ok i did a few more chops today (jesus this is getting old) The 8s make my bike scream but runs lean and the 9s sputter on the topend and seem to be normal as far as the plug goes...So i guess ill just deal with the sputtering and run a 9...If it saves my piston so be it.......................

[Dammit!]

Sputtering is not normal. There's no reason to just live with it. Sounds like it's just running too rich still. If you jetted it with a hot plug in it, it's not jetted right for a 9 (which is what you should be using). If the plug starts looking light gray/white with a 9 in it and it's still sputtering you might have an ignition problem but I doubt that's the case from what you're saying.

This Honda civic air filter you mentioned has me curious. Got a pic of this thing? Not getting enough air has the same symptom as too rich of a main jet.

[Fox250R]

i'll get a pic of it as soon as i can man....Im running a 172 now,maybe i should put the 9 in and drop to a 170 but ill let you see my air filter first...And another thing my chock on my carb use to work lol but it doesnt now it idles the same with it on or off... what causing that? could whatever is going on be messing with that too?? thanks for the help!

I should have the filter pic in the next 30mins or so.....

[Fox250R]

heres my filter its off of a honda civic :)

[Dammit!]

Is it just a normal K&N under that sleeve? You can get a Uni that will clamp right to the carb for pretty cheap. That's what I did.

Is it ONLY doing this at wide open throttle? I would try the 9 plug and a smaller jet. Like I mentioned previously, I typically end up running a 175 main down here in the valley and at the dunes. I had to drop to a 165 up in Flagstaff though. Elevation, humidity, temperature, all those things have an effect.

The way I jet most of the time is to go too rich until it sputters, then start backing off until the sputter stops, THEN double check the plug.