83 250r burnt piston

[trikelife101]

So today I was riding my 250r and suddenly it decided to stop running. Pushed it home checked for spark and gas and it was all good. The I did a compression test and it had a whopping 30 psi of compression. Took off the head and guess what I found.248904248905 obviously it comes from too lean jetting so I tore apart my carb and it had a 118 main jet in it. When I got the bike it ran great so I never bothered checking it so I just drove it. So my question is what kind of jetting do I need for a stock reeds carb pipe and silencer?


Thanks guys
Tim

[sledcrazyinCT]

Honda parts fiche calls for a 130 main and a 50 slow jet

[trikelife101]

Thanks once I rebuild it I'll try that

[lndy650]

thats some nasty detonation there. make sure to get that head milled sharp edges are the main cause of detonation. to get a better idea of what size jet you need we would need to know your elevation and climate

[trikelife101]

My elevation is 315 meters. I have a good spare head I can use

[lndy650]

ya thats why. the lower your elevation the richer you need to jet. i would start with a 140 to be safe and go from there. whats the average temperature you ride in?

[yaegerb]

You are detonating. That carnage is likely more from running an octane lower than what your motor needs. Need to check compression after rebuild and I would perform a UCCR.

[lndy650]

detonation can also be caused by pre-ignition from a lean condition. at the elevation hes at with the jet size hes running hes definitely lean. by the looks of that piston id say a sharp piece of carbon is what started the pre-ignition

[fieldy]

So today I was riding my 250r and suddenly it decided to stop running. Pushed it home checked for spark and gas and it was all good. The I did a compression test and it had a whopping 30 psi of compression. Took off the head and guess what I found.248904248905 obviously it comes from too lean jetting so I tore apart my carb and it had a 118 main jet in it. When I got the bike it ran great so I never bothered checking it so I just drove it. So my question is what kind of jetting do I need for a stock reeds carb pipe and silencer?


Thanks guys
Tim

How many "liters" of mix did you get to use? At any point did the motor seem to be running hotter than usual? Sound any different at any point?
It had to run like a pro's for a while.
Just wondering.
Hey can we see the plug too?

[atc300r]

. That's alot of black carbon for being lean.I would do new crank bearings,seals,topend and gasket kit with stock jetting.And go from there.

[El Camexican]

Any chance some shrapnel from a piston skirt could be responsible for those pock marks and not detonation?

[Doug8765]

What he said or a ring


Sent from my iPhone using Tapatalk Pro

[trikelife101]

How many "liters" of mix did you get to use? At any point did the motor seem to be running hotter than usual? Sound any different at any point?
It had to run like a pro's for a while.
Just wondering.
Hey can we see the plug too?
I have the gas mixed at 28:1. It's about -40 degrees Celsius where I'm at right now so if it was running hot I problem wouldn't have noticed. And it was only like my third ride with it. It sounded fine but it felt kind of sluggish wouldn't rev up very fast.

[trikelife101]

Any chance some shrapnel from a piston skirt could be responsible for those pock marks and not detonation?

Yea there where peices of ring in my spark plug in my exhaust and who knows where else

[fieldy]

I have the gas mixed at 28:1. It's about -40 degrees Celsius where I'm at right now so if it was running hot I problem wouldn't have noticed. And it was only like my third ride with it. It sounded fine but it felt kind of sluggish wouldn't rev up very fast.

You are about 1,033 ft altitude. Did the trike come from a higher elevation than you? I had bought a trike that was leaned way down on the main like that, still havent started it. This cold is bad but i cant imagine what you guys go through. - 40 and, nope.
Was the plug color whiteish when you removed it? Thanks.

[El Camexican]

Yea there where peices of ring in my spark plug in my exhaust and who knows where else

Looking forward to seeing photos of the cylinder wall and more so the piston when you get it torn down. I have a couple heads that look like yours in my shop and I've always suspected that they were caused by debris more so than detonation. simply because of the sharpness of the edges. I've also seen domes that had some pitting with no other explanation that detonation, but all the damage was lower than the surface of the dome and not protruding and sharp like yours seems to be.

[trikelife101]

248986248987248988
There are a few more pics. Can see some pretty good heat marks on the cylinder. And if you look close at the plug there's peices of metal in it lol.

[trikelife101]

You are about 1,033 ft altitude. Did the trike come from a higher elevation than you? I had bought a trike that was leaned way down on the main like that, still havent started it. This cold is bad but i cant imagine what you guys go through. - 40 and, nope.
Was the plug color whiteish when you removed it? Thanks.
No it came from about the same elevation

[lndy650]

negative 40 is seriously cold.

[trikelife101]

negative 40 is seriously cold.

I'm getting used to it it's been that cold close to a month already. Lol the life of a Canadian

[fieldy]

No it came from about the same elevation

How many turns out was your carburetor adjustment screw?

I am still trying to figure out why there was a smaller main jet installed? Why would this be done? I asked about that when i discovered my tecate had a 210 main and the book standard is 270 on the 86. Were they trying to compensate for worn rings and blowby? Maybe jetted down on main to run the richer mix?
Was the jetting done with a colder plug? Surprised the plug wasnt more white or chunks out of the electode if it was running so hot from being lean. .....and if the mix was to rich, why would it be lean, carburetor restriction?
By the way what has happened here, just a ring failed? Was it actually lean? The plug shure weren't tan.
Freaking confusing.

[fieldy]

I thought when one started "dieseling" and smoked the rings that the motor would rev up uncontrollably or death rev if you will.

[fieldy]

Trikelife101, did you let the coolant get up to temperature before you got into the throttle?

[lndy650]

after seeing the plug i think its possible it wasnt running lean it was detonation probably from water in the fuel or poor fuel to begin with. someone already mentioned poor fuel quality seeing the plug thats my guess.
when a 2 stroke diesels they do rev uncontrollably its a scary feeling but thats different than just pre-ignition or detonation. in this cas i dont think the detonation was caused by pre-ignition like i earlier thought it was likely from poor fuel.

[fieldy]

after seeing the plug i think its possible it wasnt running lean it was detonation probably from water in the fuel or poor fuel to begin with. someone already mentioned poor fuel quality seeing the plug thats my guess.
when a 2 stroke diesels they do rev uncontrollably its a scary feeling but thats different than just pre-ignition/detonation
Ok trikelife 101, more questions...what octane and what oil and what piston and any water in the fuel and what plug number?????
Thanks Indy, i didnt know preignition and diseling were different, could you explain further?

[lndy650]

detonation is when the fuel is ignited by a source other than the spark and by the spark and the two forces collide with each other thats kind of the easiest way to explain it. when a gas engine diesels something usually the spark plug electrode has become so hot it stays cherry red and combustion occurs without spark. pre-ignition, detonation, and dieseling all seem similar but they are all different. theres many good articles you could read on each. dieseling rarely happens and is in a way an extreme form of pre-ignition. pretty much there is something large enough and hot enough combustion doesnt rely on the spark at all so instead of a small ignition colliding with the main ignition(detonation or piston knock) theres a full combustion occuring before the plug even fires(dieseling/engine run-on)

[fieldy]

Thanks im going to save this information that took some time to do appreciate it. You seem to be very knowledgeable on these cycles.
So how come someone would reduce a main jet like that. Mix ratio or plug choice or ring wear? Seems risky.
El might know, he knows more about his engines wear than anyone I've ever heard. El?

[lndy650]

this is where i may be attacked but all those people that have stock engines that run race fuel for more power... well, they are actually losing power. one of the reasons you can run higher compression with a higher octane is because higher octane fuel burns slower and can handle more compression without igniting from compression alone with no ignition source.
Another thing you could read about if your interested in this subject is how the squish band helps combustion and helps prevent detonation.

[lndy650]

Thanks im going to save this information that took some time to do appreciate it. You seem to be very knowledgeable on these cycles.
So how come someone would reduce a main jet like that. Mix ratio or plug choice or ring wear? Seems risky.
El might know, he knows more about his engines wear than anyone I've ever heard. El?

its no problem this stuff really interests me but thank you i appreciate that. theres all kinds of reasons for a smaller jet this is why reputable aftermarket companies wont give you a specific jet size only how much to jet from a good set up. my recommendation for this situation would be to switch everything to stock recommendations at his altitude and do plug checks and read the piston wash to get the jetting correct. his spark plug doesnt look lean but the piston carbon tells a different story so this engine could have in fact been running lean. plugs can be tricky i prefer to check the piston wash when im tuning in the jetting

[fieldy]

Been here quite a while and never heard of piston wash before! I will check in later this week -30 wind chills so i will be checking in to see if the op can answer a few more of my questions about this tragedy, lol. Happy new year guys!

[lndy650]

happy new year to you too :Bounce

[trikelife101]

How many turns out was your carburetor adjustment screw?

I am still trying to figure out why there was a smaller main jet installed? Why would this be done? I asked about that when i discovered my tecate had a 210 main and the book standard is 270 on the 86. Were they trying to compensate for worn rings and blowby? Maybe jetted down on main to run the richer mix?
Was the jetting done with a colder plug? Surprised the plug wasnt more white or chunks out of the electode if it was running so hot from being lean. .....and if the mix was to rich, why would it be lean, carburetor restriction?
By the way what has happened here, just a ring failed? Was it actually lean? The plug shure weren't tan.
Freaking confusing.

Man I couldn't tell ya why it had a smaller jet I got it like this. And I'm coming from a 200 big red so 2 stroke is a very new thing to me. And my air fuel screw is 1 1/2 turns out

[trikelife101]

Trikelife101, did you let the coolant get up to temperature before you got into the throttle?

This is a airfooler no coolant here lol. But yes I got the engine warmed up first before rippin

[trikelife101]

Ok trikelife 101, more questions...what octane and what oil and what piston and any water in the fuel and what plug number?????
Thanks Indy, i didnt know preignition and diseling were different, could you explain further?

Sorry don't know what octane it is but I could find out.no there wasn't water in the fuel it was a fresh tank. The oil is some cheap stuff I had for my 600 rmk but never had problems with it. Piston is just the stock piston. The plug is a br8es

[trikelife101]

And a happy new year to you guys to!

[atc300r]

Im thinking that if crank seals are leaking the previous owner jetted it to compensate for the extra oil.2016 race season I raced my 85 250r with the ebay motor in it.The flywheel side seal was bad and my main jet was missing. The trike ran great on topend.

[lndy650]

ya a bad crank seal can wreck havoc you got lucky the main jet was missing. i blew a belt on a sled once it took out the crank seal and by the time i came to a stop the clutch side piston melted down.
Im thinking that if crank seals are leaking the previous owner jetted it to compensate for the extra oil.2016 race season I raced my 85 250r with the ebay motor in it.The flywheel side seal was bad and my main jet was missing. The trike ran great on topend.

[trikelife101]

Well I just dug a little further and the oil in my crankcase smells like gear oil and my tranny fluid smells like 2 stroke oil. I took off my flywheel cover to see if that side crank seal was bad because I'm thinking there would be oil in there then if it was bad, But I didn't find any oil in there.

[El Camexican]

How many turns out was your carburetor adjustment screw?

That wouldn’t have ever been the cause of his misery. Keep in mind that your air screw is something you can play with as you ride. As an example I use a knurled one on my dirt bikes so I can reach down and adjust them while I’m riding. A few weeks ago we rode out of town from about 1,200’ elev. and ended up at over 10,000’ a few hours later. I run the smallest pilot I can find (#35) so started off I’m about 3/4 of a turn out and by the time we were at the top of the mountain I was turned out so far I thought the screw might fall out. Regardless of that it’s unlikely you would ever load an engine up hard enough on the idle circuit to melt it down regardless of how lean you were adjusted. What you might notice though is that the engine was running away on you (high rpm) the same as when you shut off your petcock and run the fuel out of the bowl. As it runs out of fuel the engine gets lean and revs up. I’ve heard you can damage an engine doing that, but I’ve yet to have it happen to me. If an engine ever does that to you and the kill switch won’t kill it you need to open your throttle to the max, that will stop it.


I am still trying to figure out why there was a smaller main jet installed?

In my limited experience you can be quite a few main jet sizes below the best one for given conditions and you won’t even be able to tell when driving around. That’s why the rule of thumb when picking your main jet is to start out rich and work your way down until the engine stops bogging. Once the engine cleans up you can drop down another 3 or 4 main jet sizes and unless you’ve got and incredible feel for your machine you won’t be able to tell that your running lean without looking at your plug. You can smell it when you’re too lean as well, but that’s already after your engine is starting to run too hot. The factory setting are usually rich to prevent warrantee issues, so it’s nothing to see a stock bike with a main jet a few sizes smaller. Besides, when you buy a used 30 year old trike there’s no telling who did what or why.


Maybe jetted down on main to run the richer mix?

Maybe. The reality is that the more oil you put into your gas the larger your fuel jets need to be (I say fuel because your air screw would actually need to be turned in if you add more oil to your gas). Oil displaces fuel, therefore going from a mixture of 50:1 to a mixture of 20:1 means there is less fuel to mix with the incoming volume of air.


.....and if the mix was to rich, why would it be lean, carburetor restriction?

As per above, but you kind of answered yourself. You could say that more oil actually does restrict the amount of fuel that can pass through a jet that’s experiencing the same amount of negative pressure, or draw.


By the way what has happened here, just a ring failed? Was it actually lean? The plug shure weren't tan. Freaking confusing.

I think he just hit the bad luck lottery. Super cold conditions that likely called for an even larger main jet than the factory issued combined with an air leak, or leaks that probably got a lot worse with the cold temperatures. That trike may have had an air leak and been under jetted for years, but a good hard rip on a -40 day will bring out the worst in these things


El might know, he knows more about his engines wear than anyone I've ever heard. El?

You’re right, I know about the wear on my engines, but not anyone else’s LOL! You never know what you’re getting when you buy something used, that’s why I always tear apart everything I buy and look for problems. To date I have yet to open something used up and not find something that needed fixing. As someone that was young and broke a lot I get that tearing down a running engine for a rebuild seems like a waste when you’ve pay good money for something that’s running, but at this point in my life I figure I can’t afford not to open up a used engine and go through it. Bearings, rod, piston, seals and gaskets add up to about $500 and if you put it together right it will last you for years, so its pay now or pay later add a long cold walk home and maybe a head and bore job to the expenses if you wait till they pop to open them up.

[Doug8765]

I think the rings were worn out and the piston /rings were bouncing around in the cylinder ring caught a port done


Sent from my iPhone using Tapatalk Pro

[Rob Canadian]

Guessing you are going to rebuild the complete engine? Sounds like you may have other issues going on too.

Maybe something in the bottom end started this whole thing?

[lndy650]

i actually have seen where a wrong air screw setting could do this. if you engine brake while running too lean on your slow jet circuit you can have a melt down. thats why for those who like to slow down by downshifting you should burp the throttle as you do it.

[trikelife101]

Guessing you are going to rebuild the complete engine? Sounds like you may have other issues going on too.

Maybe something in the bottom end started this whole thing?
Yea I'll be rebuilding it as soon as I can... or get a hondaline 300😏

[trikelife101]

i actually have seen where a wrong air screw setting could do this. if you engine brake while running too lean on your slow jet circuit you can have a melt down. thats why for those who like to slow down by downshifting you should burp the throttle as you do it.

I definitely have engine brakes it without burping the throttle. Definitely something I'll keep in mind for the future

[fordnut79@hotma]

ethanol in the mix,
fuel

[fieldy]

You are detonating. That carnage is likely more from running an octane lower than what your motor needs. Need to check compression after rebuild and I would perform a UCCR.

What's a UCCR, special compression test?

[fieldy]

its no problem this stuff really interests me but thank you i appreciate that. theres all kinds of reasons for a smaller jet this is why reputable aftermarket companies wont give you a specific jet size only how much to jet from a good set up. my recommendation for this situation would be to switch everything to stock recommendations at his altitude and do plug checks and read the piston wash to get the jetting correct. his spark plug doesnt look lean but the piston carbon tells a different story so this engine could have in fact been running lean. plugs can be tricky i prefer to check the piston wash when im tuning in the jetting

What's piston wash?
I will have some more questions after i get to read the whole thread!:twisted:

[yaegerb]

What's a UCCR, special compression test?

Uncorrected compression ratio. Essentially it’s a solid way to determine what octane you should be running.

[lndy650]

piston wash is a way of checking your air:fuel ratio. i do take the plug into consideration also but i use a bore scope and check piston wash when checking if my jetting is on. i use it a lot when i race watercross. ill do a couple wide open drags across the pond and then check my wash. if thats good i know my main jet is good. then ill do a few ovals about 10-15 and ill check the wash and that will show me how im running over all.
its just another thing you can check to really dial in your engine. ill post some pics of what to look for.

[lndy650]

ok so there is actually a lot to piston wash and how to correctly read it. when your engine is running lean and hot the oil in the fuel mixture comes through the transfers hits the piston dome and will burn and turn to carbon and your piston will be competely dark with carbon burned onto the dome. when your too rich the cool mixture coming in from the transfer ports washes the piston and the dome will be mostly bare and wet with a little carbon in the center. when your engine is running perfect there will be a small amount of wash on the piston lined up with the transfer ports. the mix is quickly heated and burned as not to wash too much and also not heated so fast and hot as to char the oil and leave carbon on the entire piston.
i hope i explained that so that it made sense.

[lndy650]

this is a lean piston 249021

[lndy650]

this is a good example but the center one is actually still a little rich the wash shouldnt extend that far into the dome249022

[lndy650]

this is a good wash249023

[lndy650]

There is a lot you can learn from piston wash. for example when i managed a fleet of about 20 rental sleds. we bought two new sleds they were brand new 2012 skidoo gtx 550 fans. i noticed when people that seemed like they would ride hard rented them it was fine but when new riders or older people rented them they were seizing pistons and running lean. the wash showed a lean condition. so i went out rode it hard came back good wash. went back out and rode at a slow cruising speed around 1/8th throttle like a new rider or older person would ride. went about 30-40 miles came back.the wash showed it was lean. right then i knew the problem.
in order to help pass emissions skidoo was using the smallest pilot jet they could get away with so on a cold day with grandma cruising around at 1/8th throttle the engine was running lean as hell and would seize up. being fan cooled probably added to it seeing at slow speed and rpm the fan wasnt as efficient. so i went up two sizes on the pilot with the air screws set at 3/4 of a turn and tested it with good results. we had no seized pistons after that and any new 550 we bought thats the first thing we did.
After talking to skidoo tech he told me that the emissions tests are mostly run at a constant rpm so using a pilot right on the edge helps them pass emissions. i cant say for sure how true that is but thats what he told me and it seems to make sense.

[El Camexican]

Here's a rich wash. This was after my first tuning attempt on the fresh engine with a 38 pilot and a 170 main. Seemed to run good, still haven't killed a plug going on 9 years with this engine.

249027

Like I mentioned, I thought it was running good, but after seeing this I went to a 35 pilot, a 165 main and a different needle. Ran the same other that the needle clip position being a little fussier, but the mileage went up from about 95 miles to a tank to almost 120 and the pistons that followed have less washed area. I might have one around to post up.

What you don't want to see is any burning or discoloration on the bottom of the piston. If you do it's running hot.

249028

[trikelife101]

So as soon as I have the dough I'll be rebuilding it. I also just recently found out that kustom kraft is making 270 and 290 big bores for aircoolers. Has anyone tried these kits or has had anything done by them, would like to know if there my good before buying.

Thanks
Tim

[yaegerb]

Get a 300 cylinder and booya!

[El Camexican]

So as soon as I have the dough I'll be rebuilding it. I also just recently found out that kustom kraft is making 270 and 290 big bores for aircoolers. Has anyone tried these kits or has had anything done by them, would like to know if there my good before buying.

Thanks
Tim

Mark is the owner, great guy. He's done 3 different cylinders for me and one for a friend. I'll be sending him another soon. Tell him that Nico from Mexico said hi and be prepared to talk politics when you call.

249069

[trikelife101]

Get a 300 cylinder and booya!
I can get one but the piston and sleeve have seen better days and I wouldn't know where to find a piston for it

[yaegerb]

You lost me....You already have a 300 cylinder? What do you mean the piston and sleeve have seen better days?

[lndy650]

i think what he means is he knows someone that has one for sale? do they not make pistons for the 300 anymore? yaeger what are your thoughts one the stock porting with these kits? is the size and timing ok stock and do the big bore sleeves line up to the stock ports or do these big bores need porting to see big results? if i remember correctly the exhaust port has no auxiliary ports and no bridge so its pretty limited on how wide you can go. I had an old dirt bike cylinder i added auxiliary exhaust ports to once just for the fun of it. i wonder if this could be done to the 250r engine. that would definitely add some power.

[yaegerb]

You can still find pistons for the 300 Kit. You will be hard pressed to find a 300 cylinder that hasn't had the transfer tunnels massaged in some way shape or form. Typically, what I see on these cylinders is someone has hogged out the boyesen ports, knife edged the transfers and angled out the transfer roof to an idiotic degree. Most 300 cylinders need to be epoxied (saved) rather than ported. The stock transfers locations and timing are definitely better than stock due to size and volume it will push. When you say big bore sleeves line up to the stock ports?? Help me out there. The 300 does have a bridge so when you do find a piston you will need to drill oiling holes to increase life. IMO, auxiliary exhaust ports aren't needed. I would just enlarge and reshape the existing exhaust port to increase flow.

[trikelife101]

Yea I know where to get one. Here's a few pics of buddy said he had used it a few years ago but the crank bearings started seizing so he stopped running it. Yaegerb where can you get pistons for these?


249111249112249113
You lost me....You already have a 300 cylinder? What do you mean the piston and sleeve have seen better days?

[yaegerb]

Sent you a PM

[lndy650]

what i meant about the sleeve lining up is how sometimes theres ledges where the steel sleeve meets the aluminum and it has to be blended. Ive seen some that are pretty bad. the older polaris fugi engines were horrible and had casting marks you could cut your finger on. So i guess i was just asking if the sleeve meets the cylinder nicely or if you need to match the ports to the sleeve. As for auxiliary exhaust ports im a firm believer in them and i really dont care for bridged exhaust ports the bridge overheats and causes problems. and then as if the bridge doesnt get hot enough as it is you have guys that port the exhaust and take half of the material off the bride re-shaping it making it much worse than it was. Nope I personally will take a 3 port exhaust over a bridge port any day

[trikelife101]

So I just bought the hondaline 300 kit for 350 bucks. I'm just gonna run it for now and down the line get it rebuilt. Just wondering how big of a restriction is the factory pipe for the 300? And what size jets do I need?

Tim

[lndy650]

i dont have experience with these particular kits but i would just watch your temperature and make sure your not lean. i would guess starting by going up 2 main jet sizes and up one pilot if it feels lean on low end and the air screw isnt enough adjustment.
im sure yaeger will have more precise jetting i think hes ran these. the thing with jetting is that everything comes into play. air temp and density, elevation ect... its gonna be a little different for everyone. all you at sea level i envy you. you lose about 3% horsepower every 1000ft of elevation. when i was in the army i tuned some sleds for friends out west in the mountains you had to lean them right out and could feel they had less power than sleds back home

[trikelife101]

well i just did a compression on the 300 and it had 180 psi exactly so Im pretty happy with that. anyone know how much it should have new?

[yaegerb]

180 is about right if there is no porting or dome modifications.

[sledcrazyinCT]

So I just bought the hondaline 300 kit for 350 bucks. Tim

Awesome deal on a 300 kit. Any chance seller has any more kits or just oversize pistons?


You can still find pistons for the 300 Kit. Y

Been looking on Ebay and keep missing out. I bought one off partzilla three years ago but need an .050 oversize.

[trikelife101]

Awesome deal on a 300 kit. Any chance seller has any more kits or just oversize pistons?



Been looking on Ebay and keep missing out. I bought one off partzilla three years ago but need an .050 oversize.

No I don't think he has any more. I found a 76 mm Wossner piston on eBay that looked like it would work but I'm not 100% sure