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Discussion Starter #1 (Edited)
Anyone have an idea. Just installed a new cool head on my 86 250. Went to ride it seems like it just sputters and pops like it has a fowled plug Is have to check what the jetting is but it used to run good. Would a scored piston act that way? Maybe not high enough octane fuel what do they do if the octane isn’t high enough ? The plug is brown colored as well
 

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not expert. what cc?. squish?. gas?


i have the best. bdt built engines.
bdt261 oem
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bdt431 puma
bdt561 saber
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Discussion Starter #3
not expert. what cc?. squish?. gas?


i have the best. bdt built engines.
bdt261 oem
bdt363 prox
bdt431 puma
bdt561 saber
Sent from my iPhone using Tapatalk
As far as I know it’s still a 250 it’s the stock jug. What do you mean by squish. It has a pro design cool head with oring seal. Torques at 21 ft lbs. it’s pump gas 87or 91 I can’t remember it was from a year ago.
 

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thick of squish. cc dome. comp.


i have the best. bdt built engines.
bdt261 oem
bdt363 prox
bdt431 puma
bdt561 saber
Sent from my iPhone using Tapatalk
 

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Discussion Starter #5
thick of squish. cc dome. comp.


i have the best. bdt built engines.
bdt261 oem
bdt363 prox
bdt431 puma
bdt561 saber
Sent from my iPhone using Tapatalk
I wanna say the compression was 190 or so last I checked it. I will check it again tomorrow. Not sure on the dome cc was laying around and I bought it the way it was.
 

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Discussion Starter #7
they sell a pump gas and a race gas.if you have the race gas done and funning pump fuel it's detonating.
Well before the problem was I switched the head and it was an 86 head which are garbage so it would run good but after maybe 30 mins of riding it would start acting like it does now sputtering a lot of smoke and popping like a fouled plug. But I forgot the 86 heads had issues that’s why the head gasket kept going out so I switched back to the cool head which was on the bike when I bought it many years ago. I always ran pump gas back in the day and never had an issue. Yesterday I put the cool head back on it’s a pro design all you use to put those together is the 2 orings correct? I torqued the head to 21ft lbs didn’t seem like that much. After I started it it idles great sounds normal as soon as you give it some gas it sputters like it won’t clean out. For a split second it snaps out of it and goes then sputters again. Should I be putting anything else on the head besides just the orings. I have no idea what’s going on ugh shoulda just left it alone.
 

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Think it could be your ignition? I had a cr ignition start going bad on me while at the dunes it was sort of doing what you are describing.
Now that I think of it more mine was also starting to seize to and I had a bad oring and letting in coolant as well.
 

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Stumy:

That head, the o-ring glands are bad, burred and not even. Your o-ring is leaking coolant into the combustion, the top of your piston confirms what I just stated. Have the head cleaned, o-ring glands re-machined correctly, head machined flat, cylinder lapped flat, new o-rings...your troubles will go away.

Also perform a solder squish test, let's make sure the squish clearance is correct, and the piston is not interfering with the dome. Search on this site, I had a full article on how to perform.

PS: that "turbo" dome is "Snake Oil" at it's best...can't understand why they would butcher a dome that badly.

Carlos
 

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Discussion Starter #12
Stumy:

That head, the o-ring glands are bad, burred and not even. Your o-ring is leaking coolant into the combustion, the top of your piston confirms what I just stated. Have the head cleaned, o-ring glands re-machined correctly, head machined flat, cylinder lapped flat, new o-rings...your troubles will go away.

Also perform a solder squish test, let's make sure the squish clearance is correct, and the piston is not interfering with the dome. Search on this site, I had a full article on how to perform.

PS: that "turbo" dome is "Snake Oil" at it's best...can't understand why they would butcher a dome that badly.

Carlos
Is that done bad then should I be finding a different one? It’s all very old stuff that was on it when I bought it. Thanks a lot everyone all your help means a lot. I was about to give up on it honestly. I did what you said I took it apart had it all flat stone ground it had a couple burrs and was not completely flat. I cleaned the grooves out new orings in and torqued it back down to 18ft lbs. got it all together. I rode it it’s much better now but still not perfect maybe jetting now I’m thinking tho. I’m at 1700 ft elevation 190 psi compression with a 38mm air striker carb what should I have the needle position pilot jet and main? I’m going to take it apart now to see what’s in it.
 

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Discussion Starter #13
The current jets are 48 pilot 160 main. It’s also only 35 degrees today as well.
 

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Discussion Starter #14
This is the new inside oring after being run maybe 15 mins is it over torqued or why did the oring destroy like this
63803
 

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I think you have the incorrect o'ring material. The inner o'ring should be silicone because of the heat. Your o'ring looks like it melted. Once you get that sorted out and you still have the issue with it running poorly swap out your cdi with another one. I had a cdi that would make my R pop and sputter when I hit the throttle. I could fire the engine up and it would idle great. Just wouldn't rev until I swapped to my other cdi.
Loren
 

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This is the new inside oring after being run maybe 15 mins is it over torqued or why did the oring destroy like this
View attachment 63803
NOT "incorrect o-ring material"...it didn't melt, it was extruded outward from the high pressure side...cylinder bore...!

The o-ring material Brown in color is perfectly fine, actually it's called FKM aka "fluoroelastomer", similar properties/operating temperatures to Silicone, except higher tear strength. It's used in all 250R Drag cylinders like Sphynx, Lynx, Puma, and Saber....as well as all Yamaha, and High End Banshee engine Builds.

The cause of o-ring failure in your case is from high pressure extrusion of the o-ring material. Either the Head, cylinder, o-ring gland, Flatness or all are incorrect. The dome could also be sitting to low (or to high in some cases) relative to the shell.

As I stated in a previous post: "That head, the o-ring glands are bad, burred and not even. Your o-ring is leaking coolant into the combustion, the top of your piston confirms what I just stated. Have the head cleaned, o-ring glands re-machined correctly, head machined flat, cylinder lapped flat, new o-rings...your troubles will go away"

Get you're head & cylinder checked, flattened, o-ring glands cut properly, lapped, ect...until then; you will keep experiencing failures.

Carlos
 

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Is that done bad then should I be finding a different one? It’s all very old stuff that was on it when I bought it. Thanks a lot everyone all your help means a lot. I was about to give up on it honestly. I did what you said I took it apart had it all flat stone ground it had a couple burrs and was not completely flat. I cleaned the grooves out new orings in and torqued it back down to 18ft lbs. got it all together. I rode it it’s much better now but still not perfect maybe jetting now I’m thinking tho. I’m at 1700 ft elevation 190 psi compression with a 38mm air striker carb what should I have the needle position pilot jet and main? I’m going to take it apart now to see what’s in it.
Not trying to argue with you being "the all knowing ", but the op said he had the surface's ground and the burrs knocked off. I was taking him at his word. So seeing that the o'ring looked smeared/ melted after he did as you suggested I naturally thought it could be the incorrect o'ring material. As usual you feel you must contradict everyone else.
Sorry to the OP for trying to help.
Loren
 

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not contradicted. corrected. hahaha


i have the best. bdt built engines.
bdt261 oem
bdt363 prox
bdt431 puma
bdt561 saber
Sent from my iPhone using Tapatalk
 

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Not trying to argue with you being "the all knowing ", but the op said he had the surface's ground and the burrs knocked off. I was taking him at his word. So seeing that the o'ring looked smeared/ melted after he did as you suggested I naturally thought it could be the incorrect o'ring material. As usual you feel you must contradict everyone else.
Sorry to the OP for trying to help.
Loren
I’m sure the OP appreciates all help, I know I would. I still can’t understand why Carlos’ helping is offensive? It is giving the OP information that he alone can decide how to proceed. We all don’t have to agree. If he thinks Carlos is wrong he can make his own decisions about that. If it turns out Carlos is correct then it’s a good thing he chimed in after your post.

EVERYONE should continue to comment and post, that’s the point of forums.

everyone on here (even those that have issues with Carlos) should be grateful that someone as experienced as Carlos comes on here daily to answer questions.
 

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You need to do a little research my friend. There is a very large amount of people that have been screwed by this guy you say is an expert. Me included! If that is what you are after then by all means carry on.
The issue I have is the keyboard commando obviously did not read the ops post about surfacing his parts as Carlos suggested. He instead jumped at a chance to contradict someone else. I have a decent amount of knowledge when it comes to o'ring material as I work with them quite often in my line of work. Am I an expert? No I am not. I am the first person to admit that I have more to learn in my life and I set a goal of learning something new every day. If a person goes through life believing that they know everything they cannot learn.
I can't tell you what material o'ring the op used on his cylinder as I have not been told by him what it is. Has Carlos? Probably not. I do my best to ignore his condescending comments and his belittling attitude, but to ignore the op just so he can try to school me?
I'm so fortunate to have Hybrid Engineering, LED, and ESR in my area and on speed dial. I do not and will not buy anything from Carlos or accept his information. It comes a too great of a cost.
Loren
 
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