250F Honda 1986 XR250r

JJsiahMoto

JJsiahMoto

My xr250r starts fine and runs good for a bit. After a few minutes of riding it starts to sputter in low rpms and dies. Sometimes after a little riding it backfires a loud bang which scares the crap out of me. I throttle it to keep it alive but dies if I come to a stop. I've cleaned the carb multiple times and have tried a carb kit. Any clue on what is going wrong? (SOLVED)
 
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ossagp

a few. does it restart? is it flooding? what does the spark plug look like? what are your valve clearances? if you have a manual you may want to start by testing the coil and the stator.
 
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ossagp

cleonard:
Check those valves. That engine is famous for fried intake valves.

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Really? So far I haven't "fried" an intake valve on any of the xr's that I have owned in the past or still own. Heck, I still have two xl350's. Exhaust valves, another story.
 
cleonard

cleonard

It's the ones with the dual carb setup. I'm pretty sure that the 86 had that, but then again it might have been 85 that was the last year for the dual carb.
 
Mihylo33

Mihylo33

ossagp:
Really? So far I haven't "fried" an intake valve on any of the xr's that I have owned in the past or still own. Heck, I still have two xl350's. Exhaust valves, another story.
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I think it's impossible to stop a real XR motor from running. They were bullet proof and it's probably in Hondas best interest to bring back the actual original XR line again.
 
O

ossagp

I still have a twin carbed xl. it actually is labled an 82. FYI the valves seem to even have the same part number. Not sure when to expect it to spit it's intakes!!
 
2Wheels

2Wheels

Mihylo33:
I think it's impossible to stop a real XR motor from running.
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No kidding, this guys bike is still going and lord know what condition it's in.
Takes a lot of neglect and abuse to kill one, and if you do, you don't deserve to own a motorcycle anyway.
 
cleonard

cleonard

I must be a bad man. I've killed a few. It took a lot of miles to do it though. Measured in tens of thousands of miles, not tens of hours like some modern bikes. I put at least 50k miles on my 81 xr500 before it expired in the desert one day.

On my xr600's the relative lack of cooling was the bikes biggest problem. Running super tech trails where you never get out of first gear on a hot 100+ summer day was not good for it.

Had the plastic inside the tensioner fail as well as a couple of dropped valve seats due to excessive heat.

Ok back to the original question. Some back fires are not unusual. Honda even put a backfire screen inside the foam air filter on many xr models.

Make sure the foam is ok as I had one get torn on a backfie. Like was already said check the valve clearance. It's pretty easy.

Other than that look for air leaks.

Check for spark when it's cold and then after it quits. I had a couple of stators go bad. One of those failures happened only on a hot engine. When cold again it would start fine.
 
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2Wheels

2Wheels

Speaking of the xr's when checking the valve clearance the weight of the sub rocker creates a bit of drag so I lift up on it. Even then, the angle you have to come in while checking with the cover on is a bit subjective as well. My manual doesn't even give a tolerance, only .10 and .12mm. If I get a .13 in one and not the other I call it good.

Brother had an '84 250r took a beating and never complained even in slow tech. He never changed the oil, tires, or tightened the chain. Bike ran and ran one kick. One Ozark trip, other 200# brother forgot to gas up and had to ditch his bike in the bush. They two-up the little xr back to camp. Now this was a 25 yr old bike at the time. Lil red should have died but didn't. Then after being parked in a barn for 3 years, shot of fluid and 5 kicks it starts! Incredible. then of course, after a few revs the cam breaks in half.
 
O

ossagp

cleonard:
I must be a bad man. I've killed a few. It took a lot of miles to do it though. Measured in tens of thousands of miles, not tens of hours like some modern bikes. I put at least 50k miles on my 81 xr500 before it expired in the desert one day.

On my xr600's the relative lack of cooling was the bikes biggest problem. Running super tech trails where you never get out of first gear on a hot 100+ summer day was not good for it.

Had the plastic inside the tensioner fail as well as a couple of dropped valve seats due to excessive heat.

Ok back to the original question. Some back fires are not unusual. Honda even put a backfire screen inside the foam air filter on many xr models.

Make sure the foam is ok as I had one get torn on a backfie. Like was already said check the valve clearance. It's pretty easy.

Other than that look for air leaks.

Check for spark when it's cold and then after it quits. I had a couple of stators go bad. One of those failures happened only on a hot engine. When cold again it would start fine.
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I still have several the the original xr/xl 500 original motors. Many of the problems I had in building them up into the 45 plus hp range was the chain operated balance shaft. The plate that held it would get distorted. Welding it to build it up seemed to fix a lot. Then you get them built to the point that the output side of the crankshaft would start wobbling under load.

But in stock form, they seem to run forever.
 
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JJsiahMoto

JJsiahMoto

So finnaly after trying everything I figured it out. It was the wiring. Every time I turned right it died and I was like the only way this is possible is if the wiring is shorting out or something. I tinkered with the wiring by the headlight area and zip tied it up. It works and runs perfect now. Starts first kick even on a cold day.
 
Trfsrfr

Trfsrfr

JJsiahMoto:
So finnaly after trying everything I figured it out. It was the wiring. Every time I turned right it died and I was like the only way this is possible is if the wiring is shorting out or something. I tinkered with the wiring by the headlight area and zip tied it up. It works and runs perfect now. Starts first kick even on a cold day.
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It's nice to finally get an idea of what is wrong, but if that were my bike I would take the zip-tie off and actually find the problem and fix it. A zip-tie is only a band-aid, get-you-back-to-the-truck field repair.
Most likely a cheap soldering iron (if thats even necessary) and some heat-shrink tubing would make that a permanent repair.
 
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