Motor dies when warmed up.

Jake D · April 10, 2006, 12:14:28 PM

Okay, I can start the bike just fine. Warm it up with the choke turned on. Then ride away after I turn the choke off. For a couple miles it runs great. Smooth idle, revs and pulls hard. Then, after about 5 or 10 minutes of riding, the idle gets slower and I have to rev it to keep it running. Then it bogs down at low RPM when I am riding it. Then it eventually won't idle at all and stalls.

My bike has a restricted flange Wileyco, clean carbs, no re-jet, fresh motor rebuild.

Any thoughts?

scratch · April 10, 2006, 12:18:04 PM

Valve adjustment.

Egaeus · April 10, 2006, 12:19:38 PM

Quote from: scratch on April 10, 2006, 12:18:04 PM
Valve adjustment.

Likely. Also, you didn't add a fuel filter or anything, did you?

Jake D · April 10, 2006, 12:22:53 PM

The guy that built the motor said he checked the valves clearance. But it could be wrong. And the bike has a new used head with a three angle valve job, and new valves.
Could it be that the valves were just spec'ed wrong when he built it. What would cause it to run worse after it is warmed up if the valves were the problem?

Also, would the valves effect the oil pressure at extremely low idle (ie., circa 1500 rpm)?

P.S.: no fuel filter.

scratch · April 10, 2006, 12:25:27 PM

Valves would not affect oil pressure.

How many miles has it been since the rebuild?

ajgs500 · April 10, 2006, 12:26:52 PM

I like your boobs.....errr I mean I like your bike!!!!

Egaeus · April 10, 2006, 12:27:12 PM

Quote from: Jake D on April 10, 2006, 12:22:53 PM
What would cause it to run worse after it is warmed up if the valves were the problem?

Heat expansion. Very tight clearance when cold means no clearance when warm. Your valves won't close completely.

Jake D · April 10, 2006, 12:30:03 PM

Actually I was just curious about the oil presure thing because at extremely low idle, right before it dies, the light comes on.

I've probably only put 50 miles on it since the rebuild. Every time I ride it the damn thing stops running.

Jake D · April 10, 2006, 12:31:17 PM

So were saying that it is valve clearance? I bet when he checked the valves that he didn't use the correct gap.

Egaeus · April 10, 2006, 12:34:21 PM

Quote from: Jake D on April 10, 2006, 12:31:17 PM
So were saying that it is valve clearance?

It's possible, but by no means definitive. Since you just did a rebuild, then they might not have been seated fully when he checked them. I would check them because it's a cheap and easy thing to rule out.

Jake D · April 10, 2006, 01:02:33 PM

Usually, you can ride a long ass way with your valves out of spec. Right? Could they be that out of whack from the rebuild that it could run fine when cold and then not run when warm?

LimaXray · April 10, 2006, 01:07:32 PM

did you rejet for the valve job?

Egaeus · April 10, 2006, 01:09:52 PM

Quote from: Jake D on April 10, 2006, 01:02:33 PM
Usually, you can ride a long ass way with your valves out of spec. Right? Could they be that out of whack from the rebuild that it could run fine when cold and then not run when warm?

Depends on how bad they are. A little out of spec is not much of a problem. If the valves aren't closing properly, then it's going to run like crap, and eventually burn a valve.

If they're out of whack, then they're out of whack. If you're working slowly, it takes about 30 minutes to get to them, and about 10 minutes to check. So you're looking at about an hour of work to eliminate that as a possibility.

Egaeus · April 10, 2006, 01:11:06 PM

Quote from: LimaXray on April 10, 2006, 01:07:32 PM
did you rejet for the valve job?

Why would you rejet for adjusting the valves?

Jake D · April 10, 2006, 01:16:53 PM

Yeah, there was machine work on the head for the valve job to get the new valves to seat perfectly in the new head.

But it hasn't ever been re-jetted.

I guess I'll either sell the bike as is or check the valves.

Anybody want to buy it? Just kidding. I have a guy that may want it. I'll just tell him the deal. I'm buying a new bike anyway. I guess I should get in line for Kerry's valve kit.

Jake D · April 10, 2006, 01:18:08 PM

Quote from: ajgs500 on April 10, 2006, 12:26:52 PM
I like your boobs.....errr I mean I like your bike!!!!

I got rid of the boobs, as much as it pained me. There is someone very special to me that saw it was was a little saddened by my lack of maturity. So she's gone (the avatar).

LimaXray · April 10, 2006, 01:22:11 PM

he had valve job, and usually a valve job results in higher flowing heads, a higher flowing head means you need more fuel...

It was just a thought.

Egaeus · April 10, 2006, 01:25:47 PM

Quote from: LimaXray on April 10, 2006, 01:22:11 PM
he had valve job, and usually a valve job results in higher flowing heads, a higher flowing head means you need more fuel...

It was just a thought.

Oh, I missed that part. Valve job, not adjustment. Gotcha.

LimaXray · April 10, 2006, 01:26:14 PM

thinking about it, that would probably make it not run cold but run when warm, so never mind

Destro · April 10, 2006, 02:12:25 PM

Quote from: Jake D on April 10, 2006, 01:16:53 PM
Yeah, there was machine work on the head for the valve job to get the new valves to seat perfectly in the new head.

But it hasn't ever been re-jetted.

I guess I'll either sell the bike as is or check the valves.

Anybody want to buy it? Just kidding. I have a guy that may want it. I'll just tell him the deal. I'm buying a new bike anyway. I guess I should get in line for Kerry's valve kit.

PM me, we need to get together anyway, I have some extra 15wt fork oil available.

Had to check my valves not too long ago, really not that difficult... especially if you bring the beer!

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Motor dies when warmed up.