ooeddym's XR overheats THEN runs like doo

Met up with Eddy, Jason and 300 of my closest friends for an urban enduro on Sunday. I'm still working on the video of that but it was a blast and cant wait to share that!

Anyway, Eddy and I swapped bikes and it was a very strange issue we're both having a hard time troubleshooting.

When it was cold (under 200°F) it ran pretty good. But it very very quickly warms up. Just running down the road at 30mph with the occasional stop I was running 140-150°F and he was between 200-210°F. What's weird is once it hits 220°F it starts to run real funny. When I'd turn the throttle to about half it would start to miss and there was nothing subtle or gentle about it. Very abrupt, power is on, off, on, off missing until you back off the throttle and when you fisted it full throttle it would just bog out and die if you didn't back off soon enough. Once it got hotter, Eddy said around 240°F it just stopped running all together.

That's just very strange to me. We've been thinking of what it could possibly be and could use some input. Any ideas? The plug and top of the piston look pretty good. Nothing like if it were running really super lean. The carb has been jetted exactly like mine and gone through and is about to be gone through again. This time in my ultrasonic cleaner. Thermostat maybe? If its electrical what could it possibly be? We have replaced the CDI. The OEM one was doing the same thing only much worse and all the time. The new one is quite a bit better and we thought the new CDI fixed the issue. But I guess not.



Any input here will be much appreciated.

Carb running lean...jet blocked or possible intake or exhaust leak.
Coil breaking down once it warms up.

I pulled the water pump cover off and made sure the impeller was connected and spinning, pulled the stator cover to make sure the pickup wasn’t loose. I have never been able to free rev the motor just sitting there either, it would just spit and sputter. Also running down the road at 60-65 the temp would be in the 145deg range but it would run out of throttle, if I would twist it open a little further it would start to miss and spit then if I full throttled it would completely die. I’m thinking it has to be something with the carb maybe a plugged orifice or something.

ooeddym wrote:I pulled the water pump cover off and made sure the impeller was connected and spinning, pulled the stator cover to make sure the pickup wasn’t loose. I have never been able to free rev the motor just sitting there either, it would just spit and sputter. Also running down the road at 60-65 the temp would be in the 145deg range but it would run out of throttle, if I would twist it open a little further it would start to miss and spit then if I full throttled it would completely die. I’m thinking it has to be something with the carb maybe a plugged orifice or something.

Did you pull out the thermostat? Is the thermostat sticking closed?

Did you inspect the stator?

Stator or coil breaking down would appear as if you had a fuel problem. Since you don't have a problem when cold, I would look at the coil and stator or to a lessor extent exhaust manifold gaskets.

"The 3 main symptoms [of a stator going bad] is that it either won't start due to lack of spark or it'll start and idle ok but after you get higher rpms it misses a little bit (or a lot) or it will barely start and won't go anywhere."

I had the second situation - LOTS of missing at high RPMS. The worst part was the issue was intermittent, so it was nearly impossible to have someone else diagnose.

Coil; when the coil cold attach ohm meter and take a reading...now heat up the coil (running the bike or a big hair dryer) and then a ohm measurement of the coil. Is there a difference in the warm and cold measurements?

Check all or your electrical system grounds

No thermostat, new exhaust gaskets and carb boot. It does haves the stock stator, I have looked at it a couple times but have never tested it along with the coil. That is agood idea I will throw a meter on both and see what i get. I have gone through the wiring several times trying to get the baha design kit to all work.

I know that you have already checked but small debree in the jet can be hard to spot sometimes , make sure that the jets are clean .( it takes few attempts sometimes to get them clean ) .

Mad Frosty wrote:I know that you have already checked but small debree in the jet can be hard to spot sometimes , make sure that the jets are clean .( it takes few attempts sometimes to get them clean ) .

I've got the carb now and plan on cycling it through my ultrasonic cleaner a few times hitting all the jets and passages with compressed air.

If that doesn't fix it I know my bike is running pretty good so we'll start by swapping carbs then go to other parts until we get it figured out.

sounds like a combustion chamber leak, is it trying to eject coolant with the rad cap off, a cracked head wiil cause the symptoms your describing, also headgasket issues, an old sp plug with a air line fitting welded to it will help to carry out a leakdown test, hook up 120psi to it at tdc to see if its leaking

temporary kiwi wrote:sounds like a combustion chamber leak, is it trying to eject coolant with the rad cap off, a cracked head wiil cause the symptoms your describing, also headgasket issues, an old sp plug with a air line fitting welded to it will help to carry out a leakdown test, hook up 120psi to it at tdc to see if its leaking

Could be. I was thinking about possibly this issue, but he did mention ejecting coolant.
I agree. A leak down test on a warn engine woul be a good test.

I will try running it with the radiator cap off and see if it tried to spit out. I don’t have any oil in the coolant or coolant in the oil.

ooeddym wrote:I will try running it with the radiator cap off and see if it tried to spit out. I don’t have any oil in the coolant or coolant in the oil.

So no seal leak on the water pump I guess.

Have you tried to change gas?

When you remove the rad cap, after start the bike see if any bubbles are coming up.

Did you noticed any change in the exhaust smoke?

Filth in the jets, need cleaning properly.
Also, if your bike has no thermostat mount one, it needs it - 150F is too cool, the engine wears too much.

We might have a winner, i tore the carb apart cleaned all the ports on everything and sent the body over to Ma$ter_E to have him put it through his ultrasonic cleaner. While he had it he went through it looking for anything out of place. He found this in the air screw port which is strange because i have another one just like it but in much better shape on the air screw that I took out sitting on the work bench. I put it back together and it runs great. All along there were two O-rings in the air screw port and my guess is the extra O-ring wasn’t allowing me to set the air fuel mixture properly on idle and causing it to run lean. I idled it around the neighborhood for around 30 minutes trying to get it to warm up and the hottest i could get it was 198 where before it was running up to 240. Thank you Ma$ter_E, the only bad news is I’m pretty sure my bike will smoke yours now

That's a sexy look'n finger there

It'll be hard to tell who's bike's better than who's when I've gotta wait forever for you to catch up

Glad we got it fixed up and its finally running the way it should.

Now we need to go on a ride and put my new GoPro mount to good use!

DAM IT! The heating problem is better but the bike still stutters and sputters. Some times it runs great and it goes like a rocket when you twist it then other times you twist the throttle and it just spits and falls on its face, Ma$ter_E has some good video of it from this weekend. I pulled the carb and coil and he will try running them on his bike and see if he has the same symptoms, that shoudl help narrow down a few factors. His XR runs perfect, we are jetted identical and identical pipes. We did mess with the air screw and could tune some of it out but just when you thought it was fixed the problem would rear its ugly head. Makes me want to kick puppies.

ooeddym wrote:DAM IT! The heating problem is better but the bike still stutters and sputters. Some times it runs great and it goes like a rocket when you twist it then other times you twist the throttle and it just spits and falls on its face, Ma$ter_E has some good video of it from this weekend. I pulled the carb and coil and he will try running them on his bike and see if he has the same symptoms, that shoudl help narrow down a few factors. His XR runs perfect, we are jetted identical and identical pipes. We did mess with the air screw and could tune some of it out but just when you thought it was fixed the problem would rear its ugly head. Makes me want to kick puppies.

Wait till he's not looking and swap plates.....job done

LOL excellent, as long as he doesnt read this post he will never know................. CRAP

I have my fingers crossed that I put Eddy's carb on and my machine runs like poo. That'll pin point the issue and all he'll have to do is buy that pumper carb he keeps yack'n my ear off about Worst case is I swap the carb and coil only to have my bike run as strong as it ever has. At that point I think the head and jug would need to come off for inspection.

Bring a gasket kit next ride and we'll put my fancy tool kit to good use

I might have the answer to your problem. I am assuming the temperatures you listed are coolant temperatures.

Remove the thermostat and run without it. Just remember to give the motor time to warm up before hammering on it.

Possibilities:

1) the black/red wire from your stator is bad or the connection/connector is bad... Remedy: new or rebuilt stator or connector.

2) the green ground wire to the frame, under the fuel tank by the coil has a bad connection or the wire is bad...remedy check the connection or replace stator.

3) The stator breaks down when hot...remedy new or rebuilt stator.

Note: CDI normal or rarely fail

If installing a new or rebuilt stator change out the pulse generator at the same time. If buying a Honda stator it should come with a new pulse generator.


This information is provide courtesy of Rob Barnum XR650R Builder and Baja 1000 winner.

You are correct, the temps were engine temp and in F. Thermostat is already pulled.

I think you might be correct about the stator, Ma$ter_E has my carb and coil on his bike now and has been riding it around with no problems, he will be going on a big ride tomorrow with it and if no problems than your theory about the stator is about the last option. Good news though Ma$ter_E just happens to have a stock stator sitting in his garage doing nothing after he replaced it with a high output model. Now if he is in the generous mood and will let me borrow it, please

Here's a little update on the situation. Had an epic and most awesome ride on Wednesday. Unfortunately, Eddy's bike didn't have as good of a time as we did. It did some really weird stuff like completely shut down at 7k RPMS, sputter and stall like it did before but only once. But it was SO rich it was an absolute pain to start and keep running the whole day. Which is really odd because they're jetted EXACTLY the same.

So I got to thinking about it and when we had the bikes ready to put back on the trailer and go home I thought I'd take a look at what the numbers were on the side of the carb. Turns out my carb is a PE-78C and his is a PE-78B. I've got both carbs now and I intend on dissecting both of them side by side and try to figure out what in the world is different between a B and a C. Because honestly I'd rather have his carb. I get 110 miles to a 4.6g tank and by then I am on fumes. With his carb it was a tiny bit lean but at 110 miles I had at least a gallon probably closer to a gallon and a half left in the tank.

I plan to do a nice review of the two carbs and post that up when I'm done. I never gave it any thought that the two carbs were different. I've never read or have even heard of this situation before. So I'm pretty sure this will shed some light on why some people swear by certain jetting (68s) and others swear that certain jetting is terrible.

We keep getting closer and closer with every tweak we make. I'm hoping by fattening his carb up so its not so horribly lean on his bike and with a new stator/pickup (my OEM one or a Ricky) that it will fix his bike.

Stay tuned! Beer and wrenching is in the very near future

Interresting discovery , i have never heard that there are two carb versions , this can explayin loads .

Have a look at the specs.....
http://www.keihin-na.com/assets/1/7/pe_parts.pdf
Ignore that link about as much use as Frosty.....

Just done some reading and the last letter is year of build.....that sounds better to me

Mauser wrote:Have a look at the specs.....
http://www.keihin-na.com/assets/1/7/pe_parts.pdf
Ignore that link about as much use as Frosty.....

Just done some reading and the last letter is year of build.....that sounds better to me

Thanks! And after going through both carbs side by side I'd have to agree with that. I tried to find a measurable difference between them for a while then gave up. The only difference I suspect there will be between them is typical manufacturing deviations that are going to be very very tiny.

HOWEVER I did find a HUGE difference between the two that should explain why even though they're jetted the same run different. Kind of feel like a tard about it now but my carb had the little diaphragm hole epoxied over. I had seen the epoxy but really didn't give it much thought. Once I had the other carb to compare to it was really super obvious what was going on.

-------------------- Eddy's Carb ----------------------------------------------- My Carb -----------------------


My Carb Now...


So after I cleaned the epoxy out we decided to jet identical again. But this time with what we think will be optimal jetting based on running each others carbs. 68s - 4th Clip - 172 - 1.75 Turns out...

I'm very excited to see how this works now. Mostly because I'm hoping my gas mileage goes up significantly and partially because we're getting very close to fixing Eddy's bike. Now only if he'd stop riding it like a big girl

LOL, I'm going to leave that alone. The biggest problem I have found is being out of shape is a killer when trying to throw that pig around. I did pick up a used ktm fan I'm looking to mount to the radiator to help control the heat when we are picking thought the trees. Both our bikes were up in the 240deg range when we were trying to find a path through the tight stuff.