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Discussion Starter · #1 ·
I have had an issue with my Cat for a long time. What happens is when it is under a heavy load, it tends to load up and run like crap. I have checked and changed many things now. Here is a list of what I did.

New coil
New carb
Checked the stator
Checked the cam chain

I have the line with the check valve installed on the carb drain. My duck bill on the airbox is sealed. It doesn’t just do it in water. It will also do it on a long steep hill climb. It seems do be when it is under a heavy load and high throttle settings. It also seem worse with a lot of shaking or a hard jar like hitting the water fast.

Here is a video of when it did it this weekend. Any thoughts?

 

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Discussion Starter · #2 ·
Did a little work to it today. Checked the plug. Black as can be. How this thing cam be rich I don't know. Running a brand new stock carb. Uni filter, and an HMF Penland Pro pipe. It should be lean if anything.

Also did a compression check. 90 PSI. Actually about 5psi higher than spec of 70-85 psi. Not an isse.

It runs so damn good until it is loaded very hard like a long hill climb in high range, or deeper water or mud. Somewere when the engine is working very hard at high throttle. I am stumped. I am about ready to sell it and get somthing else. Can Am maybe ??
 

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According to my 03 AC service manual the listed spec is 63-77 psi so my question did the cylinder head ever get resurfaced?
What are the AFRs when it has no power like in the vid? Do you have the Procom cdi box installed now? From the vid it seems like it looses all of the power correct?
 

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Discussion Starter · #4 · (Edited)
No headwork done. All stock. The higher compression could be explained by the compression release on the cam not working as well as it should. If that were not there the compression would be in the 150 range I am sure.

The CDI is stock. I have the procomm for a spare.

What it does is like in the vid. Misses like crazy. Just like it starts to flood out. After 30 seconds or so of normal riding it is gone and runs perfectly. With my setup it should be lean, but it isn't. I have been chasing this problem for over a year now. Changed and checked everyting I can think of. I can have it up to the seat in water, and as long as I am not giving it full throttle trying to water wheelie it will run fine. I have another video I could put up of a mud hole right after that one were it ran perfect. Water even deeper. The only difference was I did not hit the hole as hard as I did on that one. It is like the sudden jar makes it act up.

I don't have the AFR hooked up now. I don;t run in the water with it. Those O2 sensors are too expensive and I go deep enough to get my muffler under water.
 

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Discussion Starter · #6 ·
The 03 500 is carburated. Also just gravity feed. No pump.
 

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The compression release just might have something to do with it. If at high rpm your valves aren't closing properly( valve float) sort of.
 

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Discussion Starter · #8 ·
If that were the case it would do it on long wide open runs on the road. It doesn't. I can hold it wide open for miles if I want. It is tied to lower RPM at WOT. The release just workes at very low RPM. Once the engine hits a few hundered RPM centrifugal force makes it move to allow full compression. If it were sticking it would run like crap all the time. In 6 hours of riding on Sat it did it twice.
 

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Have you checked the stator wires where they come through the case for rubs?
 

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Discussion Starter · #10 · (Edited)
Yes. I checked that and did a voltage check on them. Everything came out good. It will sit and idle with water up to the seat with no trouble. I have the carb out now and am checking it out good. It was brand new last fall but who knows. I am so frustrated with this thing. I m loosing faith in Cat. It goes through bearings and brakes like crazy. That and the run issue are making me hate this thing.:angry:

The thing is, if I just did "normal" trail riding, I would never have an issue. It is just certian specific conditions that make it happen. Steep long hill climbs were it looses speed and starts to lug hard, and mud/water were the same thing happens. If the RPM's climb or stay high, it will not do it. It has to start to lug and pull the RPM's down for the problem to occur.
 
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You have a CVT tuning issue, Not a carburetor or jetting issue.

You could increase the spring preload on your secondary pulley so it backshifts faster and deeper to maintain a higher RPM when under high load. Backshifting is then the secondary pulley opens when its under load and in effect gears the CVT down to maintain a higher engine RPM

Thinking the problem is, your throttle and slide is wide open, yet the engine RPM is not sufficient to burn all the fuel that is being dumped into the cylinder. Result: it loads up, misses and fouls the plug.
 
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Discussion Starter · #13 ·
You know I have never checked them. I just open the box, look at it and put it in. It can't be that simple ;) I will try it. And pull the plastic and check all the wiring. Tear the new carb down and look it over.......
 

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Discussion Starter · #15 ·
I don't care what fixes it. I have been battleing this for over a year. It is either going to work or it is going down the road after this. I had enough. I am sick of my brother in laws, beat to hell 500 Popo, smoking blue but still always running fine, and mine leaving me sit in the mud. I have to trailer to go anywere to test it and I don't have the time to test each fix or I would. I have been working on cars for 20 years, but this thing is kicking my a** :)
 

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Discussion Starter · #16 ·
Wyo- I was hoping you would chime in now that I have video. I have been thinking the same thing. In 03 they used higher gears than other years making it work even harder. It does upshift too fast IMO. Somtimes I can make it backshift by letting off and hitting the throttle again. If I do that it seems to help. In some holes it will also get me stuck if I let off. PS did cut my primary, but I think you are right on the secondary. The problem is I do not think my 03 can be re clocked. Maybe a different spring from EPI? Not sure. Don't know a lot about these CVT's Any suggestion would be great. I am willing to try anything at this point.
 

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Not knowing you bike- if the carb is new, I'm gonna stick with my plug diagnosis. Under load, you're really dumping the gas- everything else being normal- air/fuel/new coil (did you replace the wire?) the only two things that will foul your plug is a bad plug or gap (pre-ignition under load when your cylinder pressures are highest) or oil. Carb adjustment might be an issue- but it runs well at high speed on flat ground- so- I lean away from that.
 

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Discussion Starter · #18 ·
The wire is new too. I think you are right that the plug is fouling, but I bet it is from it upshifting too fast like Wyo said. I will be calling EPI for a spring. If I don't go in the mud or up steep hills in high range it will never do it. Then it runs perfectly. It is just a few high load situations that do it.
 

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Discussion Starter · #19 ·
Just called EPI. They told me to go with the yellow spring. They also have a green one for my model, but with stock tires they said yellow. My fingers, toes, legs, and eyes are crossed hoping this helps :0 Now to figure out how to change the thing ??
 

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You can drill a hole in it to reclock
 
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