2005 Bombardier Traxter 650 CVT Compression? Tops out at 20 MPH.

[BenJammin]

I did a compression test on my 2005 Bombardier Traxter 650 CVT and it's 75 PSI.  service manual only talks about leak down test.  No specification for engine compression the manual.  What does 75 PSI tell me?  Thank in advance.

 

A little history of this machine.  640 miles.  Picked it up about 2 years ago, not running. Probably the computer.  Tested all circuits and confirm it was the computer.  Long story short, I watched a Youtube video and fixed the computer. ATV now started and runs.  BUT, it tops out 20 MPH.  I cleaned the carb 3 times also using a Mikuni carb kit after the second time.  Slide in carb is going up and down.  Only adjustment for fuel is at 1.5 turns out.  NGK Sparkplug had soot on main part but brown on the electrode.  Champion sparkplug is brown.  I check CVT clutches and they both appear to engage like they suppose to.  Checked valve clearance it's 0.00, I can't get any feeler gauges in-between.  I check timing chain I believe it's in the correct position and hasn't skipped.  I removed muffler plug and drilled into muffler to try and make sure it wasn't plugged.

[Mech]

I think that will have a decompressor and so that low compression is probably normal. If it starts and idles ok I wouldn't worry about the compression.

The valves should have some clearance. Check the manual.

You don't really describe the riding and it's topping out at 20 very well.. Does the power just slowly taper off till it won't go any faster, or does it pull to that speed and then abruptly limit itself, and is the limit absolute or can you coax it a little higher by manipulating the throttle, or going down a slope ? Is that speed always the same? If you use a lower or higher gear will it go faster, or in a lower gear does it limit at a lower speed ? Are you sure it's the speed it's limiting at, and not perhaps at certain revs, or throttle opening ?

Have you tried doing a tune ? Checked the air-filter, fuel flow from the tank, valves, new spark-plug, checked the coil and and cap for the correct resistance, inspected the breather hoses and checked for vacuum leaks..

[BenJammin]

I'll check for a decompressor.  It does start and idle fine. 

Valve Clearance is suppose to be 0.015. 

Powers up 20 to no problem, maybe not full power compared to a Honda 500 I had.  No power or throttle left after it hits 20mph.  Speed is always the same.  It's a CVT transmission so I can't change gears only shift to high or low.  It could be limited at certain revs or throttle.  I can try and see if my RPM meter works on this type of coil. 

I have not tried doing a tune.  I blew out air filter.  I also ran engine without air filter and ran the same.  I've tried new sparkplug.   I have not checked fuel flow from the tank, valves, coil and cap for correct resistance and breather hoses for vacuum leaks. 

I've got some things to check,

Thank You,

Ben

[Gwbarm]

Valve clearance is rather concerning, was the valve adjusting screw loose, it should  not have changed that much in 650 miles.Unless previous owner adjusted it I would reset the valve clearances to spec and see if that helps. That would definately affect compression because clearances could actually be less than zero. Not really sure how you fixed the computer or what was wrong but that could also be limiting your revs electronically. Never had much luck at fixing computers, when something goes out it could actually take out another sector then it hard to diagnose. 

[Mech]

You could try riding it in low gear till you hit the revs you do at 20 in high gear. If it keeps going past those revs then it says it's not a rev limiter.

Then if you rode it down a hill so it had no load on it, and it still wouldn't go over 20, then it really looks like being a speed limiter.

It's possible it has a speed(or rev) limit by design,  that you've triggered by accident, either in the wiring or the ecu repair. If you figure which limit it is, )if it is not a load limit), then it might be a lead where to investigate.

[BenJammin]

Update: Correction, I did check valve clearance it is 0.00.  This Rotax 650 uses the shim type.  So not as easy to adjust. 

After some the recommendations about testing electrical components I decided to just follow the service manual. 

I've now check the rectifier for voltage at 5500RPMs = 15Volts=OK.  Manual states it should not to exceed 15volts.  Checked and measure the resistance between the Stator wire leads AC-1 and AC-2 = 0.6 Ohms. Should be 0.3 Ohms.  Checked continuity between Stator coils AC-1 to ground, AC-2 to ground. There was no continuity=OK.  Measured voltage across 2 of the Stator coils while turning over the engine, they each measure with the 4-6 Voltage AC range=OK.  Measured resistance on the Trigger Coil and it read 243 Ohms=OK.  Measure Sparkplug coil and it measured 0.6 Ohms. Not sure if this ok?

I hooked up separate gravity feed fuel tank and running it but still runs the same way. Tps out at 20MPH.

Using an external tachometer, if it is set correctly, I only reached 5500 RPMs.

FYI, I did make vides and load them to Youtube, so I know what I've done because my memory isn't the best.

I have not yet checked for breather hoses for vacuum leaks or this below.  I have it on blocks so once I get it off blocks I can try this. 

18 hours ago, Mech said:

You could try riding it in low gear till you hit the revs you do at 20 in high gear. If it keeps going past those revs then it says it's not a rev limiter.

Then if you rode it down a hill so it had no load on it, and it still wouldn't go over 20, then it really looks like being a speed limiter.

It's possible it has a speed(or rev) limit by design,  that you've triggered by accident, either in the wiring or the ecu repair. If you figure which limit it is, )if it is not a load limit), then it might be a lead where to investigate.

 

 

[Gwbarm]

You have been busy, sparlplug coil sounds weak, should be between 6 and 10 OHMs, what does the book say about that. . Do you get a good spark at the plug.

[Mech]

Cdi coils should have almost no resistance on their primary windings. 0.6 Ohm would be about right. 

Coils for switched 12v have resistance.

[BenJammin]

Bought a brand new sparkplug coil. It measured 1.6 Ohms.  It was harder to start, backfired more and ran same as old one. 

[spock58]

The BRP single cylinder 650 is a unique engine that does not have traditional valve adjustment. It does not use shims either & I believe the rocker arms have an automatic system similar to hydraulic lifters built in. The confusion is that the Outlander 650 is a V-twin with adjustable valve clearances - totally different engine.

[BenJammin]

Good to know. Thanks.

I'm kind of doing shot gun troubleshooting at this point.  I replaced the speed sensor, no change.  I bought an aftermarket carburetor and actually runs worse. 

[spock58]

Those early Can Am's weren't that popular and those engines didn't stay in production after the v-twins arrived. It's worth checking into the clutch operation, maybe there's something that's failed in there preventing the full shift and limiting the rpm's??

[Gwbarm]

Good advise. Thanks for the info, i am not really expierienced with that particular engine with automatic valve adjusters.

[BenJammin]

On 4/30/2024 at 10:16 AM, spock58 said:

Those early Can Am's weren't that popular and those engines didn't stay in production after the v-twins arrived. It's worth checking into the clutch operation, maybe there's something that's failed in there preventing the full shift and limiting the rpm's??

This ATV has the CVT clutch. I watched the clutch and both pulleys engage as I think they should.  This setup looks very similar to how a snowmobile clutch works.

[spock58]

I'm familiar with the clutches on these quads, the difference is they utilize an engine braking system which is not on snowmobile CVT clutches. If everything in there checked out, then you may still have a problem relating to the electronic module. Could be its still not working properly....

Since they are likely not available new anymore, you'd have to find a "known good" used one which would be kind of rare.

Good luck on your quest!

(BTW, that's an inside joke - the quad you have was originally named the Quest I believe, at least here in Canada it was, haha)