Just a list of possibilities off the top of my head, feel free to add to it!!!
RPM drop/fluctuation:
Most of this has been covered in various threads but though it might be a good idea to put it all together.
Clutch calibration: the first place most people look……if the the RPM was good and THEN something changed, it is highly unlikely this is the problem.
Clutch wear: this is very common, mostly primary clutch wear….bushings, arm pivots, roller bushings, roller flat spots, sometimes the ramp itself. Sometimes one roller or one bushing being sloppy is enough to cause RPM fluctuation. The spring cap bushing on ’07-’08 is VERY common, would recommend replacing with updated cap on EVERY ’07-’08 TRA7.
Belt: new belts will typically run low RPM for first 10-100 miles. Different belt #’s or brands with different dimensions and compounds also cause RPM variation.
DPM solenoid: Common enough that Doo has a bulletin on this. If the solenoid doesn’t function properly the sled will run rich and cause RPM drop….more pronounced at higher elevation. We have found this to be a common cause of RPM drop and a quick cure for “clutch”
problems. Take out the solenoid and make sure it functions, use a little WD-40 if it is sticky and make sure BOTH of the 2 O-rings are intact.
Exhaust valve: Make sure they function….check all vacuum lines are connected and snug fit.
Power output: have had several cases where they are just plain down on power. Not all sleds are equal. We had 3 identical (stock) sleds we set up identically (clutching, suspension etc...)…..2 run strong and no problems, 1 runs weak with no apparent problems. This is where compression should be checked as well as crank run-out. A couple customers have had unexplainable low RPM issues and lost cranks the next ride.
Limp-mode: There is a update for ’08-’09 (mostly a issue on ’09) for knock sensor sensitivity and reset. Make sure to get this update!
Aftermarket “performance” parts: this is a big category!! There are some combinations that just don’t work! Some pipes, silencers, heads etc…that are supposed to add power can cause RPM issues. The one we hear about and see the most lately has been too much compression for a given altitude and fuel. I’m no engine guru and can’t give a technical explanation, but in almost every case of low RPM with high compression, simply lowering the comp ratio and /or adding octane has cured the problem and shown much better power….even if there was no detectable detonation to begin with.
RPM drop/fluctuation:
Most of this has been covered in various threads but though it might be a good idea to put it all together.
Clutch calibration: the first place most people look……if the the RPM was good and THEN something changed, it is highly unlikely this is the problem.
Clutch wear: this is very common, mostly primary clutch wear….bushings, arm pivots, roller bushings, roller flat spots, sometimes the ramp itself. Sometimes one roller or one bushing being sloppy is enough to cause RPM fluctuation. The spring cap bushing on ’07-’08 is VERY common, would recommend replacing with updated cap on EVERY ’07-’08 TRA7.
Belt: new belts will typically run low RPM for first 10-100 miles. Different belt #’s or brands with different dimensions and compounds also cause RPM variation.
DPM solenoid: Common enough that Doo has a bulletin on this. If the solenoid doesn’t function properly the sled will run rich and cause RPM drop….more pronounced at higher elevation. We have found this to be a common cause of RPM drop and a quick cure for “clutch”
problems. Take out the solenoid and make sure it functions, use a little WD-40 if it is sticky and make sure BOTH of the 2 O-rings are intact.Exhaust valve: Make sure they function….check all vacuum lines are connected and snug fit.
Power output: have had several cases where they are just plain down on power. Not all sleds are equal. We had 3 identical (stock) sleds we set up identically (clutching, suspension etc...)…..2 run strong and no problems, 1 runs weak with no apparent problems. This is where compression should be checked as well as crank run-out. A couple customers have had unexplainable low RPM issues and lost cranks the next ride.
Limp-mode: There is a update for ’08-’09 (mostly a issue on ’09) for knock sensor sensitivity and reset. Make sure to get this update!
Aftermarket “performance” parts: this is a big category!! There are some combinations that just don’t work! Some pipes, silencers, heads etc…that are supposed to add power can cause RPM issues. The one we hear about and see the most lately has been too much compression for a given altitude and fuel. I’m no engine guru and can’t give a technical explanation, but in almost every case of low RPM with high compression, simply lowering the comp ratio and /or adding octane has cured the problem and shown much better power….even if there was no detectable detonation to begin with.
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