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Q: My 1999 Yamaha 700 SRX has high speed vibration in the handlebars and on my feet. The vibration is only felt at low to midrange and seems to smooth out after 5,000 rpm. I don't feel it at all at 7,000 to 8,300 rpm. I thought at first it might have been the drive clutch getting worn so I put a new one on but this made no difference. The engine runs very strong and doesn't seem to lack power. Can someone help me?
- miikkeeA: I would first check the motor mounts to make sure they're good, and then check the crankshaft. Crankshaft problems often seem to have no rhyme or reason. Sometimes, they just occur due to being a high fatigue part that takes the brunt of all stresses that the motor and drivetrain can dish out. To check the run-out on the crank you will need a dial indicator and a fixture to mount it in to hold it steady to the motor. Next, remove the clutch and flywheel, mount your fixture to the motor and set your dial indicator on the PTO or mag ends of the crankshaft. Next, set the dial to 0 and rotate one full turn in either direction and record the deflection difference. This should be no more than 0.003 in. on a 3-cylinder motor. To check the index, pull all plugs out and bring the No. 1 piston to TDC. The other two pistons should be at the same height in the other bores. This can be done with a caliper. Also, make sure your primary clutch is clean and your flyweights are balanced before you do any of this.
- Dyna-Tek Racing