Some background. The GR650 Tempter is a parallel twin sold in America for one year, 1983, but sold in Europe for about 10 years. I bought this late last fall as a project and to have to run back and forth to work with. It is completely stock and in great shape...no major rust and everything is all there, but it had straight pipes for exhausts. The PO said it had a "small ticking" sound from the top of the engine. Based on how good this bike looked, it's never been laid down, and guessing the small ticking was caused by needing a valve adjustment...I took the chance. $400.
I have since done the following: 1) adjusted and set the valves which were way off and lead me to believe this was the ticking sound, and installed a new valve cover gasket 2) changed the oil, filter and oil pan gasket. Oil was absolutely clear with nothing in the pan. 3) rebuilt the front forks 4) completely cleaned and rebuilt the carbs. 4) installed a new air filter 5) put on a stock exhaust with new exhaust gaskets
The bike fired right up the first try..great! Everything sounded just fine. No ticking sound...it all seemed good. HOWEVER...took it down the street and at about 3,000 rpms the bike just quit going up in speed and rpms. It felt like it just hit a plateau and wouldn't go any higher in speed or rpms. At this point, a knocking sound started from the left side of the engine. Turned it off. Checked the compression on both cylinders and they read almost exactly the same...130 and 132. So I don't believe it's bad pistons.
Now, this bike comes with a Suzuki "exclusive" feature, according to the manual. It reads like this..."This bike comes with a variable mass device. At low rpm, the centrifugal clutch engages the auxiliary mass so it rotates with the crank. Above approx. 3,000 rpms the extra mass is unnecessary and undesirable so the centrifugal clutch disengages the auxiliary mass."
In plain English, there is an approx. 8 lbs of weight that's attached to the crank for extra power and at 3,000 rpms it releases for better acceleration. It looks something like drum brakes with springs,...
Hopefully I have explained this correctly but if anyone can get to a manual, it's explained on page 1-9. Since my problem happens right about 3,000rpms, right when this auxiliary clutch should disengage, I'm guessing that a spring on this auxiliary mass clutch weight has broken or something invloving this system needs attention.
I'm just looking for any opinions, help, or experience with this "auxiliary clutch" system that might back up my best guess before I go looking. Thanks..
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