Rough Running

Q. I just bought a 92 zx7r about a month ago. it had been sitting for like 3 years without being ridden(tags were 1997). it ran pretty crappy on the short ride home, and I could smell the old fuel as it burned off. cleaned carbs out and adjusted the valves. all good. anyhow in the process I damaged the cdi box (don’t ask! in the top ten dumbest things i have done yet in life!!). I ordered a dyna 2000 for mine, timed it and all, fired right up and purred like a kitten. took it to the gas station to fill the tank with super(previously drained and cleaned of course). it pulls hard to about 6500 rpm then kinda surges, no change in sound, just real slow pulling rest of rpms to redline. have timing set at 35 btdc. tech info says 35-40 btdc should be good. also says the setting I have it on goes to full timing at 6500 rpms, so thinking I have too much timing? anyone that knows what this sounds like or can help please post, otherwise ill post after I find out what it is.
ok posting this update so others can have the info. I tried timing, that wasn’t it. drove it some more and it got better at night on my way home from work. so I thought jetting. bingo! Plugs had heavy carbon buildup. the fuel mixture screws were set at two turns each, turned each in 1/2 turn. rode it home tonight and its really close now, just a little more fine tuning and plug checking. ill post again when I have new info.

A. The setting on the Dyna 2000 that gives full timing at 6500 RPM would be switch position 3, which is best for Very High Compression motors. I would suggest pos. 2 or even 1 with a stock motor. A stock motor is not Very High Compression. This gives full advance at 2500RPM in pos. 1, best for stock motor. Is this really a 92R with flatslides? If so then 2 turns out on the screws is not to much, in fact not enough if running the stock pilot jet of 42. But you never know, someone could have changed it to a larger jet size. I would check that. Also I would find someone with a Leak Down Tester to see what condition the motor really is in. Compression testers don’t really mean near as much. Anything greater than 7-8 percent is nooooooo good. A leak down test is the FIRST thing I do on any bike.

Leak Down is the best check of a engines health. If your leaking greater than 7-8, you have no motor.

I have people bring me bikes all the time for jetting and cam timing and etc., if the leakdown exceeds 7-8 percent I won’t bother with it. Any bike sitting for years, and used and in an unknown condition usually leaks bad.

Ken

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