QuestionHi Mark,
I just recently purchased a 1990 Kat 600, not running, in VERY used condition, 19K on odo. Previous owner said engine was no good. I pulled carbs off and spent time thoroughly cleaning the carbs. Viola! Engine is fine.
I seem to have two problems, may be related. Every so often, when engine is warm, the idle will be at 3000 RPM. I can drag the clutch and get it down, but if I blip the throttle, it's right back at 3000. And it's intermittent. I haven't synched the carbs (other than wire-gauge on assembly).
The other problem is it flattens out past 1/2 throttle. It doesn't seem to want to get passed 6500 RPM. It runs great below 1/2 throttle and at lower RPM. I have verified correct float level, installed new float/needle/seat sets, checked tank venting, replaced the fuel lines and verified no kinks or restrictions, checked the needle diaphragms for tears and for correct operation, and installed new spark plugs. Due to suspect nature of parts in carbs, I purchased a Dynojet jet kit for this bike and installed the stage 1 jets and needles as I am running the stock airbox and exhaust. No change.
At one point, I found a straight stretch and pinned the throttle wide open through second and third just to see what it would do. It slowly crept past 7000 RPM with a few bucks and surges like it was trying to pull hard and I heard what sounded like detonation a couple of times. Rode it back to the house and noted everything seemed fine and the high idle was back at 3000. Pulled the plugs and saw that they were showing slightly rich; moderate brown.
What are the chances the ignition timing could be doing wierd things? I did a visual inspection of all wiring and components, the signal generator and wiring all look good. I couldn't find any specs on resistance. The coils ohm-test good (cold, don't know about warm). Lightly tapping on CDI box makes no change in engine running on stand. I would think that if the carbs were slightly out of synch, that WOT wouldn't be affected.
Engine temp does not seem to influence the lack of WOT power. I don't go out and flog the bike when it's stone cold, but little heat or lot of heat in oil cooler is no different.
The bike WAS a california emissions model. I HATE shotgunning parts at a problem, but there is no way to test a CDI box that I've found. Same for signal generator. I haven't replaced either at this point.
Thank you for your time, Mark.
Adam
AnswerHi Adam,
Excellent narrative description. Thanks!
Send me your email address as requested and explained in my instructions. I'll return several tech files to assist you.
The ignition is fine. Test CDI with known good unit (a luxury of Suzuki dealerships). Test signal unit for resistance and continuity as per the service manual.
Jet kits usually requires additional tuning to correct the air-fuel mixtures. It's very rare that drop-in jet kits works without some tuning.
Synchronization works at all throttle opening positions. We check and adjust synchronization levels at cruising speeds throttle opening positions (idle & about 2.5k rpm).
Measure cylinder compression and check valve clearances. Both needs to be within service limits for the carbs to function properly.
Do you have the service manual?
Reply and we'll go from there.
Respectfully,
Mark Shively
