GSXR 750 (1986) Mechanical Problem - Any Suggestions please
 

We have a GSXR 750 which has a miss - we have had it to the dealership but they cannot find the problem - they have checked plugs - leads - carbs etc It misses at low revs - slightly improved when cold - if over 7000 revs the miss is very slight but under 7000 revs its bad - any suggestions on the cause of this problem would be greatly appreciated because the "experts" cant find it. Thanks

I recommend taking it to a different shop, or start doing some deductive work yourself. IMO it has to be in the fuel delivery or electrical. If it's missing at all times, there is a problem. I would start with the cheaper of the 2, the fuel system. Change fuel hose, drain the tank, take out the petcock, check it, check the filter, take off the carbs, remove the bowls, check the jets to be sure one isn't clogged with something. Maybe even rebuild them. That's the cheaper route. The electrical will be a tad more pricey. Are you running stock coils? Change the plug wires (you can make your own pretty easily), change the plugs, check the ignition advancer to see if it's stock, check all the wiring for any splices that may be grounding. There is a ton of things this can be, so start doing your detective work, and good luck. I got a buddy I can ask, I'll check with him and get back.

thanks for that - carbs have been rebuilt - filter changed - new plugs leads checked they are ok - is it possible that valve springs could be causing the problem ? thanks for taking the time to reply and yes we will have to change shops

or maybe a cam lobe is worn, which would not be noticeable at high rpm, as its covered up by the rest of it running.
Did anyone do a compression test???

Like Phat-Boy said..a good shop with the new electronic dianostic machines they have..hooked up to it should tell you something fairly quick...since you've done about all you can do at home..let us know what you find..might be helpful to another... :cool:

Well, since all is done, the GSXR is really easy to tear apart. I would recommend the compression test. Compression tools are relatively inexpensive, and easy to use. From there, pull the valve cover off and check the cams and the springs. Perhaps you have a bad set of rings in a hole.

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If it were a cam lobe the miss would be there all the time, at all ranges of RPM's.
I would change the plugs first, a cracked plug could cause the miss. Also I would drop the Carb bowl and check the gas in the bowl for dirt, or particles (coulda got a tank of bad gas), then as Phat-Boy suggests pull the jet's (main & slow) look through them for pluggage. Also agree with Phat-Boy (we both like dancing girls & Shiner Boch too !!) my first thoughts are fuel, or electrical.....do the obvious thing first, the things you can do yourself...if that don't fix her, it's time to get someone else involved.
Also, I'm not too impressed with your dealers Tech's.....the difference between a good Tech & a bad one is the ability to troubleshoot, and solve the problem...... Good luck, & let us know what you find.

FBR:cool:

compression test was done and that was fine - carb was pulled apart and cleaned etc at the shop - the only thing that they didnt do there was check the coils as there equipment was out of order - so i think we will follow that lead - plugs etc have been replaced - coils have not - really appreciate your input guys - thanks :-))

Ahhhh, the memories. Don't know when I'll be back in Texas country my man, I'm quitting my job effective tomorrow. You might have to come my way next time. Which you are always welcome!!!

As far as the GSXR, good luck on the miss. Coils might be the problem, if not you got me stumped! I got a shop here in IA that would fix it for ya in no time, but that's probably not an option given your location!! :D

Good luck!