I'm new to this, help!

[Anonymous]

Hi everybody,
Ok, I've just bought an '82 GSX750TZ which is standard as far as I know. It's just done 20k miles and since getting new spark plugs starts without a problem and tickover is smoothish. The old spark plugs were a little black and oily but I've seen worse. So here's the problem; The bike rides fine and the engine pulls well until the rev's get up high (there's no rev counter so I'm guessing it's high). Then it bogs down, starts vibrating and won't rev any higher, and I have to drop the throttle back to were it runs "clean". In top gear this lets me do about 80mph. There is also a little flat spot right at the bottom of the rev range and I have to rev a little hard to pull away smooth. The carbs have'nt been balanced since the previous owner put a 4 into 1 on so I'm hopping it's down to that, but any other suggestions would be very helpful. Thanks!

[earlfor]

I had that same experience on my 79 750 when I removed the stock exhaust system and installed a 4 into 1 aftermarket V&H. My problem was that due to less exhaust restriction the mixture was too lean. Increasing main jet size by two increments solved the problem. My 750 came with stock size 102.5 main jets. Replacing them with 107.5 solved my problem.
BTW Its always a good idea to balance the carbs. You will be surprised in what a big difference it will make in how smooth and well it runs afterwards.
Gas milage increases also. :-)

Earl

[Anonymous]

hey; earlfor is right on about the carbs. The black plugs indicate a rich mixture so you need to check the main jets as they are what carries the load once past about 1/2 to 3/4 throttle also balancing them will definatley help. WHen all done put in new plugs and do a plug test to see the difference.

[Anonymous]

also if you have a flat spot off the bottom the pilot jet and needle need to be looked at also they might be gummy or restricted or need to be resized.