Join Date: May 2009
Location: Tampa Bay, FL
Motorcycle: 1986 GSXR 750
Re: 87 GSXR 750 fitting a B12 engine.
These engines have whats called a "wasted spark" system-
1 & 4 fire together and then 2 & 3 fire as a pair-
When 1 needs spark, 4 doesn't, but then when it's time for 4's spark, 1 doesn't need it(but it fires anyways)Same with 2 & 3-
So there's no way on your bike that 2 & 3 are out of time or anything, they both fire simultaneously-(ever tho only ONE cyl is on the "power stroke")
Have you verified you are getting spark on 2&3 coil?
(sorry if you said it already, but your post is LONG! LOL)
Check and verify you have the same voltage to both coils positive (orange) wires- I have seen one getting 11 when cranking and the other getting 8v due to bad/dirty plugs
Check ohms with a multi-meter (coils still in frame, with everything disconnected) across the coils 2 spade terminals- should be 3 to 5 ohms (and compare to other coil) also read ohms by sticking the test leads one in ea spark plug cap in pairs- should be 25,000 to 45,000 ohms[no less, no more] (1-4, then 2,3) They should be fairly close to each other-
When I first put my 86 together I was having all kinds of spark issues-
I had one coil ohm out at 19k across the plug leads and the other at 48k
(one too high, one too low)
I got a pair of coils off a 400 Bandit, (which ohm'd out the exact same, 30k)
and my bike has run GREAT ever since-
HOPE THAT HELPS BRO!
Cant wait to hear it run! GOOD LUCK!
Thats how I roll-
Last edited by GSXR Tony; 07-04-2010 at 08:04 AM.