spark issues

[L on 20s]

Hey guys new to the site. I got a 89 750 kat with 16xxx miles on it the only problem is it was sitting in milk crates for about 12 years. Im pretty mechanically inclined my dad use to own a shop my problem is i got this bike all together and I noticed it has a very faint spark its hard to see the plugs are good i tested them in my dirt bike I checked the ohms for the primary and secondary resistance on the coils and they checked good i have treid different plug wires and no change now i admit i dont know alot about motorcycles so im not sure what the problem is. The bike starts fine and runs but spudders at about 6k rpm. Is it the signal generator or the cdi box that needs to be replaced. I know it isnt a carb issue because i rebuilt them adjusted the butterflys with mercury gauges so i know they are synched properly please help I have alot of time and money into this bike and I just want to ride it while the weather is still nice any help is very much appreciated thanks

[Kreylyn]

Hey guys new to the site. I got a 89 750 kat with 16xxx miles on it the only problem is it was sitting in milk crates for about 12 years. Im pretty mechanically inclined my dad use to own a shop my problem is i got this bike all together and I noticed it has a very faint spark its hard to see the plugs are good i tested them in my dirt bike I checked the ohms for the primary and secondary resistance on the coils and they checked good i have treid different plug wires and no change now i admit i dont know alot about motorcycles so im not sure what the problem is. The bike starts fine and runs but spudders at about 6k rpm. Is it the signal generator or the cdi box that needs to be replaced. I know it isnt a carb issue because i rebuilt them adjusted the butterflys with mercury gauges so i know they are synched properly please help I have alot of time and money into this bike and I just want to ride it while the weather is still nice any help is very much appreciated thanks

Sounds normal to me (Kats are not known for real strong spark)... I'm not so sure it is a spark issue.

Is it just a range of rpms that it studders, or is it anything over 6k rmp?

Krey

[ATOMonkey]

Could it be a petcock problem?

[L on 20s]

it wont go over 6k with load in neutral it will rev to about 11k. Im not sure it would be a petcock problem I did have it set to prime instead of on but the overflows on the carbs where not leaking gas i assumed if it wasn't overflowing it shouldn't of been running too rich. That is why i thought the spark was blowing out under too much rpm. ill try it with the petcock in the on position this time.

[kevin2502000]

You have the airbox and filter on right?

[Kreylyn]

Is there a jet kit in this bike?... (do the needles have more than one slot for the clip on the top of them?)

Krey

[L on 20s]

When i synced the carbs the air box and filter was on and the jets are still stock. But I still kind of think it is a weak spark they are barely visible should i just replace the coils and the signal generator i have took the carbs apart twice now to double check and they are not plugged or dirty. I cant even hear the spark make a cracking sound and normaly on all the other vehicles iv worked on I could actually hear the spark make a sound. I have checked the 4 wires going to the coils and they look good. does the signal generator amplify the spark or just act as a distributor.

[md86]

Signal generator just tells the coils when to fire . Doubt that's the trouble point . My signal generator went , and my bike was running just fine .... up until it didn't wanna start anymore , at which point there was NO spark , not just a weak one . Moving on ....
CDI ..... possible . SOME shops can test them . accepted method is to plug in a known good and see what happens . Not always an option .
If the coiuls test fine with the multimeter , they're fine . I've tested some that were semi-close to the edge by the book , but seemed to work just fine .
Someone else take over , meds are finally starting to kick in and getting cross-eye .

[ATOMonkey]

it wont go over 6k with load in neutral it will rev to about 11k. Im not sure it would be a petcock problem I did have it set to prime instead of on but the overflows on the carbs where not leaking gas i assumed if it wasn't overflowing it shouldn't of been running too rich. That is why i thought the spark was blowing out under too much rpm. ill try it with the petcock in the on position this time.

If you think the spark is blowing out (which is most likely isn't) gap the plugs closer.

If you think the CDI is losing it's brains at higher RPM, then go ahead and replace that, but I doubt it's the problem either.

From your description, it doesn't sound like it's running rich, it sounds very very lean. Even a rich running bike will still pull all the way up, it'll just foul plugs and puke out black smoke. If you're running so rich that your actually drowning the cylinder, I doubt it would even start.

Do you have a fuel filter on the bike?

[L on 20s]

I have 2 in line fuel filters after the petcock and im waiting on new coils just bought them today. If that doesnt work it sounds like get a new cdi box i live in a small town and we only have 1 motorcycle shop and they have no way to test the cdi or plug in a spare known good one so it sounds like if the new coils dont improve anything then its a new cdi .. once again thanks guys for all your help i really appreciate it ill keep you posted if those coils work or not