1990 sling, sucking on exhaust stoke

[SMARTY]

Bike not running on all 4, 3 and 4 half warm. If i put my hand on the pipe 3,4 it has a sucktion stroke in there. Timing?

 

[Upshotknothole]

If the cams are 180 out, you'll get suction on the exhaust and it won't run at all. Any history on it?

[SMARTY]

3 hours ago, Upshotknothole said:

If the cams are 180 out, you'll get suction on the exhaust and it won't run at all. Any history on it?

Thabks mate. Its a project, evil bay parts. three year build. History i think was a motor come from crashed bike. but stood for 15 years. Engin idel fine and start easy, 1 and 2 is hot like normal operatiomal temp, but 3.4 issue. Im not shure about the coil wiring, but following the manual. White wire to 4 black wire to 3. It has a 750 cdi, but i was told they run on those aswell. Carbs rebuild. New coils, plugs. Think i need to step back and check valves again and timing. 

Cheers

 

[wraith]

Just try plugs in the cylinders that are not firing right. Had this with new NGK plugs many times, I now won't use NGK plugs.

[Upshotknothole]

Not timing if it's idling. If it's only 3 and 4, then either plugs or carbs. Coils should be wired up to 1 & 4, and 2 & 3.

[SMARTY]

Thanks

[Wagola]

Plug leads for 3 & 4 swapped over ?

[SMARTY]

Ile test, more , but swaped the coils and leads with new ones.

[TonyGee]

18 hours ago, SMARTY said:

Bike not running on all 4, 3 and 4 half warm. If i put my hand on the pipe 3,4 it has a sucktion stroke in there. Timing?

 

I fail to see how putting your hand on the exhaust you know its sucking ?????  if 1 and 2 are running then the timing is fine, check for a good spark if so then look to the carbs. 

[SMARTY]

1 hour ago, TonyGee said:

I fail to see how putting your hand on the exhaust you know its sucking ?????  if 1 and 2 are running then the timing is fine, check for a good spark if so then look to the carbs. 

I can feel it sucking in a stroke were the other just two into one headder blows. I just put my hand on the pipes to quiet it down to listen for noises when i noticed it. Iy wil actualy suck your hand to the pipe. L

[TonyGee]

time to pull the cam cover off and check clearances, and maybe do a compression test before you go any further just to rule them out.  

[SMARTY]

45 minutes ago, TonyGee said:

time to pull the cam cover off and check clearances, and maybe do a compression test before you go any further just to rule them out.  

Thanks i will do.