Topic: starting/running problems

[snjlangton]

Hi guys hope you can help.When i start my 750 it fires on 1/2 cylinders and wont fire on 3/4 the bike has been running fine up till now. I have changed the coils, reset timing and replaced plugs there is clean fuel, spark at plug caps been tested, new manifold rubbers and clips have been replaced Regards neil

[goldarrow]

You didn't mention about the points, have you addressed that yet?

[Tews19]

How do you know 1-2 fire 3-4 dont?
 Each coil should operate 2 cylinders.... 1 and 4, 2 and 3..... See if you have it hooked up wrong..

[snjlangton]

Thanks for your reply regarding checking the pionts, i have changed them for a electronic ignition and this worked fine before this problem. I did think maybe the values, i will check that out. The coils are new and each coil fires two cylinders 1/4 and 2/3 thats what iam not getting my head around why is it not firing on 4 on one coil and not firing on 3 on the other coil is the problem on the electronic ignition maybe i should put the old points back.

[Tews19]

Check the jets. Also pull the caps from the spark plugs and use a spare one. See if you can see spark.

[seanbarney41]

What year 750?...earlier bikes have a dual feed petcock.  One feeds carb 1 and 2, the other 3 and 4.  If one side is clogged, it could cause the dead cylinders you have mentioned.  I would first check fuel supply in general though. Have you pulled a plug to see if they are getting gas?  Open a float bowl drain to see if there is fuel in the bowl?   Check your tank vent is clear, petcock is clean, not plugged, operating correctly.  Fuel hoses routed correctly.  If none of this, you will have to drop a float bowl...check float operation, and remove and clean idle jets.