1972 1150, cylinders 3 & 4 not firing

[bunker108]

Been chasing ghosts all season after no problems last year. It started bogging down fully loaded so I pulled the three carbs for a good cleaning and some new gaskets. The carbs looked good but the middle carb now leaks when I prime the bulb. Could a high float level cause those cylinders not to fire? Can an adjustment be made to the middle carb?

I have compression and spark on those cylinders.

How do I verify that spark is hot enough on those holes?

The engine starts easily and idles nice. When I pull the wires on 3 and 4 it doesn't affect the idle.

Please don't tell me I will need to pull the carbs back off...

Thanks for any help!

 

[bunker108]

Re: 1972 1150, cylinders 3 & 4 not firing

I don't see any signs of water intrusion on those cylinders or any others. The plugs dont look bad either. All evidence is leading me to that middle carb.

 

[Chris1956]

Re: 1972 1150, cylinders 3 & 4 not firing

I agree, the middle carb should not leak. Replace the float and inlet needle and seat. These parts do not last forever. The #3 and #4 spark plugs are dirty right? Not steamed cleaned? Check the plug wires for arcing to ground.

 

[bunker108]

Re: 1972 1150, cylinders 3 & 4 not firing

Ok it looks to me that 3 and 4 are steam cleaned...6 is a little cleaner than the others too...

What do you all think? One is on the left, 6 on the right

 

[Chris1956]

Re: 1972 1150, cylinders 3 & 4 not firing

Steam cleaning means water intrusion. On cylinders 3 and 4, it means a leak or hold in the exhaust baffle or inner exhaust cover leak or hole.

 

[Chris1956]

Re: 1972 1150, cylinders 3 & 4 not firing

if plugs #5 and 6 are steam cleaned, water could be getting past lower crank seal. If plug 5 is dirty, it could be leaks from both areas.

 

[bunker108]

Re: 1972 1150, cylinders 3 & 4 not firing

yeah it looks like this one will need to come apart. In the meantime I am on the hunt for a substitute engine. Have a cabin rented near a lake for 4th of July!