09-11-18, 06:29 PM
Hi everyone. I am a new member. I have a cylinder misfire at low revs. Exhaust is stone cold on 3 on tick over. After cleaning the carbs seemed to be the same on starting. I reved up a bit and then went for a run, seemed ok till stopped at lights and when pulling away down to 3 cylinders again.
[size=78%]Spark is good, new plugs, swapped 1 and 2 and 3 and 4 HT leads and swapped the LT connections to the coils, still same so I don't think it is electrical problem. Compression is down 17% on 3 but still 12 Barg. 1,2&4 are 14.5 Barg. I can't remember if I did compression test after warming up by idling so may do a retest after a run. I thought that 12 Barg should still get ignition. All 4 exhausts are hot after a blast on the road. I have had the carbs off twice and cleaned them out with carb cleaner and air. Floats and needle valves al look good but I need to check the fuel levels. I thought it might be the choke plunger so swapped 1 and 3, but no. I also swapped 2 and 3 diaphragms and 3 and 4 pilot jets and pilot screws. I haven't replaced any of the bits.[/size]
I thought that the compression being down might be due to that piston / cylinder being cooler. Put some oil in 3 and rechecked compression but I think I out too much in as it went way up to 18 Barg and oil came out the pressure release valve on the tester. Not checked the valve clearances yet.
No 3 plug does appear to be fouled up a but.
Anyone got any ideas about what this could be?
[size=78%]Spark is good, new plugs, swapped 1 and 2 and 3 and 4 HT leads and swapped the LT connections to the coils, still same so I don't think it is electrical problem. Compression is down 17% on 3 but still 12 Barg. 1,2&4 are 14.5 Barg. I can't remember if I did compression test after warming up by idling so may do a retest after a run. I thought that 12 Barg should still get ignition. All 4 exhausts are hot after a blast on the road. I have had the carbs off twice and cleaned them out with carb cleaner and air. Floats and needle valves al look good but I need to check the fuel levels. I thought it might be the choke plunger so swapped 1 and 3, but no. I also swapped 2 and 3 diaphragms and 3 and 4 pilot jets and pilot screws. I haven't replaced any of the bits.[/size]
I thought that the compression being down might be due to that piston / cylinder being cooler. Put some oil in 3 and rechecked compression but I think I out too much in as it went way up to 18 Barg and oil came out the pressure release valve on the tester. Not checked the valve clearances yet.
No 3 plug does appear to be fouled up a but.
Anyone got any ideas about what this could be?