Cylinders 2 and 3 fouling

[Anonymous]

I am having issues with #2 cylinder fouling and #3 not too far behind.

A few weeks ago the battey died, so after a few quick checks of the electrical system I replaced the battery. Then the problems started - missing and spluttering. The spark plugs revealed #2 and 3 carbon fouling. I suspected the ignition system as the spark on all 4 cyclinders has never been that great so I started by checking the spark plug caps - not very good replaced with new and replaced the plugs. Better but not quite right. Checked the igniter - test failed. Replaced with Dyna III, spark a little better missing reduced but still fouling 2 & 3. Replaced the coils, leads, and plugs again. So now I have a completely new ignition system. Went for a ride on the open road - yes seems to be fixed, running perfect better than its ever gone except when I came back in to town. Checked the plugs, #2 was starting foul with #3 not far behind, #1 & #4 were looking slightly lean but not bad. Must be a fuel problem then.

Float heights and four carbs were the same and to specification, synchronisation is just fine. Petcock not fully checked at present (will be checking that on the way to work this morning) but appears to be working - no fuel in vacuum line. So I suppose the only thing left is jetting, but I have my doubts since they were all checked some 12 months ago.

One more thing if the revs are kept above 3500 then the old girl seems to run just fine - but the plugs tell a different story. I'm out of ideas, what else can I check?

Many thanks

Sorry if this seems like a novel.

[earlfor]

Re: Cylinders 2 and 3 fouling

The first thing I would do would be to put a dynamic timing light on the bike and check the marks on 1-4, then check the marks on 2-3 to see if both pairs are firing at the same advance.

I assume you have synchronized the carbs with a mercury carb stix or equivalent. I would re synch the carbs and reduce the vacuum slightly on the 2-3 cylinders and increase it a tad on the 1-4 cylinders.

Earl

I am having issues with #2 cylinder fouling and #3 not too far behind.

A few weeks ago the battey died, so after a few quick checks of the electrical system I replaced the battery. Then the problems started - missing and spluttering. The spark plugs revealed #2 and 3 carbon fouling. I suspected the ignition system as the spark on all 4 cyclinders has never been that great so I started by checking the spark plug caps - not very good replaced with new and replaced the plugs. Better but not quite right. Checked the igniter - test failed. Replaced with Dyna III, spark a little better missing reduced but still fouling 2 & 3. Replaced the coils, leads, and plugs again. So now I have a completely new ignition system. Went for a ride on the open road - yes seems to be fixed, running perfect better than its ever gone except when I came back in to town. Checked the plugs, #2 was starting foul with #3 not far behind, #1 & #4 were looking slightly lean but not bad. Must be a fuel problem then.

Float heights and four carbs were the same and to specification, synchronisation is just fine. Petcock not fully checked at present (will be checking that on the way to work this morning) but appears to be working - no fuel in vacuum line. So I suppose the only thing left is jetting, but I have my doubts since they were all checked some 12 months ago.

One more thing if the revs are kept above 3500 then the old girl seems to run just fine - but the plugs tell a different story. I'm out of ideas, what else can I check?

Many thanks

Sorry if this seems like a novel.

[Anonymous]

Cheers Earl, but I have finally identified the root cause: petcock diaphram. Disconnect vacuum line, run the old girl and plugs are now looking perfect and had a small quantity of petrol coming from the petcock.

Anthony

[earlfor]

glad to hear you got'er fixed. It seems its always the little things that will get you. :-)

Earl

Cheers Earl, but I have finally identified the root cause: petcock diaphram. Disconnect vacuum line, run the old girl and plugs are now looking perfect and had a small quantity of petrol coming from the petcock.

Anthony