Running rich on #3

[Anonymous]

I have a problem with number 3 cylinder running rich and the reason as to why remains elusive. Bike has now done 77,500km.

Plugs #1 and #4 - perfect
Plug 2 - slightly darker than 1 & 4 but close enough to perfect
Plug 3 - black: up until yesterday carbon fouled. This morning I checked the plugs (done a little 400km trip yesterday) while black it was improved on previous checks. However, it did appear wet to the eye but not to touch.

Things I have done/checked:
#3 Diaphragm (and needle jet) moved to #4 - no effect
#3 Jet Needle moved to #4 - no effect
#3 Needle jet moved to #1 - no effect (I started a thread on my BS32 SS needle jets a week or two ago)
#3 Float moved to #1 - no effect
#3 needle valve moved to #1 - no effect
#2 and #3 sparkplug leads swapped - no effect
New plugs - no effect
Plugs swapped - no effect
Needle Valve o rings replaced - no effect
Carbs resynchronised last Friday - performance improved marginally but no effect on #3
All float heights checked (23mm)
Mileage 265km till reserve (17 litres) on the open road - about what I have always got.

One thing I have noticed is that the exhaust note for #3 and #4 is a little louder - not sure on that one. One thing I have got is a leaking base gasket. If this was blown then I would have a lean problem rather than a rich one?

What can I check next?

Many thanks
Anthony

[earlfor]

Re: Running rich on #3

Check the compression on all four cylinders. It sure sounds like you dont have good compression on #3.

Earl

I have a problem with number 3 cylinder running rich and the reason as to why remains elusive. Bike has now done 77,500km.

What can I check next?

Many thanks
Anthony

[KEITH KRAUSE]

Hi and welcome back. Going back to your original post, you thought it was the needle jet. At least you know it's not that now. Earls compression question makes sense. Did you make sure any washers or spacers were correctly re-installed on the jet needles? Some needles have 2 spacers, one on top the E-clip and one under it. These spacers can be different in thickness and must be re-installed in correct order. Which carb supplies the vacuum to the petcock?

[Anonymous]

Cheers Keith.

Didn't disassemble the jet needles and they only have the one position.

As for the petcock vacuum is from #2, in fact I replaced that very beast about six weeks ago.

Compression test is a very logical next step since ignition and fuel (I think) can be pretty much ruled out.