PLUG FOULING

motobroker · Post by **motobroker** » Mon Aug 01, 2011 10:18 pm

I just rebuilt the engine on a CL72 w cl77 top end that had been sitting over 30 years.
I am fuel fouling plugs in both cylinders at about 5 to 10 miles. I have the needle on the next to leanest position, new float needles and seats and D8HA plugs
Stock pipes with hollow stock muffler.

Float level is good and possibly even a bit on the low side.
Idle mixture is about 1/2 turn past the max rpm position.
I suspect worn needle jets, but wondering what else might be the culprit.

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Aug 02, 2011 6:34 am

How did ya set the timing?. ............lm

motobroker wrote:I just rebuilt the engine on a CL72 w cl77 top end that had been sitting over 30 years.
I am fuel fouling plugs in both cylinders at about 5 to 10 miles. I have the needle on the next to leanest position, new float needles and seats and D8HA plugs
Stock pipes with hollow stock muffler.

Float level is good and possibly even a bit on the low side.
Idle mixture is about 1/2 turn past the max rpm position.
I suspect worn needle jets, but wondering what else might be the culprit.

motobroker · Post by **motobroker** » Tue Aug 02, 2011 11:45 am

I static timed to the F mark and used a strobe to make sure it hit full advance marks. I checked both cylinders.
The bike runs fine and holds idle until the plugs start fouling after a few miles.
I do have a very slight problem with the RPMs not dropping back as fast as they should. I did install new advance springs.
I'll recheck the timing later today.
Should I stay with the factory marks?

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Aug 02, 2011 12:16 pm

Did ya set the carbs as described in the FAQ section?. .........lm

motobroker wrote:I static timed to the F mark and used a strobe to make sure it hit full advance marks. I checked both cylinders.
The bike runs fine and holds idle until the plugs start fouling after a few miles.
I do have a very slight problem with the RPMs not dropping back as fast as they should. I did install new advance springs.
I'll recheck the timing later today.
Should I stay with the factory marks?

e3steve · Post by **e3steve** » Tue Aug 02, 2011 5:14 pm

'Ere we go (again) round the mulberry bush.....

When you put the slides back in the carbs, you may have got them arse-about-face. Make sure that the slides' cutaways face the filters -- not the cyl head. If the cutaways face the head, then take 'em out, turn 'em round and put the slides back in the opposite carbs.

motobroker · Post by **motobroker** » Tue Aug 02, 2011 7:46 pm

Slides are in correctly.
I could not find the FAQs on carb adjustment, but I am an experienced bike mechanic and adjusted them in a generic manner, same way I would adjust a pair of VM Mikunis or Amals.

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Aug 02, 2011 8:29 pm

Ya may want to go to the FAQ in the yellow band to the left and find <How do I tune my factory stock motor on my CB72/77 or CL72/77 for optimum performance?> as ya are having problems and it just may help. ..............lm

motobroker wrote:I static timed to the F mark and used a strobe to make sure it hit full advance marks. I checked both cylinders.
The bike runs fine and holds idle until the plugs start fouling after a few miles.
I do have a very slight problem with the RPMs not dropping back as fast as they should. I did install new advance springs.
I'll recheck the timing later today.
Should I stay with the factory marks?

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