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This weekend, I am planning to do a Carb rebuild, but not quite a full one. And by that, I mean that, for the most part, a lot of the metal parts will be reused. I'll be replacing the main jet needle, the floats, gaskets, the jet needle fastener, the float pins, the o-rings, and the diaphragms. Any other pieces that are a must-change in these procedures?

I've been experiencing an issue where my right-cylinder spark plug is deteriorating quite rapidly, and I'm 90% certain it is due to the cylinder on that side running rich.

Some of the symptoms:

misfires, backfires, "wet" appearance on the plug, brand new plugs fouling up within 50-100 miles, poor cold performance/startup, poor idle (dies frequently at idle once warmed up).

Hoping it was a relatively simple mechanical thing or electrical thing, I've performed various diagnostic steps (primarily logic-driven, and not necessarily from a service manual or guide or other "standardized" method) that I believed would help me isolate the/an issue.

To troubleshoot the *specific* symptom at the time, misfiring, backfiring, on only the right cylinder, I tried:

1. Swapping the spark plug cables (no change)
2. Swapping the position of the coils, left to right, right to left, ensuring proper configuration of positive-to-negative, etc. (No Change)
3. Testing Compression (the same and balanced on both sides, ~75 psi)
4. Swapped Spark plugs (Noticed the problem side was wet and soiled, while the "good" side was "normal" as far as old and used spark plugs go.) (This caused the opposing side to start sputtering, but didn't *eliminate* the stuttering on the right side).
5. *Replaced* the spark plugs (both). The bike ran really well, for about 25 miles. Then, at around 70MPH, and at about the 25-mile mark, it started sputtering and has been expressing the same right-side-only symptoms that started this whole endeavor in the first place.

My question for those willing to toss some insight my way is this:

Are there any simple tests I can do to try and isolate whether or not the carbs *need* a rebuild? Adjustments I can make? I'm aware that I could try *readjusting* the fuel mixture using the fuel adjustment screw, but I don't really want to mess with that, as I don't have a *great* way to balance the carbs (will ultimately buy something to do so with the Rebuild kit, when I go that route).

Logically, I don't really see another option, but I would love to hear the opinion of anyone here on what I can do to try and further troubleshoot this without pulling the carbs off/apart.

All this aside, worst case, I am prepared (as the title states) to perform an almost complete carb rebuild if that makes the most sense.

Thanks!

Not sure this has been covered, but have you confirmed that the enrichener lever is off when you physically turn it off? If one side is not shutting off, you're running around with the choke on all the time.

As part of your rebuild, are you going to look at the enricheners?

Kurt in S.A.

Kurt in S.A. wrote: ↑Thu Jun 17, 2021 2:45 pm Not sure this has been covered, but have you confirmed that the enrichener lever is off when you physically turn it off? If one side is not shutting off, you're running around with the choke on all the time.

As part of your rebuild, are you going to look at the enricheners?

Kurt in S.A.

That's a fantastic question! And something I never would have thought to check! I will absolutely be checking this tonight when I get home and make sure that the enricher is properly disengaging or not.

So, the "choke"/enricher/starter carb lever might "stick" on one or both sides, causing it to run richer, even if the carb is tuned/setup otherwise correctly?

Can you tell whether the fouling is due to a rich mixture (black, fairly dry carbon build up) or oil (wet and - well - oily)?

Are you getting excess oil blow by from the breather?

I think the '80 models still has a breather that vents into just the right side...

Rob

Not stick so much as it never gets turned off via the cable system. With the choke lever in the off position (parallel to the ground), the levers on the inside of each carb should be up against the stop. It might take some doing to see their position, like with a mirror or something, but I think you can just look down from the top and feel with your fingers.

Kurt in S.A.

Rob Frankham wrote: ↑Thu Jun 17, 2021 2:53 pm Can you tell whether the fouling is due to a rich mixture (black, fairly dry carbon build up) or oil (wet and - well - oily)?

Are you getting excess oil blow by from the breather?

I think the '80 models still has a breather that vents into just the right side...

Rob

the plug has a wet look, but when you touch the end, it's not the texture of oil, and smells like fuel.

Kurt in S.A. wrote: ↑Thu Jun 17, 2021 2:54 pm Not stick so much as it never gets turned off via the cable system. With the choke lever in the off position (parallel to the ground), the levers on the inside of each carb should be up against the stop. It might take some doing to see their position, like with a mirror or something, but I think you can just look down from the top and feel with your fingers.

Kurt in S.A.

So you're referring to the actual mechanism on the body of the carb that controls whether or not the enricher is on or not, yes?

The actual cable control is mounted on my left handlebar, and it feels like it moves into and out of place just fine, but I've yet to trace the cable down to either carb and actually check to see if it is making the mechanism on the body of the carbs perform an action on open or close.

Is this what you're referring to?

Yes, trace the cable down to the carbs and watch what's going on.

Kurt in S.A.

Kurt in S.A. wrote: ↑Thu Jun 17, 2021 3:27 pm Yes, trace the cable down to the carbs and watch what's going on.

Kurt in S.A.

Roger, Dodger. I will do this as *soon* as I get home from work tonight. Literally the first day I'm at the office and can't immediately go outside to check, and it's KILLING me lol.

But thank you! I appreciate the tip!

First things first. Start with the basics. Are you sure your gauge is accurate?
Testing Compression (the same and balanced on both sides, ~75 psi)
Insufficient compression.
Or improperly executed compression test.
You need to have the carb butterfly open and the slide jammed upwards to get an accurate reading.(or remove the carb from the head altogether) Ground the spark plugs to avoid coil damage.
If you're battery isn't providing adequate cranking power, boost it with your car.

If it is actually only 75psi, and the valves have some clearance, you're due for a top end rebuild...