Sooty Plugs

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 08, 2019 5:43 pm

I checked the plugs today after I fixed my rubbing header problem and found (as I thought I would) that it's running really rich; the plugs were really dry and sooty(which is better than Wet and sooty!).

The manual (my rather vague Japanese Original Copy manual) has the tuning process for the carbs, and I'm sure I'll peruse that again, but is there a good way to adjust the carbs without having to stop, check and replace the plugs over and over again...?

Right now the carb is set to 1 1/4 - 1 1/2 turns out, or thereabouts - I did try to tune the carbs/engine by hand, and it runs really well, but it's running rich, so obviously that needs some attention...

Would this be an Air screw or fuel screw problem, do you think...?

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Apr 09, 2019 5:31 am

Could be a jet size problem.
What are the jet sizes?. .......................lm

Dr. Frankenstein wrote:I checked the plugs today after I fixed my rubbing header problem and found (as I thought I would) that it's running really rich; the plugs were really dry and sooty(which is better than Wet and sooty!).

The manual (my rather vague Japanese Original Copy manual) has the tuning process for the carbs, and I'm sure I'll peruse that again, but is there a good way to adjust the carbs without having to stop, check and replace the plugs over and over again...?

Right now the carb is set to 1 1/4 - 1 1/2 turns out, or thereabouts - I did try to tune the carbs/engine by hand, and it runs really well, but it's running rich, so obviously that needs some attention...

Would this be an Air screw or fuel screw problem, do you think...?

Dr. Frankenstein · Post by **Dr. Frankenstein** » Tue Apr 09, 2019 5:36 am

It's been a while since I've been in there, but I'm pretty sure they're stock; I used a new kit to rebuild it, when I did, and made sure they matched what the manual called for.

The bike doesn't smoke, pulls like a champ and has great throttle response, so I think it could just be a mixture problem.

I have your chain coming back to you too, LM.

DJM · Post by **DJM** » Tue Apr 09, 2019 4:50 pm

It could also be a problem with float level.

Correct fuel level in the float bowls affects the mixture right across the throttle range so if the fuel level is wrong it's unlikely you'll ever get it to run really well.

Also the floats could have a pinhole in them, if this is the case you will hear fuel inside when you shake the floats.

Geoff Hastings · Post by **Geoff Hastings** » Tue Apr 09, 2019 5:17 pm

As DJM says, check the float level, mine was way out. The screw adjuster only affects the idle mixture, also the plug colour is a difficult one. Once you pull up and let the engine idle what you are checking is the idle mixture, you need to run it at half throttle for a while then shut the engine off, this will show needle position is right or not. Full throttle for a while, shut off and stop engine as quick as possible will show main jet suitability. Basically you need to run it at various throttle positions for long enough for the plug colour to change. If you have standard jetting and needle position then it only leaves float height or blocked air filter.

rrietman · Post by **rrietman** » Tue Apr 09, 2019 10:35 pm

if you are just running at idle in the shop (not riding) you are going to load up, plug checks are meaningless. get it on the road at better than 1/2 throttle. get it it off the idle circuit.that,s all the idle air screw controls. get going on the road and then check plugs and adjust needle clip position.
Good luck
Randy

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