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Hi all !

My break-in is finally finished, the bike is running strong but one problem still remains. It eats through plugs like crazy.

Currently, a plug has an expectancy of life of about an hour. I use the plug recommended by Kawi (B9ES), fuel is at 20:1 (recommended by kawi). My carb is stock jetting and a Mikuni VM34SS. When I take out the worn plug, it's mainly black of carbon and not chocolate brown like it is supposed to. As soon as I put a new plug in, the bike will start right away.

Any ideas ?

OMG!

Try a B-8ES and try 32:1

32:1 is recommended for the newer bikes (I run 40:1), not 20:1. Stock jetting is usually too rich. My bike came with an 8, not 9 for the plug. The new bikes come with a Keihin carb, not Mikuni, which makes me think your bike is old. Other than that, sounds like you are right on it.

On an 81 175 I don't really have much of an idea but you could start by bumping the mixture to 32:1 or 40:1 since your using modern premix. With the motor being aircooled i'd keep the b9es for the moment and see if adjusting the mixture keeps it from eating the plugs. If not i'd try one step hotter on the plug and work with the jetting a bit.

Definitely need to get some jets for that round-slider

'My carb is stock jetting'

Chances of that being correct are slim to none.

IMO...DO run the plug that is spec'd, not a different range to mask jet-reading tell-tales.

20:1? That's in the book?

That's chain-saw mix!

Changing to (example) 32:1 from 20:1 will richen the air/fuel ratio. If you're having plug problems now due to overrich, that change will make it worse.

A great thanks for all your answers.

I will start richen my mix, won't change the plug yet but will be next step.

20:1 is the actual ratio in the manual but I'm guessing that the oils back in the days were'nt protective enough comparing the oils of today.