the plugs say LEAN the bike run perfectly?????

[s head]

From 1000 rpm to redline my bike runs perfectly.
It will pull from 1500rpm in top without a shudder and it starts instantly hot or cold.It does not run hot.It is completely stock.
But the exhaust valves are chalky cream color and the plug readings at idle,3000 and 6000 all say its running lean.It backfires a little on overun and idle is slightly up and down but thats being picky.
I am thinking of trying 98 octane and in theory if its lean it will run even better???I find that hard to believe.
I am no expert so can anybody explain whats going on??

[TADracer]

If the insulators in your plugs are light grey or off-white and there is no overheating, it is probably on the mark. Before changing anything else, try switching to a spark plug one range cooler. That will dissapate a bit more heat from the head and lower your combustion chamber temp. Ride awhile and then read your plugs again. If they are still off white or light grey, stick with them.

If it is running perfect, just check it, dont change it. Like they say, if it ain't broke......

[Crazcnuk]

Exactly what TAD said.

If it is running xsivley lean, it would run very hot. Eventually you would burn a hole in a piston. Air cooled engines actually have a fairly wide range that they will run in fine.

If it is running at normal temps and everything is running fine, I would agree with TAD that you are probably really close to right on.

The 98 octane will do nothing for this issue. You can try going one heat range hotter on your plugs, so it will run slightly cooler and see what the plugs look like after a few hundred miles.

For the idle surging try running some Seafoam through it and see if it helps. Your carbs are probably just slightly out of synch, or you have a very minort vacuum leak somewhere.

The backfire on decel is usually from a lean condition, but again, a LITTLE bit is nothing to worry about.

Do ALL your plugs look exactly the same?

[s head]

yes the plugs are all the same even though I am running 110 main jets on 1&4 and 120s on the middle cylinders.I will try the cooler plugs and see
if that helps.The carbs are synced perfectly I have
a good set of gauges.As this is the first bike I have
ever attempted to tune myself I just followed the advice on this forum.I was very happy when the bike started running so well after cleaning and setting the carbs but the plug reading and valve colour did not seem right considering the bikes performance.

[s head]

Tried new plugs and got he same result.The floats were originally set at 19mm and I changed it to 23mm off the gasket face.If I lower it to say 20
would that richen the mixture up. I have read everywhere that a lean mixture is the worst thing
you can have for a motor ?

[Crazcnuk]

At this point, I am not sure why your trying to play with it at all. It sounds like it is running fine.

Keep in mind that you don't get really good readings off plugs in a short period of time. Ride it for a few hundred miles, then check them again.

[s head]

I am just worried that too lean =burnt exhaust valves.However I have not ridden the sort of miles you are talking about just 2 miles or so before doing the plug reading.I have the fuel mixture screws out to 2 and a quarter turns which has smoothed the idle out but made no difference to the plug readings.Maybe I just need to do more miles.In the end I might just stick it on the dyno
for peace of mind.

[Crazcnuk]

True plug readings take quite a few miles. People also do them after full throttle runs at the dragstrip and such, but it is a much trickier process.

You have to go out, do a full throttle run for a few seconds then pull in the clutch as you shut off the engine and coast down to a stop using just the brakes.

This is used, primarily for very high performance engines, however, ones that are usually already too rich or lean.