Sludge ????? Sure it wasn't just normal carbon buildup ?

Never fear, that does nothing more than up our compression
a bit, something that some of us spend hi dollars to acc omplish

Lets dont forget, the cavity the plug sits in gets sand & junk in it. Unless that gets blown out, then every time the plug gets pulled, theres crap just waiting to fall into the cylinder.

If it runs better w/ choke out, it is running lean not rich.
If it idles good and runs good everywhere except that slow speed surging, you likely would benefit from the "white spacer mod", or should I say thats what fixed my exact same problem.

If your bike runs good, no oil consumption, and no spark plug fouling, the carbon on the piston is normal,..... just pretend you didn't see it.

You can peruse my fuel mileages by clicking the "Fuelly" logo in my signature. There, you can see for yourself what the white spacer mod did to my fuel mileage. I didn't notice any change in performance, but the mileage got worse. I put the spacer back in. It may make a difference that I live at about 1800 feet altitude.

If an engine is not running correctly,...w/ regards to lean and rich, it is not getting the best mpg. You cannot improve mpg by starving an engine for fuel....to the point of it surging or running rough.

On the other hand, if an engine is running correctly......defined as smoothly in all ranges, I believe it is getting about as good mpg as is possible, nor is there any noticeable performance gain to be had by modding the carb.
I just don't know why anyone would do the white spacer mod (same as raising the metering rod) if the engine is running smoothly in the low and midrange throttle.

I did the spacer mod because I had a surging at slow speed in the lower gears. Had this been years ago I would have raised the metering rod by moving a clip to the next slot. Trimming the white spacer did the same thing, and it corrected the low speed surging almost perfectly. I also now need less choke for a shorter time in cold weather. I did not notice any difference in fuel miliage, probably because its not using much fuel in the low speed range anyway.
My bike always did run good at hi and WOT range, and the one time plug check showed a nice tan white color. If however, I ever did a major open exhaust mod, and/or like to run a heavy throttle in hot weather, then and only then would I be modding main jet,....depending on other things like altitude.
Yep, I have always gotten near 50 mpg, but most my riding is in very hilly country. I also believe the large differences in mpg on this site, is the rider, not the motorcycle.

Thanks for the heads up about worse gas mileage after removing the spacer. I suspected that. I'll keep mine in, even though it does "surge" (runs haltingly) at lower speeds. Gas just passed $3/gal here in SE Michigan this week. It's starting to remind me of 2008. Problem is it's been in the 30s every morning lately. I used to ride down to 30 but I'm getting old and whimpy. I don't like to go below 40. The rut is on too and I counted 3 deer carcasses in the first 2 miles of my commute (in the morning dark). It makes me nervous. I have to drive through the municipality that has more deer/vehicle crashes than anywhere else in Michigan- 8 of them were fatal 2 years ago - all involved motorcycles.

BTW What is a metering rod?

I'll see if I can get a sludge hammer at Walmart.

I must be blind,... I never did find anything about the white spacer in Fuelly.
But I do question why the drastic differences in some of your mpg stats. Or did I miss the different conditions there too ?

Charon wrote on 11/07/10 at 20:13:26: