piston wash help and rb head mod

[BryanMcc]

Hi guys,
its about riding weather, so i thought id get to my winter project of sending my head to RB for the squish band adjustment. I just wanted to have some opinions on my piston wash, let me know what you think. My goal with the RB mod is more consistent jetting. Right now as is the bike will run fine at 4500 feet but once you get to like 7k feet its a sputtering mess and RB says the mod will help. Not changing jets untill the head comes back, just need some opinions on the wash. Also Ran a compression check and got 133lbs on a warm engine (Wide open throttle, about 20 kicks) and 135 lbs with the squirt of wd-40. seems a little low doesnt it? altitude is 4k and temps were about 40 in the garage if that helps at all. PS dont mind the really shiny spots ( i wiped the carbon off before i got paranoid about the wash lol)

 

[Jakobi]

How many hours on it? How has the performance been? What jetting did you run to achieve that wash? I'd say it looks well and truly safely rich.

 

[Jakobi]

While on the topic. Whats everyones thoughts re markings on the underside of the piston dome?

From http://www.macdizzy.com/update106.html

"The color of the oil spot on the under side of the piston tells its own story. Like spark plug reading - it's a bit of an art and science. Generally, flakey black is VERY not good - way too hot. Black is still too hot - it's burning the oil as if it were in a frying pan. Dark brown and a little sticky is still hot and can be improved upon - usually acceptable for recreational use. Medium brown is kind of warm still - but getting me excited. Tan to light brown is probably the best you can do. Light tan to gold - too cool, get on it more or find someone to race. No color - Fresh from the box - looking at wrong piston."

 

[BryanMcc]

Info

Hi jake,
1 season on bike, bought it new a year ago, lets call it 75hrs maybe. Jetting is 168 main,40 pilot, JD red....what did you think of the compression?

 

[Jakobi]

36mm/38mm carb? What clip position?

I don't take much notice of cranking compression figures. I know my tester uses an adapter which adds a few cc's of volume to the head. Same as if I was running a low comp head basically so my figures aren't as high as expected. Port timing can also influence the cranking compression a bit I believe. What they are good for is comparing a fresh engine to a worn engine. Same tester. Did you ever take a reading when the bike was new? How does it feel under foot and on the bike? Any blow by visible through the exhaust ports? Does it still run strong? Ideally you'd measure up the ring end gap if you wanted to be sure of its wear.

 

[BryanMcc]

38mm I think middle clip. It runs great now just looking for some more power on the top. It was a borrowed tester from a friend, its a Mac tools one so I think it's pretty decent. Did not take a compressin reading when new.