Hi , I have a set of the new wiseco's in the post and will report back .
I have weighed my previous wiseco pistons and the cast pistons and they seem almost the same .
I have been told that wossner are good , i have been told that wiseco are good too . On prevoius bikes it was the cast pistons that broke in a big way and wiseco's would seize with no major damage .
Matt@TYGA
rebuilding my mc21 ive found two 150sp barrels in good condition what will they need to work on the 250 and what do you charge to do it thanks
Put a lubed piston in one of your bores and sit it in its normal assembled postion on the crankcase half you are working on. Move the piston down until it catches on the crank case then simply start grinding/filing in that area until the piston slides all the way down to where bottom dead centre would be if the engine were all assembled and that's it really. Matt says chamfer all sharp edges that you make with your filing/dremeling.
For the bottom case you can still sit a barrel (with piston inside) on the two remaining studs and slide the piston down to see where it catches. You dont need to take much off to get full clearance - as you'll see yourself.
I took alot of time afterwards to banish all trace of swarf and aluminium dust from all engine surfaces.
I'm in the process of doing this right now. I got it to the point where the piston skirt slid past the area where it was catching, then I ground a bit more off to allow for expansion or anything irregular catching. My question is how do you know how much is enough? I wouldn't like it seizing because I took too little off. _________________ MC21 Honda NSR250. TYGA 300 conversion.
If the piston moves past without catching and has say, 2-3mm clearance then that'll be fine. It doesn't matter if you take more off for safety. _________________ After years of moaning about immigrants now i am one...
So, in the plane of the cylinder radius, 1.5 - 3 mm, right? You can take the whole width of it (in the plane that the piston moves up and down) away, correct?
Yes, I have the full skirted pistons. Decided to go that route as it should give better balance and longevity. At present the skirt will go past the part I'm grinding away, but there is probably only 0.5 mm clearance. I need to take more off.
We just use an air grinder. Take light cuts and it'll only take you about 5 mins maximum. If you want to finish it off nicer afterwards that's up to you. _________________ If I have to take the carbs off once more...
I'm stuck with drill bit grinders. Slow going as they get full of aluminum pretty quick. Found a file works well enough, just finish with grinder then sand paper.
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