will2208 Posted March 3, 2009 Report Share Posted March 3, 2009 Hi All, This is by way of introducing myself because I'm computer stupid and can't get the "Introduce yourself" feature to work. I'm a soon to be ex road racer and am looking for a new hobby more in keeping with my advanced years. I've always fancied gently tweaking an MZ 250 to make a slightly more tractable road bike. Now whilst I've done more then my fair share of tuning various two strokes to go road racing on, I suddenly realise I know nothing about how to extract "bottom end" grunt like modern trials bike have in abundance nor how to get "mid range" tractability plus reasonable performance like modern motocross bikes develop. So here I am asking for advice from obvious enthusiasts who know a thing or two more than I do. Any port timings/experiences/experiments/books to read etc. will be greatly appreciated and might make an interesting forum topic for others too. Many thanks in advance and happy riding. Regards will2208. Quote Link to comment Share on other sites More sharing options...
treevor Posted March 3, 2009 Report Share Posted March 3, 2009 Howdo Will I have a pdf on 2 stroke tuning I can send to you via email. Send me a PM with your email addy Treevor Quote Link to comment Share on other sites More sharing options...
edholland Posted March 4, 2009 Report Share Posted March 4, 2009 Welcome Will ! A pm is short for personal message and you can pm people by clicking on their name. If you click for example on Treevor's name you get a few options one of them is "send message" Never post your email on forums ! forums are scanned and you will get all kinds of spam in your mailbox. Thats why Treevor said pm me your email Cheers, Ed Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted March 4, 2009 Report Share Posted March 4, 2009 Reducing the port sizes helps with low end grunt as does lowering the ports so they don't open for as long. Also longer strokes are better for low end power. Motorcross bikes use power valves which basically close off the top part of the exhaust port for low end power and open up at higher revs to give a better top end. A lot of two stroke tuning is archived though tuned pipes, you may be best looking in to this for better gains. For example trials bikes nearly all use a fairly straight constant cross sectional pipes, where as motorcross bikes have a pipe which gets larger and then smaller before it enters the tail pipe. The length to the belly part of the pipe determines the engine speed at which it will improve power, short = high revs, long = low revs. The angle at which the pipe tapers determines the rev range at which the pipe will have a effect, steep angle = small range (hard hitting short lived power band i.e. road drag racing), shallow angle = large range (soft broad power band but less ultimate power i.e. a enduro bike) Quote Link to comment Share on other sites More sharing options...
copemech Posted March 5, 2009 Report Share Posted March 5, 2009 Hardest part is putting metal back into a highly modded hole! Quote Link to comment Share on other sites More sharing options...
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