Has anybody used the 275cc big bore kit from Firefox racing UK?The advertisement is not that clear,the barrels shown looks like new 150 SP but states that MC21 tops are internally cut to accept the bigger bore.
The Tyga kit is very expensive for someone here in south africa. My problem is my barrels. No one can do a proper plating job in this country so I tried out the sleeves. First time out the one sleeve droped about 0.25mm in the barrel and blew the gasket. My problem now is all my ports are to big because I didn't do it myself so I need new ones. It would be best to keep the bike 250cc but were would I get barrels that hasn't seen a grinder?
We have 3 big bore options ,
Nsr150 option or bore out to 59mm piston or rm125 piston with 2mm oversize . All these have been done locally , only problem is the nikasil guys bum job !
Cool.
Yesterday I bought a MC21 in Durban and the bike would be here in Cape Town about thursday. It is the black one on gumtree for R5000. Would be nice to have one for testing purposes. I am going to try to keep my bike 250cc as far as possible.
malossi do a 180cc kit for the nsr125. if that could be made to fit it would give you 360cc.
the kit uses new barrels and costs about £389 per barrel in the uk.
Last edited by GrantA on Sun Jan 31, 2010 1:15 pm; edited 2 times in total
Harold wrote:Has anybody used the 275cc big bore kit from Firefox racing UK?The advertisement is not that clear,the barrels shown looks like new 150 SP but states that MC21 tops are internally cut to accept the bigger bore.
I mailed them about this kit, ignore the pics they are "just" boring out NSR barrels and fitting bigger pistons.
I remember talking to Andy about it and he reckoned back when Eric Gorr was doing this sort of thing that he reckoned you could go out that far as it cut into the RC valve too much.
The good thing about the 300 kit is it's brand new barrels. They alone are worth 80% of the cost of the kit.
Other than that for what you're spending on either this 275 or 300 motor you could get a better 250 motor built. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
I can't thank all of you enough. Thanx for all the advice. I will rather save up some money and keep my bike(s) 250cc. Some say you can tune a 250 motor beter than the 300 kit. Ones again thanks for all the effort.
would be great hearing from you guys again.
fontyyy wrote:
I remember talking to Andy about it and he reckoned back when Eric Gorr was doing this sort of thing that he reckoned you could go out that far as it cut into the RC valve too much.
When I spoke to Eric Gorr about this (about 10 years ago! ) I seem to recall he calculated max oversize would be 263cc (without attempting to modify the stroke) before running into port timing issues.
I know someone who persevered with an Eric Gorr oversize, and when it ran it ran strong, but it wasn't reliable. I built an MC18 motor for a friend in the states that had Eric Gorr 250 barrels, and that ran like a scalded cat! It was also reliable... but 250's usually are! _________________ Andy.
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