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Post by realnutter on Mar 6, 2012 18:33:02 GMT 1
I'm picking up a spare engine of unknown provenance soon...and was just toying with the idea of going for more cubes....
So how big can I go by boring alone???
What pistons would I use?
Does the 3 valve head stop me borrowing pistons from another bike??
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bozboz
Hits the TON !
Posts: 115
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Post by bozboz on Mar 6, 2012 20:00:32 GMT 1
Wiesco and J.E pistons both sell piston kits. They are for the bros(hawk gt) 650s but will fit the ntv. They are +3mm and 11:1 comp total will be 696cc. Not cheap tho, will set you back £270(plus delivery) for the pistons plus the cost of the rebore prob looking at a further £150-180 depending where you go...
Bought mine a week or two ago from wiesco and still waiting for them. Will post more info when they arrive...
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Post by smartiedarkblue on Mar 7, 2012 11:24:57 GMT 1
Erm stupid question here......
But why would you want to. You are boring out an engine which is d**n near bullet proof and probably the most reliable engine ever fitted to a bike. Hence why it stayed in production for nigh on 20yrs.
By boring it out to the max you are weakening the structural strength of the cylinders and you are putting massive amounts of extra power into the gearbox which will not last for long. They are designed to run at the capacity in which they were produced not more.
You will also need to look at re-jetting carbs and different profile cam shafts to get any noticable amount of anything out of it.
I stripped and rebuilt a ntv engine with 100k on it. There was nothing wrong with the bores, they got honed out by myself to remove the glaze and to aid the bedding in of a new set of rings, thats all it needed.
ed
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bozboz
Hits the TON !
Posts: 115
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Post by bozboz on Mar 7, 2012 19:59:32 GMT 1
smartiedarkblue: Less of why more of because I want to and I can in my case ;D Can see your point smartie but in all the engines that I've rebuilt and rebored to their max eg ft500/rd125lc/cbr400/rvf400 Ive never had any problems with gearboxes etc. Only problem Ive had is like you say is with jetting but thats part of the fun of rebuilding an engine like this - the trial and error of getting it to run sweet. An extra 25cc in each cylinder doesn't take much work neither. On another note these engines are so massively detuned that they can probably do with a bit of livening up! 
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