40mm 6 port sleeper head kits

[RD RACING]

i have 4 only 40mm bore size 6 port one piece cylinder / piston kits complete and ready to bolt onto your existing samauri ect 40 cc engine. these kits are tripple boost ported complete with modified exhaust durations, windowed pistons, rings , gasket ect. this kit type has been very popular in the u.s.a. with guys wanting to stick with the 40cc engine size as rpms are greater than the 49cc sleeper. these complete head mod kits are to be sold at this price each, $50.

[crash1171]

Hi there. I have recently purchased what I think is a 40cc samurai (i was told its a 47cc mta3, but I think not). I was wondering if you would recommend going with one of these 40cc 6 port heads or a 44mm big bore head kit. I'm not sure whether I should want more revs or more cc?

[RD RACING]

the easy way out is to try one of these 40mm head kits as if you do have the 40cc [ 40mm ] engine you will also have a 32mm stroke crankshaft in the engine which is really not suitable if you want to fit a 49cc [ 44mm ] head kit, the crankshaft must be replaced with a 33mm stroke for the 44mm head kit to work correctly. if you are not to heavy in body weight the 40cc head kit does perform very well, i sold one of these to robbie some months back and he has stated to me how quick his engine now is, racing against 49cc engines he is placing well in the top 3.

[Robbie]

Originally Posted by RD RACING

the easy way out is to try one of these 40mm head kits as if you do have the 40cc [ 40mm ] engine you will also have a 32mm stroke crankshaft in the engine which is really not suitable if you want to fit a 49cc [ 44mm ] head kit, the crankshaft must be replaced with a 33mm stroke for the 44mm head kit to work correctly. if you are not to heavy in body weight the 40cc head kit does perform very well, i sold one of these to robbie some months back and he has stated to me how quick his engine now is, racing against 49cc engines he is placing well in the top 3.

Just to add the other bikes in my class are ported 49/50cc engines, since this i have noticed a large jump in my bottom end.

[crash1171]

Great info guys. I noticed you mentioned my weight. Glad you did. I am a bit heavy (95 kilo). Do you think that's a bit heavy for the 40? The way I understand it the 40 is going to give me good acceleration. I don't feel the need to make this bike do more than 65 kph (thats a very liberal estimate), But I would like to get up to speed as quickly as possible.

[RD RACING]

not being rude but if you were 50 kgs lighter this kit would be very suited to you. my suggestion to you is to buy a 2 piece 50cc head kit, this will give you plenty of both low end torque plus great high end rpms.

[mac90]

yeah for the bigger blokes i rekon go for the bigger cc pinsize etc a little more suited to carry more weight and wont wear out as fast
a good pipe and walbro carb will give you a little bottem end back
remember the fatboy pipes are suited to midrange & top end in my opinion if you want to keep your bottem end up a jet pro replica type pipe works well without killing top speed

one of rds big bore 5 port heads may be better for your weight and i might try one myself if i ever wear out my 15:1 single boost port cylinder im around 70 kgs and this setup works really well for me
i get a lil front wheel lift nothing extreme (just enough to make it not steer) with my current mods and 6 6/62 thick pitch sprockets
if anyone has the converter set up for thin chains rpms and speed is it possible to convert thick chain sizes or is there a r1 converter that i can use
ill eventually test thin chains but have never streched or broken a thick one yet so like using the thick pitch for reliability in non race situations