150cc Conversion

[dapper]

Is it possible to bore out a standard cast Injun 150cc to accept a 64.5mm (185/6cc) SR piston? If so, what other mods need doing? Piston is brand new with thin wire rings. Transfers in cylinder have been opened up, and casings matched. I know about 175 conversions and that there was an old school Suzuki conversion to 185, but can this be done, and if not, why not?

[J1MS]

The Indian 150 barrel will normally bore out to 64mm, but I have never fitted an SR 186 piston to one, only ever used the Suzuki TS185 ERN piston. These are pretty cheap, tough with quality piston rings.

[mark]

im interested in this any more info?

[jonny snatchsniffer]

you will be better off starting with a tv 175 barrel as the transfers are bigger, if you can get one that is, ive done a few of these conversions but always used suzuki pistons, and also 150 barrels, the dj book is pretty good to get ya timings good, tho i raised the exhaust a bit more than what he suggested

[J1MS]

you will be better off starting with a tv 175 barrel as the transfers are bigger, if you can get one that is, ive done a few of these conversions but always used suzuki pistons, and also 150 barrels, the dj book is pretty good to get ya timings good, tho i raised the exhaust a bit more than what he suggested

I agree the 175 is a better choice barrel for this conversion.

What was the largest exhaust port timing you used, on the Suzuki 185 piston barrel conversions you have done.

I only ever took a couple of exhaust port timings past 180 degrees, usually nearer 170 degrees on mine.

[dapper]

The Indian 150 barrel will normally bore out to 64mm, but I have never fitted an SR 186 piston to one, only ever used the Suzuki TS185 ERN piston. These are pretty cheap, tough with quality piston rings.

So Jims, 64.5mm shouldn't be a problem?

Johnny, I did say I have opened the transfers in the cylinder and matched casing transfers too. I know its a lot of boring and its only an SR piston, but I'm not looking for anything special, just a bit more grunt and top speed all on the cheap. I have access to a tuner who could do the rebore and who could widen the inlet/exhaust/transfer ports. Would anything else need doing? Shave a bit off the bottom of the skirt to extend inlet duration?? I think there is enough meat in the cylinder walls to take this. Opinions please.

[Supereibar]

To nottice the difference you will probably need to cut the piston skirt. Correct me if I am wrong. Also, the ports are way different. That is why the SR190 kit has that unusual set up, so you can really take the juice off those transfer ports.

J.

[dapper]

I am basing it on this, but Sean/Dan didn't say what piston was fitted or what they did to it if anything. They didn't bore it out for more cc's. As stated I have access to a good tuner, but I don't think he has worked on Lammy engines, but he3 does a lot of work on his son's MX machines and he knows his stuff.

http://drunkmunkey6969.googlepages.com/ ... nceporting

[jonny snatchsniffer]

i dont remember having to cut the skirt as top and tailing the barrel will give you the required timings that you want, sure you can cut it if you want to increase the inlet some more, its easier than taking it from the barrel, but the way ive always done it is to top and tail, rebore then do the exhaust and inlet to what i want
the fist one i done i did it as per the webster book
then i went silly and did the exhaust to 195 and inlet to 170 needless to say below 7000rpm it was a tad useless and spat petrol everywhere, but it went ok when you could keep it in the power, i always used pacemaker boxes too and a pm pipe
but i reckon 180 exhaust 160 inlet and 130 transfers was the most rideable one i done

dapper the suzuki pattern pistons are cheap and good quality, ive never seen an sr one as when i was doing this sort of thing there was no sr, your tuner should be fine even if he hasnt worked on a lammy as the principles are the same no matter what

if the sr piston has the same crown height as standard then you will have to do things a bit different

[jonny snatchsniffer]

oh yeah its better to lower the inlet than take it from the piston because of port time area.
just looked at the stage4 150 and an asso piston was probably used with 1.5mm rings