lambretta 290 rotax

[holty]

I have made a start on upgrading my rotax to a powervalve model, ive removed the jetski barrel and pleased to see the piston in very good condition and the crank as well, carb size is being increased to 38mm the same size as the skidoo that the barrel came off. I have removed the inlet manifold and welded a bigger tube on it to match the carb and done a test fit to check position, which is good, I also did a leak test by clamping the manifold to a rubber sheet on a steel plate, found a leak and fixed that, just waiting for some base gaskets to arrive, exhaust angle where it leaves the barrel is not the same as the jetski so exhaust will need altering so that's my next job after the barrel is fitted, will add more pics later
Untitled by stephen holt, on Flickr
Untitled by stephen holt, on Flickr
Untitled by stephen holt, on Flickr
Untitled by stephen holt, on Flickr

[garry inglis]

looks good steve carb sits well in there looks odd with fuel tap on this side have you got it going out of the choke hole to turn fuel on and piston looks clean thats good jetting mate

[holty]

fuel tap just has a penny washer riveted into the slot so panel has to come off to turn it on and off, I just leave it on as a rule, not been a problem upto now, I have no route to get to the fuel rod, cylinder head is in the way, I was quite impressed with the piston condition as well, jetting is down to martin at chiselspeed, it will be going back on his dyno once its up and running and ive got a few miles on it.

[mick1]

fuel tap just has a penny washer riveted into the slot so panel has to come off to turn it on and off, I just leave it on as a rule, not been a problem upto now, I have no route to get to the fuel rod,

I fitted an electric valve on mine to overcome this. Works fine unless your battery's flat !

[holty]

fuel tap just has a penny washer riveted into the slot so panel has to come off to turn it on and off, I just leave it on as a rule, not been a problem upto now, I have no route to get to the fuel rod,

I fitted an electric valve on mine to overcome this. Works fine unless your battery's flat !

what valve did you use, sounds like a good idea.

[holty]

fitted my rave cylinder to my scooter at the weekend, had to alter a bit of plumbing, got a bit more to do before I fit some stronger clutch springs
Untitled by stephen holt, on Flickr
Untitled by stephen holt, on Flickr
Untitled by stephen holt, on Flickr

[garry inglis]

whats the rubber cap with the spring clip steve is that for coolant

[guygrrr]

At the expense of stealing Holty’s thunder, his new cylinder uses a vacuum actuated exhaust valve. The black plastic is the cover for the vacuum diaphragm. It’s a neat upgrade and should give his bike more bottom end.

[czeckson]

principle looks familar to me:

[czeckson]

carnuntum.heimat.eu/539.jpg