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So just starting to rebuild a 58 Framebreather. I have the correct 150 engine block and would like to keep it with the frame.
However there is a need for speed. I will be looking to do either a TS1 235 or the new GT240.
Can my original block be converted to big block?
Who does it?
Any recommendations or reasons why not to do it?
Any advise is welcome

Keep the original engine, buy a big block engine to transplant and change back when you sell..

Probably cheaper in the long run.

I have a small block engine in for convertion for 4 months, and got it back at the end of april in the same condition I sent it.

MB provide this service, and do a good job, but big bucks.

Do the finances...

foremanbob wrote:Keep the original engine, buy a big block engine to transplant and change back when you sell..

Probably cheaper in the long run.

I have a small block engine in for convertion for 4 months, and got it back at the end of april in the same condition I sent it.

MB provide this service, and do a good job, but big bucks.

Do the finances...

+1

Have you thought about a good quality small block kit, have it tweaked and set up professionally to your requirements.
60mm crank- gearbox-exhaust and carb you get the thick end of 20hp
Matching-gearbox and exhaust will make sure you get the power delivered how you want it.

Glad to see you back on the forum. I agree with Foremanbob. I wish I had my original engine. Store the 150 and buy a tuned engine. It will save you so much time and you can progress with the rest of the bike at speed. There are good deals out there. Regards : )

Did this with the S2, still have the original engine in the shed, and a Rapido 225 on the bike.
Just wanted the S1 all original with some useable power.... I'm no speed junkie, just wanted a nice fast touring engine.

May start to look at the small block. My fear was the S1 lump my not have been up to the conversion due to design weakness.

If you like the Rapido & it’s power/torque delivery (when set up in the manner of ‘road’ not ‘race’) then a GT kit has similar virtues & I would consider a longer stroke crank in conjunction which will all fit inside your existing case. You'd probably need a beefier clutch but the case itself does not have inherent weaknesses AFAIK.

(I ought to try & flog you the Mugello small block kit I have knocking about , but, in all honesty, having ridden a GT 186, they are a great kit)

20bhp, that's impressive. I didn't think that would get to that sort of output.
I did look at the RB20 for the S2 but it was to revy for my style of riding. Hence I ended up with a tour Rapido 225.

Out of interest anybody know what the small to large conversion would cost? Are they still done and are there any problems with this?
Thanks guys, as always great help. Long way to go with the S1. Still a box of rusty bits.

Cost me £266 including postage for a casing conversion and i had problems with it. I wouldn't do it again.

Conversely my other lambretta has a Chris Sturgess tuned gt186 with 60/110 crank, jl3 and 30phbh. It makes 22bhp.

Thanks Dicky, I had heard that there could be problems with the conversion.
Small block it is then.

Read this especially the post from Paul at Oilteck (hydra) http://www.scooterotica.org/forum/viewt ... n&start=20

I have a rapido race and an RT 195 kit. Both are great in different ways- the both knock out 18hp
The RT is easy to ride and very flexible- great on hills and keeps up with traffic.
The Rapido Race is faster but need to be revved, it likes fast A roads, + I've spent quite a bit of time and money getting it better including a reed and TS1 piston.
My opinion only- save the conversion cash and use it to get someone to optimise a GT or RT kits.
Have a look on the scooterotica site at their RT kit thread or do a search on GT186, there's plenty of information.