SJM projects

SJM projects Prototype Grand Prix motorcycles. We are a two stroke specialist currently working on a new 500 engine project based on the Rg500 and a superkart engined 250.

Just a shame bike was not at its best but nice photos from East Fortune last weekend 😀
02/05/2026

Just a shame bike was not at its best but nice photos from East Fortune last weekend 😀

Ok so we can now say our engine has been properly run in race in race conditions and came out the end of the weekend sti...
27/04/2026

Ok so we can now say our engine has been properly run in race in race conditions and came out the end of the weekend still running 😎😉
Loads of little things to iron out but milage at race speed was put on the engine which was the purpose of this weekend. Out with completely different bikes in sound of thunder and classic superbike classes combined.
Engine is now in pieces to assess how it is bearing up and all is looking very good. 40 year old cases might have flagged up a small issue but that's what we are testing for, to make sure any customer engines are checked for issues before being run.
Thanks to Richie Lambourne for riding and feeding back until I get my body in a position that it fits in the bike well enough to do it justice .

Ok so I believe we now definately have the most powerful RG500 based engine ever run. Don't ask me how but today on the ...
20/04/2026

Ok so I believe we now definately have the most powerful RG500 based engine ever run. Don't ask me how but today on the Dyno we got just under 157hp out of her 😎😜 Still trying to work out where the extra came from as we have run the same setup before. Unfortunately Richie is going to have to make do with around 149hp as the bottom pipes that gave us the 157 don't have enough ground clearance. Ignore the other curves the green one was from today's best runs.

Ok not what I wanted as it was always my intention to race this bike first but need to get some race miles on this new e...
17/04/2026

Ok not what I wanted as it was always my intention to race this bike first but need to get some race miles on this new engine and my body is not up to it yet.

Plan is for Richard Lambourne to race the 500 at East fortune next weekend. Got some Dyno time to do on Monday thanks to Bob Grant to test pipes and to make sure what I plan to run next weekend is good.

Anyone in the area please feel free to come and have a look, Melville club is a great club and you will see loads of great racing.

Licence training day 28th March
04/04/2026

Licence training day 28th March

Licence training day Saturday 28th March
04/04/2026

Licence training day Saturday 28th March

29/03/2026

Just returned from East Fortune after a crazy weekend. Licence training all done on Saturday in dry but very windy conditions.
500 engine is far more tractable that I could have hoped and is an absolute missile. Unfortunately my physical condition was a real problem. Right hip restricts leg movement and struggled to get foot on peg. Left not much better and had issues changing gear.
250 is even tighter so I could not safely ride it which was frustrating.
Today we had wild weather with extreme wind and rain. 500 is surprisingly pretty tame in the wet with the smooth power delivery.
Richard Lambourne had a ride as was as impressed as I was and he is used to a pretty quick RS250 framed RG570 😁

Well after a wee hiccup the 250 is ready for East Fortune this weekend as well as the 500.
26/03/2026

Well after a wee hiccup the 250 is ready for East Fortune this weekend as well as the 500.

19/03/2026

Well all up and running with new spec pipes ready for Dyno in the morning 😆

TL fairing modified to accept std screen and belly pan ducts etc sorted out. Primer went on today hopefully top coat on ...
16/03/2026

TL fairing modified to accept std screen and belly pan ducts etc sorted out. Primer went on today hopefully top coat on tomorrow 😆

Ok this sounded sweet yes? Well have a look at the curves below and imagine what's its going to sound like singing to 14...
15/12/2025

Ok this sounded sweet yes? Well have a look at the curves below and imagine what's its going to sound like singing to 14000 revs

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