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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.

Well that is track testing finished for the year. Time to do some checks and see how things are inside this engine I hav...
06/10/2026

Well that is track testing finished for the year. Time to do some checks and see how things are inside this engine I have been abusing all year. Then rebuild sorting out the timing issue I have found then back onto Bob Grant dyno to see if we can break the 160hp with some more adjusting and playing about with things.

Massive thanks to Bob and also Lewis for the help this year, will have some work coming to both of you over the winter πŸ˜‰

Thanks as well to Venhill for great parts for cable making, exhaust valve and throttles, Mark Dent for help with pipes and advice and Titan-X for ti fasteners at great prices.

Last but not least Franco the man behind this project at Maranello Engineering who's dream this was in the first place.

Already got a big list of things to do, but definitely been a successful year considering the abuse I gave this engine. 😬 Just under 157hp at its best, apparently according to Randy that looked at some of my data downshifts to just under 14k, last time out repeatedly revving to just under 13k and no issues apart from a mystery seize on one cylinder earlier in the year.

Hopefully over the winter we will have an update on availability of more parts for customers to enjoy the awesome engine.

Cheers and keep following the page for updates.

Well found an issue with ignition timing that I can't sort out properly without a full engine strip yesterday on Dyno, b...
03/10/2026

Well found an issue with ignition timing that I can't sort out properly without a full engine strip yesterday on Dyno, but got a healthy 146hp to go to Knockhill on Monday πŸ˜ŽπŸ˜πŸ˜ƒ
Also saved over 3kg with my new carbon/Kevlar fairing πŸ˜†

Nothing like last minute πŸ˜‰ 11pm and bike is ready for tomorrow morning 😎
04/09/2026

Nothing like last minute πŸ˜‰ 11pm and bike is ready for tomorrow morning 😎

Just hoping these get to me in time to sort for the weekend πŸ˜ŽπŸ˜‰The big HP pipes but mounted higher up so I could actually...
02/09/2026

Just hoping these get to me in time to sort for the weekend πŸ˜ŽπŸ˜‰
The big HP pipes but mounted higher up so I could actually ride the bike on track. My mistake on first versions they were way too low for ground clearance πŸ˜•

29/08/2026

We will be at the Rewind festival at knockhill next weekend 5th and 6th September. Got a bit of track time with other like minded people. Feel free to pop up and see a great range of bikes.

31/07/2026

Just a quick update on things.

1. Overheating issues last time out at Donnington, now commissioned a special radiator. Will post details once I have it but price is good.😁
2. Bottom pipes have been finalised for giving the top HP and reshaped to give best ground clearance. Now in the queue for being manufactured.
3. New fairing ordered to replace very heavy one bought. Carbon/Kevlar for lightweight and strength and hopefully with new exhausts I can get away with no cutouts for pipes πŸ˜‰πŸ‘

Once things come I will be Dyno and track testing, keep an eye on the page for more updates. 😁

24/07/2026

Enjoy the noise shame you can't get the smell! πŸ˜ŽπŸ˜‰

24/07/2026

Wee on board from Donnington on Tuesday, excuse the old fart riding! The bike is a lot faster, as was I in my day a while back πŸ˜‰πŸ˜ŽπŸ˜

Ok semi successful day at Donny on Tuesday. Managed to sort out misfire on 500 , turns out it was the quick shifter 😯Too...
23/07/2026

Ok semi successful day at Donny on Tuesday. Managed to sort out misfire on 500 , turns out it was the quick shifter 😯
Too hot for the old guy riding it though. Bike was also running hot but that was a known issue as rad is too small. Talking to guy tonight about possible options for new rad 😎
Took 250 out in last session but issue with carb rubber stopped that in the first lap. Need to find some new rubber mounts for the carbs.

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