I have got a Sinnis retrostar 125cc motorbike. I was wondering whether it is possible to put a bigger engine e.g. 200cc or 250cc etc in a 125cc bike such as this and the costs involved? Has anyone done this before?
It’s going to be tricky, since any new engine will be larger externally, too, and almost certainly wont happen to have mounting holes in the same places, or the final drive cog aligned with the rear wheel’s, so there’ll be some fabrication. And then it’ll be difficult to insure, too.
If it’s an old and common Japansese engine and you’re lucky you may find there’s a 150ish variant whose cylinder, barrel and head you can nick without too much trouble, or maybe full engine.
Why are you looking at this over getting a bike that’s bigger to begin with?
Are you by any chance looking to be the fastest chav person on the estate by illegally fitting a 300cc engine to your 125 chassis which you are riding on L-plates?
There was a young lad near me about 10 years ago who deristricted his Aprilia RS125 and didn’t tell his insurance company (I think he bored it out too but not 100% sure) he took his girlfriend out on the back and crashed up at Havering Atte Bower, she died and when the police checked the bike they found all the “illegal” mods (still on L Plates) and he got done for It and got banged up for quite some time, not sure what sentence he got or what he was charged with but it was a big one. So if you are thinking of doing this then I would be very careful, especially now you have put it on an open forum and if anything was to happen you have grassed yourself up!!
I really like my bike a lot that is why I wanted to fit a bigger engine onto it but the 250cc version has just been released a week ago I have found out!
No I am not. Firstly I am 23 years old and have a a2 license so I don’t ride with l plates. And secondly I was just asking whether there was a possibly, I never said I would proceed to illegally fitting it, obviously I would find out whether my insurers would insure it first or else there will be no point!
All things are possible, how much hard earned do you want to throw at it :ermm:
Back in the early 1970’s my Brother-in-Law had a 125cc twin cylinder Yamahaha track bike that was more haha than most and well capable of reaching 100 mph on a long enough straight.
Proper scary stuff and the the word of caution is the bigger or faster engines need bigger and more efficient ancillary equipment. Rule #1 the faster it goes the faster it needs to stop. Upgraded braking system, additional bracing to the frame, from the TT100 on the front to the TT100 on the back virtually every part of my Brother-in-Laws 125 had been either modified or swapped out, mostly in the name of safety!
Note too the modifications were made to keep within the ‘Lightweight Motorcycle’ racing classification of the day.
Yeah, you’ll probably not manage to get something that rides the same, just with a bigger engine, by swapping out the engine. There’s a lot of knock-on effects that come from the extra power, weight and volume. Probably best to get a test ride on that 250 and see if you like the ride as much as you do the 125
Your best option all round would be to part with the 125 and use the procedes to part fund the 250 if that’s what you want. Although you’ll take a big knock on your original outlay. While Chinese mo’cycles are getting better and better year on year they are still a long way off of holding their value.
The Sinnis inter webby site says
you could consider if the new 250cc bike has the same frame as your 125 then you could theoretically swap out the 125 parts for 250 parts.
but by the time you’ve finished doing that, you might as well have bought the 250 really.
you can put any engine into any frame just depends how good you are at fab i know a guy who put a z1000 engine into a cbr125 frame with r6 swing arm and 636 front end
its a stupid idea, and likely very costly. Besides, for the money you would spend there are far nicer bikes available. much as you like it, there are better bikes out here that you would love even more. bin it and broaden your horizons.