Custom Sportsbike

[chaslam07]

Can anybody tell me if this can be done, say can i get a frame from one bike, engine of another, lights of another, exhaust of another, electrics of another and get different fairings, i know you will have to modify the frame to hold new engine etc and new mounting points for fairings and lights but can this be done, I am currently stripping down a suzuki gk73a gsxr400 in the show and tell section, but had a bit of a set back today while taking the exhaust of snapped one bolt and broke some casing of the engine where the bolts goes through to, so dont know if that means new part or if you can just weld it back on but had this idea in my head aswell to just do what i want with it rather than restore it, i know itll cost alot more than just to buy one but im in no rush and there wont be any like it around so any advice welcome thanks

[G]

I'm sure Marjay will be along soon .

The question is 'why'?

Yes it can be done. In days gone by people would stick a mass produced engine in a custom built chassis to improve the handling.
This is how bimota made their living.
Now though, the mass produced chassis are excellent, light and better than most aftermarket ones would be, so no one bothers really.

There are some fairly simple swaps that require only minor modifications. However, even in those cases and in most other cases - it's so much effort that it's not worth it, especially as generally you can just a chassis/engine with it's original counterpart and have a better machine with a lot less work and money spent.

[chaslam07]

the reason im asking is because well one i dont know if what i have done can be fixed so might have to replace it anyway so then i could just replace all of it as the engine is only really the major part, the fairings and lights etc would only be minor modifications and wouldnt require the amount of strength the engine mounts would need, im not looking to put a 1000cc engine in or anything i still want to keep it light to keeps it characteristics as a 400, good handling and good in the corners.

[Kickstart]

Hi

Major components vary in difficulty. For example Yamaha are quite good at only changing things that really need changing, so often bits from vaguely similar age Yamahas can be used on other Yamahas.

However the more specialised the bits the less chance / harder it will be.

I presume it is just your engine has had a bit break off where the exhaust bolt goes into the head. Should be repairable, and with the engine out of the frame should be that difficult to find someone to do it.

However if you wanted another different engine then life gets more difficult. The Japanese 400s are fairly small bikes with things fairly well crammed in. Not much space to spare. It is possible another engine could fit in the space if you had the skills / money to fabricate all the engine mounts, but unless there is a particular reason to do so it would be a pain. While other Suzukis might have similar engine mounts, this is far from certain (ie, Suzuki dramatically changed the engine mounts between the late oil cooled and early water cooled GSXRs, despite at first glance the frames looking very similar), and even if they do there is no certainty that other bits will be in a suitable position (ie, a 400 Bandit engine might fit, but I wouldn't be in the slightest bit surprised if the head is different to angle the carbs to fit).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[G]

First off, I'm afraid this is a definite case of "if you have to ask, it's a bad idea". If you had the skills to do it, you wouldn't be asking this question.

Putting another engine in is more than just the engine - it's all the ancillaries, all designed to work with another frame.
Oh and you may well find a modern 1000cc engine weighs similar to your old 400cc!.. but you'd come with other issues as the chassis isn't designed to take the power.

Further, if you're sticking with a similar engine; why bother? You're going to a lot of effort to get the same end result, but that's going to be much harder to sell and harder to get parts for etc.

Fairings and lights often require a fair bit of fabrication too, though relatively less hassle to make work, does tend to be a lot of hassle to still get actually looking good.

[chaslam07]

thanks for the advice, once ive got the engine out il have a closer look and see if it can be fixed then, yes its the part when the exhaust bolt goes into, can that be welded back on ? il try and just restore it to itself then maybe in the future if this goes well have a crack at doing a custom bike, but one more question say for example i did a custom sportsbike would it just have to be MOT'd when done or would it need a special sort of certificate like a kit car ? and when a bike is cat c or d does that stay with the frame or engine ? could i buy a cat c or d bike and then use the engine to put it in another bike and then the new bike wouldnt be cat c or d ? hope this makes sense was hard to find the right words to explain

[Bezzer]

The write off categories refer to the frame/vin/registration numbers, put another engine in the frame and it's still a Cat C or whatever.
Put the old engine in another no marker registered frame and it's just a change of engine the marker doesn't move with the engine.
Changing the engine doesn't make it a "custom" bike or subject to a SVA but the DVLA sometimes ask for proof of the engines origin and if it's been done properly.
____________________
I used to be indecisive but now I'm not quite so sure.

[Frost]

There were a few cases of people putting a 450 4 stroke engine into an RS250. though it's a butt load of work and requires you to get a good motor off a fucked bike as well as getting an RS250 from somewhere. I hear aprillia are actually making the thing now though, which is awesome! There were also cases of people putting 500 2 strokes into the 250 2 stroke bikes.
The gsxr 400 was basically just an RGV250 with a 4 stroke motor wasn't it?