Big engine + Little bike = ..?

[dydey90]

Just having a bit of a daydream and wondered if it were possible to fit a 250cc engine in a 125 frame. It seems it's not, at least for a CBR125

Just as a little fun project, are there any small bikes (Say, 300cc or less) that will take a much bigger lump?

I'd love to have a bike like that, which looks completely unassuming and actually contains more power than the average submarine.
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This post is probably not serious and shouldn't be taken literally.
Past: CBR125,ER6f NINJA 650, ZZR600 Current: VFR750

[MarJay]

que?

Of course its possible to fit a bigger engine to a smaller bike. There have been countless successful attempts over the years, along with about a hundred failed for every success. Common swaps include:

RD350 YPVS engine in Cagiva Mito
Big single in TZR125
YPVS engine in RD250 Gamma
RD500 engine in RGV250

Etc etc. However, it's rarely a straight swap, and it involves lots of extra work to the bike to make it handle the power, and have improved braking. I vaguely recall someone on here put a 500cc engine in a 50cc or something, and managed to kill himself wrapping it around a tree.

Anything is possible with enough time, money and engineering skill. However, if the meagre research you've done indicates that it's not possible to put a 250 in a CBR125 frame, then I'd suggest that most swaps like this are probably beyond your ability. Of course it's not a straight swap, but as I said, anything is possible with enough time, money and engineering skill.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[P.addy]

300 EXC in a 200 EXC

Easiest one out there.

[dydey90]

It wasn't meagre research, it was merely the fact that the question has been asked on the forum before so I thought I'd be best asking, as people are likely to know something about it.

Engineering skills shouldn't be a problem, but I don't have the tools to modify the frame or mount the engine upside down.

This might be a silly idea, but what's the smallest boxer engine that BMW make/have made?
____________________
This post is probably not serious and shouldn't be taken literally.
Past: CBR125,ER6f NINJA 650, ZZR600 Current: VFR750

[Az]

I believe a Hyosung GT250 engine will fit into a Hyosung GT125 frame without too much trouble.

I've never heard of it being done but if what i've been told is correct a KTM duke 390 engine should fit into a KTM duke 125 frame as i've been told they share the same frame (was told from an unreliable source....could possibly be complete BS).

[dydey90]

[Az]

[dydey90]

https://www.quickmeme.com/img/4d/4d67845760cfc81c6c1b9f6622321e0f95d088e064410e68b1a9100035d0cab5.jpg
____________________
This post is probably not serious and shouldn't be taken literally.
Past: CBR125,ER6f NINJA 650, ZZR600 Current: VFR750

[Az]

Did some research myself, looks like they are the same frame.

[STONEY!]

Paddy 300 into 200 don't go, looked at trying it 200 is big bore 125 300 is big bore 250 lumps are quite different

[MarJay]

[The Shaggy D.A.]

To add to the list...

XT500 engine in a CB250RS
Virago 250 engine in a Virago 125
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[temeluchus]

GSXR1100 engine into a 750

I recall someone shoehorning a GSXR750 engine into a 400(may have been high)

My previously 50cc monkey has a 140cc motor in it.
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Some shite cruiser. Now with guns and FREEDOM!

[DrDonnyBrago]

ZX9r engine into ZX7r and Bandit6/Bandit 12/old GSXR engine swapping are also common.

[_Iain_]

What about that guy that stuffed a 500cc KTM single into an RS125?

https://www.bikechatforums.com/viewtopic.php?t=212716

https://img403.imageshack.us/img403/462/img0626i.jpg
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Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[CG Sam]

The KTM thing is the same with the new RC125/390. I suspect in a few years if licencing stays the same a lot of 17 year olds will be trying to buy 390 engines.
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CG125, SV650S, CBR600F, GSXR600 SRAD

[The Shaggy D.A.]

Ooo, just remembered. Dunno how I missed it, since it's staring at me from my sig.

GPZ1000RX engine in a GPZ750R
____________________
Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[SQL]

In terms of a big engine it's not but 180cc/200cc into a 50cc Gilera Runner is possible.

[The other Paul Rudd]

It's a crap idea. Most decent motorcycles are designed around their motor so the chassis is usually as small as it can be. Any bike that will take a larger engine easily is usually based on the larger capacity model and there is very little gain in doing the swap over just buying the larger machine.

Speaking from personal experience, with the Yammagamma (YPVS350 lump in an RG250) you need to remove the top end in order to fit or remove the motor. And then once it's in, it's in, there is zero room to work on it in situ. Slabside 7/11 you need to drop the motor out of the chassis, so the cam cover can be removed, to access the valve adjusters. It can be a massive ball ache.

[smegballs]

[dydey90]

[G]

As above the KTM 300/250 are the same and 200/150/144/125.

For the OP - why not put a smaller engine in to a bigger bike?

I always thought there might be some business in selling, say, getting an R6/R1 with a blown engine and chucking a 50cc engine in there. Then sell to some spoilt 16 year old that wants to be seen riding a 'big bike' but parents want him to be legal .

Some kid on here stuck a CR500 engine in a 50cc chassis.
He ignored advice to strengthen it.
He died hitting a tree. The frame was broken, I believe.

If you are creating something that genuinly isn't available, or isn't available cheaply, I can understand it. But most cases that doesn't really apply and you'd be better buying the bike you want from the off.

[wr6133]

There was a guy selling a 125 AJS (Chinese) on Ebay last week with a 550cc engine shoehorned in, so anything is possible with some welding skills (and possibly insane mind).

I like G's idea of chucking baby engines in knackered bigger bikes I bet they would sell as quick as you could turn em out.

[CHR15]

[smegballs]

How does the "send in letterheaded invoice from a garage as evidence of engine change" come into play when doing an engine swap at home? Assuming it is going to all be above board notified with dvla and insurance.

Especially with some of the old 2 strokes, where you could just change the top end from 125/150, 250/300 etc etc (I'm thinking MZs for instance) you wouldn't even have a new engine number. The engine is the same, just swapping out barrels and pistons.