Topic: honda 750 motor on 500 frame.

[kranta]

so, is it possible put 750 motor on 500 frame with some modification??

[bwaller]

Anything is possible.......................Are you a sucker for punishment?   

[kranta]

yes!!!!

[calj737]

Good luck 

If you're that committed, why stop at a 750. Go for a CBR900 engine. Just as much effort and LOTS more horsepower.

[kranta]

i have 750 motor and i have too 500 motor but its pretty #$%*. and i like more 750 motor than 900 and the bike is going to be chopper so 750 motors looks better than 900.

[SOHC4 Cafe Racer Fan]

In addition to modifying the frame to fit the much larger engine, you will need to strengthen the frame significantly to accommodate the drastically higher weight PLUS the stress that the added power will place on the frame.  You would be better off as Cal said, swapping a lighter, modern engine into the frame BUT then you'd still need significant reinforcement and bracing to keep the frame from folding from the added power.

Another issue is that you would need to nail the placement of the heavier engine (which is an unwieldy hunk of metal) so you do not throw off the weight distribution of the bike.  Screw that up and the bike will NEVER handle properly.

You would be better off slapping a modern engine like a Ninja EX500 bored out to a 600 and bracing the frame.  It's been done by Twinline and it's called The Thorn.

[vames]

...do not throw off the weight distribution of the bike.  Screw that up and the bike will NEVER handle properly.

He's making a chopper, so I don't think handling is really on his mind anyway.

To the OP -- I'm pretty sure there are chopper frame kits and frames that fit a 750 engine. If you're going to go through all the welding work and heartache of getting a 500 frame to be a chopper that fits a 750 engine, why not just get a chopper frame? Or at least start with a free or semi-free 750 frame -- you'd be way ahead because it already fits the engine.

Or forget about the welding and just duct tape it in. Just make sure to use a lot of tape. 

[calj737]

He's making a chopper, so I don't think handling is really on his mind anyway.

To the OP -- I'm pretty sure there are chopper frame kits and frames that fit a 750 engine. If you're going to go through all the welding work and heartache of getting a 500 frame to be a chopper, why not just get a chopper frame. Or at least start with a free or semi-free 750 frame -- at least it starts out fitting the engine.

Exactly! But why spend a few hundred dollars on a frame when you can spend many hundreds, if not thousands re-welding and cutting a frame? Even a chopper should handle. It may not handle like a street/sport bike, but any numbskull who builds and rides a bike that is unsafe, is, well, a numbskull.

I hear the abomination thread clearing its throat in the background...

[Don R]

don't forget the dry sump oil tank.

[kranta]

bike gone be so called "finnish" chopper so there not going to be any hardtail. there gone be longer fork maybe 750 fork and 70s style paint.

[kranta]

750 engine is 2-4 inch higher than 500 motor and 750 front mounts have to do again. other mounts should do be same like 500 mounts and i have to by 750 carburetors and exhaust and hold this swap is going to hapen on next year winter.

[kranta]

and one reason is this modification thing is that my 500 motor is pretty #$%*ty and because i live in finland so all parts are hard find and parts are really really expensive. and 750 motor is so much durable and its so much better designed than 500 motor in finland is no one who sell 500 parts.

[trueblue]

Get hold of a 650 engine and put it in. Close to the same hp as the 750 and will drop straight into the 500 or 550 frame.

[kranta]

that is good idea but in finland 650 are very expensives and really hard to find.

[PeWe]

other side of the baltic sea... Sweden (Ruotsi)  http://www.blocket.se/stockholm/HONDA_CB500_motor_56463071.htm
Might still be available

[calj737]

...and 750 motor is so much durable and its so much better designed than 500 motor

Not sure where you've derived that conclusion, but it's hardly accurate or widely held. Actually, the 750 is much more complex motor and therein more opportunity for mechanical failure. It certainly is a very good motor and more powerful, but "more durable"? Don't think you're right there...

[SohRon]

One thing you haven't told us is just what it is you have to work with. Is the 500 a complete bike with a trashed engine? Do you have all of the rest, like wheels, airbox and handlebars? If so, than the truth is you'd spend far less time and treasure rebuilding the 500 than you would have to shell out trying to stuff a 750 motor into the 500 frame. It would be like trying to fit a Boss 302 engine into a VW Bug... It can be done, but at what cost?

Sorry folks aren't giving you the answers you want to hear, but facts are facts and no amount of wishing is going to change that. If I were you, I'd sell the 750 engine and concentrate on getting the 500 up and running. That way you'll have a running bike rather than a cluster f*ck you could be messing with for years to come.

JMHO

[754]

Here is the big problem. 
 750 motor leans forward 8 or 10 degrees,500 does not. Therefore huge amount of work just to get the front downtubes repositioned and neck back in place..th even good part.. Easy to rake while doing these mods.

[754]

I never consider the 754 complex..simple really compared to even a 350 twin.
 As for durable.. I know of numerous 100,000 my leg 750,s,..... Has anyone seen a 500 do that?

Maybe heard of one..a messenger. Bike in the UK maybe?

[kranta]

the bike have every think else than rear fender seat and hold this chanse think is not yet sure.  and bike is builded one time earlier. but maybe i just fix my 500 motor