Stuffing an 850 in a 650.

[gsrick]

Has anyone tried this yet. I've got an 82 650GL I'm turning into a scrambler, but I'm not sure of the engine condition yet and was curious if anyone has put an 850 engine in one. I have a few 850 engines and it would be a boost in power over the 650 if it fits. Nothing really planned as of yet, just considering it. I figure it may be too tight of a fit, but then it never hurts to ask if anyone has gone down this road before or have see it attempted in the past.

[Steve]

I have not tried it, but have owned both bikes and can tell you that the 850 is much larger than the 650. Since things are VERY tight on the 650, I don't see stuffing an 850 in there without modifying the frame.

"Boost in power"? Dream on. Factory numbers show the 650 at 72 hp, the 850 at 78 hp. Yeah, there is a bunch more torque, but outright horsepower isn't that much different. The 650 will outrun an 850. Partly because it makes almost the same power, but mostly because it's about 80 pounds lighter.

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[hampshirehog]

There was a bloke on here who claimed he'd managed to shove a 750 lump in to a 550 frame without cutting things. Might have been BS but I seem to remember he posted a photo.

The shaft drive set up would probably add some other issues as well as the size difference.

[Steve]

The shaft drive set up would probably add some other issues as well as the size difference.

Considering that the 650 that would be the intended recipient is already a shafty, it wouldn't be as bad as you might think, but the 850 is definitely wider and taller, probably longer fore-and-aft, as well.

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[gsrick]

It was just an idea. I may try stuffing an 850 lump in there when I tear it apart and see just to see.

[Steve]

It <might> slide in if you have the valve cover off, but you'll never get the valve cover installed later.

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[gsrick]

It <might> slide in if you have the valve cover off, but you'll never get the valve cover installed later.

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[Chuck78]

I don't believe the exhaust spacing will work out very well whatsoever, and may be a complete deal breaker. You will want to double-check that before even considering it, interference with the frame cradle front tubes.

Besides, the 673cc closed chamber raised intake runner engine is far more efficient than the 850 Hemi.


I was looking at doing the opposite, putting a 740cc GS650E chain drive engine into a Rickman road racer frame that had the spacing for a GS 750 / 850 / 1000 / 1100 and Z1 z900 / kz900 / KZ1000 / GPZ 1100.
The 650 engine can be hopped up pretty nicely and you can put web camshafts in it, and it is significantly narrower and substantially lighter than the 850 engine. It did not make sense for a retro roadracer or even Cafe Racer / sporty twisties canyon-carver corner-burner bike build to put the bigger heavier wider engine in if I could fit the 650 engine in there. Far superior top engine design, weight, and size.

Unfortunately the frame cradle tubes were completely in the way and the 650 engine would not fit the frame that was designed for the 850 cylinder head spacing.
I'm fairly confident in saying that the same would be true in reverse. You would have to fabricate new frame cradle tubes, and you would have a much wider and heavier engine. 135 lbs versus 195lbs on the chain drive versions.

[scratch]

Here in the western world, most of us ride motorcycles because we enjoy the ride not just because we need to get somewhere. Mosly when I ride, I'm not going anywhere and... I'm smiling.
It doesn't have to make sense to be a fun project.
So the question becomes.
Is it worth doing it for the fun of it?

[gsrick]

I don't believe the exhaust spacing will work out very well whatsoever, and may be a complete deal breaker. You will want to double-check that before even considering it, interference with the frame cradle front tubes.

Besides, the 673cc closed chamber raised intake runner engine is far more efficient than the 850 Hemi.


I was looking at doing the opposite, putting a 740cc GS650E chain drive engine into a Rickman road racer frame that had the spacing for a GS 750 / 850 / 1000 / 1100 and Z1 z900 / kz900 / KZ1000 / GPZ 1100.
The 650 engine can be hopped up pretty nicely and you can put web camshafts in it, and it is significantly narrower and substantially lighter than the 850 engine. It did not make sense for a retro roadracer or even Cafe Racer / sporty twisties canyon-carver corner-burner bike build to put the bigger heavier wider engine in if I could fit the 650 engine in there. Far superior top engine design, weight, and size.

Unfortunately the frame cradle tubes were completely in the way and the 650 engine would not fit the frame that was designed for the 850 cylinder head spacing.
I'm fairly confident in saying that the same would be true in reverse. You would have to fabricate new frame cradle tubes, and you would have a much wider and heavier engine. 135 lbs versus 195lbs on the chain drive versions.

It is just a question of curiosity, as I seem to have gathered a bunch of 850 engines over the years. Nothing is in the planning stages and I have no desire to start reworking the frame to make one fit