KZ550 with... 550 trans, 650 block/head, 750 jug?

Hey guys!

So, I have an 80 or 81 KZ550A (I believe, haven't looked at the title or the frame in a long while). I took the bike on a year ago as sort of a "stupid project" by choice. I'm a tinkerer. I'm a big fan of one-off stuff, even if it doesn't make much sense or there is an easier route. Clearly this is one of those projects. I've dug the bike back out of the secret corner of the barn, and I'm pulling it off the back burner and finally getting around to trying to maybe kind of make a decision of which direction I might want to go with it... maybe? Haha.

I have thought a lot about what kind of powertrain I want to use for the bike. Something nuts but that still has the factory café vibe, no big radiator or throttle bodies or anything like that. So I got to researching and thinking... Apparently, the 650 block will bolt to the 550 6-speed transmission. The 750 jug can be used on the 650's with their head for essentially a high compression 750. So, if I were to find the right parts, and fabrication/wiring gets sorted out... I'd like to use the 550 6-Speed, 650 block, 750 jug, and 650 head. I assume I'd have to use all of the ignition control from the 750 as well as carbs. I'd probably have to fab up a header, and wiring could get interesting...

I couldn't find much using the search function. Has anybody done this before? Any articles or threads on the subject you guys could point me to?

-Travis

Don't know for certain but having messed with both the 550 and 650 I think you have some machining to do at the base gasket to get a 650 block onto 550 cases. Only a 100cc more, but they are different and have unique base gasket configurations to my knowledge. Also not sure how well 550 crank will take 750 connecting rods. Sounds fun, way too ambitious for my talent level. Good luck. A 750/650/550 hybrid with a 6 speed would be cool tho' on the 550 small frame. the thing might fly :woohoo:

Where I come from the "block" refers to the bank of cylinders. The KZ650 bank of cylinders will not hitch up to the KZ550 engine's bottom end. The KZ550 6-speed transmission can be installed in the KZ650 bottom end and others have done this, but to do so you must remove the kick starter mechanism. Mixing some parts between the KZ750 and KZ650 can be done, but you need to make sure the cam chain types match. Some use a roller chain and some use a hyvo chain. The cam chain, crankshaft, and cam chain sprockets all have to be made for the same cam chain type. Ed

Sounds like a career choice to me. I like the 6 speed tranny in a 650 though. Squeeze a 650/750 in a 550 frame?
Steve

Uh, the 650 already has issues with the starter clutch. I don't think you want to use the presumably weaker one from a 550. Plus the 550 has no kickstart provision if the starter clutch fails. The older 650's use a roller chain for cams. The 550 crank is hyvo for the cams. (I suppose it's possible the 550 has the same starter clutch as the 650. I haven't checked. But 550 starter clutch issues are rare compared to the 650/750 motors.)

Oh, yeah, there is also the minor detail that the 550 cylinder spacing is different from the 650/700/750.
As Ed said, the 650 block does not bolt to a 550 trans. The actual gears and shafts of a 550 6-speed trans can fit into a 650 5-speed transmission housing, which is why some 650 owners talk of running a 550 trans with a 650 motor. But it is only the actual gears and shafts that can swap.

The 650 motor will not bolt into a 550 frame without heavy modification (cut, expand, weld). The 550 frame is also lighter, thus weaker. ... so much easier to just start with a 650.

If you are really looking for a big power increase, put in a ZX550 motor (block/pistons/crank/head/cams with the ZX ignition) along with a 615 kit, and throw on Zephyr ZR550B carbs. That's about the best you're gonna do without a huge leap in money/effort. You will also need an oil cooler for that, so you will need a gpz oil pan.

Ironically, the one thing you would not have to swap is the ignition. It's pretty much the same except for the advance curve. (Your 1980 550A1 should have come with points.)

650ed wrote: Where I come from the "block" refers to the bank of cylinders. The KZ650 bank of cylinders will not hitch up to the KZ550 engine's bottom end. The KZ550 6-speed transmission can be installed in the KZ650 bottom end and others have done this, but to do so you must remove the kick starter mechanism. Mixing some parts between the KZ750 and KZ650 can be done, but you need to make sure the cam chain types match. Some use a roller chain and some use a hyvo chain. The cam chain, crankshaft, and cam chain sprockets all have to be made for the same cam chain type. Ed

Thanks Ed, we were on the same train of thought, I just used different terms haha.

I imagine some frame hackfabulation will be necessary to get the 650 motor to fit into the frame with a 750 jug on it, but hopefully not too much. I assume I'll have to mess with mounts anyway to get the sprockets to line up properly. Now it's just on to tear the 550 engine apart and source a 650 engine and some 750 goodies.

Is anybody familiar with the 750 jug swap on the 650 and what is recommended running as far as ignition components and such? I'm not super concerned about a kick starter as long as the electric works "okay" (The bike isn't going to be getting me back and forth to work, it's just a long-term probably-never-going-to-be-finished project lol).

Also, for those interested in the transmission swap, I've just stumbled across this:

KZ550 transmission swap

Thanks for the immediate responses and information so far, guys. Much appreciated.

-Travis

Unless you already have a 650 bottom end it makes no sense to try to put 750 top end on a 650. Just buy a 750 engine and be done with it.

I'd say the best thing to do with a 550, if you want to hot rod it, would be to get a big bore kit, header, and bigger carbs. Maybe cams too. Lots of 550 guys go this route.

Nessism wrote: Unless you already have a 650 bottom end it makes no sense to try to put 750 top end on a 650. Just buy a 750 engine and be done with it.

I'd say the best thing to do with a 550, if you want to hot rod it, would be to get a big bore kit, header, and bigger carbs. Maybe cams too. Lots of 550 guys go this route.

I think you've misunderstood the purpose of the project. It has very little to do with sense. Lol. I may end up buying a 750 instead of a 650, but sense has nothing to do with it I might even use a 750 engine with a big bore kit and a 650 head and run the whole dang thing off Microsquirt and E85. You're talking to someone who comes from a family that stuffs 5.3 Chevy LS truck motors with a turbo into a '74 F100. We don't do things that make much sense at all. I chopped and fabbed a café tail onto this bike, solely because the frame was free and I was bored one weekend

-Travis

How about fitting 750 sleeves into the 650 barrels, then a 811 kit?
Steve

Since you don't have a 650 already I'd jump straight to the 750. You can then bore the cylinders out to 810cc and slap in some of those cruzin image pistons. Do this and that 6 speed transmission will be needless too.

Nessism wrote: Since you don't have a 650 already I'd jump straight to the 750. You can then bore the cylinders out to 810cc and slap in some of those cruzin image pistons. Do this and that 6 speed transmission will be needless too.

That sounds way too easy... :laugh:

-Travis

Another option for something different, is to get a 70s KZ650 & install a 2000 or so ZR750 motor. or an engine unit from 90s 750 Zephyr. the zr engine numbers begin with KZ750EE, so the zr might be direct fit. the horsepower is about the same as the KZ750. I don't know if there's a wiseco kit for the ZR750.