swapping for a newer engine

Hey guys, looking for some opinions on something I'm considering.
I've got a '78 KZ650 and it's never run right since I've had it. I think the engine is just done and it needs some valve work at the very least.

Since it needs some engine work I was thinking maybe just swap the engine instead and put something newer into it.

What do you think about dropping in ZR7 engine, or similar? I figure something air cooled with carbs between 650 and 750cc's.

How about dropping a twin in there?

Anyway, just wondering what I'd be getting myself into, and if I might just be opening a can or worms...

Thanks.

Forget the 750 twin as that would require major surgery, it's entirely too tall.

A later air cooled 750 like the ZR7 might work, don't know though because I've never had a ZR7 motor.

Sure would like to try and bolt a GSXR750 motor in one though

How many miles on your motor?

I'm in early stages of a Katana750 swap into a 550 frame . I have stripped both the '99 Kat750 and '81 GPz550 that I am using . When I get some time I have to start fabricating the motor mounting hardware . Hope to have it done by next spring .

You would have more room to play with in the 650 frame . The ZR7 or even a ZR750 Zephyr should go into a 650 pretty easy . You could probably get the 1100 or 1200 oil cooled Suzuki into the 650 frame , it has more height than the 550 I'm working with .

It's funny you say that about the GSXR750. There's a '98 with 15000kms near me for $500.

One thing I'd really like to avoid is having to install the motor to find out if it's running properly or even at all. Any thoughts on how to inspect a disconnected motor, or is it just a gamble?

Thanks for the advice on the twin - I had no idea.

saszta wrote:

...got a '78 KZ650 and it's never run right since I've had it. I think the engine is just done and it needs some valve work at the very least.

Since it needs some engine work I was thinking maybe just swap the engine instead and put something newer into it...Anyway, just wondering what I'd be getting myself into, and if I might just be opening a can or worms....

On existing engine, have the valve clearances been checked, followed by a compression test, and a leakdown test? If not already done, could be very informative.

Good Luck!

Patton,
I've adjusted the valve clearance, changed coils, electronic ignition, cleaned and rejetted carbs etc... but I was kinda stubborn when I did the compression test and found that the pressure was low in 1 cylinder. Figured it couldn't make that much of a difference but now I can't ignore the blue smoke out the back and I can't synch the carbs due to valve issues.

Guess I'll have to get new coils and ignition and a few other things if I'm going to swap the engine to a different model. I'm sure that list will grow pretty long if I drop in a gsx750 injected engine. It'll probably cost me a lot less to just tear down and rebuild my current engine or would it? My current engine has 36000kms on it.

If you are the King of Cheap (like me) you can rebuild your top end into a GPz750 for around $100

Cost a lot more ($500-$750) if you are a normal person

Used GPz750 pistons Free
NOS GPz750 Standard rings $35
KZ750 cylinder block $25
KZ750 complete gasket set $35

Bore case and hone cylinders Free (I do it myself)

Icing on the cake:

KZ750 cylinder head $25
83-85 GPz750 cams $25

Took me over a year to collect the parts at those prices though, two years to get the rings.

To justify my title of King of Cheap:

Started out with a uninsulated two car garage with 15 amp 110 volt power, filled with junk.

It's now insulated with 3" fibreglass in the walls, covered with 3/4" plywood with metal on both sides, 100 amp 220 volt power with 3 phase 220 for the two metal lathes, vertical mill, surface grinder, and drill press. 5hp vertical air compressor, large sand blast cabinet, parts washer, 8 4 tube 4' fluorescent light fixtures mounted in ceiling, and a couple of work benches.

Total out of pocket expenses $0.00

King of Cheap

Wholly!
What a tight-wad you are,Steve!:ohmy:

Sandy wrote:

Wholly!
What a tight-wad you are,Steve!:ohmy:

And proud of it!

Can't hold a candle to my friend though, he has a 1/2 million dollar home with $0.00 out of pocket investment, and he owns it free and clear. He's my mentor

saszta wrote:

It's funny you say that about the GSXR750. There's a '98 with 15000kms near me for $500.

One thing I'd really like to avoid is having to install the motor to find out if it's running properly or even at all. Any thoughts on how to inspect a disconnected motor, or is it just a gamble?

Thanks for the advice on the twin - I had no idea.

You would probably have a hard time swapping any GSXR motor after '92 , but Katana's of all years are the same as early GSXR .

i know this isnt reall the route ur going but i just swaped a 05 honda 600rr motor in my z1..

"Started out with a uninsulated two car garage with 15 amp 110 volt power, filled with junk."
That's MY garage! Except that it's a one car garage.

Yes, you are King of Cheap and what you've accomplished is pretty impressive and inspiring. I'm not sure what to start on first, the garage or the bike. lol.

So, did you start out with a 650? I'm wondering if you needed to change coils, ignition, carbs (besides rejetting) or anything else other than what you listed.