1981 Kz650 head questions

Hello everyone. I have not been on here for a number of years. I have my bike torn down for some engine work and could use some advice.

1. I cannot seem to remove the head from the block...any tips? I have the block removed from the crankcase and I have the cams out.

2. Since I have had everything torn down for so long I was thinking I need to do some engine upgrades. If I recall I can get a 750 block and bore it out to a 883.... do I only need a 750 block or do I also need the head? I am just trying to get some more power since my wife will not let me get another bike

Thanks guys!


Jeff

Did you remove the 2 bolts that are down inside the camshaft tunnel? Sometimes folks overlook them and break the fins of the head trying to pry it off the engine. Ed

650ed wrote: Did you remove the 2 bolts that are down inside the camshaft tunnel? Sometimes folks overlook them and break the fins of the head trying to pry it off the engine. Ed

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I don't think I did. I did not break any fins I just put it aside for a few years

Ooops....

Well onto question 2. Anyone Work On The 1981 kz650 car h1?

The later zx750 unitrack motor is the most powerful at 86 hp, it has more cam and bigger valves and would be a better head for power tuning.

I'd be cautious about boring out too far, the liners get really thin and can cause problems.

So would this bolt right on and allow me to go to a 810 kit later?

pages.ebay.com/motors/link/?nav=item.vie...391191665382&alt=web

Also what's with the $149 810 kits on ebay? Anyone use one?

Thanks,

Jeff

The cheapo 810 kits are made in China, despite shipping from Japan. lots of people have used them with no big problems yet it seems. There has been quite a lot of discussion on these all over the net and here.

Not sure on the 750 block, I know it can be done and have ridden such a conversion.

Your kz650 has the later hy-void camchain I take it?

Tyrell Corp wrote: The cheapo 810 kits are made in China, despite shipping from Japan. lots of people have used them with no big problems yet it seems. There has been quite a lot of discussion on these all over the net and here.

Not sure on the 750 block, I know it can be done and have ridden such a conversion.

Your kz650 has the later hy-void camchain I take it?

Not sure. Clearly I need to do some research on capabilities. Those pistons are temping at $149. But I will probably wait until I can get quality parts this winter (bonus time). I am trying to get a head start on tracking down and figuring what used parts I need to source.

The earlier kz had a bicycle type camchain, later ones and GPz/ZX series were hy-void. You really want to check this before going further.

What I really like about the z650 is the smooth and tractable motor, not as peaky as the late GPz but maybe the bottom and midrange power is worth more than 10 or 15 horsepower at the top. Keeping the mild 650 cams but using the 750 block could be a good solution. the bike I rode was just this and had a really nice tourquey feel.

Tyrell Corp wrote: The earlier kz had a bicycle type camchain, later ones and GPz/ZX series were hy-void. You really want to check this before going further.

What I really like about the z650 is the smooth and tractable motor, not as peaky as the late GPz but maybe the bottom and midrange power is worth more than 10 or 15 horsepower at the top. Keeping the mild 650 cams but using the 750 block could be a good solution. the bike I rode was just this and had a really nice tourquey feel.

OK it looks like I have the hy-void. I have the rubber cam chain guides instead of the idler sprockets.

The hyvoid camchain makes tuning easier. The later GPz zx750 unitrack cams have a 0.5mm base circle cut and 286 degrees duration, so check your piston/valve clearances carefully if you start mixing GPz and 650 bits.

OK I bought a 1983 Kawasaki KZ750N Spectre cylinders with Pistons ($75).

I think I want to do some performance upgrades but I don't want to dump in a bunch of money.

Plan:

1. kz750 block with pistons.

2. Do some head work myself. I could use some tips here if anyone has some good threads to point me to. I think I will keep the kz650 head and do some porting and polishing since that is mostly my time instead if money. I will probably be doing what is considered a mild porting since I don't want to ruin anything.

3. Carbs I have the Mikuni vm24ss right now. I would guess that even with a stage three jet kit these won't be powerful enough..... any ideas?

I am not sure if I want to stick with the stock airbox or pods.... if I get different carbs I assume I would just need to get air box hoses and carb boots to fit the stock box if I don't want to go with pods?

4. Exhaust. I was looking. To go 4 to 1 with the exhaust at z1. Anyone have these and like them?

Thanks for taking a look and any help would be great. I will start a new thread once I get my parts together.

Jeff