TOPIC:

i am starting to build up my '77 kz 1000 engine for my bike. i just removed the head and found 2 bent intake valves. this worries me.

i would like to know the benefits of putting on a "j" model head to my engine as far as power and torque.
and also what year of j model head would be the best.

thanks

Bent valves = timing chain stretched, cam chain timing wrong, shot valve springs, sevely over-revving, lack of valve clearance, or probably a number of other potential problems. I suggest you figure out why these were bent before putting a new head in. If you do go with a "J" head, they have bigger valves and if you are running cams and/or higher compression with some porting, will allow better breathing. The downside is that you need to use adapters for the cam chain to work... APE makes these bits and I don't have any info so you will need to check their catalog and talk with them.

Checkout this link at APE for details about installing a 'J' head on older Z1/KZ engines. There are many things that must be considered:

www.aperaceparts.com/tech/techkz1000.html

Putting our adaptor in the head is the easy part. The J head has larger combustion chambers and this will cause a compression loss of about two points.

Higher compression pistons are a must.

Jay
www.kzzone.com

What does '2 points' mean?

Is it like 8.7 down to 8.5 or is it 8.7 down to 6.7?

That's right... 8.7:1 to 6.7:1... if you decided not to go with higher compression pistons you would have some great advantages:

1. You would no longer be forced to burn expensive gasoline... you could burn fuel oil or something

2. No more speeding tickets!

3. Bike will start at 125 degrees below zero easily

(JOKE)...

On a more serious note, I would figure out what bent the valves before putting more money into new ones. If you have a cam chain that slipped a tooth or something, you will only damage new valves if the problem isn't resolved.

WierdGeorge sez,

That's right... 8.7:1 to 6.7:1... if you decided not to go with higher compression pistons you would have some great advantages:

Ah-ha! So this is the ticket if I want to add a mechanical blower! Else, I bore the block, buy some stock GPZ1100 pistons, swap the head and crank from the 'J' donor bike, and away we go with less complicated mechanicals/tuning.

On the topic of mechanical blowers, I can't find much on-line.
Any pointers?

Guess I'd need some modded guides as well??? Manual is at shop and can't get a look at it.

Bet it's a lot less work to put KZ1000 pistons in the 'J' for lowering compression prior to blowing. Too bad it puts an end to styling with the kickstart.

Not that I'm actually gonna do any of this stuff, I'd rather spend time riding and stock has plenty of power for this old guy. It fun to imagine though and who knows, maybe one day when I don't have to work...

BTW, do you know where to find kz1000A and police service manuals on line? Have a paper copy for KZ and nothing for police. Would be nice to have both on the laptop for back of envelope engineering at the bar...

Thanks again for BS carb tips on my GS1000. She's running good now. Alas, I have decided I do not like the feel of a shaft drive bike. Too much lower brain stem reflex required in corners and I'm too old and brain is slow. It's getting to be so bad that a hot babe will walk by and by the time my reflex says to turn and look for the rear view, she's too far away for any (in)decent detail


-Duck

KZ pistons and J pistons have the pin holes in different locations. J models have shorter rods, so the pin holes are lower in the piston. The difference is about .050"

Jay
www.kzzone.com

well took some of the engine apart. didn't see any marks of valve hitting head. but i did find that the front timing chain guide is broken.

head still looks good. no valve seat or head damage. i think this might have happened when i tried to turn the engine over by hand and it got stuck. also the old timing chain tensioner was broken. so i will dive into the bottom of the engine and repair all of the broken parts with new cam chain.

i am going to run this engine, but i will be rebuilding all parts of it.

thanks for the information and help!!!!!