Dr. Jekyll and Mr. Hyde ( a pair of KZ400s)

[Nebr_Rex]

Been busy at work putting in some hours.
Lost some pressure on no. 2 cylinder. Found out why when I disassembled
the top end. The intake valves looked good and the exhaust have carbon build up.
The problem was the sleeve on no. 2 had rust rings about half way down and at the top.
Was able to hone just about all of it out. I was also reminded of why I dislike old
base gaskets. Up next is to reassemble, find true top dead center and install my
degree wheel to take some measurements. Did some math and by removing the
base gasket reduces the volume by 1.7cc and retard cam timing 1*.


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[Nebr_Rex]

Top end is back together. Ran a compression test after a quick 1/4 turn from tight lash adjustment.
Right cylinder tested 155 psi and 162 psi for the left. This is without the engine being ran so the parts
can take a set.
2 more points of interest.
1] The timing mark is not top dead center on this engine.
2] Modified a cam sprocket. If anybody is looking to have one machined just contact me.


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[doc_rot]

Interesting...When I set the ignition on my kz750 twin I found TDC using a piston stop and the factory TDC mark was 2 degrees off.

 

[Nebr_Rex]

To index my degree wheel I had to use a dial indicator. Never paid any attention
to the timing marks before, mainly because they were hiding behind a degree wheel. Looks
it's off 4 or 5 degrees.


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[canyoncarver]

To index my degree wheel I had to use a dial indicator. Never paid any attention
to the timing marks before, mainly because they were hiding behind a degree wheel. Looks
it's off 4 or 5 degrees..

Man, that's surprising that it's off that far.

 

[Nebr_Rex]

Man, that's surprising that it's off that far.

And the removal of the base gasket should only account for 1 degree.


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[Nebr_Rex]

And the removal of the base gasket should only account for 1 degree.


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Scratch that, brain fart, has nothing to do with the altered timing of the cam because of the base gasket removal.


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[Nebr_Rex]

Installed a dial indicator on no. one intake valve.
Measurements were taken with lash set at 1/4 turn from tight and at zero lift.
Kawasaki measures at zero lash.
Valve opened at 18* BTDC and closed at 73 ABDC. Lift is .308 with lash.
That is 271* duration and 117.5 lobe center. Factory specs say 113* lobe center.
Base gasket removal can account for 1 degree, the rest has to be from chain
stretch and wear. Advancing one tooth will equal 102* lobe center.


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[Nebr_Rex]

Set valve lash to zero and duration increased to 276*.
Reset lash to .004 while checking at .040 and .050 valve lift.
At both of those measurements lobe center jumped to 115*
so I'll go with that. Valve lift with zero lash is .317 in..
Duration at .040 is 218*. Compression tested at .004 lash was
150 psi on cylinder 1 and 140 psi on cylinder 2. Advanced the cam 1
tooth, 15.65 degrees. Compression increased to 185 and 167 psi.

 

[Nebr_Rex]

Picked up some KZ400 parts. I have almost a whole bike. Basically missing the tank, seat, side covers, carbs, tach and headlight.
No title with a 3-74 build date. 2445th bike built with a 2418 engine number. Odometer shows under 7100 miles. Engine has compression.
Going to check engine over with a compression test and then flip the cam sprocket. Plan is to punch it out to 67.5mm, port the head
and some cam work.


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[Nebr_Rex]

I worked on getting the engines compression up. Started at 65lbs. on no. 1 and 90 lbs. on no.2.
Reset the valves at .007 in., two were at zero lash. Sprayed PB Blaster and carb cleaner into the
ports and spark plug holes to wash down the valves and seats. Ended up having them test at 140/150
no. 1 and no. 2 respectively. They would probably seal up some more if the engine would be run for a
while. I can't leave well enough alone. I flipped the sprocket like I posted earlier. Ended up with 165/170.
The bore diameter for the 'Cruise Image' head gasket is 66mm. That rules out a 67.5mm piston. But I
do have a set of nos KZ650 66mm big bore pistons. Bad part is it is old enough to have a 1 piece oil ring.
If I can't find a three piece oil ring. 66mm x 2.4mm I will have to use it. Compression works out to 8.9/1
before any head milling. Now to source some engine seals.


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[doc_rot]

What do you mean "flip the sprocket" ? Also why are 1 piece oil rings bad? That what I ended up with for my KZ750 pistons. I had never seen a ring like that before.

 

[Nebr_Rex]

The top of page 20 is where I started to explain what can be done to improve
the factory cam timing for the KZ400/440.
One piece oil rings were used in automobiles before the advent of three piece.
Three piece have better oil control and last longer.

 

[doc_rot]

interesting. I will have to look into some new oil rings for my build.

 

[Nebr_Rex]

Located enough seals in my 'stash' to replace any that need to be.
I have my eye on some rings with a three piece oil ring also. The cam
out of my other 400 is pitted on the nose of the cam lobes. Which
makes it a good candidate to be welded up. Plan is for 66mm pistons,
stock valves with head porting and milling to achieve 9.8/1. As for the
cam I'm looking to just add to the nose and not alter the ramps. The
eccentric valve lash adjustment will not allow much of the base circle
to be removed. To ensure I don't go to far I cut up an extra rocker box.
Going to add 1mm to the lobe to get about .350 lift with valve lash.


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[Nebr_Rex]

Accomplished a little something this weekend.
Welded up the nose on the KZ400 cam lobes.
The ground them back down on the lathe.
They are roughed in at about .015 in. taller then final size.


https://www.youtube.com/watch?v=FcFNuwdrXHU


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[doc_rot]

cool setup. think you could grind a starter sprocket for me?

 

[Nebr_Rex]

I could do a good job of grinding the teeth off.
PM me if you have something more specific.


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[Nebr_Rex]

Finally found some rings for my pistons.
Nicked a ramp on the cam. Since the plan was to use the stock ramps and just add lift.
I evil bayed another one. All the cams I've seen for the KZ400/440 have been forged steel.
The new one is cast iron. So I'm going to weld up the original cam from the engine and use
the cast iron one for a stock reference. I'll post up some pics this weekend.


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[Nebr_Rex]

Here are some pics of the piston with a KZ440 piston on the left and KZ400 on the right.
My guess is the dome volume is 9-10 cc compared to the stock pistons.
Also the two different cams, hollow forged and cast iron.


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