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

More.
 

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Be careful using hardware store rubber couplers. They will suck in at higher rpm's, and it get's worse as things warm up and they soften. This can suffocate you're engine and make it lean out. If you have metal almost all the way inside it, then no worries.
 
Thank you for mentioning that. I did not take that into concideration. But I think I'll be okay.
What is not supported by metal is basically what's between the hose clamps. And the rubber
is also a 1/4 in. thick. I changed the jetting. Jet needle is now a straight shallow taper 10A.
Not an abrupt taper like the other two sizes of Keihin jet needles I have, 1A and 2A. Increased
the main to a 160 Keihin with the needle shimmed remains at .060. Idle is good and off idle
response is great. Now the top end is lean starting around 5k. Looks like I either need a little
more taper on the needle or take the shims out and use a bigger main.


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Swapped out the needle jet from a 10A to a 1A and rode it around the lot.
Definitely lean on the bottom. Swapped in a richer 2A and still a little lean.
I will try raising the needle again and maybe a smaller main.

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Picked up some 145 jets to try. But that is going to be put on hold for a day or two.
I have a few 440s to rebuild over the winter and one of them showed up Friday.
This machine will also be getting rebuilt forks and a chain n sprockets.

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Bad part about it is that the engine had a knock. So this is a reminder that you need to check
and change your oil regularly. Because they do not make some parts for these old bikes
anymore.


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Nebr_Rex said:
Bad part about it is that the engine had a knock. So this is a reminder that you need to check
and change your oil regularly. Because they do not make some parts for these old bikes
anymore.


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what part is this?
 
On the left is one of the rod bearings for the right side cylinder. On the right
is the left side bearing. The big end of the rod and the crank were both worn
down by about .005 in.. and the exhaust valve hit the piston.

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Not much to report lately. I do have something to share.
The KZ750/4s cam sprocket bolts to the KZ440 cam.
I'll post some detailed pics later.

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Bolting the KZ750/4 cam sprocket to the KZ440 cam can alter valve timing.
Using the different holes can result in advancing or retarding the cam. Rotation
of the sprocket is counterclockwise when mounted on the engine. The following
pics will show the different positions. The first pic is of the 440 sprocket with the
highlighted teeth showing the one closest to the top bolt hole. Then the 12th
tooth to where the timing mark is that lines up with the top of the head when
installed on the engine. The second pic is the 750/4 sprocket. The same sprocket
is used on the intake ( round hole ) and exhaust ( one of the other holes dependent
on the model ). The different marks correspond with tooth closest to the top bolt
hole and the 12th tooth for timing alignment.

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With the ( round ) bolt holes lined up with the 440 sprocket holes.

The cam will be advanced this much. 1 tooth is equal to 15.6° at
the crank. I'll let you do your own calculations.

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The ( square ) hole is advanced this much.

This information is for entertainment purposes only.
I take no responsibility for any actions taken by anyone
modifying their machine.

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Just to let everyone know I haven't abandoned my projects. I've just been sidetracked lately.
Along with the KZ440 LTD bobber engine rebuild etc... . My cousin asked if I would look at his
sons mini sprint engine. They only got three races on their ' race preped ' r6 Yamaha. I was told
it never seemed to run right. Which turned out to be the titanium valve were shot and out of
adjustment. But on the third night out it started a nocking/squealing noise I was told. And this
is what I found, a broken tooth on the crank gear that drive the clutch basket. Looks like something
got caught between the teeth.


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Pics of the head for that bobber.
The exhaust port.
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And the intake port.
If you look at the first pic. On the valve seat from the 12 o'clock to 2 o'clock
position is some serious pitting. I had to break out the old Sioux valve seat grinder
to remove the pitting on the 45° cut. I usually get by with just grinding the valves
lapping the seats, but not this time. Then I narrowed the seat down by cutting the
bottom 60° cut.
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Cousin and his kid brought me a head today for their r6 mini sprint motor.
I can understand trying to keep the cost down. So instead of buying all
new titanium valves for their old head I was going to freshen up this one.
That would include a dip in the cycle shops ultrasonic cleaner and maybe
a touchup with stones by hand on the seats. Checked an intake and exhaust
valve on no. 1 cylinder and the seat and valve looked really good. Probably
be no need to touch the seats I thought. Until I seen an intake hanging open
on no.4. Maybe they should pony up the $1100 for new valves for their old head.


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The bobber is done, owner is picking it up this weekend. Besides the engine
I rebuilt the forks, installed the new chain and sprockets and fabricated a brake
stay bar. The 'builder of this machine' just bolted it to the frame, not allowing
for chain adjustment. Also started regrinding a cam today. It's not a KZ but
the factory color is also green.
 

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that's a neat process, do you plan on any post grinding heat treatment? I've heard the chill hardening on cast iron isn't all that deep
 
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