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

firebane said:
I love how it hits 9k and just takes off

I was slowly throttling up until around 7k and then just pinned it.
And Lord knows how accurate that old tach is, because it sounded like it achieved a higher
r.p.m. than what the tach was showing.

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Might have cured the off idle stumble, especially the dead spot between 3k & 4k.
I made some plastic bushings to reduce venturi size from 34mm to 29mm.
These are temporary and I'll have to make some smaller throttle bodies or
new bushings out of aluminum. They did add 1 in. of vacuum though.
But before that I dug out the modified fmu ( fuel management unit ) from
before. With it I gain about 10 p.s.I. when the throttle is pinned. I still use the
other pressure regulator to hold a base line fuel pressure. Without it the
pressure will drop to about 0 when the throttle is chopped causing the bike
to sometimes to stall. I also replaced the counter weight I cut up and the
heavier spring with stock pieces, thus speeding up the advance on ignition
and fuel curve. These all made some difference but what made the most was
adding 2 10k resistors to the top igntion module. Now the throttle can be
manipulated easily between 3k & 4k. I will need to take it for a spin tomorrow
to be sure.


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Took it for a test ride and realized more fuel was needed because
it wouldn't pull past 5k in 1st and 4k in second. Went back and turned
up the fuel pressure by 5 lbs., it ran better with more r.p.m.. Put it
back on the lift and stared raising fuel pressure. Ending up being rich
at idle. Leading to the next step. Using a wide band o2 sensor hooked
to a pulse width modulator to control the fuel pump.


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The wide band o2 sensor and pulse width modulator didn't live up to expectations.
The voltage signal out from the o2 sensor was not enough to run the pump past 20
p.s.i.. I am going to pull the fuel injection stuff off until I can save enough pennies to buy a
used oscilloscope, probably a Fluke series 90. That way I can see exactly when the
injectors are firing and for how long corresponding to cam and ignition timing. I will also
be going thru the top end with Wiseco KZ750 pistons and some work on the cam.
That will take displacement out to 463cc.

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Got the head back,had it milled another .030 of an in..
Pics are of the stock chamber, next milled at .030 and
then at another .030. Found a belt to fit my tool post grinder
so I can grind down some base circles on the can.
The cycle shop was busy so the block isn't bored yet.


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Got the block and pistons back from the cycle shop.
I have made some changes to the ignition pickup.
Moved the plate out so I could put the pickup for the
injection behind it. This was changed to fire the injectors
when the intake valve is opening at around top dead
center vs. being at bottom dead center. Firing at the
bottom of the stroke most of the fuel was injected when
the intake is closed. By moving the point when the injectors
are fired. Half the fuel is injected when the intake is open
and half when closed. Because it fired once every revolution.
Also started on grinding down the intake base circle on the
cam for this engine. That was until I about burned up the bearings.
I filled up the oil cup several times but the shaft must have
been totally dry. Disassembled the shaft and still need to clean
it up so I can finish roughing in the base circle. Then I can
dress it with a die grinder. After that it will be check by degreeing
it in the engine after the the big bore pistons and milled head
are installed. When I'm satisfied with the results I'll polish it up
with some emery cloth. The factory retarded the intake timing
several degrees compaired to other engines. If I was
going to change that, might as well advance it a few more.
Add a few more degrees of duration and .040" of cam lift. Below
are some pics comparing a stock 750 plate and modified KZ400
points ignition advancer that I was using to the new setup. That
is a 440 ignition advancer and 750 plate modified as stated above.


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More pics.
 

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Pics of the ' cam grinder '.
 

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The bearings for my tool post grinder won't be here till Monday.
So I did a little porting.



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Bearings came in today. Bought an extra pair just in case. Problem was this is the first time I used the machine. I put oil in the cup a few times, but that wasn't enough. Bearings, felt liner, the whole housing was dry. When it acted up the first time, I tore it down, cleaned it up and made sure it was full of oil.
Thinking the roughness would come out of it, which it did during assembly and the first bit of use. Now
with new bearings and some spares I'm ready to start up again.

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Done grinding the cam for now. It just needs to be cleaned up to be
checked with a degree wheel. Also did my valves. This method is a
little more accurate than my old Sioux valve grinder. That thing is out
of round about .002 for .004 total. Good enough for old pushrod V8s,
but not small engines. Next is to lap the valves, since the seats are in
great shape. Then I can tear down the top end and install the other
block and Wiseco pistons. And see what the new lobe profile looks like.
And one last thing, there is a Fluke oscilloscope on the way via eBay.

Pics are of the same lobe, before and after getting dressed down on
both ramps. And an exhaust valve.


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The valve.
 

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Pics of the old pistons and the new. Head is torqued down and I stared
to degree the cam. With valve lash set at zero on the intake, valve lift is
.358 vs. .288 on the cam.
 

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Cam is finished. Will post final specs tomorrow.
But valve lift is .350.
Pics of the opening ramp.

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Pics of the closing ramp.

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Cam timing turned out to be

43/73, 296 dur., 105 c.l., 350 lift intake, vs. 27/73 stock
63/39, 282 dur., 102 c.l., 308 lift exhaust. vs. 70/30 stock

I still need to open up the slots on the cam gear so I can advance
the timing some more. That way the exhaust will be at 110° c.l.
like the stock setting. And the intake will be at 51/65, 97 c.l..
Which is 21° more overlap, 16° more dur., and the valve closing
5° sooner. Resulting in more cylinder pressure and better breathing
because of valve events and a 10.3/1 compression ratio.

It was time consuming to get equal cam profiles by hand. I only used
a die grinder a couple of times. Otherwise it was a file and emery cloth.
Typical procedure was to remove the rocker box, cam caps, chain, cam.
Remove some metal and reinstall everything. The check the degree
wheel pointer for t.d.c., then valve lash and set up the dial indicator.

.

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The mailman dropped off a package the other day.
 

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Finished with the cam. Had to trim down the right side base circle.
It had some negative valve clearance by a few thousands. Advanced
the cam one tooth (15.6° ?) ending up with these measurements at
the valve at zero lift.

Intake 48/65 (stock 27/73) 98.5° l.s. (113°), 293° (280), .350 ( .305?)
Exhaust. 71/28 (stock 70/30) 111.5° l.s. (110°), 279° (280), .308, 76° (57°) overlap

Summary: intake advanced 14.5°, 13° added duration, closes 8° earlier
exhaust advanced 1.5°, overlap increased 19°
 
Fired it up for the first time today. Ran 'alright' up top but lousy down low.
Swamped jet needles, that made an improvement. Then I noticed the head
pipes turned a blueish/purple. Checked the timing mark against the rotor
reluctor alignment. Yep, timing was little retarded. Elongated the holes in
the timing plate by about an 1/8 in. Timing looks real close. Need to
retorque the head before I can check it with a light.


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Update:
Welded up some duct work to run filters while I experiment
with the relocated pickup coils. I used some of that aluminized
exhaust tubing from the auto parts store.The low carbon crap
doesn't weld for shit. Along with some rubber plumbing connectors
from the hardware store. Topped with some K/N filters for a
Triumph. It idles ok and top end sounds good. But just above idle
to about 6k is lean. Jetting is; stock 35 pilot, raise .060 in., idle mixture
screws 3 1/2 turns out and main up from 88 to a DynoJet 130.
Needle is a 2A, same taper as a 1A but starts sooner. And way
smaller then a 10A. Going to try raising the needle some more.
Thought I would throw this out there, maybe it could help someone
else running CV carbs.

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