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

Nebr_Rex

Member
Thought I'd post up my latest project(s).
My pair of KZ400's.

First pic is of the Dr. Jekyll bike. Plans are to keep this one basically stock
except for the 440 with a milled head, round slide carbs,440 forks (flipped caliper).

Second pic is of the second go around for this bike.
It was first built a couple of years ago with the engine that's now in the other bike.
It was has 36mm forks, KZ550 swing arm, dual disk brakes and 2.15(wm3?) rear rim.
(120 rear/100 front)
Still have to reinstall the quarter fairing,seat, rear sets, aluminum
fenders and non stock gauges.
Need to modify the upper shock mounts and redo the tail.

Over on the KZ400 site someone claimed to make 55 h.p. with a bored out 440.
I think I can do better then that, stock being 40h.p. at the crank.
I've already acquired some n.o.s. Wiseco pistons to use.
Going to back cut the transmission also.
 

Attachments

Nebr_Rex

Member
Got a few things done to Mr. Hyde this weekend.

First removed the tail and old battery box,will be using a ballistic battery mounted in the tail.

Second, moved the upper shock mounts for two reasons,
1, shocks to be used are longer
2, KZ550 swing arm is wider than the original
But.....the down tubes are to wide so I'll have to put them back behind and up against the frame.
Will be only be gaining an inch or so in distance between mounts, but should work out better for ride height and clearence.

And 3, fired up the lathe made a rear axle spacer.


.
 

Attachments

Nebr_Rex

Member
Started tearing down the engine for Mr. Hyde today.
Everything looks good, now to see about taking some weight off the rotating assembly.
And bore the block,back cut the trans....


...but first the head needs some attention.....
 

Attachments

Nebr_Rex

Member
Found something out about the rods also.
I knew the bearings and pins were the same,excluding the turbo pin at 16mm.
The 440 rod is about 1/4 in. longer.

(Correction...bearings and pins are the same as the KZ650/750 4s.)
 

Attachments

Nebr_Rex

Member
Not much to report.
Finished tearing down the engine and sent the head the machine shop to be milled.
Soaked the head and cases in Pine Sol over night.
They needed a little scrubbing , but all deposits were softened up for easy removal.
I think with a little agetation or movement of fluid such as a pump it will work better.
Might have to replace the solvent in the parts washers with Pine Sol. 8)
 

Shermanator86

Big guy on a little bike
Nebr_Rex said:
I have some new carb boots for the vm34s,look a little bigger then the original.
Looks like you got a nice start man.

Just something for thought, on the original head on my bike the previous owner had over tightened the screws on the carb boots and actually busted up the threading and surrounding boss. Don't know how easy that is to do but to prevent it from happening with my new one I just made some studs out of some bolts I just cut the heads off.


I'll be watching this thread for sure though, I know ever since I read the thread on that guys race bike over on the twin owners forum I've wanted to throw some money at my motor like that to.
 

Nebr_Rex

Member
What gave you the idea I have trouble with intake bolts?
The big carb boots are on purpose.
They are for vm34s Mikunis which are a round slide carb not the stock bs36 Mikunis.
Along with the port that is going to be bigger,but relocated 3/16 in. horizontally and 3/16 in. vertical.
 

Nebr_Rex

Member
Also while I was home this weekend I picked up my head
Had it milled just enough to remove the lip the factory leaves.
This takes off 3 cc from the chamber.
I measured the head on the other bike that I had already had milled before(33 cc) vs. a stock(36 cc) vs. a early 400 head (34 cc).
Along with 1 cc for removal of the base gasket and using 1194.
Will bring the piston to zero deck height.
And a static compression ratio of about 10.6/1 from the factory 9.2/1.
If the factory rating is correct then my math should be close.

221.5+27/27=9.2. 27-4=23. 221.5+23/23=10.63

You can see the line I scribed on another heads combustion chamber for reference.

But,I am not using stock pistons.
The pistons are from an old Wiseco big bore kit for the 400.
Same bore as the 440 with a dome like the early 400s.
Listed at 10/1 on the paperwork, on my application it'll be 11.8/1. ;D
And if that's not enough I have other option yet.
 

Attachments

Nebr_Rex

Member
And one last thing, stock crank weighs 15 lbs. 5.2 oz..
Mine weighs 12 lbs. 4.0 oz. so far with a couple more or so to come off.
Here is a pic of the crank as pulled from stock engine.
 

Attachments

teazer

Active Member
DTT BOTM WINNER
Interesting project. Are you sure about those 34mm carbs? That's a big carb for smallish 4 stroke cylinder.
 

Shermanator86

Big guy on a little bike
Nebr_Rex said:
What gave you the idea I have trouble with intake bolts?
The big carb boots are on purpose.
They are for vm34s Mikunis which are a round slide carb not the stock bs36 Mikunis.
Along with the port that is going to be bigger,but relocated 3/16 in. horizontally and 3/16 in. vertical.
Wasn't saying you would have any problems, just stating what happened with mine.
 

Nebr_Rex

Member
Shermanator86 said:
Wasn't saying you would have any problems, just stating what happened with mine.
Sorry about sounding a little harsh.
Did you use the little trick I learned the hard way years ago?
That is leave a nut on the bolt to help clean up the cut so you can get a nut on said bolt.
But by all rights when inserting a bolt/stud into aluminum we should be using anti seize.
And how many of us have used anti seize on carb boots? I know I have'nt.

On a side note about head milling and pistons for the 400,use the Wiseco KZ650 piston with the above mentioned milling will net you :65x62,411cc,10.45/1( early head ) and 9.65/1( late head )
With the 440 use the Wiseco KZ750/4 piston with the above milling will net you :69x62,463cc,9.3/1.
The valve pockets are not at the same angle but will work with the stock cam.
 

Shermanator86

Big guy on a little bike
Nebr_Rex said:
Sorry about sounding a little harsh.
Did you use the little trick I learned the hard way years ago?
That is leave a nut on the bolt to help clean up the cut so you can get a nut on said bolt.
But by all rights when inserting a bolt/stud into aluminum we should be using anti seize.
And how many of us have used anti seize on carb boots? I know I have'nt.

On a side note about head milling and pistons for the 400,use the Wiseco KZ650 piston with the above mentioned milling will net you :65x62,411cc,10/1
With the 440 use the Wiseco KZ750/4 piston with the above milling will net you :69x62,463cc,9.3/1.
The valve pockets are not at the same angle but will work with the stock cam.
No worries, I wish I had thought about using a nut on the end of the bolt. I just ended up hitting the end with a file to clean it up.

How much porting are you planning on doing to the intake side of the head? I've heard that there is a lot to be gained with these engines getting them to breath a little better.
 

Nebr_Rex

Member
The 440(and late 400) head is actually really good for stock or slightly modified engines.
The ports have just about the same crossection area as the early KZ1000, (73 - 80).
And the valves are the same size as the late KZ1000(81 - 2002), which are bigger than the early .
What I am building is not going to be fun to ride stop light to stop light, pretty much to the limit.
There are some things that can be done and I'll show them later.
A person will have to be carefull because some places that could use a little 'improving' are thin walled in the casting.
 

teazer

Active Member
DTT BOTM WINNER
Nebr_Rex said:
Yes I'm sure about those carbs.
Stock the power peaks at 8500, Mr. Hyde will peak at 10000.
62mm stroke, 10,000 Revs mean piston speed just over 4,000, so that's possible if rings are thin enough, but pushing things as you said. Gas velocity through the carbs is 252 to 280 depending on how large you go on the bore. 300 is a nice number for that which equate to 32mm carbs.

It's doable but may be a little short of low to mid range. It'll be interesting for sure.
 

Nebr_Rex

Member
I haven't had much time to work on the crank lately.
But it's a little lighter now,down from 15lbs. 5.2oz. to 11lbs. 8oz.
Still have a little polishing to do on the crank and the rods are next.
After that off to be shot peened etc..
Also the forged pistons are matched and only 2 grams heavier the stock.

.
 

BLSully

New Member
Nebr_Rex,

You just posted on my thread making sure I knew about the 2stroke vs 4stroke restrictor on the VM30s for my KZ400.

Your thread, while short, is exactly what I needed to read! I don't have near the skill or resources you do, but this is the direction I want to go with my motor...slight compression bump....I'm not too worried about a 10k redline, but I am curious about a couple things.

1) I know the KZ400 has a balancer due to the 180 firing... how does the lightened crank affect that? or... does it not affect the balancer as long as the crank itself is balanced (like any normal engine w/o balancers?)

2) I take it the Weisco's were a straight drop in since you said the pins are the same, and they have the same 64mm bore as the stock 400 motor?

Appreciate your documentation here... I'm sure I'll have more questions as the bikes progress through the winter.
 

DTT Sponsors

www.dimecitycycles.com
www.cognitomoto.com
https://www.townmoto.com/collections/vanson-leathers
www.speedmotoco.com
www.CITYLIMITMOTO.com
www.jadusmotorcycleparts.com
www.lostapostlejewelry.com
www.sparckmoto.com
Top Bottom