Conversion from twin to inline 4

Bike is the 1980 KZ750 with the twin cylinder.

How practical would it be to swap in a four cylinder from a similar
KZ750? I ask in light of a leaking head gasket, carb problems, and a
better reliability record for the 4-banger.

 

I guess there's a lot involved in the conversion?
I'm going to have to take out the engine and carbs anyway because of
current problems.

 

What Mark said about the insanity of engine swaps. I've done one
wildcat engine swap, and the details of the installation are what
ruined the car, even though it had three times as much power as
originally, the handling was atrocious. And I measured everything and
thought I had it all figured out. If I'd put the engine 1/2 an inch
further back, I would have been OK...

The devil is in the details. To start with, you must locate the
countershaft sprocket of the I-4 at the same height above the frame
rails and distance from the motorcycle centerline as the sprocket on
the
twin is located. That's so the drive chain will be properly tensioned
through out the entire arc of motion of the swing arm. If the swing arm
length is different, you may need to locate the countershaft sprocket
higher or lower.

This may mean you need to make up entirely new motor mounts and have
them welded in. Of course the frame will need painting afterwards.

And then, will the camshaft covers clear the tubes that brace the main
tube that goes to the steering head? Will you be able to remove the cam
cover for valve adjustments?

You might want a quiet stock exhaust system for the I-4 and this may
require you to fabricate and weld muffler brackets to the frame.

The centerstand of your twin might not fit with the clearance dents in
the I-4 mufflers, you might have to remove the handy centerstand.

You might decide to install an aftermarket 4-into-1 pipe. Those pipes
have a bad interaction with the camshaft timing from 5000 to 7000 RPM,
they make a flat spot. So you'd have a tuning problem. And you'd
probably need to make a megaphone bracket.

How do you hook up four carburetors to an airbox designed for two
carbs?
You make an adapter if you're handy with sheet metal, but maybe the
volume of the airbox and the frequency it resonates at is wrong for the
I-4 that runs at higher RPM.

So, maybe you install separate K&N filters instead?

And after you have the engine swap in place and you need any parts from
Kawasaki, any time you go into a $tealer$hip to buy parts, you're
always going to have to lie to the idiot behind the parts counter, in
order to avoid confusing him.

You can never say to him, "I've got an 750 LTD-2 with a KZ750 motor in
it and I need----"

Just as soon as he hears the KZ750 engine in an LTD-2 frame his
eyeballs will spin in circles and smoke will come out of his ears and
he'll say, "We don't have a parts fiches for *that model*..."

 

Quite likely as they are totally different bikes with different frame
designs. The 750E was a totally new design.

You might check out http://kzrider.com/forum/ for tips and parts resources.

- Nate >>

 

Completely impractical. Forget it.

 

Impractical and unreasonable people add flavor to motorcycling.
Otherwise, why go to Sturgis or any other big ralley?

I saw a Greeves 250cc MX-5 front half welded to a Montessa 250 rear
half once. The guy told me the most difficult puzzle was whether to
call the
monstrosity a Mongreeves or a Greentessa...

He was riding in the same motocross race as me. The race organizers
made him remove the horns from his Viking helmet, leaving only the
leather straps and rivets...

 

Well, yes, but people who do this sort of thing out of a "wtf not?"
impulse are fine. People who just think it might be a good idea without
appreciating the work involved aren't.