TOPIC:

I've started working on my 76' kz750B1 twin that has a bad stator and recitfier.
The stator pieces are in a box with the stater gear and chain, so I have to use the kick start to get her to run.
And she does run.
My questions is, when I use the kick start, sometimes the kick start KICKS BACK!
And it kicks back with so much power that I feel like I've hurt my foot.
I have 2 650 with kick start and I've never had this happen like this. Is there that much compression with a 750 two cylinder, or am I missing something?


Limping around, looking for an answer...

i'm no expert, but desperation has caused me to read ALOT of info on the internet,
i don't think i would be concerned too much, it has somthing to do with your ignition timing, causing the kickback, (mine does it too sometimes) but i have also read that the ignition timing set right there is preferred, remember the 750b's pistons run togehter, parallel, so you're getting all 748?ccs punching back at you at the same time, hope this helps,

Fours are easier to kick over than big twins, and big twins are easier to kick over than big singles.

cratgo wrote:

remember the 750b's pistons run togehter, parallel, so you're getting all 748?ccs punching back at you at the same time

not really, they dont fire at the same time, only one side has compression at a time, same as the 4 cylinders, the outside pistons run up and down at the same time, and the middle pistons are the same, the cams determine when the cylinder is compressing air, and the pistons are never doing it at the same time. a 4 cylinder compresses a quarter of its displacement at a time, a twin half, and a single all at once (but i didnt have to really mention the last one did i:silly: ) so, theoretically speaking a 750 twin is twice as hard to kick over as a 750 four if the compression ratio is the same for both motors, the frictional forces are the same, and the rotating mass is equal;)
Scott

I was afraid that might be the answer....so, I would like to get the starter motor hooked up on the chain with the crank to get it working.
In my box of parts I have the starter chain and gear for the crankshaft and the gear for the starter motor.
But the gear that sits on the crankshaft spins freely. Does the rotor somehow attach to the starter clutch gear to help turn the crankshaft?
I believe the rotor that was in the box of parts is the wrong one, because the center threaded hole is quite a bit larger than the threaded hole in the end of the crank. I'm still trying to get the parts sorted out.
I've looked at kawasaki.com and the starter clutch assembly goes over the protruding end of the starter gear. Should that be a tight fit? The (wrong) one I have is fairly loose.

Thanks for the answers so far, more stupid questions to come.

mariozappa wrote:

I was afraid that might be the answer....so, I would like to get the starter motor hooked up on the chain with the crank to get it working....

Hmm. I'm not sure I'd bother. It's only going to fail eventually anyway.

Both my 750s start on the first kick *most* of the time. Sometimes the second kick in the cold after having not run them in many days.

You get used to it, and you don't have to kick it much - by "much" I mean All the length of the kick stroke. If you have a good spark, half a kick stroke will get you running.... it does for me anyway...

They are bit much on the compression though. Every rare once in a while, I will get up on the kick lever with the usual average force, and I don't go down. I bet it looks kinda sill to an observer... All I have to do at that point is get back up, focus my weight, and straighten my leg and... vrooom!

I dont know. In a kick start there is a sort of a clutch with teeth and once the bike starts the teeth somehow disengage and I think yours might be locked up somehow, I can't tell but have you noticed that once your 650 starts you can actually keep your foot on the kickstarter and feel the clicking of teeth inside of the kickstarter itself? and it doesnt kickback?

mariozappa wrote:

I was afraid that might be the answer....so, I would like to get the starter motor hooked up on the chain with the crank to get it working.
In my box of parts I have the starter chain and gear for the crankshaft and the gear for the starter motor.
But the gear that sits on the crankshaft spins freely. Does the rotor somehow attach to the starter clutch gear to help turn the crankshaft?

The starter clutch is attached by three bolts to the back of the rotor, inside the starter clutch are four rollers that sit in tapered notches with springs. When the starter is engaged, friction causes the rollers to try and slide into the tapered notch where it wedges between the crank and the starter drive, and causes the crank to spin with the starter (a picture is worth a 1000 words ).

I believe the rotor that was in the box of parts is the wrong one, because the center threaded hole is quite a bit larger than the threaded hole in the end of the crank. I'm still trying to get the parts sorted out.

The threaded hole in the rotor is the same size as the threaded part of the rear axle, quite a bit bigger than the hole in the middle of the crank. I use the rear axle to remove the rotor.

I've looked at kawasaki.com and the starter clutch assembly goes over the protruding end of the starter gear. Should that be a tight fit? The (wrong) one I have is fairly loose.

It should be a loose fit, if it was tight you would be replacing lots of starters

Thanks for the answers so far, more stupid questions to come.

That's ok, I have lots of stupid answers

Thanks guys, that helps alot! Maybe I do have the right rotor.
I'm going to post in the electrical section for the rest of this stuff.
It looks like the PO was trying to convert the 77 B1 charging system to a B3/B4 system.

I would convert it to the 78-80 style also, the 76-77 reg and rec are separate and trouble prone after almost 30 years

I've seen 350 Big Horns launch guys nearly off of the bike when they kick back so it isn't a surprise that a 750 twin will kick back hard on one side.

If the 750 twin is a 360 crank like the 400's were then there is a counterbalance system in there which adds more rotational mass than inline fours but at least it's balanced!

Post edited by: KZ_Rage, at: 2006/11/21 10:06