Kickstart issues continued...
Well it took me a little bit to gather up some photos. Recall that among the engines and cases that came with some parts bikes were examples that have the cases blown out in the area of the kick starter shaft.
My guess is that this not some fatal flaw in this motors but rather something that can crop up if maintaince is not kept up or if one does not check certain wear points from time to time.
First, let me say I don't think the 465/490 has to be a hard starter at all. As an example, my 490 starts within 3 kick cold and one hot. But this only came after elimination of air leaks, a carb cleaning and some careful jetting. Obviously less kicking will greatly reduce the wear in the kickstarter mechanism (not to mention the owner!).
Minimizing kickback is also important. Ther are a few sources of kickback but certainly incorrect ignition timing is a big one. This can happen if the stator plate is off the factory timing marks or perhaps from a misaligned flywheel. In fact, one of my parts motors had a bad key and there were marks where the flywheel spun on the crank at one time.
If the bike kicks back, it seems the kickshaft shaft can rotate backwards until the paw to jams against the case stop. This is because the gear # 2 is unable to release as it would if the bike had started with normal rotation. Under this condition I think the shaft tries to rotate around the paw. If there is enough energy it busts out the case.
It is interesting to see in the photo how the case is broken in a straight line from the paw stop through the center line of the hole for the kickstart shaft.
As far as other wear issues, I ran across several. The clutch cover is made of light weight magnesium that is subject to wear in the kickstarter shaft bore. When the bore is worn the shaft can wiggle a bit and the seal can leak.
The face of the hole can also wear letting the shaft move in and out of the case more than is normal.
As I had a good cover to select from, I made no attempt to fix this for now. In the future I may resize the bore by making a bushing.
I found that one of my kick start shafts had rounded off in the paw area. Someone had repaired it by welding up the paw in order to square it off again. I am speculating that the paw was able to jump over the case stop because of excessive play in the clutch cover. Or maybe it was just reassembled incorrectly.
Here are photos of the welded kickstart shaft and the kickstart assembly in the engine case. Note the kickstart return spring.
I mention the kickstart spring as this needs to be checked also.
Here we have 3 springs. The tang on the right spring that goes in the shaft is broken but the other two look fine...
But wait, a closer look reveals this
More to come...