Why does the small bevel gear go out?

R

Rudz

New Member
Had to replace mine on a new motor, never had a problem before. I did grease the new one I installed, and I had greased my old one.

I know it's a fairly common problem, just wanted to know if it was just because the motor was running dry or something else.
 
Probably poor quality control. I've seen a bunch machined off center and wobbly, which increases wear.
 
Crank might be bent. Turn it by hand and look for wobble. See which part is off. A good gear won't help a bent or mis-machined crank
 
had first wobbly bevel gear in many years today - as usual it missed the taper - loosened it, re-seated it on taper tightly, all good now

anyone know who sells a kit with black allen bolts in side covers, slant head & external CDI? got 2 more here to work on & now will check that gear on each
 
opened 2nd motor today - couldn't call bevel wobbly, but it obviously wasn't quite true - tamped it with a drift & I was able to tighten bolt a full 1/2 turn - looks good now

who makes these kits ?? are these BEkits in cali?
 
opened last of the three and the gear was good on this one

looked around some more & now I'm thinking that these kits are from CaliforniaMotorbikes
 
This is something I check on ALL new chinadolls. They tend to assemble them with a ball pein sometimes.
 
Here is one problem. This gear was very noisy producing a pulsating whine.

The center bore isn't so 'center'. Look closely and you'll see it is not concentric with the outer diameter. When it spins on the shaft it is elliptical which causes it to engage the large gear unevenly. Wear, noise and even gear failure can result.

Tom
 

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not sure I understand that pic, if that's a gear threaded onto a puller, then I'd first guess the puller is off a bit
 
crassius said:
not sure I understand that pic, if that's a gear threaded onto a puller, then I'd first guess the puller is off a bit
Click to expand...
No it isn't the puller, crassius.
You should have seen the wobble in the gear when I'd spin the crank with drill motor on the magneto side. Not only did it wobble but it's drilled way off center. So much so that it would bind against the secondary gear and then move away so the gear teeth barely meshed. The wear pattern on the teeth also showed the same condition. Anyway, when I replaced the gear with a good one the noise and pulsations went away.

Tom
 
strange, I've seen several over the years (tho not lately till this week) and all but one centered nicely once reseated on the taper - the one that didn't was due to a woodruff key too tall and pushing it one side, some filing on the key made it good
 
I've had a couple of them split or crack, which is suprising considering the high standards of Chinese quality control.The main problem I have with the bevel gear is that darned soft key. The key shears and FUBARS the key slot, So now yer talking new crankshaft to fix it right.
fatdaddy.:-||
 
They seem to come in cycles, I have seen a few machined off center lately too. And even when they are good, they often need to be reset on the key properly.
Sometimes these engines seem to be final assembled with a ball pein and a vise!
 
Hey maniac, Thats how I put them on, With a hammer and an old socket. If ya dont get it all the way down, the screw will come loose and then yer screwed. First, I make sure it's on the key properly, then beat it all the way down, then use a air hammer tool to set that darned screw in tight. A loose bevel gear will destroy the gear AND the shaft. So dont be too quick to dismiss a hammer as an assembly tool.LOL
fatdaddy.usflg
 
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