Zoom Gears Not Aligned

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xlite

New Member
I noticed on 3 of the slant 80cc from Zoom that the gears on the right side are not alligned. Aside from the gear wear issue on one the crank is so far right the flywheel is contacting the case. Shim something up on the magneto side?

On another it appears the clutch shaft is too far to the right causing gears to be offset in the other direction. Maybe something shifted when banging that shaft out to work on the clutch. Shim something up on the drive gear side?
 

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I did notice a few washers on the crank when i took mine apart.
No rubbing issues anywhere though.

My primary drive gear is offset a little right of the clutch gear.

What exactlly is rubbing the flywheel is inside the crankcase?

The clutch shaft "Countershaft" should be shimable.
Put an indicator on the end of the shaft and measure the side to side movement.
That measurement is prolly the most you could offset it.
It would have to be shimed inside the Case.

Other than that i think you could use some shims to space the gears out some.
But the shaft and bore of the gears are tapered for a press fit.

I'll have to go over some of my pics and see if i could figure a way to shim things.
 
Riding Rich said:
My primary drive gear is offset a little right of the clutch gear.
What exactlly is rubbing the flywheel is inside the crankcase?
Click to expand...

A guy I did a bike for last year said it started making a huge racket then locked the back wheel. Pulling the top end showed no problem with piston/rod but then noticed flywheel was jammed against engine case. I then inspected two of mine and noticed alignment issues.

They are running fine but it can't be a good thing with those gears not fully meshing. At least it's encouraging to know others are out too.

Riding Rich said:
The clutch shaft "Countershaft" should be shimable.
Put an indicator on the end of the shaft and measure the side to side movement.
That measurement is prolly the most you could offset it.

I'll have to go over some of my pics and see if i could figure a way to shim things.
Click to expand...

My clutch shafts are locked solid into the left side bearings. No play at all. Very difficult to remove w/o damaging that soft thread on the chain drive gear end. Two very thin keyed washers between that gear and the bearing. I'd be very interested in what you come up with.
 
guess i'll have to take a look.

Soundls like something wore out on the one with the jammed flywheel.
Did you get the bottom end apart to see what happened.

This is interesting.

How many miles are on that motor? any idea.

My Pk sure runs strong, very strong, but this is my first 80.

My other motor was a Grubee GT-2B 48cc.
I have about 3000 / 3500 miles on it and it's wooped.
Will still run but not so good.
Never seemed to pull me like this PK.

I suppose if i run into trouble down the road i'll create a Grubee / PK hybred.
Take the good Grubee Parts and the good PK Parts and have an engine that is the best of both wotlds.

With the shaft being tight it would have to be the way the cases are machined.
Hopefully the 4th Q from this year fixed some of the problems.
 
Riding Rich said:
Did you get the bottom end apart to see what happened.
How many miles are on that motor? any idea.
Click to expand...

I didn't go beyond pulling the clutch and top end. Zoom sold me another engine almost for free so I never even sent it back. I love those guys.

The speedo said 24 miles. Against my recommendation he was using 20:1 synth but I'm sure that had nothing to do with it.

Riding Rich said:
With the shaft being tight it would have to be the way the cases are machined.
Click to expand...

Looks like brearing hole vs shaft dia clearance issue. Next one I'm probably going to take some metal off the shaft so it fits loose so a hammer won't be needed to get that clutch back in.
 
Well hammering could have damaged the bearings enough to cause premature failure.

Being too loose would be bad too.

I was able to slide my crankcase halves together over the shafts.

Wonder if the shaft wasn't bent a little.
 
Riding Rich said:
Well hammering could have damaged the bearings enough to cause premature failure.

Being too loose would be bad too.

I was able to slide my crankcase halves together over the shafts.

Wonder if the shaft wasn't bent a little.
Click to expand...

No bearings ever got hammered on that engine. The one on my bike did get hammered but there was never any failure at all. And you are confusing crank shaft with clutch shaft. Personally I've never split an engine case.

I'd be glad to part with this engine however I'd have to charge more than Zoom would for a new one seein' as how attached I've become. :)
 
you had mentioned a hammer.
I guess that was a bad assumption on my part.

My PK is running so sweet I hope it lasts.

My grubee cant even begin to compare.
 
Riding Rich said:
you had mentioned a hammer.
I guess that was a bad assumption on my part.

My PK is running so sweet I hope it lasts.

My grubee cant even begin to compare.
Click to expand...

We are taking about two different bikes (actually 3 in post #1). One that I built for someone that failed due to flywheel hitting case. Another bike that I currently ride myself and hammered the clutch shaft in and out a few times. I'm encouraged to find all these bikes probably suffer from some misalignment of the engine gears and it's no big deal.

There is no doubt these slant engines got more balls. Just trying to start them tells you there's big time compression going on.
 
When I first got my zoom engine, I took off the clutch cover to take a look
at it. On the engine I recieved, I noticed the gears were misalignment a little.
I also notice the flower nut was turned way out also. I had a hard time trying
to get the clutch arm adjusted right. I did not want to back off the flower nut
anymore than it was already. I could pick up the back of the bicycle and the
rear tire turned pretty fast with the clutch handle lever in on the handle bars.
So I decided to run the engine as is and let the clutch pads wear down enough
till the back tire stopped turning when I picked up the back of the bicycle. The
clutch pads did finally wear down enough for the rear tire to stop turning with the
clutch handle in on the handle bars. Whether doing it this way was right or wrong ,
the engine still runs great and pulls good. I am just hoping the clutch holds up enough
till I finally get to adjust the flower nut in.
 
Hey charged.

I know Norm has a thread on adjusting the clutch spring thats inside the motor.
Guess that coulda been adjusted but i dont see anything wrong with letting it wear in a little.

I'ts gonna do that no matter what.
 
xlite

I have measured and caluclated the compression to be in the 9:1 + area.
And i am fairly accurate with my methods.
So yup i'm sure that is the major contributor to the huge power.
Along with real nice stock porting.

I'm not wooried about the gears myself either.
The parts are soo cheap if i can get 4000 mi on and engine for 99 bucks i'm more than happy.

Hopefully there won't be any trouble getting parts in the future.
But really i don't expect there will.
 
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