Garelli Monza Broken Internal Sprocket

What we got here is a Garelli Monza GT with a broken pedal shaft sprocket, the larger internal sprocket that connects the pedal shaft to the transmission.

Exploded.

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When I initially bought this it ran fine but had a weird knock to the pedal shaft. It was alarming at first but never seemed to get worse (seller had an explanation for it). Upon inspection there was dark dust and metal debris in the transmission oil and cases. I cleaned the internals and replaced the affected bearings and seals. When the pedals finally got mounted it was revealed that metal was rubbing on metal internally and it needed taken apart again...

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Re: Garelli Monza Broken Internal Sprocket

Clutch cover off

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Starter Plate off

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Order of clutch pieces

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Re: Garelli Monza Broken Internal Sprocket

Grab it

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Pull it

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Bop i...All Clear

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Re: Garelli Monza Broken Internal Sprocket

Here's the wiring harness

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This grounds the engine to the frame

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Disconnect all that and remove the flywheel

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Re: Garelli Monza Broken Internal Sprocket

M19 x 1.0 Puller

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Order of the sprocket pieces

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All clear

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Re: Garelli Monza Broken Internal Sprocket

Remove the engine mounts and take the top mounting piece off; the engine will not come out unless you do.

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Remove the little rubber mounts in the case

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Remove more things

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Re: Garelli Monza Broken Internal Sprocket

Remove the cylinder

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Piston has cute little port

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Super Rare Pic of monza cylinder porting

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Re: Garelli Monza Broken Internal Sprocket

Undo the case bolts

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Don't forget these lil' guys

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Split that shit

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This last picture is from the first time the cases were split

Re: Garelli Monza Broken Internal Sprocket

Left case w/ primary shaft

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Output Shaft

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Right side case w/ pedal shaft and broken sprocket housing

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You can see a lot of the black dust/grit and little chunks. all that came from inside the cases

Re: Garelli Monza Broken Internal Sprocket

This shim goes on the primary shaft and is super important. Don't forget it.

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These are from the last time the cases were apart

Re: Garelli Monza Broken Internal Sprocket

Which brings us back to the original topic, the metal on metal grinding from the pedal shaft. The culprit turned out to be the woodruff key on the pedal shaft.

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I removed everything off the pedal shaft except that circle piece, making sure that nothing would interfere with the transmission gears. Which it didn't. Sadly, I did miss that the woodruff key could hit the cases if the pedalshaft moved. Total oversight that I should've caught but nothing ruined.

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Re: Garelli Monza Broken Internal Sprocket

I used a torch and hammer to remove the circle piece and woodruff key

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I put everything back together and decided to cut spacers so the pedals would feel smooth, have a little resistance, and stay centered.

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Re: Garelli Monza Broken Internal Sprocket

This spacer was some aluminum tubing I had that luckily fit perfect. I got it from onlinemetals "0.5" 0.84" OD x 0.11" Wall x 0.622" ID Schedule 40 6061 T6 Extruded Aluminum Pipe". The washers were originally inside the engine on either side of that circle piece. All in all it worked out very well. Eventually I would like to paint the spacers black.

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This is that broken sprocket and how it went on that circle piece. This is probably a common design of some sorta freewheel. The chain is really close in size to a tomos internal chain except the internal chain on the Garelli has slightly thicker rods/posts and way less links.

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Ultimately there probably was some way to leave all that stuff on the pedal shaft or to internally space it. This is how I did it and don't think it makes a difference. Only advantage is when converting to footpegs down the line, the cases won't have to be split.

Re: Garelli Monza Broken Internal Sprocket

What ya go do wit da pieces ya took out?

Re: Garelli Monza Broken Internal Sprocket

Looks like it uses noi 1 speed internals.

Re: Garelli Monza Broken Internal Sprocket

> live ɘvil Wrote:

> -------------------------------------------------------

> Looks like it uses noi 1 speed internals.

Some of them do

Re: Garelli Monza Broken Internal Sprocket

> Stephen Simmons Wrote:

> -------------------------------------------------------

> What ya go do wit da pieces ya took out?

I saved everything in a bag, even the broken sprocket. The chain is still in good shape.

Re: Garelli Monza Broken Internal Sprocket

> LGN Bruiser Wrote:

> -------------------------------------------------------

> > Stephen Simmons Wrote:

>

> > -------------------------------------------------------

>

> > What ya go do wit da pieces ya took out?

>

> I saved everything in a bag, even the broken sprocket. The chain is

> still in good shape.

I have a sprocket that's not broken. If you decide to throw that stuff out I want it.

Re: Garelli Monza Broken Internal Sprocket

> Stephen Simmons Wrote:

> -------------------------------------------------------

> > LGN Bruiser Wrote:

>

> > -------------------------------------------------------

>

> > > Stephen Simmons Wrote:

>

> >

>

> > > -------------------------------------------------------

>

> >

>

> > > What ya go do wit da pieces ya took out?

>

> >

>

> > I saved everything in a bag, even the broken sprocket. The chain is

>

> > still in good shape.

>

> I have a sprocket that's not broken. If you decide to throw that stuff

> out I want it.

Ooh I'll have to think about that sprocket. Personally I'd rather not have the pedal shaft connected to the transmission. I won't throw the parts out, they'll stay with the bike unless the next owner doesn't take 'em. Will keep you in mind, thanks.

Re: Garelli Monza Broken Internal Sprocket

this thread is fantastic! thanks Bruiser!

two of my monza engines have snapped sprockets (or chains), and as of yet i havent had the nerve to get in there and split the cases

ill finally get around to them in the next decade perhaps but at least this info and pictures are out there

Re: Garelli Monza Broken Internal Sprocket

> Potr zebie Wrote:

> -------------------------------------------------------

> this thread is fantastic! thanks Bruiser!

>

> two of my monza engines have snapped sprockets (or chains), and as of

> yet i havent had the nerve to get in there and split the cases

>

> ill finally get around to them in the next decade perhaps but at least

> this info and pictures are out there

Thanks! The info needed to be out there (even though it's torture taking pics). Honestly this one is easier than it seems. Don't let the rare bird thing stop yah.

Re: Garelli Monza Broken Internal Sprocket

From both of your accounts above, it seems to be common problem with the vertical or "VIP" motors over others that use the same parts. That leaves me wondering why.

Re: Garelli Monza Broken Internal Sprocket

sick thread I used to have a monza gt 1. sold it to a smoggy doggy a long long time ago

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