Puch E50 Engine Air Leak

Hi everyone,

I been trying to get my 1976 Puch moped to start. I want to rule out air leaks so I made an engine leak tester.

On my first attempt, I heard lots of air escaping. So I thought it was a gasket. I heard it on the top of engine. So, I removed engine and found where the air escapes. There is a hole on the top of gear box. I assume this is normal.

Can someone please confiirm. Is this normal for the air to escape from this hole.

Second, if it’s normal, can I block and retest.

There shouldn’t be any leak, correct.

I have a feeling this is why no gas is getting into piston cylinder and why my compression is low. I may be wrong but I changed the piston rings, rebuilt carburator and still no go.

Thanks in advance

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Re: Puch E50 Engine Air Leak

Overpriced Parts /

You’re supposed to block the exhaust port to when you pump it up and you can’t use too much force like this guy did or or you will blow the magneto side seal out

(Looks like he’s operating a seal making machine Haha hahaj

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Good chance you blew the transmission side seal If you didn’t use pressure gauge but it sounds like it was bad to begin with With air leaking out the transmission vent hole

You’re gonna have to take it apart and rebuild it with new seals,

When you rebuild the carburetor you Gotta make sure the a vent hole in the carburetor body is clear or else you won’t get gas either

Re: Puch E50 Engine Air Leak

Will Janssen /

Its normal dont blok it it need to be open

Re: Puch E50 Engine Air Leak

No, i used a pressure guage and only pumped 10lbs.

If I understand you correctly the seal in the transmission must be no good if air is leaking out this hole. If I block it, i have mo leaks. So I assume it is not suppose to leak throw this hole.

Am I correct?

Thanks

Re: Puch E50 Engine Air Leak

Also, i did block the exhaust port as well.

Re: Puch E50 Engine Air Leak

Dirty30 Dillon /

If you have air from the combustion chamber leaking through the trans vent, then your trans seal is roasted.

Also, 10PSI is patently alot. Typically, you only want to do like 5 psi and have it hold

Re: Puch E50 Engine Air Leak

I ran the air through the intake port and the air came through the trans port. Does this mean the seal is fried. I want to make sure before rebuilding the seals.

Also, if I need seals, where could I get them. Thanks

Re: Puch E50 Engine Air Leak

Dirty30 Dillon /

Yes, NO air should be getting from the combustion/crankcase to the trans, ever.

If you need seals, you should replace bearings at the same time.

Treatland.tv or Doscycles.com for all your moped needs.

Re: Puch E50 Engine Air Leak

I can assume this is why my comptression is only 25 psi. Am I correct?

Re: Puch E50 Engine Air Leak

Dirty30 Dillon /

Well, not necessarily the only reason, but it's not helping.

Re: Puch E50 Engine Air Leak

Pretty much all shaft seals made 44 years ago are bad, you can almost guarantee any moped you find needs the engine rebuilt

Re: Puch E50 Engine Air Leak

I ordered the bearings and seals. Now I will need to make up a pulley to get them off.

Don’t really want to spend extra for a one time shot

Re: Puch E50 Engine Air Leak

You can make the puller of you have a friend with a lathe.

Re: Puch E50 Engine Air Leak

You can borrow the puller at most auto parts stores.

Re: Puch E50 Engine Air Leak

I have got the engine apart, just wondering if it’s necessary to change crankshaft. It seems to be good.

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Re: Puch E50 Engine Air Leak

Looks pretty grotty to me .

I'd clean it with diesel fuel and insure the connecting rod big end bearing runs smoothly with no tight spots or growls .

Re: Puch E50 Engine Air Leak

Overpriced Parts /

> P D Wrote:

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

> Looks pretty grotty to me .

>

> I'd clean it with diesel fuel and insure the connecting rod big end

> bearing runs smoothly with no tight spots or growls .

Seal area on crank rusted = junk

Re: Puch E50 Engine Air Leak

i've cleaned up far worse, but a new roller bearing crank would be nice if you have the dough, if you dont then clean it up real nice n shiny, wire wheel etc, prep n polish the sealing surfaces end up with 600 grit or so and make sure there no pits or gouges in that area, if u can feel w your finger nail dips/gouges/pits then just stop cuz its a waste of time.

obviously check the bearings as well.

Re: Puch E50 Engine Air Leak

So far so good, not rust but just very dirty. i used steel wool and it cleaned up very well. no pits. the connecting rod spins well but not sure about piston as i didn’t see any bearings. Will double check.

Will give everything a clean bath and see what unfolds. Took everything to get old bearings off. Some required a torch.

Re: Puch E50 Engine Air Leak

> Overpriced Parts Wrote:

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

> Seal area on crank rusted = junk

I've had to take the seal contact area down on cranks . When I'm satisfied that surface is good , I measure it and order a seal that will work . ;)

Re: Puch E50 Engine Air Leak

It just looks like a lot of residue from the photo, that case seal has been leaking and the trans oil has been gunking up the crank.

It's probably ok for a stock bike but it's impossible to know what that big end bearing looks like, if it were me I'd throw a clean stock crank or a $100 aftermarket crank in there and not worry about it

Re: Puch E50 Engine Air Leak

i wish but I am in Canada and after exchange and shipping, it isclose to $200. I brought bearings and seals and after exchange and shipping $140. Cost US was $50.

what I know today, would of purchaes everything, would of been cheaper

Re: Puch E50 Engine Air Leak

Can't you buy bearings and seals locally ?

I'd think there would be bearing jobbers in your neck of the woods .

Re: Puch E50 Engine Air Leak

Probably but I thought they were specific to the E50.

Oh well, i have the right ones now, just didn’t expect to pay through the roof.

Re: Puch E50 Engine Air Leak

Yes, I got the moped in 1977. It sat in my shed for 33 years. I took it out, cleaned it up, put fuel in it and on the third crank, the moped ran. I was about to redo the electrical and it just stopped. Now I am slowly rebuilding it. Covid hobby. Really do not want to put lots of money into it as there’s really no market to sell. It is just a challenge for me.

I will clean crank as best as I can anf if I see its not healthy, i may theow a bit more i to it. There’s still no guarantee it will start. I may have compression issues. Who knows

Re: Puch E50 Engine Air Leak

Just fix it .

Then you can ride for the 3 days at the end of July before you get more snow . LOL

Re: Puch E50 Engine Air Leak

Dirty30 Dillon /

I love a good stock crank, but the Puch stock cranks on the E-50's were not that amazing anyways. I would replace with the non-stuffed roller crank from Treats any day.

At least than you are future proofed if you decide to add more power later.

Re: Puch E50 Engine Air Leak

Yeah or post here on buy/sell, if I had a clean stock crank I'd send it to you as cheap as possible but I don't think I do.

It will probably be fine all things considered, if you don't plan on doing performance upgrades later, it will last a long time

Re: Puch E50 Engine Air Leak

Brandon Weiss (Detective brandon to you) /

I'm pretty sure I have a usable stock crankshaft, ill check when I get home. If I do, you can have it for free, just pay shipping

Re: Puch E50 Engine Air Leak

That would be great, please let me know and we can work something out. Really appreciate it.

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