Puch E50 compression issue

Jeffrey Strichart /

I recently put a new top end on my Maxi e50. After I put it on I checked the compression and it was five pounds. I took everything off and found that I had a cracked piston ring because I installed the piston incorrectly. So I got a new piston ring from treats but even though it said it was the right size, it was a little too big (end to end, not thickness) and the cylinder would not go on. I had to file a little bit off the edge on one side of the ring to get it to fit. When I had everything back together I checked the compression and it was 30 pounds. Could I have filed too much off of the ring? Could that cause the problem? Thanks

Re: Puch E50 compression issue

Do a search of this forum for gapping your rings. It’s required standard procedure for all proper top end work. Could be a few other issues working against you on that top end, so make sure you’ve searched through the wiki as well on how to do a top end correctly. Checking compression isn’t as simple as a gauge screwEd into the head. Search that too...

If you redo it right and still have issues, that’s when the crew here can be of the most help. Ask me how I know...

Re: Puch E50 compression issue

Jeffrey Strichart /

I just ordered a replacement piston with a fitted ring on it, which is identical to the one that I cracked the ring on by not aligning it properly.

Re: Puch E50 compression issue

Jeffrey Strichart /

I have been doing some studying and came to the conclusion that I filed too much off of the piston ring and caused a leak that lowered compression. No Maxi is going to run with 30 pounds of compression, but at least it is going up. It was 5 pounds LOL! Hopefully third time will be the charm.

Re: Puch E50 compression issue

Sometimes when you first build a kit, the compression will be very low until it breaks in. Do you know how to properly gap the ring?

Re: Puch E50 compression issue

Jeffrey Strichart /

What happened was that the piston ring I ordered was a little too big the fit in the cylinder so I filed just a little bit off and then it fit. Put it back together and got a reading of 30 pounds compression. Will the bike even start with only 30 pounds of compression?

Re: Puch E50 compression issue

Moped Lar (OFMC) /

Doubtful. 90 psi is pretty much the minimum psi you need to start a bike.

Re: Puch E50 compression issue

Do you have feeler gauges?

Re: Puch E50 compression issue

Jeffrey Strichart /

Yes I do

Re: Puch E50 compression issue

Jeffrey Strichart /

The entire top end is new. Every part of it. The bike has spark and fuel. The compression ratio after everything was put back together was 35 lbs. I do not understand why the compression is so low. Needless to say it still won't start and I am at the end of my knowledge. The bike has not been timed but I moved the timing several times and if the bike wanted to start it would have at least sputtered on one of them. But no luck. I don't know what else to do.

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Re: Puch E50 compression issue

Wesley Ambrosini /

Are your gaskets ok?

Re: Puch E50 compression issue

Jeffrey Strichart /

Brand new. The cylinder head uses an o ring.

Re: Puch E50 compression issue

Wesley Ambrosini /

Are your cylinder studs ok? Did you torque the head down? Throw another head on it and check it again. Or better yet another kit. Maybe you can eliminate some variables

Re: Puch E50 compression issue

Jeffrey Strichart /

I torqued the head nuts to 7 foot pounds as it says in the manual. I tried to turn the studs and they all seem tight. And this is the second kit. I bought a new piston/rings all new gaskets even though the previous ones were only installed one time. Today I am going to try another head.

Re: Puch E50 compression issue

Bad crank seals could cause loss of compression too, correct?

Re: Puch E50 compression issue

> Aaron Goldman Wrote:

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

> Bad crank seals could cause loss of compression too, correct?

Please explain exactly how and why you think that .

Compression only happens when the piston passes the ports on the up stroke .

That happens no matter what is in the crankcase , unless that something is an immovable/solid object hindering the crankshaft rotation .

Re: Puch E50 compression issue

Jeffrey Strichart /

I just went through three different heads and different gaskets but nothing worked. Still at 35 pounds. Right now it is sitting their looking pretty with a metal head gasket AND the o-ring. No, that did not work either. Besides lapping them myself with sketchy results perhaps a machine shop could mill the head and cylinder to make sure they mate perfectly but I have a feeling that would not work either. I am ready to give up. I really want this bike to be 50cc but I am not buying anymore 50cc parts because I am having so much trouble. I would more or less be forced into a 70cc kit. At least then the head and cylinder would come as a matched pair, whereas my head and cylinder did not come together. They are both TCCD high compression parts but were purchased separately.

Re: Puch E50 compression issue

Did you try a different compression tester ?

Re: Puch E50 compression issue

Jeffrey Strichart /

It's running! I noticed I had the gas off. I must have turned it off last night. So I turned the gas on and it fired up on the first, gentle kick. Not even a full kick. It fired up easily. Thanks for all of your help. Oh yes what is the best break in procedure? (edited)

Re: Puch E50 compression issue

Wesley Ambrosini /

Ok so your compression tester sucks?

Using a plate of glass and sand paper is a totally acceptable way to mate heads and cylinders a shop will charge you $80+ and hour to do essentially 5 minutes of work.

Re: Puch E50 compression issue

Jeffrey Strichart /

> Wesley Ambrosini Wrote:

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

> Ok so your compression tester sucks?

>

Looks that way. F'ing Harbor Freight. I wasted hours because of that tester. I will be returning it tomorrow.

Re: Puch E50 compression issue

Jeffrey Strichart /

> Wesley Ambrosini Wrote:

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

> Using a plate of glass and sand paper is a totally acceptable way to

> mate heads and cylinders a shop will charge you $80+ and hour to do

> essentially 5 minutes of work.

I hear you. Thanks. At the time that I wrote that I did not have any faith in myself to do it properly because it seemed like I couldn't get anything right. As if I didn't build the bike in the first place. But thanks to a faulty compression tester I didn't feel like messing with it anymore. I didn't know what else to do at the time. I spent half a day swapping heads out and testing for no reason. It was a good learning experience though.

I got a lot of help and support here so good job guys. (edited)

Re: Puch E50 compression issue

> P D Wrote:

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

> > Aaron Goldman Wrote:

>

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

>

> > Bad crank seals could cause loss of compression too, correct?

>

> Please explain exactly how and why you think that .

>

> Compression only happens when the piston passes the ports on the up

> stroke .

>

> That happens no matter what is in the crankcase , unless that something

> is an immovable/solid object hindering the crankshaft rotation .

Was just asking, I'm always learning more but I assumed something can blow by the rings even when freshly installed. Thus a vacuum issue where you're pulling air through gaps in the shrunken seals.

What you said makes sense though.

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