Piston Hard to Move in Cylinder Too Much Resistance

I started work on a Puch Newport that came with the head, cylinder and piston off of it. Piston came with rings on it. I installed the piston and put on the cylinder and head. This is my first time doing this. The piston fits very snugly. I can get it to move by turning the flywheel by hand, but it is not easy. I put a drive chain on the bike and tried to pedal start it on the stand. It pedals perfectly fine, back wheel spins, but as soon as I pull the clutch the pedals stop dead. If I hold the clutch in and try to pedal, standing on the bike, the pedals don't move an inch.

Wondering what the possible causes could be!

I've heard about having to file rings down to the right gap, but since the rings were already on the piston I assume they are either the old ones (and should fit fine) or new ones (and should have been gapped). Would failure to gap them cause this much resistance?

Could this be a problem with the clutch?

I coated the piston with 2 stroke oil when I installed it. It moved nicely on the crank w/o the cylinder on. There was some movement from left to right, (piston sliding left/right along bearing in crankshaft, not crankshaft moving left/right) but a friend said that is fine. It is, right?

Thanks for the help!!

Re: Piston Hard to Move in Cylinder Too Much Resistance

Piston and cylinder look nice, no signs of having seized

Re: Piston Hard to Move in Cylinder Too Much Resistance

Hepatitis J [OFMC] /

Don't assume the rings have been gapped or even the correct rings for the piston/cylinder.

Place the rings in the cylinder to check the gaps. Place the rings on the piston and confirm that they compress fully. If they don't, make sure that the ring lands are clean, clear, and unmarred.

You can probably borrow a feeler gauge from autozone to check the ring gaps.

Re: Piston Hard to Move in Cylinder Too Much Resistance

Was it hard to turn by hand before cylinder install? Piston should pretty much drop in cylinder wo rings installed. Take some time and read how to inspect and rebuild a puch in the wiki. (edited)

Re: Piston Hard to Move in Cylinder Too Much Resistance

Maybe the rings were not lined up on their pins. Otherwise even with the rings in it should still slide thru easily. I always make sure I lube up my cylinder and piston with some 2t oil before I insert the piston. Slides in like butter

Re: Piston Hard to Move in Cylinder Too Much Resistance

@Hepatitis J, Pistons rings had not been gapped, but there seems to be another problem. Something with the clutch or drive gears maybe? I put the cylinder and head back on with no rings on the piston. It's a lot easier to move the piston around by turning the flywheel with my hand now. But when I pull the clutch in and try to pedal, I am unable. Pedals stick and don't move an inch. If piston is set up at the right moment in it's rotation and I start pedalling, then pull in the clutch, piston and flywheel do half a turn and stop dead. At this position, if I try to pedal then pull in the clutch, I stop dead and the piston/flywheel don't budge. All of this with no rings on the piston.

Ring lands look unmarred to me:

IMG_8564.jpg

(edited)

Re: Piston Hard to Move in Cylinder Too Much Resistance

> Was it hard to turn by hand before cylinder install?

No, easy peasy

> Piston should pretty much drop in cylinder wo rings installed.

Idk about "drop in" but it went in pretty easy.

> Take some time and read how to inspect and rebuild a puch in the wiki.

I read the E50 rebuild wiki

Re: Piston Hard to Move in Cylinder Too Much Resistance

Thanks, Jay

Re: Piston Hard to Move in Cylinder Too Much Resistance

Gap the rings, seat them properly, and try turning the flywheel with the whole thing assembled. Remove the clutch cover and try to turn the clutch bell by hand. What happens when you do this?

Re: Piston Hard to Move in Cylinder Too Much Resistance

Post some pictures of the whole thing. Piston cylinder head gaskets cluthc, clutch cover inside, etc. Im suspecting atleast three issues.

One being spark plug hitting top of piston at tdc.

Two being damaged cylinder that needed to be honed thus the larger rings....

Three something up with clutch starter plate/clutch/ tranny side. Nut backed off, something floating around lever worn out

Re: Piston Hard to Move in Cylinder Too Much Resistance

I’m thinking hard about this extra difficulty in pedal movement when the starter clutch is engaged.

Like, the starter clutch normally is too slippy for one reason or another.

The piston and cylinder my be a red herring.

You said you recieved this thing disassembled. Maybe the clutch is shimmed stupid or not at all? Have you popped that off and checked what’s going on in there?

Re: Piston Hard to Move in Cylinder Too Much Resistance

> Papa _ Wrote:

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

> I’m thinking hard about this extra difficulty in pedal movement when the

> starter clutch is engaged.

>

> Like, the starter clutch normally is too slippy for one reason or

> another.

>

> The piston and cylinder my be a red herring.

I agree, I think piston is not the real issue. I do plan on gapping the rings but want to figure out the clutch thing first.

> You said you recieved this thing disassembled. Maybe the clutch is

> shimmed stupid or not at all? Have you popped that off and checked

> what’s going on in there?

I popped off the cover and went in as far as I could without a puller tool. Looked fine to me. It was greasy and I wiped it off. Here's a pic:

IMG_8570.JPG

Re: Piston Hard to Move in Cylinder Too Much Resistance

> Chinatown Kicks Wrote:

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

> Gap the rings, seat them properly, and try turning the flywheel with the

> whole thing assembled. Remove the clutch cover and try to turn the

> clutch bell by hand. What happens when you do this?

Haven't gapped rings yet but with whole thing assembled and no rings on it I can turn the flywheel by hand (clutch not engaged) and turn the clutch bell by hand. (Clutch bell is the outer part of the image above, right?)

Re: Piston Hard to Move in Cylinder Too Much Resistance

> pat splat Wrote:

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

> One being spark plug hitting top of piston at tdc.

I'll try pedaling with clutch engaged and no spark plug, all assembled minus rings.

> Two being damaged cylinder that needed to be honed thus the larger

> rings....

Could be but it looked good to me (not an expert though obviously). I'll post pics soon.

> Three something up with clutch starter plate/clutch/ tranny side. Nut

> backed off, something floating around lever worn out

These are my suspicions as well.

IMG_8572.JPG

^ ^ new gasket and the ring is just resting there. It was holding this piece below in place as it should. v v

IMG_8569.JPG
IMG_8517.JPG

These are just the pics I had, I'll post more when I take them.

Re: Piston Hard to Move in Cylinder Too Much Resistance

IMG_8515.JPG

Re: Piston Hard to Move in Cylinder Too Much Resistance

Was there oil in your transmission? It looks pretty dry in your pics

Re: Piston Hard to Move in Cylinder Too Much Resistance

Hepatitis J [OFMC] /

Holy hell that's a lot of ultra grey. Your engine has definitely been rebuilt. You'll want to fully disassemble that transmission and double check that everything is in there and in the right order.

It sounds harder than it is.

You may have to buy or make a puller, though.

To pull the nut off you can loosely assemble the top end, without rings, and use a piece of rope through the spark plug hole as a piston stop.

Pay close attention to the pieces as you disassemble and don't lose anything.

Here is an exploded view of the transmission:

C004140-4.jpg

Again, it's much easier than it seems.

Re: Piston Hard to Move in Cylinder Too Much Resistance

Hmm by the looks of the generous amount of sealant used it is possible theres a loose chunk in there binding up your nice crank. Id peel all that crap out and blow air in there too to get it till its buttery smooth. Yes outer ring is clutch bell. Inner dished plate is starter plate.

Re: Piston Hard to Move in Cylinder Too Much Resistance

> Was there oil in your transmission?

Yes it was nice and greasy, I wiped it out before learning that it is supposed to be that way lol. I put ATF on the shopping list.

Re: Piston Hard to Move in Cylinder Too Much Resistance

I'll clean out the sealant for good measure, but unless the sealant is getting in the way only when the clutch is engaged, I think the problem is elsewhere. But maybe a chunk of sealant could be stuck somewhere on the clutch or in it's vacinity, so things work fine when clutch isn't engaged but when it engages it pushes the chunk somewhere it shouldn't be.

Also, I tried turning pedals with clutch engaged, everything together minus rings and spark plug. Still stuck. So piston hitting spark plug at TDC is not the issue.

Re: Piston Hard to Move in Cylinder Too Much Resistance

Added clutch puller to the shopping list as well.

Love the exploded diagram, thanks for sharing, Hep J.

It'll be a minute before I pull it all apart (shipping time and a trip for a wedding coming up) but thanks for all the help so far everyone!!

Here's a pic showing off the sweet seal job from the outside:

IMG_8630.JPG

Re: Piston Hard to Move in Cylinder Too Much Resistance

Hepatitis J [OFMC] /

The silicone is not getting in the way of anything. I only pointed it out because it makes it clear that the engine has been rebuilt. So, you can't take it for granted that any part of that engine is assembled correctly.

Start with your transmission since you've got it open, but you can also take a look at your electrical side to make sure there isn't something loose or stuck that's keeping your flywheel from spinning.

There are lots of E50 diagrams out there.

Re: Piston Hard to Move in Cylinder Too Much Resistance

Aside from the sealant for the case halves getting in where it shouldn't, having too much sealer on the halves can allow the halves to be improperly gapped when put back together. Everything could be shifting slightly when put under torque, causing things to bind up.

You want no more than a 1/4 bead on the case before assembly which, when properly torqued down, will seal everything and keep it in it's proper place.

Re: Piston Hard to Move in Cylinder Too Much Resistance

Before you tear the case apart. with the bike on the stand and cylinder off see if you can spin a full revolution with the starter clutch lever pulled, either by spinning the flywheel or spinning the pedals slowly by hand. If it goes all the way around it likely is your piston hitting something. You said it came in pieces so maybe the previous owner just grabbed any 38mm piston and not one meant for a puch. I had an issue when I kitted a za and the con rod was making contact with the piston skirt half way between top and bottom dead center(when the angle of the rod was at its steepest ). I fixed by grinding 1/2 cm from the skirt and all worked fine. It's up to you to figure out where that contract may be. But if it'll go all the way around without the cylinder on and the starter engaged I would ignore the transmission for now.

Re: Piston Hard to Move in Cylinder Too Much Resistance

> Jared Rut Wrote:

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

> Before you tear the case apart. with the bike on the stand and cylinder

> off see if you can spin a full revolution with the starter clutch lever

> pulled, either by spinning the flywheel or spinning the pedals slowly by

> hand.

I can't. With starter clutch lever pulled, if I try to turn the pedal, the piston usually doesn't budge. If it is at the right spot to start, it will do maybe a quarter turn and stop near bottom dead center. If it is near bottom dead center to start, it doesn't move at all. I can put all my weight on the pedal and it won't move. The same applies when I try to turn it by rotating the flywheel.

So seems not to be a problem with the piston but one with some part of the transmission.

Clutch puller arrived today but I had to leave town before I could put it to use

Re: Piston Hard to Move in Cylinder Too Much Resistance

I keep thinking about this.

Pedaling the bike turns the front sprocket, which turns the main gear, which turns the clutch bell.

Pulling the clutch lever raises the actuator arm on the clutch cover, which rotates a semicircular rod inside the clutch cover, which presses the clutch bell plate against the starter clutch, which makes the crank turn along with the clutch bell.

When both of these things happen at the same time, the rotation of the main gear should be transferred to the crank by way of the clutch.

I’m having a hard time identifying what could stop that rotation while the clutch lever is pulled but not while the pedals or crank turn independent of one another, but I bet it’s gonna jump right out at you when you open up the case.

Re: Piston Hard to Move in Cylinder Too Much Resistance

I think he says its hard to turn by hand with piston installed. So if pedals easy then it has to be on the crank piston side. Looking at the crank picture it looks way off center wich could cause a side load on the piston?

Re: Piston Hard to Move in Cylinder Too Much Resistance

> pat splat Wrote:

> crank picture it looks way off center wich could cause a side load on

> the piston?

I didn’t see that before. Looking at the pics, the crank is way off center and there is a seal sicking out from the clutch side. Which should not be there at all; if that is indeed the green looking thing.

*should not be protruding like that.

Pics for comparison: (edited)

19F8FB3F-43E3-4986-8B4F-98D603DEED11.jpeg
07D937B9-E0E3-4CD4-81E5-1AE3B21995D3.jpeg

Re: Piston Hard to Move in Cylinder Too Much Resistance

Whoa, nice catch!

Re: Piston Hard to Move in Cylinder Too Much Resistance

For the off center, maybe the crank was rebuilt without the snap ring bearing on one side? Still I think there would be enough play between the piston and con rod to eliminate side load on the piston? Looking at the original picture is there a shiny bit on the ledge by the left transfer, that could be a point of contact. I'd try removing the piston and spinning the flywheel with the clutch engaged . Just to completely rule out the piston as the culprit.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account