moped lost power and died - now won't start and has low compression

Nate K /

Jul 10, 2019 12:21PM

I lost all power after about 45 min of riding on country roads(~20 miles). almost all at WOT. around 26mph average. after losing power, it rolled another 50ft idling like shit and then died. wouldn't start so i verified spark and compression. that's when i noticed low compression. I had tested this motor before with the same compression tester and was right about 120. from the pics, it's now at ~85.

a friend had me pull the head/top aparts and take pics.

first time opening a motor. wooooo!

https://imgur.com/a/fCfKUrQ

friend of mine says top end needs replacing(piston/rings). thoughts?

stats on the ped

it's a 82 puch maxi. 5100k miles. all stock cept the exhaust(circuit). 14mm OEM bing, 2.22 atomizer, 24 slide. 65jet, stock airbox. 50:1 mix,needle 2nd up. b6hs

Re: moped lost power and died - now won't start and has low compression

Dirty30 Dillon /

hydra

Jul 10, 2019 12:36PM

Top end is soft-seized and worse off your bushing at the small end is galled and will probably fail immediately.

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 10, 2019 12:46PM

> Dirty30 Dillon Wrote:

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

> Top end is soft-seized and worse off your bushing at the small end is

> galled and will probably fail immediately.

"bushing at the small end is galled" first time i've heard this phrase and can't decipher it using https://www.mopedarmy.com/wiki/Category:Moped_Jargon. Can you explain?

Re: moped lost power and died - now won't start and has low compression

Mike Boyd /

Go to branch

boyd

Jul 10, 2019 01:18PM

Piston and cylinder show a classic "4 corner" seize pattern, indicating that the piston got too hot and swelled and grabbed inside the cylinder.

The brass bushing at the small end of the crank is damaged as well. What 2 stroke oil/premix ratio were you using?

If this were my engine I would replace the crank, seals, and bearings with one of these.

You can try to hone the cylinder reuse, and maybe sand the piston and replace the rings, but with stock cylinder it's probably cheaper and easier to find a good used replacement for both on the buy/sell forum or buy a newer cylinder kit.

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 10, 2019 01:21PM

> Mike Boyd Wrote:

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

> Piston and cylinder show a classic "4 corner" seize pattern, indicating

> that the piston got too hot and swelled and grabbed inside the cylinder.

>

> The brass bushing at the small end of the crank is damaged as well. What

> 2 stroke oil/premix ratio were you using?

>

> If this were my engine I would replace the crank, seals, and bearings

> with one of these.

>

> You can try to hone the cylinder reuse, and maybe sand the piston and

> replace the rings, but with stock cylinder it's probably cheaper and

> easier to find a good used replacement for both on the buy/sell forum or

> buy a newer cylinder kit.

50:1

Re: moped lost power and died - now won't start and has low compression

live ɘvil /

themotorhead

Jul 10, 2019 04:35PM

I see no mention of ignition timing anywhere in this thread.

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 10, 2019 04:50PM

> live ɘvil Wrote:

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

> I see no mention of ignition timing anywhere in this thread.

to the best of my ability I believe it's about 14 degrees/mm. Used a screwdriver to determine TDC and then a mm tape and that's what I came up with. you can see on the first photo , TDC marked on the flywheel with permanent marker.

Re: moped lost power and died - now won't start and has low compression

Dirty30 Dillon /

hydra

Jul 10, 2019 04:53PM

https://en.wikipedia.org/wiki/Galling

It's a "smeared," the you can see that the brass bushing where the wrist pin goes is blackened and you can see rotational friction scarring.

If I'm not mistaken, it also looks like it has spun in the con rod. You can tell when the oiling hole in the rod doesn't match up with the hole in the bushing.

Re: moped lost power and died - now won't start and has low compression

live ɘvil /

themotorhead

Jul 10, 2019 05:14PM

...and I see no mention of what the temps of the motor got up to.

Re: moped lost power and died - now won't start and has low compression

Saabsonettguy . /

saabsonettguy

Jul 10, 2019 05:17PM

You can probably reuse the cylinder if you remove the aluminum smearing with a bit of muratic acid on a q-tip (follow safety precautions, its nasty stuff). You can probably also knock the high spots off the piston and reuse it as well. That said, stock top ends or 50cc kits are cheap. The small end connecting rod bushing needs to be replaced for sure. At this point I agree that it would make sense to go ahead and do crank bearings and seals. I'd probably bump your mix up to 40:1 as well. Get it back together and then get your jetting and timing dialed in to keep the temps under control.

Re: moped lost power and died - now won't start and has low compression

live ɘvil /

themotorhead

Jul 10, 2019 05:25PM

If you had a Trail Tech all this could of been avoided.

Seems to me that ought to be the first concern.

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 10, 2019 06:29PM

Thanks everyone for the tips. Best way to get that stock pushing off the small end?

Re: moped lost power and died - now won't start and has low compression

Den 23 /

den23

Jul 10, 2019 09:53PM

> Nathan Kuebelbeck Wrote:

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

> Thanks everyone for the tips. Best way to get that stock bushing off the

> small end?

Fashion a bushing puller tool.

Re: moped lost power and died - now won't start and has low compression

Probably Fred /

roffman

Jul 11, 2019 12:27PM

> Den 23 Wrote:

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

> > Nathan Kuebelbeck Wrote:

>

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

>

> > Thanks everyone for the tips. Best way to get that stock bushing off

> the

>

> > small end?

>

> Fashion a bushing puller tool.

But then after you press in a new one you have to ream the new one to fit the piston pin with correct clearance her manual

Without these tools and knowledge/feel that’s not gonna happen

Even if you had the tools you probably screw up the first or second try so your best bet is to get an aftermarket crank, one that has a needle bearing in it which is better anyways

I have the tools and I’ve replaced them and I don’t like doing it I’d rather rebuild a e50 engine with a new crank,

The only time I really replace the bushing if it’s on a Za50 engine which is a lot harder to replace the crank

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 11, 2019 05:44PM

> Ken Roff Wrote:

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

> > Den 23 Wrote:

>

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

>

> > > Nathan Kuebelbeck Wrote:

>

> >

>

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

>

> >

>

> > > Thanks everyone for the tips. Best way to get that stock bushing off

>

> > the

>

> >

>

> > > small end?

>

> >

>

> > Fashion a bushing puller tool.

>

> But then after you press in a new one you have to ream the new one to

> fit the piston pin with correct clearance her manual

>

> Without these tools and knowledge/feel that’s not gonna happen

>

> Even if you had the tools you probably screw up the first or second try

> y so your best bet is to get an aftermarket crank, one that has a needle

> bearing in it which is better anyways

>

> I have the tools and I’ve replaced them and I don’t like doing it I’d

> d rather rebuild a e50 engine with a new crank,

>

> The only time I really replace the bushing if it’s on a Za50 engine

> which is a lot harder to replace the crank

I was advised to get this one

https://www.treatland.tv/malossi-needle-bearing-p/malossi-needle-bearing-663973b.htm?fbclid=IwAR3HaGFM1fFKoWkJPYnMWCJvghR9UBx744V_uzi_PNa-zUMoSGi8v4FnnnU

Re: moped lost power and died - now won't start and has low compression

Mike Boyd /

Go to branch

boyd

Jul 11, 2019 05:48PM

That's not plug and play with your stock crank

Re: moped lost power and died - now won't start and has low compression

Nate K /

wisenuts OP

Jul 11, 2019 06:30PM

> Mike Boyd Wrote:

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

> That's not plug and play with your stock crank

Well shit.

MOPED ARMY

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