Fixing locked piston

JT /

May 01, 2001 12:22PM

Last night I found that my QT50's piston was locked in place, this bike as been sitting in storage for over 15 years (unforunatly with a full tank of gas, yuck)

After removing the head and cyclinder I was able to get the piston free. I've clean any carbon off the piston from the inside of the cyclinder, but can't get the piston to fit back inside the cyclinder. It's almost like the rings have expanded. Any hints on how to get these parts working together again? Is it possible for the rings to have expanded over the years?

Thanks,

jt

Inserting Piston into Cylinder

Chris Robertson /

May 01, 2001 01:23PM

Hi JT:

Are you making sure that the rings are closing over the pins in the ring groove?

If you look at the ring grooves, they will have a little nub somewhere around their circumference. The ring must close at that point or it will not go into the cylinder. Often the pins are on the bottom of the cylinder which is why it can be hard to notice them.

When you aren't used to it, putting a piston into a cylinder takes a while (it took me an hour-and-a-half the first time I did it). Make sure to coat the inside of the cylinder with a lubricant when you're finished (WD-40 is fine). Keep a rag loosely tucked inside the crankcase while you work to prevent dirt from getting into the engine.

Good luck and keep your hands clean!

Chris.

Re: Fixing locked piston

Ron Brown /

May 01, 2001 01:46PM

JT,

Chris is exactly right about the locating pins. Also, make sure that you have removed all the gumm and crud from the rings and grooves so that the rings are free to move.

Ron

Re: Fixing locked piston

JT /

May 01, 2001 02:44PM

Oh, the rings should be able to move! Hmmm, guess I'll have to go back and work on them some more. Mine don't move at all.

jt

Ron Brown wrote:

>

> JT,

>

> Chris is exactly right about the locating pins. Also, make

> sure that you have removed all the gumm and crud from the

> rings and grooves so that the rings are free to move.

>

> Ron

Re: Fixing locked piston

Fred /

May 01, 2001 02:45PM

No... it is not possible that the rings have expanded.

There are a couple paragraphs in my guide on how to put the piston back in correctly.

See below >> How to fix your Moped.

Re: Inserting Piston into Cylinder

JT /

May 01, 2001 02:46PM

Thanks Chris,

I'll take another look at the piston and it's rings. I really wasn't sure of what I was looking at, now I at least have something to look for.

Yeah right on keeping my hands clean, there's so much gook on this little motor!

jt

Re: Fixing locked piston

JT /

May 01, 2001 02:48PM

I guess I need to print out the entire document you posted yesterday so I'll have it on hand with me while I'm looking at the engine.

I thought I had cleaned the piston pretty well, but I think I need to take a second look at the rings.

Thanks,

jt

Fred wrote:

>

> No... it is not possible that the rings have expanded.

>

> There are a couple paragraphs in my guide on how to put the

> piston back in correctly.

>

> See below >> How to fix your Moped.

Re: Fixing locked piston

Ron Brown /

May 01, 2001 04:46PM

JT,

Be very carefull when freeing up the rings. They are typically about as flexible as glass!

Do not tap on them with anything metal and only very gently with anything soft.

If you get them loose, they will expand by themselves to protrude significantly from the piston. If you need to remove them, have someone hold the piston, then try to spread the ring by using a thumb nail under each end of the ring. Spread the ring just enough to clear the piston and lift it off. If you had to drive the piston out of the bore, look for peened over edges on the ring grooves, you may have to scrape these off before the rings will free up.

Ron

Re: Stuck rings

Fred /

May 01, 2001 05:04PM

Hey Ron... there might be a "new" (not really), easier solution to this old 2 stroke "stuck rings" problem.

I haven't tried it yet.

But OMC (the boat people) make a liquid solution called.. Techron?? (or something)... which you mix with the gas (or spray continuously into the carbs?) ... which will dissolve the old goo without disassembly.

Normally I don't believe in this kind of "fix in a can"... but it comes highly recommended from a somewhat renowned 2 stroke "guru".

And this guy is not in any business associated with bikes/boats... just a highly respected 2 stroke officionado.

Now... most mopeds are so easy to take apart that it's probably not worth it... to some.

But others might like it.

Just something to keep in mind.

Re: Stuck rings

Ron Brown /

May 01, 2001 05:16PM

Fred,

This sounds like something that Click and Clack have mentioned on Car Talk. They also had no evidence as to it's effectiveness. They allways recommend the use of something in a can with "Miracle" somewhere on the label, after which, you strip the engine anyway and fix it.

I suspect JT's problem is a liitle beyond this solution, especially after the "they should move?" comment.

Ron

By the way, you going to the barbeque?

Re: Stuck rings

Fred /

May 01, 2001 05:34PM

I hadn't planned on it.... When is it?

You and Ree are both studs and are planning on riding there on Peds?

I don't think I would trust mine to go that far.

The blamed thing will never maintain the top speed for more than 20 miles.

Thats just too weird.

My gut feeling is it would not make it for any of a number of reasons.

Re: Stuck rings

Ron Brown /

May 01, 2001 05:43PM

Fred,

I am riding with my bartender who will ride my spare ped. Of course, I expect him to dispense beer on the way!

Ree said he was going in a pick up truck, wimp :-). Maybe you can hitch a ride.

It's Memorial day, I think the last monday in May.

I am still tuning and testing my peds to try to get them ready for the 200 mile round trip.

Ron

Re: Stuck rings

Reeperette /

May 01, 2001 09:59PM

Ree's goin inna pickup truck cause his roomie has utterly and completely refused to ride the Suzuki...that, and I got time/work pressure and stuff.

(The roomie thinks we're insane...btw, lets reinforce that belief, shall we ?)

And, I wanted to be able to grab anyone and thier ped on the way who wanted to come...there's just gonna be one ped in the pickup, and two folks in the cab of the truck (we'll see if they gotta king cab er somethin if we have to)..so we should have room for a couple of folks.

Dunno how bitchy state of MI is about folks in the back of a pickup, some states are real pricks about that, and all.

Howell is definately on the way, and I still need to fork over $5 and get that ratio thingie from ya.

Also, we're having some kinda ride event fundraiser up here on May 12th...it's fer motorcycles, but I will be there even if I do hafta suck exhaust all 30 miles worth of the run....

I have a bit of rope I use fer tiedowns, but if you've a fav method of securing yer ped, have it ready and stuff.

E-mail addy is up there, fer any that could use a lift.

-Ree

Re: Stuck rings

Reeperette /

May 01, 2001 10:02PM

Oh yeah, and Ron ? pack a cell phone...and I'll drop the number fer my roomies cell to ya, that way if you have a mechanical failure I might be able to get to you en route with tools, or a lift...should somethin happen.

Always good to have a backup plan,

-Ree

Re: Stuck rings

Ron Brown /

May 02, 2001 10:47AM

Ree,

I have ridden for a long time and my principle has allways been:

Truck, I don't need no stinking truck!

So far, this has worked. I have allways ridden home. Then again, the Harley/BMW tool kit (cell phone+credit card) may be a good idea.

I'll take you up on that phone #.

Ron

Re: Stuck rings

Fred /

May 02, 2001 12:05PM

I think if you are going to make it in time... you better leave now... :)

MOPED ARMY

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