How screwed am I ?

SteelToad /

Well after trying to get my ped started after a soft seize, I finally took the thing apart. It will give me compression when I pedal it, gas is going in (wet spark plug), and I'm pretty sure I'm getting spark.

The pictures below will show you what I've got to deal with.

The wear marks dont appear to be that thick at all, less than the thickness of a piece of paper. The "smudges" on the piston seem to be holding the ring in place on one side. Also the piston does not seem to have changed shape at all, but maybe I'm being too naive or hopeful

<img src="http://www.mopedmagazine.com/mm/piston1.jpg">;

<img src="http://www.mopedmagazine.com/mm/piston2.jpg">;

<img src="http://www.mopedmagazine.com/mm/cyl1.jpg">;

<img src="http://www.mopedmagazine.com/mm/cyl2.jpg">;

Re: How screwed am I ?

it doesnt look to bad. check out the article on fixing your ped. if all else fails, head for your dealer or repair shop

Re: How screwed am I ?

SteelToad /

Thanx, that's what I was hoping to hear. The fact that it's a 70cc kit rules out the dealer, and the fact that I live in Delaware rules out a repair shop.

Re: How screwed am I ?

Ron Brown /

First, a sieze is a sieze. Some may be "softer" than others, but they are still a sieze.

There is no way to tell from the pics, what shape the cylinder is in, but if any aluminum was transfered to the cast iron liner, you need to remove it somehow. Hopefully, without removing too much iron. Possibly you can scrape it with something soft and finish it with some really fine wet or dry paper. Make sure you wash it well afterwards to remove all the abrasive.

As for the piston, you need to loosen up the ring and get it off the piston. This may be as simple as working it back and forth until it comes out, or you may have to scrape the galled metal away that is holding the ring.

Then look at the piston and anywhere thew is a bright spot caused by the piston tightening in the bore, remove it with a fine flat file. Use the ring turne backward and clean the ring groove by scraping/filing the edges only until the ring will rock in the groove the same amount as you roll it around the piston.

Do not use abrasive papers on the piston as they tend to become embedded in the aluminum and are difficult to wash off.

Re-assemble, increas the oil a bit and do a plug chop.

Ron

Re: How screwed am I ?

those responses were quick. how come i can never get my questions answered?

grrrr!,

louie

Re: How screwed am I ?

Ron Brown /

Jeez Louie,

It took me this long to search for and find my last post on tire changing. If 10-15 minutes is too long to wait, you will have to sign up for our premium service contract.

Please click on the PayPal donation button on the main page and pay the $10.00 fee immediately.

Ron

Re: How screwed am I ?

SteelToad /

Awwwwm come on, you're supposed to tell me that it was gonna be really simple and painless. well, I got the ring out, and in only 5 pieces. The piston cleaned up pretty easily with some wet paper, and then washed up with carburetor cleaner and then brake cleaner. The cylinder ought to be fun, the deposit isn't that thick, but it's just a pain reaching in there.

Thanx much for the advice !

Re: How screwed am I ?

Ron Brown /

Toad,

What did you not understand about this part?

Do not use abrasive papers on the piston as they tend to become embedded in the aluminum and are difficult to wash off.

Btw, be carefull with the ring as it is very brittle. : )

Ron

Re: How screwed am I ?

InfectedBootSector /

Won't the jug have to be honed again? Just wondering...

Re: How screwed am I ?

Ron Brown /

Now that he has broken the ring, yes.

Ron

Soft seize my A$$ !!!

Where does all this crap about "soft seize" come from ?

A bunch of kids who don't know what the fork they are talking about ?

I guess so.

THAT ain't no "soft seize".... you have smeared aluminun over the rings and onto to the BORE !!

There ain't noting "soft" about it !

That is a MAJOR seizure.

And any fix that does not involve a new piston and rings is a half assed el-cheapo goof-up.

Re: Soft seize my A$$ !!!

Is that an aluminim cylinder with a chrome bore ?

(I can't tell from the pics)

If it is... you can use muriatic acid swabbed onto the aluminum smears in the bore and let the acid eat the aluminum.

(takes several swipes.. and a few days)

If it is a cast iron cylinder you can still do that... but you need to be more careful that you keep the acid off the cast iron.

Then when the smear gets real thin... you should take it to a cylinder boring and honing place and let them do a quick clean up hone on it.

You can probably save the cylinder... but don't even think of using that piston or rings again.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Orrr... right off the bat take it to a local cylinder guy who can do it... and let him take a look at it... he will tell you if he can do all the work... or whether you can save some money by doing the muriatic acid process yourself.

If you are going to try to find a local cylinder guy over the phone... tell him what the bore diameter is.. (like 1.75"... be accurate)

This is because many of them don't have the tooling to do the real small bore for 50cc motors.

Re: Soft seize my A$$ !!!

if the bore guy says the cylinder can be saved... order a new piston and rings immediately.

While you are ordering the new piston... ask if they come in 'oversize' for that cylinder big-bore kit.. (this is in case the cylinder can't be saved).

If the bore guy says the cylinder can't be saved (seems unlikely)... then order an oversized piston (if available).

Then you have to wait for the piston and give it to him with the cylinder and he bores it a little bigger to fit the bigger piston... then you are good to go.

Definition of &quot;soft seize&quot;

First of all let me say I have heard alot of nonsense over this "soft seize" term... here.

I don't think I had ever heard it except on this forum.

If a piston seizes... it seizes... that means it has grown hot enough to expand in the bore till it no longer has any clearance... then it ceases to move up and down... it seizes.

I guess what people mean by 'soft seize'... is.... in rare cases... it seizes gently enough to NOT smear any aluminum over the piston and bore... and the piston 'unseizes' seconds after it seized... (its free to run again).

Any seizure that smears aluminum is NOT a soft seize.

In my day... (which is then AND now... by the way)... we called it a "major seizure"... (smeared aluminum)... or a minor seizure... (no smeared aluminum).

I have probably 2 or 3 minor seizures in my life... and maybe 3 or 4 majors.

I once seized a race bike on the first lap (minor) and let the clutch back out and broke the piston back loose seconds later... then went on to win the class anyway.

No aluminum smeared during a post-race teardown.

I ain't buying it Ron

.. done right.. sandpaper is fine.

I have used sandpaper on pistons many many times... it is common practice.

A Yamaha owners manual from 1974 will tell you to do the break-in according to a certain riding practice... then after that time period is up.... >

... to remove the piston and use sand paper to remove any apparent high spots showing on the piston.

A Yamaha manual from 1994.. (and 2002 frankly)... will tell you the EXACT same thing... (mine does)

I do it... I've done it many times... so do all experienced 2 stroke race mechanics under many scenarios.

You simply need to thoroughly clean it all... first with solvents (thats how I start)... then with hot soapy water.

There will ne no damage or bad results this way.

I will also lightly sand certain minor scuffs in the cylinder bore on both chrome bores and cast iron ones.

Just clean it up good.

Re: I ain't buying it Ron

Ron Brown /

Fred,

To each his own, I don't want to sell the idea, it's yours for the taking if you want it.

>so do all experienced 2 stroke race mechanics

I do take exception to this statement, how the hell do you think I learned?

I have no problem using sandpaper on cast iren because it does not get embedded in the metal as it does in aluminum. I am sure that most of the time it is fine, but why risk it?

Incidentally, I can't claim to have done it often, but when a piston is not badly scored and the ring groove is stil in good shape, I have re-used it at least several times with no bad results.

Re: Definition of &quot;soft seize&quot;

i just found my Tomos' old piston, from before i replaced it, and one whole SIDE looks like that, complete with embedded rings. now i honed the bajesus outta the cylinder, till i couldnt feel any of the smeared aluminum that the piston had left on the walls (they felt smooth) do u think its ok, or should i tear it back down & go get it bored to oversize and get an oversize piston? i can take pics of the piston if you want and post them in another thread. the whole side of it, like right up2 where the wrist pin circlips are, looks scratched like that, do u think there may still be problems with that cylinder? even after using a heavy duty brake hone & WD40 as a cutting oil.

-Garret

Re: Definition of &quot;soft seize&quot;

SteelToad /

I'm referring to a "soft seize" as one where you can get the piston and cylinder apart again, a hard seize is one where you just chuck it all in the trash.

Just trying to interject a little humor.

After seeing what kind of shape it was all in while trying to get the ring out, I had pretty much decided to get a new cylinder and piston. Now I'm just going to clean things up for a little experimenting until the new parts come in.

I wanted to experiment with porting the cylinder, now if the piston (cleaned up) with a new ring will work with the cylinder (cleaned up), then I'll port it just to see what it does. If I screw it up, then I'm not really loosing anything

Re: How screwed am I ?

SteelToad /

See my response to Fred below, I pretty much had given up on these parts and decided to get new ones (no shops anywhere nearby). The brake cleaner did a fantastic job of cleaning the piston off once I was done sanding. I used a really fine wet paper, and had more of a problem with aluminum filling the sand paper than the other way around.

Re: Definition of &quot;soft seize&quot;

Ron Brown /

Garret,

You say I did. How long ago and how does it run?

Ron

Bore or not ?

Garret wrote:

>

> i just found my Tomos' old piston, from before i replaced it,

> and one whole SIDE looks like that, complete with embedded

> rings. now i honed the bajesus outta the cylinder, till i

> couldnt feel any of the smeared aluminum that the piston had

> left on the walls (they felt smooth) do u think its ok, or

> should i tear it back down & go get it bored to oversize and

> get an oversize piston? i can take pics of the piston if you

> want and post them in another thread. the whole side of it,

> like right up2 where the wrist pin circlips are, looks

> scratched like that, do u think there may still be problems

> with that cylinder? even after using a heavy duty brake hone

> & WD40 as a cutting oil.

>

> -Garret

Heck Garrett.. if you are running it and its OK... just keep running it.

Using a brake hone is alright... and using WD40 was good.

But the problem is the hone prob removed material from the other side too... (not just the aluminum).

So your bore is probably not very true and smooth.

But if it runs OK... just leave it till you HAVE to bore it out.

(just maybe don't do any trips from Ohio to Florida... )

Plan on eventually having a nice bore job done... if you plan to keep it and ride it much.

Re: Definition of &quot;soft seize&quot;

it runs good, except for some 4 stroking cuz my carb jet is too big, i get 95psi on compression tests (higher than stock i think) so i KNOW the bore is ok. i think the hone may have just taken the aluminum off without taking off too much of the cast iron bore, because as u know, aluminum is a HELL of a lot softer than cast iron. also, i used a 3 stone brake cylinder hone to do it, and the stones werent that abrasive.

-Garret

Re: Definition of &quot;soft seize&quot;

Ron Brown /

Fred's right, except for the Ohio to Florida trip, I think you should do it.

Ron

Re: Definition of &quot;soft seize&quot;

Matt Wilson /

Steel toad how did the engine sieze up?

Too lean?

Matt

Re: Definition of &quot;soft seize&quot;

SteelToad /

I'm pretty sure it was too lean. I had a long running problem getting the carb to fit with the intake (70cc kit). On the day it was last running, it was running great. Got it up to the mid-upper 50's. The bike has color changing paint, and I had just been riding on the highway alongside a cage with similar paint and getting a big smile/thumbs up :-) About 2-3 minutes later, cruisin all-out, somebody put on the brakes.

Luckily I was in the slow lane of the three lane road when it did. Even more luckily only about half a mile from home.

You KNOW the bore is OK ??

If you KNOW the bore is OK.... Why did you ask this question ?

>> .. do u think its ok, or should i tear it back down & go get it bored to oversize and get an oversize piston? i can take pics of the piston if you want and post them in another thread. the whole side of it, like right up2 where the wrist pin circlips are, looks scratched like that, do u think there may still be problems with that cylinder? .. <<

and... NO... 95psi ISN"T very good... that is pretty low.

No way is a stock Tomos less than that... no way.

... a good stock engine should be getting 120 or 130.

Race engines get 175... 185... even 205psi.

What is the top speed of yours now ??

You will probably be surprised how much a fresh bore perks your motor up.

A bore that has been seized bad and then messed with ... (but no professionally honed or bored)... will never be as good as new... (this depends somewhat on how bad the seizure was.. and how much fiddling was done to 'fix' it)

It also depends on whether you put in new rings or not.

Re: Soft seize my A$$ !!!

SteelToad /

Where does one get "muriatic acid" ???

Re: Soft seize my A$$ !!!

Ron Brown /

You can buy it at any hardware store. As for using it to remove aluminm from a cast iron bore, get some input from Fred. I have never done this and have no idea how dilute it should be or how you avoid pitting the cast iron

Ron

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