OS 18TM cylinder too big for case

[dpk136]

I bought this engine used and it has no cylinder, piston, or rod...I bought the stuff (its the stuff from OS for the 18TM). For some reason the cylinder will not fit into the case, it seems like the case is slightly undersized. How do you get this thing into there...should i put some after run oil on it and see if it will go in that way? Can someone help?

Thanks,
David

 

[vbgagnon]

are you sure its a case from a tm/tz?

 

[jetmechG550]

That's my thought too. Make sure it's not an RG case or even something smaller.

Oh yeah, the p/n for the piston and sleeve are different between the TM and TZ too.

 

[dpk136]

Everything says TM on it. the case says OS Max 18TM. The cylinder and piston are part #21913000 and say right on it for: 18TM

 

[olds97_lss]

Does it say OS Max 18TM on the side of the crank case?

Like this one: http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHKV3&P=7

EDIT
Sorry, you posted the same time I did.

That is odd that it won't fit. I've had them be snug, but they would fit. Is there varnish built up inside your crank case? I'm guessing your replacing it with new because the originals are so worn out that they aren't pinchable?

 

[dpk136]

The inside of the crank case looks fine...it doesn't look dirty or any different than it would out of the factory..

I'm not sure what there is that i could do.

 

[Monkey Wrench]

Lather it in ARO and heat the case up with a heat gun and give it a shot. I do know the case and sleeve are a tight fit, so you need to finesse it in there.

 

[Tarant]

Put the sleeve in the Freezer and use a heat gun or hairdryer on the case, then try. The sleeve should shrink abit and the case will expand.

 

[dpk136]

If i put the cylinder in the freezer, won't that make it smaller and then the piston won't fit or should i put the whole assemly in? I'll give that a try and let you know. Thanks for the tips.

 

[jetmechG550]

The sleeve is tapered. Freezing it will temporarily constrict it in theory but IMO and standard household refridgerator freezer will not get it cold enough to make a big difference.

 

[Tarant]

It is only a very small difference But it works. and after a little while it will be back to normal size. And yes it works, I had a hard time getting my HPI .25 sleeve to fit, and I didnt have a hair dryer or heat gun, I put the sleeve in the freezer for awhile and I was able to get the sleeve in.

It wont hurt anything and any little bit helps IMO.

 

[ThunderTiger]

Try putting the crank case in the OVEN for a while on the top shelf (or the middle one depending on what your personal view is), it helps a huge amount by expanding the size of the crank case. Also, aluminium (aluminum to those in the U.S) picks up heat faster than steel, just dont set the oven temp too high. The suggestion of the freezer trick will help, but remember to put it on the BOTTOM shelf, cold air drops down.

The combination of the two will allow an easier fitting of the new sleeve, juist dont burn yourself in the process like i did when fitting a sleeve for a friend.

 

[dpk136]

ok...i got the sleeve to fit...
now i can't get the connecting rod onto the crank. i can't manipulate it enough to get it to slip over the end. Anyone have any tricks for this?

 

[Monkey Wrench]

You're going to hate this, but you need to put the piston in before you put the sleeve in. I know it sounds backwards and hopefully someone does have an idea, but I've always had to pull the sleeve out, put the piston in and connect the conrod, then put the sleeve back in when I've done that.

 

[dpk136]

how do you do this with the connecting pin??? or, do you mean put the whole piston assembly in first (with connecting rod) and connect that. Then slip the sleeve over?

Ok..so if this is the case...how the hell do i get the sleeve back out. haha..this is turning into a shitload of fun.

 

[jetmechG550]

You put it in as an assembly then slide the sleeve into place. With the problems you had getting the sleeve in. Try to use something non-metalic to push the sleeve up from the bottom. If possible maybe even a heavy duty pick and try and pull the sleeve up a little at a time.

 

[olds97_lss]

or, do you mean put the whole piston assembly in first (with connecting rod) and connect that. Then slip the sleeve over?

That's how I normally do it.

I drop the piston with the con-rod attached to it down into the crank case, attach the con-rod to the crank, rotate the crank so the piston is at it's lowest point. Then I work the sleeve down into the crank case. Once you get so far with the sleeve, manipulate the crank and piston to get the piston up in the bottom of the sleeve properly, then finish pushing the sleeve into the crank case.

Then I normally apply a light coat of ARO to everything prior to final assembly.