Help/advice needed

[MalaysianFlyer]

HI, I need some advice/help regarding the TT21 OB. I recently modded mine and it was running well, then I decided to mod further removed material from the shim to get .008" headspace. However when I reassembled the engine, I found that the compression is very low when turned by hand. Is this normal for the mods I did? Or could it be that I now have got a bad seal between the sleeve and the button?

I am quite new to engine modding, so any help would be appreciated

 

[VansRacing]

Put it back like it was and see what happens.

 

[waltr]

HI, I need some advice/help regarding the TT21 OB. I recently modded mine and it was running well, then I decided to mod further removed material from the shim to get .008" headspace. However when I reassembled the engine, I found that the compression is very low when turned by hand. Is this normal for the mods I did? Or could it be that I now have got a bad seal between the sleeve and the button?

I am quite new to engine modding, so any help would be appreciated

What do you mean when you say that you removed meterial from the shim.Shims come in different thicknesses for that reason.Did you grind on the shim to thin it? :huh: If so,throw is away and install a new one.The shim is the head gasket.It must not leak.If so,you WILL loose compression.

 

[VansRacing]

LOL....I missed that!

Walt is right, if you removed material from the shim, that is most likely the problem.

Waltr, how's that boat coming along?

-Carl,

 

[Jerry Wyss]

You Guy's Just Spead Out an Give Me a Little Room :lol:

First off you can't get to .008 headspace in that motor unless you have cut the button in a lathe.

I've owned Way Too Many of them motors and All of them come stock with .023 H/S and

with a .010 removeable shim.

If you tried to sand or grind the stock shim down, like others have said,,

your just ask'n for a problem and it ain't gunna get you to where you want to go anyway.

If you can find someone with a small lathe have them take the bottom of the "largest diameter"

part of the button down until the section that goes into the sleeve is .115" thick.

This will give you .006 H/S ( Now Nobody Grown Here) The TT button has Enormous Volume,

with a "slanted surface" squishband face,,It will be more than enough H/S cause it's

only .006 out at the very edge of the squishband.

We ran them that way for 5 years and never had a problem with'em.

Jerry

 

[Scooter12195]

Now that sounds like some sound advice from somebody that has experience on Thunder Tigers. If I ran TT's I'd go with that!!

 

[VansRacing]

Go Jerry, Go...

LOL. I have never even seen a Thunder Tiger so that's how much I know about them.

-Carl,

 

[MalaysianFlyer]

Whoops. big apology to everyone, I meant that I removed material from the sleeve, not the shim. My mistake, typing while half asleep!! :blink: sorry for wasting your time with that one guys

Jerry, when you say cut the largest diameter of the button is this the outermost "rig" or the channel into which the top of the sleeve fits?

Since waking up I think that it is most likely caused by the removal of material from the sleeve, as none of the other mods caused this problem. I suspect that it means the seal between the button and the sleeve is bad, but would like to hear the opinions of more experienced people on this before I do anything st*pid and junk the engine by mistake

 

[Jerry Wyss]

Flyer, Most machinist's won't want to try and remove material from just that channel.

They will want to remove the material out from the channel, past the head bolt holes

and on out to the edge. This is all Ok, it won't hurt anything,,they will take all that down

until it's flat.

The section that goes into the sleeve is about .108"stock ,,,,so .115" is only .007"

deeper than the the surface that is there now, with the aluminum shim removed.

If you have removed material from the top of the sleeve flange , I hope it was done

in a lathe. There's no other way to do it and get it square,, if that has happened then

it will have to be "dressed up" on a lathe and all this info I just gave you will have

to be adjusted.

EDIT: If you get in a "Jam" and need a good piston, sleeve and already cut head

button,,I have some here that are a little used. I would run them myself, they're

that good.

But I would need to know what else you have done to the engine,,does it have a

pipe , what % of nitro and stuff like that.

You can e-mail me personally at <[email protected]>

 

[MalaysianFlyer]

Jerry your obviously very experienced with this engine, The sleeve was done by hand on a flat surface with glass paper. My mistake for wanting to rush I guess. I am tempted with the idea of the parts you have, but I think I will try to see what I can do on my own first, as I am enjoying tinkering with the engine at the moment. Actually during all my years of flying, I never touched the engines even once, only now that I got into boats I have a huge interest in the engines.

Will try to hunt down someone with a lathe tommorow, or if not will have to try using high temp silicone gasket maker to see if it helps, but not sure if that would last. Still, it has been very interesting, and will probably be looking at the OS outboard for my next boat (JD WOF)

Thanks again to everyone for helping me out

 

[Jerry Wyss]

Aww gawd, he went to the "Dark Side" :lol: :lol: nah really, the O.S. OB is a good motor, just

don't try to modify it too much or it can get more expensive than the TT and it doesn't respond

well to "TT Like" mods. In other words, it runs best in stock form

 

[Bob Kensill]

Jerry

Doesn't taking the material off the bottom side lower the timing,or is that the goal. I normally remove all material from the top of the flange. That way it is easy to get a flat surface. Just wondering.

 

[MalaysianFlyer]

:lol: :lol: Not quite into the dark side just yet, I still want to be able to "cook" my TT enough to beat the OS

I do like the OS features like the removable exhaust and self lubricating shaft, and it would make a good match with my next boat, the JD WOF ( just got the plans), as I 1. can't afford a MAC or Rossi 2. No support for those engines over here anyway

Now even toying with the idea of using a car pipe on the engine if i get this problem sorted out :huh: I know, sounds nuts but what the heck, it will be a good laugh

 

[Jerry Wyss]

Jerry

Doesn't taking the material off the bottom side lower the timing,or is that the goal. I normally remove all material from the top of the flange. That way it is easy to get a flat surface. Just wondering.

Hey Bob, I think "Flyer" was trying to get to .008" headspace that's what I responded to anyway.

He said he did try to remove material from the top of the sleeve flange with a piece of glass

and "sand paper?",,,so timings weren't involved, yeah? :unsure:

 

[Eric Bourlet]

:lol: :lol: Not quite into the dark side just yet, I still want to be able to "cook" my TT enough to beat the OS

I

Wow! Maybe we have a new TT guru on the forum, if you got a TT to run with an OS. While Jerry has got more out of the TT than anyone else I know he still hasn't been able to get a piped TT to run with a NAMBA legal Stock OS . :lol: We luv ya Jerry!

 

[Jerry Wyss]

Niether has anyone else dip stick. You just on a single man mission

to be a Pr&ck or What? What is the reason for a statement like that for anyway?

To show us How Great You Are? It just show's me how small you are,,so keep it

up and you'll end up taking a single man race to the bottom of the pond!

 

[Slideblues]

06 should be a interesting year, Anytime a combo starts to dominate the class it makes others work harder to come up with new stuff, Competition could get exciting....... Just a overview

Gene B)

 

[MalaysianFlyer]

Jerry, thanks for the tips. Hopefully I will get the engine running by the weekend and see what it does. Looks liek I will have to try and seal up the head with high temp silicone, as I havent had the time to look for a machinist. Wondering if it will hold, or if i will be sat there with a face full of red goo when it blows out the motor :lol:

Now i just need to get the hull set up better. I am running the TT falcon3.5 hull with a little modding, some 3mm ply plates under the sponsons to help it plane better. Not just need to get it balanced right with the correct angle for the engine. I have managed to at least keep reasonably close the the ABC boats LiquiMoly thats got the OS on it, so hope the new mods help. I knw the boats we are running are not exactly the of the pedigree that you guys run, but we have to grab what we have available locally

 

[Jerry Wyss]

Flyer, I haven't tried such a thing with the silicone and I don't know how it's going to

stay out of the way of the piston.

But ya never know, in some strange way it could up your compression,,,OR

destroy the rest of your engine,,,you think that's worth it?

 

[MalaysianFlyer]

Jerry, I agree, it is a risk but considering that this is the first time I have tried modding an engine and haven't killed it yet, I'll risk blowing it up. Besides, my LHS has one in stock with my name all over it already. (though many darth vaders over here are tempting me to the dark side with the OS). The silicone shouldn't get into the combustion chamber as I only put it on the outer part of the sleeve flange, so hopefully it will work. The compression seems to have returned, BUT... now the thickness of the silicone will have put me out of the headspace I was aiming for. Still, it is better than the stock version, so should be fun to run it.

It is my own fault for not doing the mods the right way, but at least now with the info you have given me, the next one will be spot on. I figure the amount of knowledge I picked up is worth it as I can apply the same knowledge to my planes and buggy as well.

Just as insurance, will be praying very hard before the weekend :lol: And will let you guys know how it went. And now to finish my seawind, so that I will have something to play with if the engine blows up