racing motor question

[mhero]

I have a KT100 motor built by Stencil Racing Motors - which after searching around I have found out was a great motor builder in California in the 80's and 90's. The motor needs to be gone through, I can work on motors, but have never done anything w/ 2 strokes, so I had a friend talk to his buddy who has worked on dirtbike motors for years, and he said because it has been built I should take it to someone who works on race motors. I'm not sure I want to race, and throw alot of money at this motor, what would have been done to the motor when it was built - (best guess) and where would I be able to find parts, and would they be custom rather than off the shelf. I'm only looking for the best guess from someone who understands what is done to a motor when its built for racing

 

[jandj]

Was going to say vintagekarts.com - but you're already there!

 

[FatCat]

There is no way to accurately guess. You won't know until it's opened up. I'm not familiar with cart racing. Were there displacement limits? The big gains in a 2 stroke engine is more in the porting, pipe, carb, and getting those all to work together rather than changing hard parts. I'd bet it's just stock kt internals. Can you try to get pics inside the intake and exhaust ports? First thing I'd do is trash that crappy paper air filter.

 

[walker187]

There is no way to accurately guess. You won't know until it's opened up. I'm not familiar with cart racing. Were there displacement limits? The big gains in a 2 stroke engine is more in the porting, pipe, carb, and getting those all to work together rather than changing hard parts. I'd bet it's just stock kt internals. Can you try to get pics inside the intake and exhaust ports? First thing I'd do is trash that crappy paper air filter.

No, the engine internals are not stock. If the engine was built by Stencil, it is most likely a blueprinted engine. It may have a modified crankshaft, different piston, and maybe polished and ported. It might actually be a good idea to put $100 to $250 into it because engines like this one are very desirable. The air filter may still be usable lol... just clean it of with air and oil it.

 

[FatCat]

No, the engine internals are not stock. If the engine was built by Stencil, it is most likely a blueprinted engine. It may have a modified crankshaft, different piston, and maybe polished and ported. It might actually be a good idea to put $100 to $250 into it because engines like this one are very desirable. The air filter may still be usable lol... just clean it of with air and oil it.

Why do you feel the internals are not stock? Unless the changed rod length or stroke there would be no reason to change it. OEM parts are as good of quality(I'd say better) than the aftermarket stuff that's available. Could have a wiseco or other replacement piston but it won't make any more power than a stock one would. A "blue printed" engine just basically means it was built right. From the factory engines are designed without the best tolerances in mind. This is for speed of production. They simply can't spend the time it takes make each one perfect. This is why we use gaskets. A perfectly built 2 stroke wouldnt require gaskets. Gaskets give us room for tolerances that aren't perfect. I wouldn't doubt that the internals have had modification. Any engine built right will. When you get new parts out of the box they should be prepped(modified)before use in an engine. I bet it has been ported. Polished I doubt.(maybe exhaust port but just a waste of time. Only really helps with carbon buildup. Long before the carbon builds up the engine should already have been pulled down for inspection.) I'd definately spend the money to make this engine right. Old racing engines aren't easy to come by. I've got a few really cool setups for my Odyssey.

Oh and the paper filter thing. No LOL! Please do clean it with air as this will assure me that it's destroyed. I don't find comedy in people having their stuff damaged. Guess it's easy to recommend that with a LOL when its not your stuff being ruined. Take a look at this link. It shows what these filters do. Cost people engines, that's about all.


http://www.pilotodyssey.com/PO/viewtopic.php?f=9&t=5491

 

[anderkart]

mhero,

My 'best guess' is: Its simply been blueprinted, and is still 100cc so it could compete in the KT100 racekart classes, although some guys used to instal 125cc kits to have a better chance of winning in the open classes.

You'll find lots of KT100-blueprinting info in this google search link:
http://www.google.com/search?source...rlz=1T4GZAZ_enUS369US369&q=Kt100+blueprinting

Have you tried starting your engine?
If not, does it seem to have much compression?
Is it seized?

The outside looks very corroded, like maybe it was stored in a wet or very humid location, hopefully the crank isnt all rusty inside... I think you should just take the head and jug off to get a look inside before making any further decisions. Post some pics when you get it apart, maybe it just needs the top-end freshened up. Sounds like you could handle that yourself

That motorcycle engine builder prolly ran into some type of problems working on racekart engines before, and simply doesnt wanna risk working on any engines he's not totally familiar with...

 

[mhero]

I have not tried to start is, as the fuel lines were cut, and with the condition of the air filter I was afraid of doing damage - it is not seized - I can turn it over by hand, I am not familar w/ these @ all, how would I know what's stock or not when I open it up?

 

[walker187]

Why do you feel the internals are not stock? Unless the changed rod length or stroke there would be no reason to change it. OEM parts are as good of quality(I'd say better) than the aftermarket stuff that's available. Could have a wiseco or other replacement piston but it won't make any more power than a stock one would. A "blue printed" engine just basically means it was built right. From the factory engines are designed without the best tolerances in mind. This is for speed of production. They simply can't spend the time it takes make each one perfect. This is why we use gaskets. A perfectly built 2 stroke wouldnt require gaskets. Gaskets give us room for tolerances that aren't perfect. I wouldn't doubt that the internals have had modification. Any engine built right will. When you get new parts out of the box they should be prepped(modified)before use in an engine. I bet it has been ported. Polished I doubt.(maybe exhaust port but just a waste of time. Only really helps with carbon buildup. Long before the carbon builds up the engine should already have been pulled down for inspection.) I'd definately spend the money to make this engine right. Old racing engines aren't easy to come by. I've got a few really cool setups for my Odyssey.

Oh and the paper filter thing. No LOL! Please do clean it with air as this will assure me that it's destroyed. I don't find comedy in people having their stuff damaged. Guess it's easy to recommend that with a LOL when its not your stuff being ruined. Take a look at this link. It shows what these filters do. Cost people engines, that's about all.

I never said everything had to be perfect... the internals, as in parts are probably made of a lighter metal or other modified parts. I didnt mean anything bad by the air filter thing either, maybe save this guy some money?

I have an old kt100a rotary valve and its worth quite a bit, maybe this one is too.

 

[anderkart]

I have not tried to start is, as the fuel lines were cut, and with the condition of the air filter I was afraid of doing damage - it is not seized - I can turn it over by hand,

__________

I am not familar w/ these @ all, how would I know what's stock or not when I open it up?

It might be best to pull the head/jug for a peek inside first, but you could test-start it without an air filter.
__________

You probably wouldnt be able to detect any of the blueprinting mods, but you could measure to determine if it still had the stock bore/stroke.
That would be:
Bore: 52 mm (2.05 in)
Stroke: 46 mm (1.81 in)

 

[FatCat]

I never said everything had to be perfect... the internals, as in parts are probably made of a lighter metal or other modified parts. I didnt mean anything bad by the air filter thing either, maybe save this guy some money?

I have an old kt100a rotary valve and its worth quite a bit, maybe this one is too.

Everything being perfect is what a blue printed engine is. I was just asking what you thought was different. I've never played with kart engines. Was wondering if you knew some squirrel secrets I didnt know about. Don't mean to jump on you on the filter thing but recommending that would do exactly the opposite of saving him money. You may have meant it as humor but that can't be seen through text. If he didn't know better he could have took that advice and used it. Bad plan