Building a Racer

[smudvapor]

Ok guys, I am thinking about building a racer. Here is what I have to start with. I’ll be using an Attex Colt. I have a T20 transmission, a JLO 440 with dual carbs, Salisbury 910 clutch, and all of the sprockets and chains for the Colt. Any suggestions? I realize that building a winner takes time but I want to try this with a small budget because I am building another Attex for my wife at the same time. If all goes well I will have all three at Pine Lake in June.

[Don]

It sounds like you have the start of a very good racer. The clutching and gearing of the machine is just as important (maybe more important) than the engine. The 910 is a great clutch, although it's not as easy to tune as a Comet 102C or 108C. I don't remember what the gearing was on the Colt. What you're looking for is about a 26 tooth driven sprocket.

Good Luck!

[George]

I had a Colt 15 years ago. I think I remember mine having pretty big sprockets (as big as you could go before hitting the bottom of the tub). That will keep you from reaching top speeds on the straight-a-way but will be helpful in getting back up to speed in all the twists and turns of the track.

[smudvapor]

Any suggestions about exhaust?

[jpswift1]

Any suggestions about exhaust?

Use a pipe off a Scorpion 440 snowmobile. If I remember correctly, one flows better than the other model......the Whip I think is the model to get one from, although I can't say for sure. Also, if your JLO 440 is a 4 bolt head, upgrade the heads and jugs to 6 bolt ones/5 port. This makes for a very potent engine. My 440 Thunderchief racer has a 440 5 port/6 bolt head and it will outrun a Superchief.........ask Hydromike, he has the same engine in one of his racers and his will do the same.

Here are most of the parts you'll need to build one hell of a 440. These will all simply bolt right onto your JLO 440 bottom end.


Scorpion Cuyuna 440 6 Bolt Cylinder Jug 1 PTO | eBay

Scorpion Cuyuna 440 6 Bolt Cylinder Jug 2 Mag | eBay

1979 Arctic Cat Scorpion 440 Cuyuna Exhaust Manifold w Muffler | eBay

[Don]

My 440 Thunderchief racer has a 440 5 port/6 bolt head and it will outrun a Superchief

Any Superchief, JP?

[jpswift1]

Any Superchief, JP?

Haha, well Don always has tricks up his sleeve. We'll have to play at Ashtabula in June. What might you be cooking up next?

[hydromike]

........ask Hydromike, he has the same engine in one of his racers and his will do the same.

The five-port JLO/Rockwell/Cuyuna engines really, seem to go like stink when you have them dialed in right. The original engine that I had in my D/stock Superchief was one of the newest models of the engine (a 2Si, but basically identical to the last Cuyunas). A loose spark plug caused the demise of that engine, but a slightly older 440 Cuyuna is in it now, and it really goes. There's nothing really special about the engine I'm running, and I wish I could claim I did lots and lots of modifications and had tons of technical advice to lend. It's just a 0.020" over Wiseco'd five port with a CDI, a 36mm Mikuni and a main jet big enough to get a golf ball stuck in. I'm running an ultralight aircraft exhaust manifold/muffler, and even though it's not an elegant design, it seems to breathe really well.





I'd agree with JP and say that converting over to the more modern 5-port jugs and heads would be a big improvement. The only downfall is that it might take a bit of fiddling getting everything dialed in right if you're pressed for time.. You'll need a new exhaust manifold, a new intake manifold, a new carburetor, etc. It's not impossible, but building more than one machine at once is never easy. THAT... I know...

[rodp]

Just out of curiosity, is there no way of sticking a Jap bike engine in a racer ? Too much power may be a problem then though

[jpswift1]

Just out of curiosity, is there no way of sticking a Jap bike engine in a racer ? Too much power may be a problem then though

It's not too much power, the T-20 is actually very stout, it's just that it would require too much time, money, and extensive modifications to do.