Rotax 257 in UAS...

Ted Hamilton

Ted Hamilton

Helmet Painter / Racer
Anyone done it? I got a whole microsprint with complete alky 257 and comprehensive spares, including what appears to be 1 complete 125 and 1 partial, lotsa' pipes, etc. I need to reinstall the clutch and have someone look things over, but I was wondering if anyone's used one for UAS before -- 2 cycle, 250cc, 6 speed gearbox.

Chris Seay?

Anyone?

Looks like I may have a "competitive" powerplant this year after all...
 
I raced 257s the last three seasons in gold cup roadracing. It's a good motor but takes some sorting... You need the correct combination of carb/ignition/pipe to be competitive with the best CR250s. Also DEFINITELY get a cylinder girdle if you don't have one already.
 
Also when you are installing the clutch, make sure you set the airgap correctly or it will slip - they are very sensitive to this.
 
Mine has a billet head, and motoplat ignition. Not sure of timing. I have the ATK manual, and will set air gap accordingly. I am thinking it would be wise to get new springs, etc. soon, and I'm hoping the previous owner included all the parts he removed. I'll post a pic of the pipes I have sometime soon.
 
Motoplat is a good analog ignition and works well. If you want big revs and max power, try to find a PVL digital.
 
I've been told this is a torque motor in general, and to keep it below 14,000? Where do you run yours?
 

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missing clutch area...
 

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if i remember correctly now im not positive on this but on the old forums seay sold a excentrik with a 257 rotax on it race ready so he might know a little about these too not certain it was him though
 
Yes Chris Seay had one sold it to mike Grady. Not sure who mike Grady resold it too. Matt green SC also ran one I n the Uas . I have 2 here now from the Greens and have cast cases to convert them. They have a very thin cylinder casting and need the billit girdle head to keep them from cracking. 57mm stroke so you can turn them up some . not sure if I'd run them to 14,000 thou.
 
seems like a nice package to run i know whoever got the last one was a lucky lucky guy as it sold for just 2500 i think???
 
Ted Hamilton said:
I've been told this is a torque motor in general, and to keep it below 14,000? Where do you run yours?
Click to expand...

Compared to the average CR250, they are a bit less torquey and a bit more mid-top. The edge they have is that they have a 6-speed trans vs. CR's 5-speed. The other nice thing is that Rotax 256's came with a variety of transmission gears so it is possible to change the ratios for your type of racing.

I was geared to go 130-135mph, but I wouldn't rev it anywhere near 14k. Much lower. Maybe with really short track gearing it could go that high- but I definitely wouldn't recommend it. You'll go through pistons, rods, and cylinders pretty quick at that speed, and there is really no need for it.

I've never seen that head before- looks interesting. You'd pick up some power with a VForce cage and a Dellorto 39mm.
 
Hey Ted-Call Mark Croslyn at (770)924-9420.He knows a lot about the 257s.Also, I think Cruz Vandall bought the one Grady had.
 
Thanks for the info... Now I gotta' figure out if the clutch nut is a LH or if it's just on TIGHT... I'll start looking for VForce reeds and D'ellortos. I suspect I'll have to adjust timing if this one's set for Alky and I go back to gas... I'll keep this thread updated.
 
Wiseco Piston Kit # 701M06800 : 3 ounces lighter than stock: faster rev.
Wiseco Wrist Pin Bearing # B1003A
Wiseco Top End Gasket Set # W5566
Boysen Reed # 670
Moto Tassinari V-Force 3 # V306A-M
 
Hey ted got the wedge almost done, fit up real good. Like the turned up wing in the rear. Gonna put a wicker bill on it get a little more downforce that way. Send some pics when Iam finished. Thanks Mitch
 
Ted Hamilton said:
Wiseco Piston Kit # 701M06800 : 3 ounces lighter than stock: faster rev.
Wiseco Wrist Pin Bearing # B1003A
Wiseco Top End Gasket Set # W5566
Boysen Reed # 670
Moto Tassinari V-Force 3 # V306A-M
Click to expand...

FYI, depending on the cylinder you have, you may need a 67.5mm piston. Make sure you double-check cylinder clearance - not all Wisecos are identical and your cylinder won't last long if you get it wrong. Also, you can use V-Force 2 reed cages too (they're generally easier to find, and some say they work better).
 
Any idea what part no. in the VF2 vs. 3? Chris Seay did send me a message about a couple guys who have done this for UAS, so we'll get 'er sorted out. :) Maybe even in time for the GN....hehe As if I'd ever show up to DRIVE at a racetrack?! LOL
 
I turned mine 12k, max. Hot rods stopped making a rod kit for it but they have a kit that will work if you shorten the crank pin. Mine is going to a vintage road race guy.
Mike
 
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