et 250 oval racer

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connor1

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Jan 7, 2010
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54
Location
NY
building an et 250 oval racer. I need a gear set up for big track(1/2 mile) and a short track set up. I can do anything internally to the motor up tp.060. over on the bore. I have to use stock exhaust .also need a clutch setup. where is the best place to send the motor to get the work done? I already have a 71 lynx W/ 338 hirth. can the et250 be made to run with it and the gp292 or am I wasting my time. My son is running the sled. got 52 out of the lynx on gps at boonville. thanks in advance for any info I'm starting from scratch and don't know much about the yammies. I already converted it to a mikuni. thanks again
 

The 250's can actually out run the 292's. We proved this at eagle river winning the single cylinder fan up 340cc class. We ran a ported motor with stock bore at eagle river. You had to run the stock pipe. We ran the stock primary and secondary on the sled because our rpm's were dead on with a slight increase in gearing. We ran stock because it is less weight to throw around then any other primary on the market. We ran a mikuni 36mm carb with 240 mains and 75 pilots. Needle was in stock position. (These numbers can change drastically from setup to setup) The motor made great power and pulled all of the other sleds we raced there in the straights. Put a slide lubing system on the sled if you can. I do not suggest punching out the bore in less you intend on cutting up the cylinders alot to account for the increased bore. You must remember that what ever you do to the motor, it still has to go through the stock exhaust pipe.

With identical setups, our ported motor made 700 RPMS more than our stock motor.
 
what rpm does the et run at stock and whats the stock engagement. What was your rpm after the porting and what are you engaging at. are the stock et around 23 horse? the gp292 are around 28. I want as much info on the performance mod I can do to the et. thanks
 
We changed the clutching to make the RPM's spot on for both motors but you want to be running around 6800-7000 RPM. We have been running an engagement of about 4700 RPM for both motors aswell. I am not sure on the stock HP of the machine. I do know that none of the 292's at eagle river were pulling me in the straights. When we ran the same setup as eagle river, our RPM's dropped from 7000 to 6300 from ported motor to stock in the same conditions.

What year ET are you running cause you might run into a big problem with the primary...

We were running 58-59mph on the straights at eagle river
 
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it is a 78. I heard the 1980 primary is lighter. what gear set up are you running. I also heard et250s have a problem with the primary exploding. what is your belt deflection supposed to be. 1 1/4" ?
 
i run a 78 enticer with a gp 292 motor ported and polished. cut the crank for a taper clutch, 38mm flat slide, 260 main jet, stock enticer pipe, let the motor run high rps to get in the pipe rpm range. my brothers stock gp 292 in a 100 foot I will have 3 sled lenghts on him and in a field his speedo reads 60 and I can fly by him. great sled with a better motor. 2ooosrx is right my enticer last year was a fast sled with porter and polished motor
 
the 1979 and down ET's have a splined crank. This means you cannot run aftermarket primary's on it. The 1980 and up run a tapered crank so it is easy to change to different primary's. The splined primary's are very limiting and not much can be done to change RPM's the way you want. The gearing all depends on what distance you are going to run. If you are going to run a half mile track, you can probably get away with running stock gearing.

As far as your question regarding 250's running with 292's...There were about 4-5 250's running at eagle river against the 292's. 1st, 2nd, and 3rd place were all 250 enticers...
 
we will be running both short and long tracks we run two different organizations. the et will mainly be run on a short track and one1/2 mile once a season. I can run a different pipe if a jump to the mod class. does a pipe make a differece and what pipe i used and what engine mods need to be done. approx what horse with pipe
 
I am unfamiliar with running an aftermarket pipe on the sled because no races we attend will allow that. Running a pipe will make a huge difference but you will spend a lot of time trying to dial in the pipe with jetting and figuring out what rpm's to run the pipe at. If you are racing against SR 292's in the mod class, don't waste your time. Most of those SR's with a good tuner are putting out low to mid 70's in the HP range.
 
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