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Cyclenorthman
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Discussion Starter #1
I have a Yamaha air cooled engine with serial number S433-0236XX and I am trying to id what it came out of. It has two into one exhaust and intake manifolds with reed valves and a 50 mm carb intake opening(larger than a TIL HD). I'm thinking a GP but what year is it?
Any idea where to get performance specs on this unit and how it would perform in the summer weather?
Thanks,Cyclenorthman
 

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HMM! single pipe Free air or Fan cooled? Twin carb or 2-1? Reed valves???

It would have to be rejetted but would run depending on aplication and how hard you run it, how long it will perform!

Oh and welcome to the snow show!
 

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Cyclenorthman
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Discussion Starter #3
More 433 info,needed

Engine has "Y" exhaust pipe so single pipe.("SS" models had dual tuners and dual carbs,right?)Single carb but I can see it would be easy to remove intake "Y" and install rubber carb mounts(but oil injection hooked to left side,no carb on it now)Has reed valves.
Cooling fan on flywheel.
To do it correctly for warm weather use I would use a dual egt and cht gauge set and burn 91 octane instead of our 10% alcohol 87 octane we get in MN.Or mayby 100 octane LL avgas to reduce preignition chances.Unit MAY go in an ultralight aircraft but I am leaning toward a liquid cooled Rotax but have seen many air cooled engines that work fine in UL use. Max rpm is6000 -6500.
Trying to ID engine because it needs at least a top end job (LOW compression) and I don't know what engine model 433 cc to order parts for(mayby some differences between reed and non reed models?)
Anyone know of someone who used this type of engine in a ultralight application and lived to tell about it? I am leaning towards the Rotax unit because it has a track record and useing the Yamaha in a sled or atv/go cart or ?.
I welcome your comments pro's and con's.
Thanks,Cyclenorthman
 

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The SS 440 had a single exhaust. The reed valves is what is throwing me? Are the plugs straight up or angled?
 

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yes this is an exciter motor. it either has the wrong fan shroud, or it has the wrong cylinders on it if the serial no says that it is a 'S'433. the exciter shroud should say 'SS'433, this might be a first year motor, a 77, but it has reeds, and it is an exciter. All of the 433 motors had the same bottom ends, this includes the older style 338cc yamaha motors from 76 and down. it also does not have a point ignition, so that means that this is an exciter motor because that was the only sled to use that style of ignition with that motor. it is the best of the 433 motors.

For running this motor in the summer, you will need to find out what the original jetting was, then go about 2 to 3 jet sizes down. i could be wrong, but it looks like it has no carb? i would go with a mikuni 38 to 40 mm size slide carb. it should be easier to tune and use. in an ultra light i would not know what to jet it at due to where the engine has to run at, like in the sky :) well good luck, and i hope it works
 

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ss440

I have what appears to be the same motor. on the left hand jug sitting on the sled it has ss433ccsf, and the chassie number starts with 8e8-0074xx

can someone explain the reeds to me?

Thanks:dunno:
 

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ok, on the yamaha motors, you will know that it has reeds if the intake goes into a big rectangle that bolts to the motor. i do not know why yamaha strayed away from there piston port design, but the reeds seem to make more power at low rpm's. all of the early exciters have reeds, they look like the gp, sl, or pr (the model of the snowmobile) motors, those motors all have the markings 'S433'. the exciter SS433 also has 8 head bolts, 4 big, and 4 small. the S433 has only the 4 big main bolts, the bottom ends are interchangable between the two motors, and the Y pipe. the reed cages themselves go right into the piston port (which doesnt really do anything, other manufacures put them into the crankcase, it makes more power) and there is a notch cut out of the piston. the piston also has two rings instead of one. bullet proof motor, but a lot of people beat on them, and the sleds didnt last. they were good motors, and very relieble.
 
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