Why not one more. Snowmobile engine board track "replica"

Hurco550

Keep er' Between the ditches
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This will be a slow going mod podge of bike/ snowmobile parts I have laying around. Cb550 frame with a weld on hardtail. Planning on using a late 60's NOS hirth one lunger smoker engine I picked up a while back. Looking for a 40 spoke 2ls hub. Cvt clutches so she will be an automatic. Gas and brake is all I'll need to wrangle down the road.

Without further adu, here is to one more project.



 

stroker crazy

crazy as a fox
Re: Why not one more. Snowmobile engine deadtail

hurco550 said:
early 70's NOS hirth one lunger smoker engine …
Could you tell me more about this motor? (We don't have much of a snowmobile culture here in Oz).

Crazy
 

Hurco550

Keep er' Between the ditches
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Re: Why not one more. Snowmobile engine deadtail

I am not the foremost on this motor,but I'll do my best lol. I changed my post, i was made by hirth in the late 60's, and from what dad said, they were a utility engine mainly used for ruining pumps. They were used by several snowmobile manufacturers in the day (boa ski, bolens). Best described as heavy and under powered. Most places say right around 15 horse at the crank. The plan is to 180 the cylinder, hang the carb off the front, and throw a spandy out the back.
 

Hurco550

Keep er' Between the ditches
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Re: Why not one more. Snowmobile engine deadtail

Disclaimer: the engine in the pic is identical to mine, but it's at dad's house right now, so I grabbed an image off of Google lol

And yep, she is pull start
 

Hurco550

Keep er' Between the ditches
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Re: Why not one more. Snowmobile engine deadtail

I decided not to use my NOS engine for this bike. I'm gonna save it for the sled restore I originally bought it for, which is a Bolens Diablo Rouge like pictured here.

Here is the nos engine. Still has the factory intake and exhaust covers on it.


I'm going to use this one instead. Needs a rebuild, but these things are rediculously simple.



Quick sit in the frame. She will do fine.


 

Hurco550

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Re: Why not one more. Snowmobile engine deadtail

stroker crazy said:
Looks positively agricultural!

Crazy
Ha, I'll try to fix that as much as I can
 

Hurco550

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Re: Why not one more. Snowmobile engine deadtail

Well I'm gonna have to track down an oversize piston. Bore isn't terrible, but not great.

 

Hurco550

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Re: Why not one more. Snowmobile engine deadtail

Neat thing about these engines, they are actually designed to turn the cylinder 180 from the factory to suit the situation. Even down to a threaded hole on the opposite side of the crank case to run a hose to the carb for the fuel pump.

 

Hurco550

Keep er' Between the ditches
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Re: Why not one more. Snowmobile engine deadtail

a little more engine tear down last night. New crank bearings are a must. there has to be .020" of play in the crank haha I should know by tonight if its completely trashed or not...
 

irk miller

You've been mostly-dead all day.
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Re: Why not one more. Snowmobile engine deadtail

This is cool, man. I'm enjoying learning about these motors.
 
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