Purpose built snowbike

fgauvin7

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Oct 14, 2012
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On another note, huge thanks to eric82930 for the advice on the rear engine mount!

I did not have any space with the new tank for a cross brace so I ended up just building the strongest mount possible in the space that I had! I was lucky to have some space available in the tunnel just bellow the mount. So I was able to fit two 1in square tube .125in wall into the tunnel flush with the sheet metal and build some strong mount from that.

Tested it yesterday, the difference is outstanding! Most of the problem is gone I think, I have to test it more but it is definitely a big improvement. for the rest of the vibration, well it is a 8-9000rpm single cyl.... It won't change that much

I hope It will be easier to have some reliability now! So I can do more riding!


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Arctic cat actually has actually applied for a patent to build basically the same thing but using the blast 400CC engine but turned around exhaust straight out the back.
 

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Thanks @fgauvin7 for your detailed thoughts on the various components. Your thinking about the a-arm front suspension makes sense. I'm still on the fence whether it would be a real advantage or not but I like the concept and I'm gonna continue to entertain it.

For something easy, I'm with @eric82930 on lowering the head tube and using a short ski spindle. I have another bike that I've been screwing with over the years which is now obsolete since I no longer use motorcycle engines. It's the perfect candidate for some front end experiments. This bike's engine will get replaced with a sled engine and clutches. @fgauvin7 I cannot encourage you enough to give a sled engine a try. Don't be afraid of the width. I originally was but found it is non-consequential. Center the power plant so that the flywheel/stator cover and the primary clutch stick out equally on both sides of the machine. The cylinders will be offset to one side under the hood but this makes no difference. Anticipate the total width at around 24 inches (60cm). It's totally acceptable in my opinion.

Again, good work and I hope you will continue to post info about what you're up to. I love this stuff!
 
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One more thing for what it's worth. I've screwed around with rake angles from 25 degrees to 30 degrees and to be honest, I can't really tell much difference. It would be neat to build up a machine where you could easily adjust rake and trail to really get a feel of the differences.
 

fgauvin7

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Thanks @fgauvin7 for your detailed thoughts on the various components. Your thinking about the a-arm front suspension makes sense. I'm still on the fence whether it would be a real advantage or not but I like the concept and I'm gonna continue to entertain it.

For something easy, I'm with @eric82930 on lowering the head tube and using a short ski spindle. I have another bike that I've been screwing with over the years which is now obsolete since I no longer use motorcycle engines. It's the perfect candidate for some front end experiments. This bike's engine will get replaced with a sled engine and clutches. @fgauvin7 I cannot encourage you enough to give a sled engine a try. Don't be afraid of the width. I originally was but found it is non-consequential. Center the power plant so that the flywheel/stator cover and the primary clutch stick out equally on both sides of the machine. The cylinders will be offset to one side under the hood but this makes no difference. Anticipate the total width at around 24 inches (60cm). It's totally acceptable in my opinion.

Again, good work and I hope you will continue to post info about what you're up to. I love this stuff!
Thanks @Brett Kobernik, yes I think I will go forward with the sled engine and explore that trail for the moment! As you said I dont mind having a small 3-4in bump on each side to make room for the engine. I just want to keep the overall machine compact and slim. I'm on the same track as you I think on the varous point for the next build, lowered fork with long stem tube, short ski spindle, low CG 2 stroke twin centered in the chassis. I would retain most of the geometry of my actual bike since it is working good, I will just improve some point as talked before. I think a steeper fork rake could be a winner but an ajustable setup sure would be nice and not too hard to acheive.

My frame jig is done too! I just need to fab some mount for the component, this jig will allow me to assemble and test new layout without having any frame work. When I will have something I like I could then run some tube and build some structure to support everyting. Also it will be pretty easy to trasnfer the machine layout to the 3D modelling software since I have some reference to measure form.
 

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Dec 19, 2007
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I agree the rake itself isn't that big a deal but what I notice is the steeper rake feels better in hard snow and slack rake is better in soft snow. It is mostly due to the fact the the side wings on the ski dig in more with slack angles which makes the ski more aggressive bite in pow but miserable on hardpack. We could get the same affect by swapping between the backcountry and traverse ski.

The low center of gravity is important too. my raptor is a tall engine and the head is massive. It really makes me struggle to lift up after a tip over. Having a wide cvt cover on a sled based engine might actually help make it easier to flip back up. When sleds tip over the bars might be in the snow but then the track is in the air as a counter weight pivoting on the cvt covers.
But I keep coming back to the over all weight issue can't be totally ignored which must be one of the problems of the snowhawk. and there is a fun factor that a 217lb bike with a skinny short track will always win over a 400lb bike with a long wide track. My goal is to have one of each some day.
 

Hawkster

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That's good
An adjustable rake makes way to much sense , an eccentric bolt or cam bolt kit with a death lock lever making it adjustable in the field . The ski seriously scrubs ponies when needed .
I like it :)
 
Dec 19, 2007
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So field adjustable might be tough but here is my plan. I will turn down the outer tubes on my forks so they are the same diameter as the top all the way down. Then I will get an extra top clamp to put on the bottom down by the lower seals. I'm thinking of not using a stem at all but instead possibly ball joints with adjustable threads. Sourced from a utv or slightly hd than a sled ball joint.
 

Sheetmetalfab

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So field adjustable might be tough but here is my plan. I will turn down the outer tubes on my forks so they are the same diameter as the top all the way down. Then I will get an extra top clamp to put on the bottom down by the lower seals. I'm thinking of not using a stem at all but instead possibly ball joints with adjustable threads. Sourced from a utv or slightly hd than a sled ball joint.

Big ball joints are very stiff to turn unless you get the bronze oilite version.

Stay away from the ptfe race.
 

fgauvin7

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Little update on the project!

Snow is mostly gone around here, it has been a very short winter over all with not much snow to to play with. But I enjoyed the snowbike experience a lot even with this amount of snow. For me it is an advantage over my M8000, I need a lot less snow and spot are very easy to find.

I didn't put a lot of hours on it, but my main goal for this winter was to dial it and solve the issue there might be. On this part I can say that most issue are gone now, vibration is very minimal with the new engine mount and the addition of a rubber mounted handlebar. Last ride I did I had some trouble with an iced up carburetor, but since then I added a carb heater and a neoprene blanket. This should solve the problem for next year. Body panels would help a lot through, we will see this summer if I can add something to cover it. It won't be simple since the chassis is not designed to have a body... I'm on the V2 at the moment, so there is a possibility that I will put the effort on the new one to make something look nice and leave the actual build as is if the carb is covered enough.

On the chassis side, I did not touch anything this winter, rear suspension, front suspension, steering.... Everything just worked! I need to work with a friend to do a custom suspension valving that would suit more the build.

Next build should have a bit more seat height, 33in is a bit low, feels good in the shop but out in the snow it is a different story. Around 2in more could improve foot drag and still provide a user friendly seat height.

This winter I was also lucky enough to participate in a tv show and describe what I have done with this project! I was a pretty fun experience and I have had a lot of feedback in the last few weeks! Unfortunately it is in French but some of you may like to see it...


Thanks for everyone input along the winter! There is still a lot to be done and many idea to try, but it is nice to be able to ride something and learn to be able to make the next one even better! By the way I'm looking to name this project, I have not found anything yet that I like... So if some of you have some proposition I'm all open! :D

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Dec 19, 2007
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We call our naked home builds "Skelator"
There is a brand new cheap counter balanced 17 250sx motor to be had on the local classifieds here that would love to find a home in that frame! But I'm guessing your out of the country?
 
Dec 19, 2007
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I was told a prototype was built but cat isn't persuing it because of demand. the Polaris rep also told me they'feel a kit is best because it can be used year round. Nothing new to get excited about this year it seems.
 
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