'99 RMK 700 Track/Tunnel Extension Question

[jp83669]

I have a '99 RMK 700 with the x-tra 10 136" skid that came stock, and have purchased rail extensions that will fit a 156" track. My primary question is whether a tunnel extension is needed? If my math is correct, the track should be effectively 10 inches longer at the back. The current tunnel is slightly longer than the track. Here is my main question: With modern snowmobiles, everyone is cutting tunnels. I'm not worried about dragging my tunnel, this thing isn't doing wheelies for sure. However, if i don't need to order a $100 extension and the exchanger will get enough snow, then why not just shorten the snow flap and leave the tunnel stock? Any thoughts are appreciated.

 

[BeartoothBaron]

You probably won't be able to run a snow flap that does any good with that long a track in that tunnel. The track is likely to hit anything that hangs down at all from the tunnel; I'd think if you keep some sort of snow flap, it'll have to be angled straight back. Also, most sleds have a cooler that runs back to just over the top of the rear idler wheels – that big turn helps spray snow, so a fair amount of cooling comes from there. The snow flap also helps catch that spray so the track can circulate it to the bulkhead cooler. You'll probably run into cooling issues to some degree if you don't extend the tunnel, but it may be acceptable depending on how far you have to trail ride and such. Nothing wrong with trying it out without an extension, but you'll probably be better off with one.

 

[jp83669]

You probably won't be able to run a snow flap that does any good with that long a track in that tunnel. The track is likely to hit anything that hangs down at all from the tunnel; I'd think if you keep some sort of snow flap, it'll have to be angled straight back. Also, most sleds have a cooler that runs back to just over the top of the rear idler wheels – that big turn helps spray snow, so a fair amount of cooling comes from there. The snow flap also helps catch that spray so the track can circulate it to the bulkhead cooler. You'll probably run into cooling issues to some degree if you don't extend the tunnel, but it may be acceptable depending on how far you have to trail ride and such. Nothing wrong with trying it out without an extension, but you'll probably be better off with one.

Thanks Beartooth, I think I’ve arrived at a compromise. Local salvage guy sold me a tunnel he cut off an edge chassis for very reasonable price. Means I have to do a little metal work, but I enjoy tinkering anyhow. Also, when I looked at the RMK on the trailer over the weekend I won’t have to move the heat exchanger. One because it’s rather permanently designed, but also located in front of the current factory tunnel extension.

 

[retiredpop]

The coolers in the tunnel are so far forward it's going to be hard to get enough snow thrown up onto them. I had a 99 RMK with the 136 and it wasn't the best at cooling even being stock. I figured they just left the coolers in the tunnel at the same location as the 121" tracked sleds which is why they weren't above the rear idler wheels. If you could hook up an auxiliary cooler at the back of your tunnel extension that would be ideal.

 

[jp83669]

Thanks retiredpop, I think your assumption is correct about why the exchangers are where they are on this sled. My 2001 RMK had the exchanger at the rear of the tunnel extension. I may just see how it does without the extra exchanger for now. Have a teenager riding who isn't overly aggressive in his riding style, just trying to help him not get stuck so often when he leaves the trail.