Well, here we sit, a shop full of riders with no snow to ride on.
And trailering down to the ice isn't a whole lot of fun when you're
not setting up a sled for the race track.
Well, here we sit, a shop full of riders with no snow to ride on.
And trailering down to the ice isn't a whole lot of fun when you're
not setting up a sled for the race track.
Scotty booked a week off to snowmobile months ago, and now he's just twiddling his thumbs! "Boy I wish it would snow. I didn't take this week off to sit home with the kids."
I shrug, "There's always performance tuning..."
"Sure," says Scotty, "But if I had any spare cash to play with, I'd already be loaded and gone to the mountains riding instead."
Old Bob grins, zips the top of another can of coke, and says, "Besides, haven't you ever heard that if it ain't broke you shouldn't fix it."
Scotty nodds, "Yup, the sled is running pretty good. Far as I remember anyway."
Rusty as they are, the wheels start to turn in my head, remembering all those million hours we used to spend getting a race sled ready. "So how much time do you have left anyway?"
"Six days -- and I hope they're all not as boring as the first one. There are only so many cartoons I can watch," responds Scotty. "That Blue's Clues show is too much for me."
"Well," I say, "there is one thing we used to do, even with our brand new sleds, which won't cost you anything. And it should improve your performance. But it could take you all week."
Scotty's face lights up, just like the Christmas lights we took down yesterday. "Anything! Just give me a reason to get into the shop and out of the house! But how much will it cost me?"
"Nothing." I smile. "Nothing but time..."
Alignment of every moving part is critical to how easy the sled will roll, so performance gains can be made by making sure all parts of the sled are properly aligned. Whether you've got a brand new sled that you're looking for top performance out of, a relic you're restoring, or something in between, these are a few alignments you can examine:
In addition to basic tools, you'll need a carpenter's square to align various parts. The complete sled will be torn down, except for engine, which is only removed from the frame. While this isn't absolutley necessary, it makes life a lot easier!
The hood, seat and gas tank may also be removed, for complete ease of working on the chassis. In the long run, this will likely save you time.
Drive sprocket spacing should correspond with the space between the drive lugs on internal drive tracks. While the sample shown has three separate wheels, yours may only have two, or as many as four. Each wheel has paddlesides, on one or both sides, that fit into the drive lugs in the track. The center of the drive wheel should sit exactly in the center of the space between the track lugs.
On external drive tracks the sprockets should run to the outside of the holes in the track. This type of track works by having the drive wheels actually drive in the holes to turn the track.
The manufacturer provides specs for your particular drive wheel spacings. You will have to ask your local dealer for this information, or purchase a shop manual for your model of sled. Check each measurement as shown in the manual. Remember that your sled is assembled on a production line, so you may occasionally find one that it is 1/16 of an inch or so out. For maximum performance this can be corrected.
The drive sprockets must also be aligned to one another. This is done by using the indexing marks that appear on one of the top edges. The marking is usually a dot or an arrow. This is done to keep the drive lugs or teeth [necessary on internal and external drive tracks] in time with each other. Most drive axles are hexagonal or have six sides, so unless you had either six or twelve teeth they wouldn't line up with each if one sprocket was out 1/6 of a turn.
It's rare that you would find a new production sled has a problem in this area. However, if the indexing marks don't line up, you'll need to press off the sprockets and press them on correctly. This will require more than basic mechanical equipment.
If you are working with a used sled, or one you are restoring from scratch, you may find that an error has been made with a previous installation, or they are worn out and need to be replaced. Press off the worn drive sprocket and replace with new or used parts.
Also, you should check to make sure the axle is not bent or that the splines for the chain sprocket are not twisted or worn as shown in the picture above. A visual inspection should be sufficient. If you lay the drive axle on a flat surface, rotating to all six sides, it should consistently lay flat. To check for a bent end on the chain sprocket side, measure the distance of the tip to the flat surface on all six sides -- it should be the same with each rotation.
Manufacturer's tolerances may allow some leeway, so if you want it exact in your new sled you may have to make some changes. If it's not square, you will have to slot the mounting holes [see illustration below] in the frame with a file or a die grinder, on the bearing cap side until it is. You will need to move the drive axle forward or backward until it is completely square with the frame.
Once the drive axle is square, mount the rear suspension. To check rear suspension alignment you begin by determining if the sliderails are running at 90 degrees to the drive axle. Measure the distance from the outer edge of the sliderail to the inner edge of the tunnel at both ends of each each side. It should be the same in all measurments. If they are running to one side or the other, you cut off a portion of the suspension mount and shim the opposite side.
In the image above, you can see the drive axle and suspension mounted into the tunnel of the sled.
If you're working on an older model, you'll also check for wear at any moving part. A rear suspension that is bent will not be able to be aligned, and must be replaced. Once bent, a rear suspension is weakened, so shouldn't be straightened and reused without reinforcement.
Many older models of snowmobiles didn't have grease nipples on major moving parts, so this is an ideal opportunity for you to add some. Without lubrication the old suspensions seized and were frequently damaged.
Join me next month as we continue aligning the moving parts of your sled.
Dr. Dave