1968-1971 Mark I, II, III Track Replacement

[admin]

This thread is for posting any information and knowledge you can share about replacing the original track on the 1968-1971 MARK series Bubble Nose hood sleds.

Please post any information you have about finding replacement tracks and upgrading from the original tracks with external drivers (square open windows in the track) to the all Polyurethane type track that uses internal drivers. The Poly track is found on newer model sleds such as the 1970 Stinger, and the 1971 Stinger and Super Stinger models, and can be swapped into a 1968-1971 Mark series sled if you use the front and rear drive components and all the wheel assemblies from the 1971 model (for example).

Your input and corrections are welcome.

[admin]

I found this at another site and will give credit by posting the link to the original site,

reocities.com/yosemite/falls/9634/trackswap.html

Rotten 68 to 70 Scorpion Tracks

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This is for all of you out there who have a '68-70 Scorpion Trail-A-Sled and have a bad track. Evidently, you have also found out how hard it is to find an original track for these machines! So this is a simple how-to conversion to change the original sprocket-hole-track over to the more reliable and much more plentiful poly track/internal drive. Despite the work involved, this is by far the easiest way to make your Scorpion track reliable and ready to go again for many years to come. And should you ever need to find another track, it will be much easier to locate.

THE INGREDIENTS NEEDED FOR THIS SWAP ARE.......



- One '68-70 Scorpion in need of a track swap.
- One complete drive system from a 1971 Scorpion Stinger with the 15-inch narrow track. (note. MUST be from a '71 and Widetrack model components will NOT work in this case.) The exact parts you will need off the '71 parts sled are three sets of bogie wheels, the internal drive poly track, a rear idler set with wheels, and a front driveshaft with good sprockets. These internal drive sprockets are commonly prone to cracking, so carefully check each one to make sure they are not cracked. Check bogie wheels for bad or junk bearings. And inspect track for small rips or tears or excessive wear.
- You will also need a small variety of american wrenches, sockets, a ratchet, and a can of WD-40.



To get started...

The first thing you need to do is take the old track, rear idler arms and wheels, bogies, and front shaft out of your sled. Since you're going to be spending some time underneath the sled (which is the easiest was as opposed to lying it on it's side.) make sure the rear o the sled is tied up off the ground enough for you to comfortably sit underneath it. Also make sure the sled is adequetly supported so it won't fall on you while you're working. This involves taking the lower rubber plug out of the chaincase and unbolting the lower gear. (P.S. you WILL have oil all over for this step, but there is really nothing you can do about it!) Before you try and remove the gear, take all tenstion off the chain by loosening the chain tensioner on the chaincase. With the bottom gear off, you will have three carriage bolts to undo on each side of the track and a small steel collar on the inside of the tunnel that come off with an allen wrench. The the front shaft is out.


The next step requires you to take the front shaft and track from your '71 Scorpion parts sled and put bolt them back into the sled the same way you removed the old shaft.


With the new '71 shaft and internal drive track hanging under the sled and bolted in, (you may also put the lower gear back on your shaft and put the chain back on, adjust tension, put plug back in, and refill with oil.) 90wt gear oil is reccomended for this chancase, and make sure the oil level is even with the bottom of the lower inspection plug. You may need to remove the inspection plug again to check oil level. Next, use the rear idler arms and wheels from the '71 parts sled and bolt it into place the same way you removed the old one. DO NOT tighten track yet. Next, install the bogie wheels from the '71. If you compare the '68-70 bogies to the '71 bogies, you will notice the difference and that only the '71 bogies will work with this track swap.


Install the front bogie wheel first, because if you wait to install it last, it will be nearly impossible to wiggle and jam into place. Next, install the other two pair, tighten your bolts, and adjust track tension.


Make sure you tighten the track the same amount on each side to avoid it bieng uneven in the tunnel, which leads to track failure and fringing. When adjusting the track, NEVER over tighten the track, make sure that when the machine is raised in the air that the track sags up to an inch and a quarter from the middle bogie wheel. Run the sled lightly while it is raised up, just slowly enough to let the clutch engage and make the track turn. Watch for spots of rubbing or friction and make your adjustments, then check again. Once you have the bugs worked out, go through and make sure all your bolts are tightened well and then you're ready to go!

[admin]

Title: scorpion track rotted
Post by: scorpmyride on December 12, 2009, 08:10:29 PM
2utp U%m just bought a 70 scorpion mk II, 15" track. the track is very cracked, dry rotted. i remember seeing somewhere about a conversion to a newer style track. anyone know about this? any help appreciated. d.r.i.n.k.

Title: Re: scorpion track rotted
Post by: stinger440 on December 12, 2009, 08:51:15 PM
Thats an easy one. Find a 71 on up stinger with bogeys. Remove entire driveline, driveshaft to rear axle. Reinstall under your sled. Done da$ You will need to use the gears off whatever sled you snag because I believe the spline changes after 70. Other then that, its pretty darn easy.

Title: Re: scorpion track rotted
Post by: duane on December 14, 2009, 07:13:29 PM
What he said. Lil Whip is the donor for the Mark I

www.vintagesledders.com/forums/index.php?topic=2578.msg30694#msg30694

[admin]

From the Yahoo Scorpion Club

From: Mike P.
To: [e-mail]
Sent: Thu, March 17, 2011 10:48:04 PM
Subject: [Vintage-Scorpion] 1970 suspension conversion

Good evening everyone. I just recently acquired a 1970 Mark III and it has what
remains of the external drive and suspension. I have been told that converting
this to an internal drive set up is not to difficult. Just need to find the
right donor sled. That's where I have he question. Does anyone know what sled I
shold be trying to find that will swap over? I believe a 72 or 73 Super Stinger
will do the job but not sure. If there are others that would work that could
widen my search as well! If anyone has any thoughts I would really appreciate
the help.

Thanks everyone.

________________________________

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Re: 1970 suspension conversion
Posted by: "some human" humanbreathing
Fri Mar 18, 2011 6:07 am (PDT)


yep. my 71 mark II (bubble nose) track died some time back.... it was a
simple conversion to swap parts (involute drive cogs and shaft, rear idler and
shafts, bogie suspension, and 15" track) from a 72 stinger donor sled. I took
the opportunity to upgrade the chaincase, gears and chain to the 72 style as
well. EVERYTHING bolted right on...no problems.

remember, if you don't already have them, you will need the bogie suspension
(the metal tubes themselves) from the newer donor sled, the wheel spacing is
different between the external cog and involute style tracks which necessitates
the swap.

[admin]

From the Scorpion Yahoo Site,

involute track conversion on the Mark II series.
Posted by: "Krash"
Sun Feb 6, 2011 12:14 pm (PST)


My 40 y/o track failed yesterday. I am in need of a rear idle wheel assembly for an involute track. I would think anything pre-pararail that ran boggie and involute would work. 1971 stinger etc. Anyone have ideas on converting the old external drive idler over to involute idle style your input would be welcome too.

thanks,
Daran

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Re: involute track conversion on the Mark II series.
Posted by: "Gary B" snowmoboyle
Sun Feb 6, 2011 1:08 pm (PST)


I have 69 Mark III - 18" wide track. My dad did the conversion for me - using a
1971/1972 parts sled I believe? Pretty much everything bolts right in - few
adjustments needed but it still gets back on the trail!

Gary "SnowmoBoyle"

Father and Son Vintage Snowmobile Enthusiasts

[admin]

From the Yahoo Site,

To: [e-mail]
From: firemedic
Date: Thu, 27 Jan 2011 06:55:27 -0800
Subject: [Vintage-Scorpion] Looking for a lil whip involute track.

Hey,

I have a '70 Mark 1 that someone butchered a larger involute track w/parrarail under it. I would actually like to switch it back over to closer to original style... boogies etc. Problem is this track is too long. Anyone know where I could get a lil' whip involute track? I have everything ready, just need the track.

thanks,
Daran

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nos lil whip tracks and drivers
Posted by: "scorpsrus2"
Thu Jan 27, 2011 12:27 pm (PST)


I still have new old stock lil whip tracks and New New 2.52 pitch drivers , not the old cracked white ones ...... plus tons of other scorpion parts and windshields...... I will be at waconia mn on the 29th only (saturday) and will be at the SCORPION REUNION feb 5th ..if any one needs parts email me at [e-mail] or [e-mail] or call or text me at 414-719-4497 ..........
see you you all at theses up coming events !!!!!!!!!

[admin]

Team,

Can we simplify this track swap procedure?

Is it accurate to say you need the internal poly track, front drive shaft and drivers, all the bogie assemblies and rear drive shaft assembly with idler wheels from a 1971-197X Stinger to swap into a 1968 to 1971 bubble nose to replace the old external drive track?

What is the actual date range of the stinger needed to do this swap?

Same rules, Stinger years, and swap procedure for 15" and 18" track?

Any other tips or is that it?

[ddub]

admin,
The track needed will depend on the sled.

This update was for the Silver Scorpion which is a Mark I chassis.

They use the "Lil Whip" track. A Mark II would maybe use a "Whip" track? I don't know but would guess it would work. I suppose a Mark III would need a 18 inch donor but those would not be so common as that would have to be 71 and 72?

ddubstoys.com/scorpion_track_installation.htm

I had been "told by a expert" that it was pretty much bolt in and had purchased the NOS parts that I was told that I needed to complete the job. I had to do a lot of fabricating of the boggie's and axles because they did not line up with this track and I was on a time crunch to get it done. If I were to do it again, I'd find a donor sled. We learn by doing. It appears as if the wheels are in different positions width wise depending on the year as I had a 71 that I parted out and the wheels did not match up with that track so the boggie's must match the track.

The rear adjustment hole had to be moved about 1 inch.

I have two more tracks waiting for the next project.

[mooreperformance]

The original 1969 and older rubber track sleds have a boggy wheel assembly that, when used with an internal drive polyurethane track, will hit the internal drive lugs.

These boggy assemblies have four boggy wheels in a 2 and 2 offset boggy wheel arrangment.

Boggy assemblies used with the internal drive polyurethane tracks have five boggy wheels rearranged into a 2 and 3 centered wheel set and will clear the internal drive lugs.

When Scorpion started installing the Internal Drive polyurethane track on the 1970 Stingers all boggy wheel assemblies were changed to the 2 and 3 centered wheel set (both rubber tracks and poly tracks could use the 2 and 3 centered assemblies).

Scorpion might have had some 2 and 2 offset boggy wheel sets sitting around from 1969 and they may have been installled into some rubber tracked 1970's. I don't know about that.

When installing an internal drive polyurethane track you need the five wheel 2 and 3 centered boggy assemblies to clear the internal lugs.

The early Scorpions had a reputation for being a bit "tippy". This was due to the 2 and 2 offset boggy wheels. When the 2 and 3 centered assemblies were installed the Scorpion was much more stable.

I hope I didn't repeat anything stated earlier in this blog.
Dennis Moore

[admin]

May 30, 2011 15:20:54 GMT -5 said:

- One complete drive system from a 1971 Scorpion Stinger with the 15-inch narrow track. (note. MUST be from a '71 and Widetrack model components will NOT work in this case.) The exact parts you will need off the '71 parts sled are three sets of bogie wheels, the internal drive poly track, a rear idler set with wheels, and a front driveshaft with good sprockets. These internal drive sprockets are commonly prone to cracking, so carefully check each one to make sure they are not cracked. Check bogie wheels for bad or junk bearings. And inspect track for small rips or tears or excessive wear.

I want to clarify the above bold text. If I have a 1969 MARK III with 18" track, I think I can use an 18" track, bogies, front and rear axles, lower chaincase sprocket, and drive cogs from a 1971 wedge hood 18" donor machine.

Am I correct?

What is the 1971 wedge hood 18" machine called, a Super Stinger, a Stinger III?

[admin]

From another thread,

Jan 19, 2012 17:25:23 GMT -5 mooreperformance said:

The first snowmobile to use the Gates Polyurethane track was the 1969 Evinrude/Johnson. In 1970 Scorpion and Chaparral started using the polyurethane track.
Scorpion needed to redesign the boogie wheel trucks to clear the internal drive lugs. Instead of the 2 and 2 offset arrangment they went to a 2 and 3 centered arrangment. The difference in stability (having each assembly three boggie wheels wide) was very noticeable.

The Scorpion rubber track had a heavy internal chain and really pulled hard. The Skidoo rubber track was lighter and would spin much more freely. This put Scorpion at a disadvantage in early racing. Scorpion sold replacement hard plastic drive sprockets to try and spin the rubber track with less friction (the rubber drive sprockets really created friction against the rubber tracks metal lugs) but they weren't much help.

When the polyurethane track was installed in the Stinger in 1970 the Scorpions really started dominating racing particularly in grass drags and the 292, 340, and 400cc oval classes (with the Sachs single cylinders).
Those of us that had 1969 297 Mark II sleds couldn't hope to keep up with the 1970 293 Stingers (with that poly track). They were much faster!

[oldscorpman]

on the wide track sleds with the 18 " track you may use a 1971 or 1972 stinger III as a doner sled. i used a 72 to repair my buddys 1970 mark III back in the late 90 's. he still uses the sled for ice fishing today. also the center tubing on the narrow track boogies is the same from 1971 to 1973, however the left and right outside tubes you need to use 1971 stingers. for the front drive shaft and sprockets you can use the 71 stinger , 72 stingeroo,72 stinger or the 73 stingers. of course they must be the narrow track. the rear idler shafts and plates from 67,68,69 70 and 72 and 73 boogie suspenions are the same only the wheels and spacers are different. 71 plates are a little different but the shafts are the same. hope this helps.

rick

[admin]

Thanks oldscorpman!

Here's a a post from another site,

toadspaghetti said:

Yes, I switch out the original track for the involute drive, vulcanized rubber track. A track and drivers from a 1973-1975 Super Stinger will fit right into a bubble or wedge chassis. The para-rail will also fit right in. To put a new track into a Mark I or Stingeroo you will need a track from a Lil' Whip.

www.vintagesledders.com/forums/index.php?topic=9670.0

What about that 1973-1975 advice above? Is that accurate?

[admin]

I'm adding this link to our other track thread,

scorpionsleds.proboards.com/thread/300?page=1#

[admin]

Just to clarify, the donor sled needs to be a bogie wheel equipped sled (not the Pararail equipped sled) in order to fit correctly AND because we need all of the bogie assemblies from the donor sled.

Is this accurate?

[admin]

And the (shorter track sleds) Stingeroo (only available in 1972) and all year Mark I sleds use the lil' Whip track conversion, correct?

[admin]

To summarize and add more information for those wanting to do the track conversion on your 1968-1971 Mark II or Mark III, to get everything you need from one donor sled including: front drive axle with drivers, the bottom chain sprocket that comes with this drive axle, the bogie wheel assemblies you need (because the spacing on your original bogie wheel assemblies will not work), the rear axle with idler wheels and left and right rear axle mounting plates, and the track, you need to find a 1971 or 1972 Scorpion with a black seat AND a black back rest. The 1971 and 1972 sleds with black seat AND black back rest appear to be equipped with the bogie wheel setup and everything else you need.

You will also need to make sure you find a donor sled that has the same width track as the sled you want to upgrade (15" or 18" track). The Mark III needs a donor sled with an 18" track whereas the Mark II sled needs a donor that has a 15" track. Note the track width listed in the spec sheet below.

Here's the 1972 Scorpion offering so you can checkout the black seat/ black back rest reference for example,




ALTHOUGH,there are some exceptions to the black seat/black back rest generalization:

Some 1972 Stinger II 400 models appear to be available with bogie wheel suspension OR the "Stinger-Glide" suspension (that would not provide bogie wheel assemblies you need).

One more exception is the 1972 Stingerette 290 that also appears to come with the bogie wheel setup you need.

Feedback is welcome to confirm or correct these statements!

[admin]

Will the track, drive axle, drivers, bottom chain sprocket, rear idler shaft end caps and wheels, and the bogies wheel assemblies from a 1974 Stinger 440 wide track work for the 1968-1971 Track Replacement?

[admin]

Related thread,
scorpionsleds.proboards.com/thread/1083/1970-mark-track-replacement-ideas

[admin]

Found this picture on vintagesleds.com classified section. It is listed for a 1970 Mark III with 18" track.

It's a little out of focus but from left to right you can see the flange that you need to remove the carriage bolts from that is holding it to the sled chassis. Immediately next to that in the photo, and not much larger then the axle itself, you can see the collar that you need to loosen the set screw on (the set screw is an Allen head I think and you can kind of see it in the photo). I hear this set screw can be tough to loosen up so you should probably soak it with some kind of penetrating oil. A few more inches to the right and there is the first external driver (drive sprocket/cog).