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Discussion Starter · #1 ·
Got the plus running perfect. Took her out on the lake to see what she could do. Pulled like crazy all the way up and topped out around 126-127 km/h on the gauge. Everything is stock. 3800km original.

According to my calculations (using the calculator at hurricaneperformance.com) my top speed should be 78.00 mph. Roughly 126 km/h; exactly what I'm running...all good things. 20/38 gears, 9 tooth drivers, 2.52 pitch, 6900 rpms, clutch ratio 1:1.

What I'm wondering is, what exactly do u have to do to stretch her out and get it moving on top end? I can't imagine it's as simple as putting a 24 tooth on top and off we go.

Do I need to do a swap on both gears to ensure I can use same chain?

Would I need to release some secondary tension due to an increase in strength coming from the taller gears?

Any changes to the primary?

What I would like to accomplish is the ability to set the sled up for speed or back to stock depending on the riding conditions. I live on a 5 mile long lake that's long and narrow so I've got the perfect spot for testing....right out the shop door and onto the lake.

I know the simple solution is to just buy a faster sled blah blah but there's something about being faster than your buddies new 600 with a 30 year old 521.

I did some calculation on some different gearing and here's what I came up with.

All using 6900 rpms, 9 tooth, 2.52 pitch

20/38 = 78.00mph (stock gearing)
22/38 = 85.80mph
24/38 = 93.60mph
26/38 = 101.40mph
20/40 = 74.10mph
22/40 = 81.51mph
24/40 = 88.92mph
20/36 = 82.33mph
22/36 = 90.56mph
24/36 = 98.80mph

I would love to run in the 90s but I don't she's up to it. Is there hope for me or am I out to lunch. Would love to hear what you guys think.
 

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Doing the opposite, I swapped the upper sprocket from a 15 to a 14 tooth (35 bottom, double chain) on my old Olympique to get a bit of power to haul stuff. The difference was noticeable. It was plug and play, got the 14 tooth from an Elan twin chain case. I would suggest sourcing a compatible upper sprocket(s) and experiment starting at 22 teeth. Don't forget, engine power might then limit your top speed, rpm might drop off with the taller gearing. I don't know that the clutch ratios are 1:1 at maximum speed, I thought the secondary turned much faster than the primary when it was fully open, so minor changes to the final drive ratio seem multiplied, maybe some else here could explain?
 

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Discussion Starter · #3 ·
I think I'll do what you're suggesting and step it up 2 teeth at a time on top. I just got back from a good 20 mile run on the lake and it seems as though there isn't much left as far as engine power goes. With a 22 tooth on top i should hit 85.80mph at least on the gauge. If I make it there, I'll try a 23 or 24. I guess eventually it just won't go anymore and I'll lose speed.
 

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Discussion Starter · #4 ·
I think I'll do what you're suggesting and step it up 2 teeth at a time on top. I just got back from a good 20 mile run on the lake and it seems as though there isn't much left as far as engine power goes. With a 22 tooth on top i should hit 85.80mph at least on the gauge. If I make it there, I'll try a 23 or 24. I guess eventually it just won't go anymore and I'll lose speed.
 

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Keep in mind that Bombardier set it up for max acceleration and top speed based on the available HP. Sure, changing gears may give you some top end speed but unless your're running on hard packed snow or ice, you might find that you will loose out in both lower and top end. It all boils down to the limits of the 521...keeping up with a modern 600 is not going to happen. Find a healthy 670 motor from a Mach 1 that will bolt in and you still won't keep up but at least your buddies won't be on their second beer at the end of the 5 mile lake when you catch up.

You may not beat them on MPH, but you're miles ahead on the cool sled scale.
 

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I think there is probably something not quite right with your sled. I would be sure clutching, belt etc. Is all good before going away from stock. I would get an app on your phone with a gps to give actual speed. Something tells me you are not getting what you should out of it. That sled should be much faster than 78 on the speedo. I don't know about your calculator but something is off, especially considering you don't really know how fast you are going, you may be only doing 70. I would expect speedo reading somewhere around 90 plus mph, with actual speed somewhere in the 80's.
 

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Discussion Starter · #9 ·
I think there is probably something not quite right with your sled. I would be sure clutching, belt etc. Is all good before going away from stock. I would get an app on your phone with a gps to give actual speed. Something tells me you are not getting what you should out of it. That sled should be much faster than 78 on the speedo. I don't know about your calculator but something is off, especially considering you don't really know how fast you are going, you may be only doing 70. I would expect speedo reading somewhere around 90 plus mph, with actual speed somewhere in the 80's.
I'll give a shot tomorrow when it's light out see what my gps says...be good to know my true speed. I ran the numbers on a couple other calculators and I get the same 78mph number. I got some specs with other years and I seems I bought the slow one. Here's what I found:

All formula plus models
1987- 521cc, 7800rpm, 20/38 = 88.17mph
1988- 521cc, 8000rpm, 20/38 = 90.43mph
1989- 521cc, 7250rpm, 20/38 = 81.95mph
1990- 521cc, 6900rpm, 20/38 = 78.00mph
1991- 521cc, 7000rpm, 22/40 = 82.69mph
1992- 583cc, 7250rpm, 23/40 = 89.53mph

Seems as though all the plus sleds before and after are geared to go faster than mine. Also the earlier models have a type 537 and the later ones a type 536. Anyone know the difference between the two engines? The 88 revved out to 8000rpm. My adjustments on the clutch are already at no. 6 so I can't get it revving higher without lightening the weights.
 

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Discussion Starter · #10 ·
Just for fun here's the 1993 plus x:

583cc, 7600rpm, 26/44 = 96.45mph

Hard to beat the 93 x...one of the nicest snowmobiles EVER.
 

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Discussion Starter · #11 ·
So I did a little research on my favorite site (this one) and found that the type 536 is a detuned version of the type 537. Anyone know what they did to detune It? If it's just carbs and clutching maybe I can get some more out of what I have. If we're talking differences in the ports than that's a different story. Now that I know the difference between the years I know what to look for when buying parts and sleds
 

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This seems slow to me. When you say you have the sled running perfect just what do you mean by that?

If the engine is running perfectly you need to take a close look at the clutches to see what they are doing. You say the clutches are running 1:1. At top speed the primary (drive) clutch should be in overdrive.

Mark the face of the inner primary clutch face with a soft crayon and take the sled for a full out run. The crayon mark should be wiped off almost to the very outside of the clutch. When I was running F Plus's I ran the secondary clutch with 12.5 to 13 lbs. breakaway tension.

The clutches need to be absolutely clean, all the bushings and sliders in good condition. A new belt is an absolute must. A belt is no better than the alignment, center to center distance and the deflection must be set correctly.

Gobs of available HP can be used up through the drivetrain and the suspension bearings. Free bearings and good track slides are free HP. A bind in the front driveshaft will rob usable HP.

While the engine might seem perfect to you there are certain things which should be checked. Ignition timing, carb jetting for your altitude, rotary valve timing and engine overall condition.

I may not win a popularity contest for saying this but after 1988 the Formula Plus was not as stout as the '86 - 88 pluses were. When the Mach 1 was introduced in the 1989 model year I believe the F Plus was somewhat detuned so it wouldn't compete with the new Mach 1.

I can say this because I bought a F Plus new in the fall of 1984. I traded sleds each year for new F Plus sleds until I bought a Mach 1 in the fall of 1988. The '89 Mach was a disappointment the first time out. The first night out my son went by me like I was tied and he was riding a 1985 Formula SS 472 with a single carb. (His mother's sled)

The next day I had a whole bay in my garage filled with parts off the Mach 1. It took a little time and patience but I finally got it where I wanted it.
 
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I have done the same thing as you are wanting. Mine was a 90 safari 467. I went up one size on the drive sprocket in the chain case. I was able to use the same chain. It did make a small difference up top. About 5mph and didn't seem to hurt the bottom. By the way it lost speed when there was more snow, I could tell I was at the engines limit. But on a hard packed road it flew....for a safari. At 130 km/h a safari's big wraparound windshield will bow in against the wind! As mentioned above, lots of things can rob speed. Ski alignment, track alignment and tension are very important as well as the belt and clutch alignment/maintenance previously mentioned. By tweaking everything and testing, I was able to squeeze 140 km/h on a cold night down a road with a fresh top end on a single carb 467. So I believe there is some left on the table with your 521. It's fun to play with these old sleds but a word of caution, they will not stand up to repeated long full throttle runs forever.
If you are attached to that sled and want to keep it to ride with your buddies, it might be better to keep stock gearing and do a sc3 suspension swap with a good lug on the track. That and some good carbides would make a woods weapon and your buds would have a hard time shaking you off their tail on the trails.

Sent from my CLT-L04 using Tapatalk
 

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I here all that you are saying, and yes your motor is detuned compared to 88 and older. Regardless, and in spite of the calculator, which I admit make sense on some other sleds, I still believe your sled should be a fair bit faster than what you are saying.

Now, I will give you a couple of examples of sleds having different speeds. Years ago, in our group we had a 5500 Blizzard and a Motoski GPS, same sleds, one guy tuned and played to get best performance and the GPS was much faster, blowing away the Blizzard consistently. My brother in law and his brother each had nearly new Formula MXs - late 80s, and one would blow the other away every time. Absolutely no mods on any of the sleds, just the tune and drivers about the same weight.

If you ever attended or competed in drag races or radar runs, you would regularly see guys show up and get beat by the guys or dealers that knew how to set them up. All stock sleds, all in the prep. I could be wrong, but man I would think your sled should be somewhere in the 80s mph. on hard pack or ice and cold temps.

Not to be mean, but at the speeds you are talking, you will get beat by a good running Formula MX. Just trying to encourage you to keep tuning and checking, get it at its best before do any modifications.
 

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Discussion Starter · #15 ·
I hope you're right Pete...ill get back to basics, replace sliders and bearings, driveshaft bearings then get all alignments and tension spot on before I go crazy. Anyone out there have the clutch specs for the machine? Vintage snow cuts me off at 1989 for service manual....ill take a look at the 89 anyway...clutch spacing is likely the same.
 

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Run that track a bit on the loose side.

Sent from my CLT-L04 using Tapatalk
 

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Had that sled new, it will do much better that that, has the primary clutch been rebuilt? I remember at about 2300 miles I started losing top speed and the clutch would not shift all the way out. I think it's time for rebuilding and new springs in both, also check your cam bushing in the secondary

You can put magic marker lines on your clutches and go for a spin, see how far to the top the front one is gone and how far down on the secondary it is worn off
 

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The 1990 Plus was Detuned, to make the Mach1 look a little better.

TRA clutches are Over Drive Clutches, there fore Gearing is different than older Plus's with RSSR Clutch. The original Plus had a Type 537. then with the Mach 581cc, they came out with a type 532 521cc. Smaller Ports and Smaller Carbs.

A Plus with a Type 537, would run well into the 90's (long Lake Run.) The 532 would be in the 80's. Because the 581 Mach's (TRA only) wouldn't hit the magic 100 mark.
 

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Correct, they basically artificially slowed down the Plus.

Conditions are everything also. Sleds can delta 10 mph easy, from one day to the next. Radar proves it.

Also, guys that say "My old Invader would top 100 easy.... " were full of it. They didn't.

What lake are you running on?
 
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