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1986 Formula MX Attempting to add Electric Start

408 Views 15 Replies 5 Participants Last post by  turbopete
7
I'm attempting to perform an electric start retrofit on my '86 PRS sled. The parts seem very hard to come by but at this point I think I've collected most of them. Mostly want to ask, is there anything I am completely overlooking? Below is the parts I've acquired. I think I have pretty much everything minus the battery. My only question is which ring gear to use.

From a couple different '91 PRS Sleds:

* Clutch Part# 417202100 : My '87 clutch didn't have the posts to mount a ring gear. Looks like despite having the posts that this one never had a ring gear installed either as the holes are not tapped. I was worried at first but then read the screws are self tapping.​
* Ring Gears Part #414807500 & Other Part# 414604300 (maybe)?: Below are two different styles and I'm not sure which one I should use. The right one looks like images I've seen online and comes with the Phillips head self-tapping screws which I believe are part# 309903100. The left one I think was the newer replacement once the right was marked NLA by skidoo and looks to use hex head screws part# 732601120. Any idea which gear I should go with?​
* Startor & Engine mounting bracket:
* Wire Harness from a 91 sled with E-start: I believe the missing "pins" marked 1, 3, etc. from the large 8-pin connector are the ones coming from my stator but I'll have to compare my'87 harness there.​
* Ignition w/ E-Start
* Voltage Rectifier
Just want to say that I wouldn't have been able to get this far without Hudson's Sled Salvage awesome parts diagrams w/ oem numbers. Anyhow, am I nuts to attempt this? Will something I've purchased not work the way I think it will? Thanks!​
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Obviously you will need the battery and battery tray.
Do you have the shop manual and wiring diagram that also could help you?
Obviously you will need the battery and battery tray.
Do you have the shop manual and wiring diagram that also could help you?
I have a shop manual on the way!
Looks like a good start.
What's your plan for drilling out the ring gear mount holes? I would think this would have to be done perfectly for balance purposes.
Here's an 86 shop book on pdf.
Looks like a good start.
What's your plan for drilling out the ring gear mount holes? I would think this would have to be done perfectly for balance purposes.
Here's an 86 shop book on pdf.
As explained by the Op in post #1 The holes are already on the clutch, the self taping screws will take care of threading the holes.
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The holes are already on the clutch
Got it. Missed that part.
Got it. Missed that part.
Yep I was going to mention that. Now just have to decide which ring gear I should be using.
Once you put the ring gear on, you should check the balance. Any local machine shop should be able to do it.
Once you put the ring gear on, you should check the balance. Any local machine shop should be able to do it.
Agreed it would be ideal, but did anyone actually rebalance after installing an e-start kit or was it recommended by BRP? Are the gears not made to a certain spec. that it wouldn’t be necessary?
Now just have to decide which ring gear I should be using.
I agree with your earlier comment that the 7500 is simply the replacement for the earlier ring gear. Looks like it was used into the late 90's at least. I would go with that.
As for the fasteners I believe either fastener will work with either gear but given the choice I'd use the hex head.
Good luck.
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They are different in that the older one that you have the screws for are a tapered head, the holes in the gear are basically countersunk. The newer one is cut down for standard head bolt.
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Once you put the ring gear on, you should check the balance. Any local machine shop should be able to do it.
You thinking similar to balancing a tire that they'd just mount the clutch on a spinning shaft and check balance?
Agreed it would be ideal, but did anyone actually rebalance after installing an e-start kit or was it recommended by BRP? Are the gears not made to a certain spec. that it wouldn’t be necessary?
They balance them at the factory. I've only done two and both times had a shop spin them up and test for balance. Doesn't have to be perfect, but the better it is, the less wear and tear on the crank bearings and seals.
They balance them at the factory. I've only done two and both times had a shop spin them up and test for balance. Doesn't have to be perfect, but the better it is, the less wear and tear on the crank bearings and seals.
If it's found to be off balance what do they do? Try to mount the ring gear by rotating it to the next set of screw holes? It's not like a tire where they can add weights, right?
If it's found to be off balance what do they do? Try to mount the ring gear by rotating it to the next set of screw holes? It's not like a tire where they can add weights, right?
Yes try to rotate the ring, they can't add weight but they can remove weight from the whole assembly by drilling some off on the opposite side.
They balance them at the factory. I've only done two and both times had a shop spin them up and test for balance. Doesn't have to be perfect, but the better it is, the less wear and tear on the crank bearings and seals.
Absolutely I agree, the more balanced the better. The question was that Bombardier sold lots of electric start add on kits, was it mentioned or recommended to check the balance, or did hundreds or thousands of kits get installed by dealers without balancing? I could try to look it up in a one day school book, it likely is mentioned. If the gears are made to tight tolerances, there would be no need to balance.



To balance as an assembly, doubtful they would try moving the ring, would likely just remove material as mentioned. Time is money, too much wasted time moving the ring, plus risk wearing the holes etc. Screws are locktited and pretty much intended for a one time install.
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