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Discussion Starter · #1 ·
I have a mint condition 1970 TNT 400(399) that someone gave me to get her ready for the winter, My only problem so far

is the track turns when it idles to the point that if I apply brake she will stale.

Put a new Belt that is for this sled, loosen the belt between pulleys. Still have the same problem, belt is loose but will not

seat at the bottom of the drive pulley at all. missing 1/4 inch maybe before she touch bearing.

Am I missing something here, and suggestion would be greatly appreciated

Thank you
 

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Discussion Starter · #3 ·
Yes The primary (drive pulley) seems a little to close, (is there a adjustment ?) this TNT came off a museum, did not ran for a long time.( they rebuild, start and parked it, had the wrong belt on her also ) we did lower the idle a little but will stall. I had to order a new oil seal for the top of the chaincase,, oil leaking on the secondary (driven pulley).

Maybe primary need to be cleaned or lubed. I think its a comet but the Model I dont know, in the manuals says (speed clutch) for the 399.

Thank you for your help
 

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Can we have a close picture of the drive,dont think you have the original clutch ,you got the "wrong" cover color for this year.
 

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it's a powerblock clutch from what I can see in the pic. it's probably not set up properly for the width of the belt you have installed.
 

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Discussion Starter · #6 ·
To: HiOctane

Im not at home, I will be in a couple of days and will take a few close PiX of the clutch

To: Flatland_mike

That would explain a lot, I will be home in a couple of days and open the clutch and take a few PiX to see what we got and take it from there

Thank you for your response
 

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Discussion Starter · #7 ·
To: HiOctane

Im not at home, I will be in a couple of days and will take a few close PiX of the clutch

To: Flatland_mike

That would explain a lot, I will be home in a couple of days and open the clutch and take a few PiX to see what we got and take it from there

Thank you for your response
here are the pictures, let me know if you need more
 

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The powerblock is easy to tune by adding weights inside the plastic slider things. Maybe previous owner put too heavy weights in and it engages at idle?
 

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Discussion Starter · #10 ·
The powerblock is easy to tune by adding weights inside the plastic slider things. Maybe previous owner put too heavy weights in and it engages at idle?
thank you for your help, they are 52 grams/ each, if I take off weight will this help me stop the track from turning at idle and put the trak at the bottom where the bearing is ? please note I think they just putting together to make it look nice at the museum..
 

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I'm not sure the details of the factory weight, or if reducing it would help, but maybe you could remove the weights completely and see if it still catches the belt, if so thats not the cause.
 

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Have you measured the width of the belt? I have found those fancy top ribbed belts tend to run a little wider and thicker than the cheap OEM style belts

1034 should be 1 3/16 inch wide
 

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Discussion Starter · #14 ·
Have you measured the width of the belt? I have found those fancy top ribbed belts tend to run a little wider and thicker than the cheap OEM style belts

1034 should be 1 3/16 inch wide
this belt is 1 3/16 inch on the button, thx for you info
 

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Discussion Starter · #15 ·
Just off hand, that belt looks too wide for that sled, how is it sitting in the secondary? I am quite sure it has nothing to do with the weights. There are lots of places to make adjustments on those clutches. I will see if I can find some instructions. You should be able to shim it to increase the distance between the sheeves, but I would check the belt first. Surprised that for an old sled like that with low hp that they would make a belt with the ribs on top. Any belt I have bought for an old sled has always been smooth on top.

By the way, those are great little clutches, very tuneable, and work well with little to go wrong.
Belt is 1 3/16 right on, That would be great is you have instruction how to shim it, thank you very much., I dont think I need much to shim it, do you know the model number of that powerblock ?, maybe I can find a PDF file that had a picture of all the parts for the clutch, maybe its missing parts?. thank you again
 

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ok the clutch did not come with shims, so I started with small shim, still sticking, bigger one still sticking, so I put thick washers, still sticking .. wow

Im think that the middle bearing or bushing in not thick enought....puzzled , I put one behind and after the spring holder... see pix.
 

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at least you're narrowing it down. think about how much you didn't know what was wrong when you were starting. I had a shim/bushing piece that was missing in an old moto-ski clutch from 73, and the clutch would immediately chew a chunk out of the corner of the belt. when the clutch engaged, the belt was sitting too low to the axis of the clutch, and it would just take a 1/4 inch chunk out all the way around the belt. went through 3 or 4 belts before I finally figured it out …

actually, it was my neghbor, don't think I would have ever figure it out
 

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Dumb question but is the bearing free to turn? The "wrong belt" that was on it - how was it compared to the one you have on? How is the alignment to the secondary- is it dragging sideways enough to catch - if you know what I am saying?

I was just looking at NOS clutch the same Powerblock Alt that you have, it is listed for many applications( needing correct spring/weights for each ofcourse). Interestingly it said " uses 1 1/4" belt".

I have put a couple of these on last year and used the OEM belt. I will have a look tomorrow at ones I have. I do seem to recall seeing one with quite a stack of shims beside the bearing so you may just need to add more. I will try to get you some info., pics and I think I have an instruction sheet.
 

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Note that in the diagram in the link it shows a bushing instead of a bearing. I think earlier or certain models used a bearing, others just a bushing, I have seen both. As I said, I have seen several shims beside the bearing. I put a NOS one a single cylinder Sachs motor last year, it had the bearing with several shims beside it. Let me do some checking tomorrow, but as others said, it was just probably never set up properly for that sled and may just need more spacers to allow the belt to not drag.
 
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