Invader 340 Clutch Spring - Source

[jskal]

Anyone have info on the correct spring for 78 Invader 340, and a good source for replacement Kawi clutch springs?   I removed the Comet clutch and put on a clutch from an LTD (with a black spring).  It pulls good until 40, then flattens.  A new belt helped a little, but not much.  I gave a shot at radar runs last weekend and put up a whopping 54mph in 550 ft (was hoping for a little more )

I should mention that the secondary is a Polaris button style.  The sled was built for oval racing and chassis modified & lightened.  It is ridiculously light, and just seems to rip up to 50 mph and sit there.  Gearing is 17-39 which appears to be stock and spec'd for 73mph @ 8200.  thanks!     

[Tory944]

  I know this doesn't answer your primary clutch spring question, but as for the gearing...  try the old "black magic marker" trick.  Start your black marker line in two places on your primary sheaves from hub to top of clutch.  This will tell you how high the belt is traveling up the primary.  Too short of a belt will also hinder top end speed (grind on hubs).  You want a 1:1 ratio at the end of the track.  Power will drop off considerably in overdrive.  Also, lighten the spring tension in your secondary.  Make sure your brake adjustment is "loose" and your track tension is set a loose as possible without ratcheting.    Hope some of this helps!     Tory

[Tory944]

  This is just my opinion...  if that Invader has been lightened up considerably, you would probably benefit from taller gearing.  I know others on here might argue this...  but a taller gear will be much easier to pull with a lighter than stock chassis.  I would have suggested a gearing change anyway, but after re reading your post, I firmly believe you will benefit from a gear change.

 You aren't running LTD weights in that primary are you?

I volunteer this info because I have tried a lot of different strategies with clutching, gearing, etc.  and a lot of these suggestions have worked for me!!

[jskal]

Ahhhh yes.  The clutch is literally straight from an LTD.  I've been coming up empty trying to find specs for the 340 and need to track down a manual for it.  I was planning to bump the gearing.  I've got 17T & 22T tops and 37T, 38T & 39T bottoms to choose from, otherwise would have to add to the collection.  I wonder if the belt length is culprit?!?  When I got the sled it was setup with Comet 102C primary and Arctic Cat Secondary.  The jackshaft is the keyed type rather than spline, and braking system has been converted to Polaris hydraulic.  The drivetrain appears to have very little drag.  On the stand you can turn the secondary by hand with very little resistance through to the track. 

[Tory944]

O.k......     I am seeing something in your combination that makes me wonder....    so you are running a Kawi clutch which was originally designed to run a 1 1/4" belt.  Your Arctic Cat primary (I believe) was designed to run a bit wider belt...   like 1 3/8'".  I know the early 80's Eltigres w/the reverse cam secondary (and newer) used the wider belts.  I am wondering if this could be a contributing factor to your problem.  It might be worth a look. 

[Tory944]

....   I'd run the stock 440 Invader gearing 1:86...     

[jskal]

GOLD STAR! on the belt call. 

I tried a couple of random belts I had and WOW!!!!  Pulls VERY hard and keeps pulling.  Will give it a shot on the lake tomorrow to see what difference it made.  One of the belts I tried is:
Carlisle 144-4640,
Length: 46-13/32"
Width: 1-7/16"

Engagement with the Kawi clutch is definitely all messed up with this belt/clutch combo but it gives me some idea of what has been going on.  I think the belt was just maxing out on length before clutches fully engaged.  I've been running the 1078 belts.

[Tory944]

 That's why we are all on here...   to help!  You know what you're doing...  sometimes we just need to be reminded of simple things that get overlooked!  Keep us posted on your speeds.

[rminier]

Wow, lot's goin' on here...all good. I will add some more. The stock 340 Invader gears shown in my '79 service manual are 18/37, a 2.06 ratio. There is a cool chart that shows the MPH with various gears. The stock gears are shown to give 79 MPH at 8000 RPM with the clutches at .96 overdrive. Your 17/39 would only be good for mid 60s at 8000...or about 67 at 8200. Does yours still use the stock track drive lugs?
  Those Invaders came with a yellow spring as stock. The black spring is better IMHO, it raises the engagement speed around 400 RPM but the shift pattern stays the same after engagement.
  The LTD clutch probably has way too much weight for your 340. I have those specs if you need them.
  Are you sure it had a 102C previously? Might it have been a 108C set up to use a 1 3/8 belt, as to Tory's point about the secondary being set up for the wider belt?
  Is the motor hitting 7900-8200 RPM at full acceleration?
  May take some tunin' to get this dialed in...

[Tory944]

  Yup,   probably a 108 on there w/that Cat secondary...  good point.

[jskal]

Confirmed that the original clutch is 102C, however it looks like they are adjustable for belt widths.  When I bought the sled it came with multiple belts, all 1078 and labeled Track, Race, Test, etc.  I'm thinking these were all incorrect for the modified clutch setup.  Plan for tomorrow is to give another shot with the Comet and a 1 3/8 belt.  Will keep you posted.  Thanks Guys!

[jskal]

102c is definitely not setup for wide belt.  So I have an issue of incompatible clutches.  Sounds like completing the change to wide belt is best for for this sled.  I have a p85, from what I'm reading the taper is correct but need to shave the back?

Of course that leaves me guessing weight/spring setup.  Other option is to get the Kawi clutch setup with the right weights and figure out the belt length issue for the Polaris or Cat clutch.  I would have to change jackshaft to go back to the Kawi secondary.  What fun!

[Lloyd (ljm)]

 I have a p-85 on a Liquifire.  I had to have the back shaved a we bit. You also will need a longer mounting bolt if you go that route. There are lots of tuning possibilities with a p-85. I can't advise you on a starting point. Mine is still step up like a Indy 500, but I need too do some changes. engages early and causes a bit of a bog.