Jackshaft Bearing

[Truder78]

Finally got the 78 invader up and running nice after rebuild. Decided to check the timing using a light and when i rev it up to check it I noticed the secondary clutch would shake. Should there be any play at the secondary? it moves up down front back about 1/8 inch? it looks like its between the shaft and bearing. also noticed the book calls for a retainer on the backside of the bearing was that optional or is it missing? Found a replacement bearing at automatic dist which is local for me. [love that place] that comes with the retainer. Haven't removed it yet figured I would check here before I open another can of worms any help would be great. Nice to see the site is still running Bob Good Work

[rminier]

 The jackshaft should not have an ounce of play behind the secondary clutch. Hopefully you have the correct replacement bearing which definitely has the locking collar.
 If you get the correct bearing installed behind the secondary clutch and still have a vibration problem, post again.
 Also, verify the alignment arrows are still lined up in the secondary clutch.

[Truder78]

Thx for the reply these are my choices any better than the other?

[Truder78]

Secondary is off no shims behind it missing or sometimes not needed? u shims were under the block.
No retainer was attached to the bearing I know that's missing. manual pic where the 24 is shows the 2 lines is that what i'm looking at on the shaft? no apparent  scoring marks in the shaft or inside the bearing it almost looks like it was machined down is this shaft correct or should it be the same dia all the way? thx for any help

[Truder78]

Sorry for the big pic

[rminier]

 Yikes!!! The jackshaft should be absolutely symmetrical and smooth.
It looks like a previous bearing ate into the jackshaft......that will not work....
All is not lost, however.
Give me a couple hours to get home from work and I will take some pictures of my Invader showing a possible solution.

[gixxer6]

The shaft should be the same diameter.  That is where the bearing was wearing into the shaft because of the lack of locking collar.  You will need to repair or replace the shaft. 

The secondary shims go in the bottom of the hole in the secondary between the secondary flange and the very end of the jack shaft.  Sometimes the shims will stick inside the secondary and sometimes people leave out/loose this stuff.  Being that the locking collar was missing I suspect the latter. 

[rminier]

 After looking at the pictures of your jackshaft some more, what I was going to suggest probably won't work for you.
 Many years ago I had a high speed vibration problem near the left footwell. It turned out there was a minor imperfection on the bearing area of the jackshaft.
 I flipped the bearing carrier around backwards. This moved the bearing about 1/2 inch further onto the shaft. The bearing collar now faces outward. This moving the bearing in to a perfect surface completely solved the vibration problem.
 I would agree with anyone that this increases the forces on the bearing....slightly.
The perfect fix would be to have the jackshaft remachined by a competent shop...but I have put thousands of miles on my Invader with the setup in the picture.
 I'm afraid your jackshaft may be too far gone....even if you reverse the carrier and get the bearing to some undamaged part of the shaft, the locking collar would then be over the badly damaged part of your jackshaft.
 Only 2 other options I see.
 Replace the shaft....I don't always trust what one might get from eBay or a salvage yard. You might get a pile of junk.
Perhaps someone on this site has one they would sell.
 Or, yank the shaft and take it to a good machine shop that could build it up and turn it down to be like new.

[Truder78]

Thx guys for your help... common sense told me the shaft was worn but i was grasping for straws. I picked this sled up years ago did some work last owner did a lot to it. I rode it 3 times and the engine blew. then it sat for 3-4  more years until this full rebuild.I agree parts were lost and left out that i'm now finding out. Going to look at bearings later this week maybe find one with a wide retainer and see what I can figure out. i'm not going to race it but ice fish and fly around out front on the lake. I hope

[Truder78]

I walked away from the jackshaft saga for a few days kept getting tears on it I did find a local machine shop who will look at the shaft when i remove it. I did find that in the 78 parts manual it shows the 340 440 invader and the  intruder all have the same shaft part #39069-3502

The jackshaft should not have an ounce of play behind the secondary clutch. Hopefully you have the correct replacement bearing which definitely has the locking collar.
 If you get the correct bearing installed behind the secondary clutch and still have a vibration problem, post again.
 Also, verify the alignment arrows are still lined up in the secondary clutch.

Putting the top arrow on the secondary at 12:00 the second arrow is set to 4:00 was that done to change the shifting

[gixxer6]

I might have a good used shaft if you need.

[Interceptor398]

There should be plenty of good jackshafts out there.

[gixxer6]

There should be plenty of good jackshafts out there.

Unfortunately this issue is quite common.  I have parted out several Invaders with this same issue.  So there isn't as many out there as there should be.   

[kawhead]

after replacing a jackshaft I run the sled on a stand before locking the collar.....lets everything find "home" ,no side thrust on bearing....this was common, redesign with no lock collar on later sleds

[Interceptor398]

after replacing a jackshaft I run the sled on a stand before locking the collar.....lets everything find "home" ,no side thrust on bearing....this was common, redesign with no lock collar on later sleds

Never heard of that before but it makes cense.