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upper gear bushing

Running a full one inch bushing right now and I'm sitting right around 2000kms and it's still very snug in the shaft. Time will tell.
 

STAIN said:
I thought those shafts where the older models? I know my buddy bought a Scott Taylor shaft to fix his 14 Cat. I haven't heard of any newer ones with shaft problems, maybe I missed it?
I am trying to understand HOW/WHY this bushing wears. 99.9% of the time it it rotating with the upper shaft. Only in reverse does it spin on the shaft. It must be side pressure from the chain which wears the bushing????If the chain is over tightened it must contribute to bushing wear. High HP the same. Tighter tolerance needed? Bushing that slightly extends beyond the gear on both sides?
There is enough brain power here that we can up with SOMETHING?
Click to expand...
No they still pop up now and then. Either way a needle bearing needs a extremely hard surface to run on. I am trying Clutchmaster’s solid bronze bushing. It’s cheap and seems like easy solution for more life.
 
NYTurbo said:
Running a full one inch bushing right now and I'm sitting right around 2000kms and it's still very snug in the shaft. Time will tell.
Click to expand...
Interesting. I was thinking about that and running more washers to snug the gear up front to back on the shaft.
 
With the 1 in wide bushing it is snug , no washers required.
 
Still trying to understand why and how that bushing wears so much? It turns with the jackshaft (1:1) when riding. The only time it turns on the jackshaft by itself is when you're in reverse which is only a tiny tiny fraction of time. See pic of my top sprocket (2017 Cat ZR9000, 280HP tune) which has 3700 miles on it. Looks like new still.
 

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Turboflash said:
Still trying to understand why and how that bushing wears so much? It turns with the jackshaft (1:1) when riding. The only time it turns on the jackshaft by itself is when you're in reverse which is only a tiny tiny fraction of time. See pic of my top sprocket (2017 Cat ZR9000, 280HP tune) which has 3700 miles on it. Looks like new still.
Click to expand...
I posted this last week, sorta just my theory.....
https://ty4stroke.com/threads/shift-fork-shoes.156975/#post-1479914

Rockerdan Quote:
As I said in our call....I think chain tension may be the one thing we must stay on top of to help top gear bushing longevity. With your massive race tune power you are putting down, my guess is the chain stretches alot quickly, even though it is Scotts.

I spent alot of time looking at this when open, and just dont understand the 1.5 turns out that is spec'd in the manual. I have used 1 turn out for a season and half, and now have gone to 3/4 turn out after finger tight. I am of the thinking that the chain tensioner(being spring loaded), gets pushed back against the bolt head under hard acceleration, which in turn applies massive force onto that chain and top gear bushing, all at once. The top gear is splined into the reverse gear, but where chain is, the bushing underneath is taking the hit, and this hard hit wears the bushing, which in turn does not allow for easy sliding fork motion when going into reverse. The more the bushing wears, the harder it becomes to go into reverse/forward and therefore plastic shoes wear/break.

I feel that with a normal tension back off....that chain does not take as much of a hard hit(when hitting the bolt) under hard acceleration, as its tighter to begin with and has little space between tensioner and bolt head. Which in turn would not put so much pressure onto the top gear bushing.

See what Dan H. comes up with on how tight your chain was, how many turns inward can he turn the bolt until its hand tight would go a long way to proving if this may or may not help everyone. I know many sled top gears with/or without oil holes, have great life, while others have short life. I see no rhyme or reason. So Id like to see if those who kept chains tighter may have longer top gear life or not. I think its a viable question to such a poor design we have to deal with.

Dan
 
No rhyme or reason on our end ether. My 17 has had stock oil for 500 miles, synthetic diesel oil for the remaining 8000miles. Chain is streched, and I’ve had my idler almost come off. The stock top gear with no oil holes looked mint when I put it in 800 miles ago. (Most of the adjustments to the chain have been done with the case open. Felt the chain, didn’t count the turns out)

Our 18 has had from new diesel synthetic up to 3000 miles. His bushing was toast, even eat at the gear. The outer section was close, but the inner gear got oppened up quite a bit.

Judging by the amount of stretch I’ve seen in my chain from adjustment to adjustment and the gear wear, I think a loose chain is the culprit. But I don’t know. One thing I do know. Gettin’ Scott Taylors’ gears next year with Wtv oil he says to put in there lol
 
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