Replacement Top Gear Bushing

[cannondale27]

DLC coated bushing

 

[ClutchMaster]

These are the bushings I ordered from bronzebushings.com
AA-1110-1 | Oil Impregnated Bronze Sleeve | 1 ID x 1-1/8 OD x 1 OAL
101493 $3.39
Ordered: 1
Shipped: 1
$3.39
16BU16 Sleeve, BU (PTFE Composite), 1 " ID x 1 1/8 " OD x 1 " OAL
16BU16 $3.36
Ordered: 2
Shipped: 2
$6.72
EXEP161816 | Oil & PTFE Impregnated Sleeve | 1 ID x 1-1/8 OD x 1 OAL
EXEP161816 $2.27
Ordered: 1
Shipped: 1
$2.27
BBEP161824 | BB-16 Sintered Iron/Copper Sleeve | 1 ID x 1-1/8 OD x 1-1/2 OAL
BBEP161824

I ended up using the first one.

Absolutely! The bushing your using is the softest and it last about as long as stock but that’s before replacing the chain and running loose. It will also do the least damage to the shaft.
All those bushings will need trimming but no big deal.
I’m tempted to try the 4th bushing, that’s a hard sucker!

 

[STAIN]

I tried the last bushing but when pressed into the gear it would not go on the shaft. I did not try to ream it to fit. Maybe it will be next.....

 

[SPM]

Cast bronze would have a higher load rating than oil impregnated bronze (sintered bronze). Being oil impregnated is really not needed as well since it is in a oil bath.

Although expensive at around $40/ea, this one may be one of the best if it isn't too hard and wears the shaft. It is made of ToughMet 3 Alloy (copper-nickel-tin). The "P Value" is 5X what the cast bronze (McMaster-Carr) bushing is (20,000 vs 4000). P Value represents static load.
https://catalog.buntingbearings.com...ze-c96900-toughmet3-alloy-bearings/tmcb161808

As I have said before, I do not believe the wear is rotational wear that is being seen. I believe it is from shock load since the bushing does not spin on the shaft while moving forward.

I ordered one of the toughmet3 bushings today to get a look at it. I'm struggling to replace the OEM bushing with the same kind knowing it probably won't last. 1500 miles and .008 taper on the factory bushing. The gear has 3 holes but the bushing was not drilled.

 

[cannondale27]

I tried the last bushing but when pressed into the gear it would not go on the shaft. I did not try to ream it to fit. Maybe it will be next.....

Did the bushing go on shaft before being pressed into gear? If so maybe the gear Id itself needs to be honed a bit bigger.

 

[SPM]

I tried the last bushing but when pressed into the gear it would not go on the shaft. I did not try to ream it to fit. Maybe it will be next.....

Take it to a engine machine shop. Most of them have a Sunnen pin hone machine and would be a piece of cake to enlarge the I.D a bit.
1 inch diameter is just slightly larger than the wrist pin size for a big block chev so chances are that any race engine shop should have a pin hone.

 

[twyztid]

I ordered one of the toughmet3 bushings today to get a look at it. I'm struggling to replace the OEM bushing with the same kind knowing it probably won't last. 1500 miles and .008 taper on the factory bushing. The gear has 3 holes but the bushing was not drilled.

Let us know what you think of it.

I am also thinking that the bushings that are made of a solid material (not layers of different materials like the OEM bushing) could possibly be honed out with a brake hone if they are too tight on the shaft once pressed in the gear.

 

[SPM]

Let us know what you think of it.

I am also thinking that the bushings that are made of a solid material (not layers of different materials like the OEM bushing) could possibly be honed out with a brake hone if they are too tight on the shaft once pressed in the gear.

I won't see it for about a week so bare with me, but I will give my opinion on it.
I would be cautious with the brake hone idea as it could hourglass the bushing depending on how much needs to be honed, a very small amount would probably be fine.
I still feel like there is a different issue causing this problem like chain/gear, alignment, endplay, lube, ect, and we're trying to correct the issue with better bushing material. I'll do whatever it takes to make it better.

 

[ClutchMaster]

I won't see it for about a week so bare with me, but I will give my opinion on it.
I would be cautious with the brake hone idea as it could hourglass the bushing depending on how much needs to be honed, a very small amount would probably be fine.
I still feel like there is a different issue causing this problem like chain/gear, alignment, endplay, lube, ect, and we're trying to correct the issue with better bushing material. I'll do whatever it takes to make it better.

I changed my top gear and chain, left it at least one turn out on the adjuster, wear is 10 times better. Canondale did everything but change his chain, and still had premature wear so you might want to change yours. Use authentic Borg Warner chain.
Holes in the gear probably help but I know guys who had no holes and had no issues.

 

[SPM]

I changed my top gear and chain, left it at least one turn out on the adjuster, wear is 10 times better. Canondale did everything but change his chain, and still had premature wear so you might want to change yours. Use authentic Bog Warner chain.
Holes in the gear probably help but I know guys who had no holes and had no issues.

Where to purchase authentic Borg Warner chain and how to verify brand? Part # ?
Did Yamaha/cat use more than one brand of chain and that's why some guys are not having bushing issues?

 

[Turboflash]

I won't see it for about a week so bare with me, but I will give my opinion on it.
I would be cautious with the brake hone idea as it could hourglass the bushing depending on how much needs to be honed, a very small amount would probably be fine.
I still feel like there is a different issue causing this problem like chain/gear, alignment, endplay, lube, ect, and we're trying to correct the issue with better bushing material. I'll do whatever it takes to make it better.

I can't prove it but I have a theory that harmonics/resonance plays a part. I've seen cases before where ultrasonics/resonance/harmonics destroyed stuff for which there was no other explanation. Just my theory.

 

[SPM]

I can't prove it but I have a theory that harmonics/resonance plays a part. I've seen cases before where ultrasonics/resonance/harmonics destroyed stuff for which there was no other explanation. Just my theory.

Yeah, harmonics can be tricky. I had to deal with that when I built race engines, especially with valve springs. Maybe all this has something to do with the tensioner spring and that's why chain adjustment seems to affect bushing wear.
Like Clutchmaster is saying about changing the chain....might be just enough to change harmonics for the better if that's what is causing the issue.

 

[ROCKERDAN]

Hard to believe it would be from rotating as gear only turns when in reverse. I can't prove it but I have a theory that harmonics/resonance plays a part. I've seen cases before where ultrasonics/resonance/harmonics destroyed stuff for which there was no other explanation. Just my theory.

Agree, the reason it wears is certainly NOT from reverse....

It's how the gear when in forward meshes on the outer portion with the reverse gear(to go forward) while the inner portion where chain pulls tension is where the bushing rides....so when you hit the throttle with big power that chain tensions and wears hard on bushing on inner portion, yet outer portion is meshed into reverse fork gear, so it sorta rides half on meshed gear and half on bushing. Wearing it out. HORRIBLE design.

Dan

 

[ClutchMaster]

I’m telling you guys it’s the design of the HYVO chain. The gears have a rounded tooth crest. If the chain wears and becomes longer it climbs more in the tooth.
Even a brand new chain will climb somewhat in the tooth. Under load the root of the sprocket never touches the crest of the chain profile.
If we could only run our machines with the chaincase cover off I could prove it buy leaving the tensioner loose. When under power the slack side of the chain will actually tighten up. The more the pitch of the chain changes as it stretches, the more it will climb in the gears.

That’s my theory, and I’m sticking too it!

 

[Rerhardt]

Well after some thinking, measuring, pressing, fitting and more thinking I am going with the oil impregnated bronze sleeve in my upper gear. It fits the tightest without binding and is different than the stock configuration. Drilled the oil holes.
I have spent FAR to much time on this bushing......

Did the bronze 660 bushing hold up