Whats it to ya know?

[taber hodaka]

Primary gears different but same spline, all are straight cut. What do they all go to? first three are 59 tooth straight cut.

The two gears are 63 tooth straight cut but one is much thinner. ----- Clarence

[dcooke007]

Clarence,
The 59 tooth gears are for the mdl 93b super rat, 95 combat wombat, 97 super combat and 98 super rat.

The top left 59 tooth gear with the rivets was a redesign aimed at the 97 super combat and 98 super rat. There are rubber cushions internally on the rivets to absorb sudden shock loads and help the trans live.

The top right 59 tooth gear is the stock unmodified 934502 gear and the one with all the holes looks like a drilled version. Not sure if drilling is a good thing or not.

The 63 tooth gear is 914506r and are for the mdl 93 and 93a super rat. Well...at least one of them is. Not sure which thickness one is correct and not sure why one would be thinner.

Danny Cooke

[taber hodaka]

Thanks Danny. The Primary gear marked 63 is .91 thinner but Looks original. --Clarence

[Bullfrog]

? 0.910" thinner? That's purty hard to do with gear that starts out a bit over 1/2" wide. So that must be 0.091" thinner right?

(. . . and I don't know why it would be thinner either)

Ed

[junker2k]

The 63 tooth ones are the ones that work great in a trials bike.
Jack K

[taber hodaka]

Thanks Ed I you are correct. I measured the thick or normal one at .526 and the thin one at .435 and the difference is .091. But I wrote them down as 5.26 and 4.35 nobody home was not thinking. Ed after all of these years we make a tiny mistake and we become normal, did I include you in that? Thanks ----Clarence

[racerclam]

Its weird that the 93b came out with the higher geared primary gears then brought it back down with a larger rear sprocket and ended up with the same final drive. I had asked Harry about this and he had no idea why they did that . They also went to the weird 423 chain at the same time .

Rich

[Bullfrog]

The 423 chain move is at least slightly understandable. 423 is essentially narrow 428, and is a bit stronger than the earlier 420. We used to run 428 chain on the 423 sprockets if we knew things were going involve a LOT of sticky mud.
Ed

[racerclam]

I guess that would flig the mud out better, good idea

Rich

[matt glascock]

At first blush that really makes sense, but do you trade self-clearing for an increased potential for derailment and faster chain/sprocket wear or are the discrepancies negligible in that regard?

[Bullfrog]

Faster sprocket wear would be expected when running 428 chain on 423 sprockets . . . but keeping the chain "on" was predicted to be slightly better due to improved ability to "shed" mud in really, really bad mud conditions. This was a technique used for competition, so regular maintenance was expected to stay on top of things like sprocket/chain wear.
Ed

[matt glascock]

Thanks Captain. If I would've thought about it a bit, we have all done things to stack the deck in our favor while accepting an enhanced wear and tear component to the equation. Digging a bit deeper, around these part, the MX dirt is either loamy or dry pack. However, on the handful of tracks with the really tenacious, greasy dirt and mud, and in many off-road courses, there would be so much mud and crud jammed in the chain wheels the chain would be riding out of the sprocket valleys. That factor probably accelerated wear much more that a minor mismatch and at the loss of the "mud flinging" benefit. The happy medium would be to pick the chain/sprocket combo based on anticipated conditions. Great point, Ed. Thank you!