Topic: Undercut transmission, or rev limiter?

[Terry in Australia]

I've been wondering to myself why, rather than spending 400 bucks (plus) getting the transmission undercut, I can't just hook up my new Dyna rev limiter that's been sitting in a box for the last couple of years?

From my limited knowledge of racing transmissions, undercutting the gear dogs stops a bike jumping from out of gear and over-revving, possibly leading to engine damage, and an adjustable rev limiter will stop an engine from over-revving by cutting the spark at a determined RPM, if my bike jumps out of gear.

Sooooo, I'm leaning towards just using the rev limiter at this stage, unless someone here wants to chime in and tell me more about why I need to get the transmission undercut? I won't be racing my 1060cc bike, so a missed shift is neither here nor there, as long as no damage is done. Cheers, Terry.      

[Bill/BentON Racing]

Terry,you may not be racing,but the frustration factor alone would be enough.Missed shifts no fun..miss enough,may start jumping out of gear,not fun and will require splitting the cases to fix.Fix tranny now.Electronics can always be added later.Just my .02.Good Luck,Bill

[mick7504]

Terry
I agree with Bill.
Aside the insurance of it staying in gear, you'll notice a big difference in positive gear changing.
Splitting cases to fix a tranny problem does ruin your whole day mate and is a PITD.
They'll take a fair bit of punishment but will also chuck the towell in eventually once the rot starts setting in.
Mick

[bwaller]

Plus what's another measly $400 compared to what you've sunk into it already. 

Ride with one & you won't regret it Terry.

[Terry in Australia]

Yeah, thanks guys, is there a tutorial anywhere on "How to"? I emailed Ken piper, the builder of my gold bike and he said that the dogs are ground, not cut, so maybe I can do it myself? Cheers, Terry.

[scottly]

the dogs are ground, not cut, so maybe I can do it myself? Cheers, Terry.

I did it myself. (I was also told I was nuts! )

[Terry in Australia]

the dogs are ground, not cut, so maybe I can do it myself? Cheers, Terry.

I did it myself. (I was also told I was nuts! )

Woohoo! Can you give me some pointers mate? I don't know anyone around here that can do it, but it doesn't look difficult, so why not? Cheers, Terry.

[scottly]

Use a transfer dye on the edge of the hole the dogs engage, fit the gears together and note where the dye shows on the dogs; the contact should be closest to the gear. Using a Dremel with angled stones, carefully undercut the dogs, making sure to remove the same amount from each dog, so the load is evenly distributed. The dye will guide you. Work slowly. Only a small amount of under-cut is necessary: too much will make shifting difficult without "floating" the throttle.
By the way, this process is only for those with more time than money.

[Terry in Australia]

Thanks mate, I'm a very wealthy man, time wise at least................. 

[scottly]

Ahhh... It's nice to be rich, indeed!

[scottly]

Oh, yeah, almost forgot: don't bother to undercut the decel side of the dogs...

[Terry in Australia]

Why's that mate?

[scottly]

Back tire will break loose before the trans pops out of gear, at least in my experience. All the wear is on the accel side.

[Terry in Australia]

Back tire will break loose before the trans pops out of gear, at least in my experience. All the wear is on the accel side.

That's good to know mate! Cheers, Terry.

[Jon]

Been thinking of trying to undercut a transmission set myself.

Current thought is to try and set up a jig in a chainsaw sharpening machine (like a small drop saw)

What are peoples thoughts?

[bwaller]

Don't bother undercutting the first gear set either Terry, it just makes it tougher to find neutral.

[Terry in Australia]

Don't bother undercutting the first gear set either Terry, it just makes it tougher to find neutral.

Good point Brent, I wouldn't have thought of that!

Been thinking of trying to undercut a transmission set myself.

Current thought is to try and set up a jig in a chainsaw sharpening machine (like a small drop saw)

What are peoples thoughts?

That sounds like a good idea mate, I've got a chainsaw sharpening machine, you can set the angle so all the cuts will be be uniform, you might just need to attach a simple rotating table on the machine's base to attach the gears to, so you can rotate the gears from a fixed position to ensure each cut is made from the same angle as the last. I'll have a look at it tomorrow.

[bear]

Ya gotta do it Tez.
Once the dogs start wearing they just get worse until the bike is not worth riding.
We used to grind our own dogs until we started using Rexy Wolf's gear sets.
I think we used about a 7deg. back cut.
By the by, Ozz titles are at the Island this weekend.
Coming down for a look?

Cheers,
Brian

[Terry in Australia]

Ya gotta do it Tez.
Once the dogs start wearing they just get worse until the bike is not worth riding.
We used to grind our own dogs until we started using Rexy Wolf's gear sets.
I think we used about a 7deg. back cut.
By the by, Ozz titles are at the Island this weekend.
Coming down for a look?

Cheers,
Brian

G'Day Brian, does Rex sell them to the public, and if so, how much? Phillip Island this weekend coming mate? Hmmmnn, if the weather gods are kind to me I might take the Triumph down on Saturday, it's Father's Day on Sunday so I won't be going too far. Cheers, Terry.

[scottly]

Ya gotta do it Tez.
Once the dogs start wearing they just get worse until the bike is not worth riding.

Been there before!!! It sucks!!!


We used to grind our own dogs until we started using Rexy Wolf's gear sets.
I think we used about a 7deg. back cut.

I personally don't think the back-cut needs to be such a severe angle. As long as there is an angle, say 1 or 2 degrees, the gears will be forced together under load.

[bear]

G'Day Brian, does Rex sell them to the public, and if so, how much? Phillip Island this weekend coming mate? Hmmmnn, if the weather gods are kind to me I might take the Triumph down on Saturday, it's Father's Day on Sunday so I won't be going too far. Cheers, Terry.
[/quote]

As far as I know Rex still supplies them.
Never had them fail.
Four dogs instead of three, but the last set cost me $1500.
Probably a bit of overkill for a road bike.
I'll PM my phone number.
If you decide to come down I'll scrounge a pass.

Cheers,
Brian

[bear]

I personally don't think the back-cut needs to be such a severe angle. As long as there is an angle, say 1 or 2 degrees, the gears will be forced together under load.
[/quote]

G'day Scotty,
Your probably right.
But our old girl is running 125 to 135HP @ RW and even at 7deg we where doing 4th gear every three meetings.
At 7deg never had a prob. with gear selection, any more and we would rip the dogs off.

Cheers,
Brian

[Terry in Australia]

1500 bucks? I'm clutching my chest as I type this Brian, I think I'll get my dremel tool back out again! And yeah, a free pass would be great, thanks mate! (but if it's pissing down, don't expect me!)

[scottly]

G'day Scotty,
Your probably right.
But our old girl is running 125 to 135HP @ RW and even at 7deg we where doing 4th gear every three meetings.
At 7deg never had a prob. with gear selection, any more and we would rip the dogs off.

Cheers,
Brian

And just how much weight are you pushing with all that HP? No wonder you need a $1500 trans!

[bear]

And just how much weight are you pushing with all that HP? No wonder you need a $1500 trans!

Gee'z not more fat jokes.
The $1500 only gets you 2nd, 3rd and 4th gear sets.
Aussi dollars though, so it only breaks down to $15US.

Cheers,
Brian