1-2 Auto Trans Pros and Cons

Picked up a 1-2 Auto trans with neutral on the bottom, thinking about running it this season. Would like to everyones opinion. Do you have to do a burn out differently with this trans ? Other things that have to be done differently?

I have never ridden one but have talked to guys who have. They are mostly used on big CC high HP setups (Turbo engines) on combo's that run below 9 seconds. Most guys I have seen running them have Turbo car tire bikes that run low 8's or quicker.

I do know you can't get out of the gas for any reason or you will bend shift forks at the very least, and possibly destroy some gears. They are not really a "automatic shift" but can be setup for zero kill time on whatever electronics your using to get really low 60 foot times. No special burnout that I have seen.

Never heard of anybody using one on a small engine small tire combo bike, but I could be wrong. Two speed would be good for 1/8th mile if you have enough HP, Top Fuel bikes only have two speed shifting even for 1/4 mile (now 1000FT)

Someone more knowledgeable will probably chime in on if I got most of this right.

Injected wrote:

 They are mostly used on big CC high HP setups (Turbo engines) on combo's that run below 9 seconds. Most guys I have seen running them have Turbo car tire bikes that run low 8's or quicker.

 

I'd be one of those guys - guilty as charged!  In a former life, my  last dragbike was a turbo 1395cc Kaw in a car tire chassis (the bike shown in my avatar).  Trans was from Orient Express and was just a 3-speed and full auto (aka no-kill) 

Southpaw - I'm almost 100% sure that you're talking about a 5-spd trans whereby the 1-2 shift is auto (no-kill) and then the other subsequent upshifts 2-5 are full-kill.  
Advantages - it is thought that the auto shift is not as hard on the gears in that there is less of a shock load.  Makes sense.  Also, you might see a very slight decrease in ET since you're not letting off the power at all by killing the ignition.
Disadvantage - as Injected mentioned, you will not be able to back off the throttle when in first gear, as the dogs will try to back out of the ramped engagement slots in the trans gears.  This only happened to me once with bent shift forks and a fractured bottom half of the engine cases(!) as a result.  The gears were unscathed, fortunately; a testament to the robustness of the tranny (the gears looked like they came out of Chevy 4-spd, or something similar).

Regarding burnouts - you cannot use 1st gear, and shouldn't be anyway as general practice.  I 'think" that you should be fine in 2nd gear, however.  On my turbo bike, I would use high gear (3rd) to do the burnout.   

Hope this helps.

Mike

On a side note about the "not letting off" the gas part. I have seen a lot of car tire bikes get out of shape and almost hit the side wall or cross the center line. Once a car tire gets up on the outside edge you really have to be skilled in shifting your weight to get it back in the groove.

I have never seen a small tire bike do that, and especially one with a 5" tire as they ride more like a street bike.

Sorry guys i should have been more specific in my description. Yes a 5 speed transmission with 1-2 no kill (auto).

So what i'm reading you cant ride it around in 1st gear need to be in 2nd except for the actual launch. So if something goes wrong after I launch but before the 1-2 shift if I let off the throttle its going to break or bend the forks? 

Southpaw wrote:

So what i'm reading you cant ride it around in 1st gear need to be in 2nd except for the actual launch. So if something goes wrong after I launch but before the 1-2 shift if I let off the throttle its going to break or bend the forks? 

Correct.  And, you will bend the shift forks unless you can get the clutch pulled in right when things start to go south.  The challenge is that there's a lot going on as you come off the line.  You're not covering the clutch lever after the launch and by the time you realize that you've got a problem and try to react by reaching for the lever and pulling it in, it's usually too late...