Dont waste your money with auto decompression. It does not make it easier to start, you actually have more control with the manual decompression. It makes it a breeze to push start if you ever get into a situation. It also comes in handy when you drown your bike.
This is the voice of someone who hasn't ever owned auto decompression. I grew up riding big British singles, and I'm completely familiar and well practiced in every technique involved with the use of manual decompression. Let me just tell you right now, there's no way I'd give up AD for manual under any circumstance. It would be nice to have both, because the manual setup is handy once in a while to deal with certain odd situations, but the thing is that with the pre-'06 bikes, you have the option of retaining the old system. It absolutely does not interfere with the auto decomp at all.
Starting is normally more a matter of tuning the carb correctly, mostly the idle circuit. After that, you have to get the technique right with the manual arrangement:
- Find the compression stroke (push up against the "hard spot")
- Pull the decomp lever and move the kick crank about 1-1 1/2" farther down (too far and you'll go past TDC and it won't fire; not far enough, it won't move)
- Reset the kick crank to the top and kick through
By contrast, with auto decomp:
- Find the compression stroke
- Reset the lever
Or, just kick. Works better if you do find compression and start from there, but you can just jump on and start kicking as if it were a two stroke, too.
And I'm sorry, but bump starting? Don't make me laugh out loud. There's no way the manual is easier:
- Pull and hold the clutch and the decomp
- Push or let the bike roll if it will
- Release the clutch and let the engine start turning
- Ease off on the decomp to restore compression (this must be done gradually enough that the next compression stroke doesn't lock the engine, but quickly enough that momentum isn't lost)
- Pull the clutch as it fires up
Try that as you come barreling into an uphill turn and kill the engine with a brake stomp. Or, imagine you have AD:
- Push or let the bike roll
- Drop the clutch or snap it into gear
- Done, it's running
In the killed-it-going-into-the-turn situation, you do exactly what you would on any 250 2T; pull the clutch to free the wheel, let off the brake and dump the clutch back out to restart the engine. Just like a 250cc two stroke. OK, a bigger, heavier 250cc two stroke, but just the same. In fact, before my Rekluse, I could let mine roll down any slope that would produce 3 mph and bump it off every time when it was warmed up. AD makes bump starting ridiculously easy.
The manual setup is definitely useful. One quirk with the way that the AD works on the YZF is that the decompressor pin can be trapped in the retracted position in which it sits while the engine is running if the bike stalls suddenly against its own compression stroke. In that case, without the manual release, you'd have to have the bike in gear and pull it backward just a little to free the mechanism, after which it will work normally. With the manual setup, you'd just pull the lever once to get past that and be back to normal.
At least 95% of everyone who has done this has called it one of their most worthwhile mods in terms of making the bike enjoyable to ride. Very much worth it.