dead start hiccup

[Happyboy]

OK, most people will never see this problem. And its not so much of a problem as a minor annoyance with racing. I race harescrambles (GNCC) and we have a deadstart. This only happens on a deadstart. I hit the start button, it fires up and when I stab the throttle it boggs for a second, sometimes dies, and then runs great. This will not happen if i come to a stop and then stab the throttle, only if i turn the quad off, and start it and stab. One other thing, I have a rekluse so there is no revving the motor up then letting the clutch out. Once it hits the right rpms, like 2200 it starts engaging.

I don't know if this is too much fuel from the start or if it can even be cured. Let me know your thoughts.

[cannondale27]

Adjust the coldstart fuel mass in the map leaner.When motor first turns over there is four (?)large shots of fuel then normal.This controls the amount of the big shots.

[zoommx]

Sean,
You get this fixed? I noticed the same issue last week when riding. It'll be important when I hit a scramble.
Roger

[acarli3]

Don't ask me how or why this works... but bump your throttlebody leakage to .5 and you'll notice that hesitation smooth out or go away.

[banzairx7]

Could it be the air bypass stepper not having gotten to the right postion when you hit the gas?

If it is eliminating it would solve the problem.

[Canniboomer]

It seems we may need to come up with a remote-control activated bump of the system, to wake up the ecu, prime the fuel pump, and position the stepper.... that would be trick, and kind of MI III sneaky (he he). Easy to test by just bumping it, pausing for however long you need, and then trying a so-called half-dead start. If the problem goes away, visit the junkyard for a keypod and 12V solenoid! LOL.

[Happyboy]

I did play with the cold start setting and it did get better. Now it hesitates but doesn't stall. Not the best but it is better. As for blocking off the IACV I did before and it ran horrible on startups. I am not going back to that. Something I have thought about is a manual IACV like the LTR450 has. I don't know how to get to that point but I am going to examine the option.

I will also try and play with the half dead dead start this next weekend.

[banzairx7]

You can remove the IACV and still have a high idle while cold. There is a write up on cannondaler I believe. Involves an air toggle switch, a custom plate, hose barbs and some hose.

[Easy E]

Also check the TS setting on your map. I've checked many of these "stroker" maps and the TS has been changed to 110 - far too low on the Transient Sensitivity for any motor with increased air volume via stroker, airbox or exhaust mods. I've mapped a stroker motor with TS at 130 and would recommend the stock setting of 150 to compensate for that volume.

As a quick refresher, the Transient Fueling is for just that purpose noted in this post. The values in our maps come from a motor running at a steady state (constant throttle and constant RPM). When the throttle is cracked open, there needs to be compensation for the rush of air - a low TS will cause a lean condition and a stall.

As Acarli noted the Throttle Offset will also help as it adds fuel to compensate for air that "leaks" past the throttle body butterfly.

[zoommx]

Thanks for the feedback guys. All very interesting. I'll make a change or two and find out what works on my bike. Probably start with the ts; its at 110 right now, then the tb leakage number Acarli mentioned. Could be a week or 2 though before I have the chance to do that.
Roger #491