I'm fine-tuning my settings for the Mikuni TM36-68, and while I know they aren't perfectly spot-on, I'm getting quite good response at all throttle openings.

A recurring issue I have, however, is that if you rapidly and repeatedly blip the throttle from closed to slightly open, RPM starts to drop from the excess gas and eventually the engine stalls out.

I know this not something you would even do in normal operation of the bike, so I'm wondering...is this actually supposed to be possible on a bike with an accelerator pump? Or, should it not be possible under any circumstances to stall your bike with throttle only and in neutral, and I just need to continue tuning my idle & pump settings? I am assuming it's the latter, but want to make sure I'm not trying to fix a bug that isn't one.

 

You have two adjustments for the AP on the 36mm Mikuni. One for when the squirt starts and the other for how long the squirt is. It sounds like the second one is the one that needs adjustment.

Ride on
Brewster

 

if this is happening in actaul real world riding then yes, cause for concern. If your just wacking it open in nuetral than, no, it's not an issue. My experience is with FCR's not mikuni so take this tip FWIW. Before you even put the carb in the boots rig it up so you can wack the throttle and watcj the pump spray, set the timing so it JUST misses the slide as it lifts. There's usually a gap measurement of the pump linkage, I've found it to be spot on in most cases and passes the test without adjustment.

 

I can kill the engine sometimes in neutral with snap throttle of my FCR. Its my understanding that the Taffy Mod would correct this? No?

 

yes..

to the OP brewster is right

 

I can't actually make my engine stall, but I can make it bog like hell if I repeatedly keep opening the throttle wide-open in neutral. I have to purposely try to make it bog though - in real-world riding it's never been a problem.

You set up the Mikuni TM36 the same way. It should translate to about 1/8 throttle before the accelerator pump starts pumping. Also, make sure the AP stream actually hits the needle. Fuel should splash off of it. That's per the Mikuni tuning manual. If the fuel doesn't hit the needle, it doesn't atomize well enough and causes giant bog.

On mine, I have the AP stopping point set at 3/4 throttle. If the throttle is immediately wacked wide-open, the AP pumps for about 1 second before stopping.

 

I think I have both screws about right (well I guess the starting one still needs a little adjustment) because for quick wide-open throttling it works great and revs right up with no hesitation or stumbling. What kills my engine is if I rapidly open and close the throttle again and again from 0 to like 1/8 of the range, which of course isn't something you'd normal be doing while riding. This quickly makes the RPM drop and if I do it for more than a few seconds the bike stalls.

Seems like the verdict is, if I were to get on a properly set up bike with a pumper carb installed, I might be able to bog the engine a little bit with the AP, but being able to stall it is a little extreme and a sign of incorrect adjustment?

 

Yup. I could open my throttle from closed to 1/8 all day long and it would never miss a beat. Only when hammering the throttle from closed to wide-open repeatedly in neutral can I get the engine to start bogging.

I noticed in your sig that you're running a TM36 with the stock bore. Mine is a 340. Because the stock bore will have less of a vacuum signal at idle than mine, you may have to adjust the accelerator pump to start even later that 1/8 throttle.