Throttle stop reset........... Oh no!!!!!!

[Bitza]

OK hi all, it's cold and wet so an ideal opportunity to fiddle with the devil. You guessed it I've decided to take on the adjustment/balancing? of my injector throttles. I first used these throttles when I used a 900ie lump then simply swapped them over for the S2r 1000, I just changed the tps and away I went. Didn't touch the stop adjusters of course!! Golden rule etc. OK so back to yesterday checked things out, throttle stop determined by vertical throttle only, when balanced out via linkage adjustment horizontal throttle open more than the other one. Conclusion some fiddler has been here before me. Look on Google no advice no nothing, apart from don't fiddle, no fix it advice at all. So my approach went back to points technology, extra thin fag papers, turned out to be less than perfect, butterflies tend to tare papers and fit of flaps is not precision. But "I Paper" paper pretty good (note Dailey Mail tends to give a false perspective of reality). So I worked from the vertical throttle setting which is least vulnerable to fiddling and matched the horizontal to that via the stop screw. So my measure of the butterflies minimum opening was where the fag paper will just slid between one side of the butterfly, (note the butterfly flaps aren't necessarily exactly central so they gap could be either side)
but the I Paper paper just caught. So with equal gaps and both throttles synchronised, I've now got a starting point to sorting my injection via the air bypass screws and trim settings.

 

[slob]

carbtune.co.uk

 

[Dukedesmo]

Don't know about 900ie but the butterfly flaps on my 916 weren't properly central when I fist 'went in' and so didn't quite close in sync. no matter how the linkage was adjusted. The 2 screws that hold them to the shaft are slightly slotted to allow for this and can be adjusted accordingly.

Fundamentally the starting point is to set TPS position correctly and this requires the front flap (TPS) to be fully shut, I find that disconnecting the rear by popping the ball joint out as is advised by many doesn't work well for 2 reasons;

1. The spring weight of just the front flap is insufficient to get a reliable and repeatable full closure, it needs the extra push of the rear spring.
2. Disconnecting the (plastic) ball joint between the 2 weakens it, making it a loose fit and potentially breaking it.

To this end, I wind the rear flap open on the linkage rod so that it is not on the stop and wind out the idle stop screw, meaning all the spring force from both flaps is now definitely fully closing the front flap - I can then get a repeatable 150mv reading when closed and, despite what some say about never altering the rod, it is very easy to re-balance and sync afterwards. As for balancing, start with the air bleeds closed and set the CO using the trimmer on the ECU (I aim for 4 - 5% CO). It is very likely that the cylinders will not be equal CO wise at this point so adjust air bleeds as necessary to bring them to the same reading.

It takes a bit of juggling backwards/forwards with the CO trim/vacuum/air bleeds but worth persevering for as close as possible to identical, both CO and vacuum as the end result is an engine that runs smooth, idles well, has immediate throttle response with no flat spots or hesitations and makes good power.

The above applies to a 916 and I don't know how much of this applies to the setup on an M900ie but I doubt it's much different.

 

[Bitza]

You are right of course vacuum gauges would have been easier/more accurate. But initially I was just trying to improve things on a cold wet day. I'll have to give it a more serious attempt when I get some gauges. But I was surprised at the "Net's" total lack of info on how to set stop screws. One amusing glimpse into the limitations of AI is when you ask Google about the typical range of trim setting for say a 1000ds. Because if you repeat the question it comes up with differing info each time.

 

[slob]

"I'm sorry Dave, I can't do that"

 

[Dukedesmo]

Don't bother with AI, try 'bradthebikeboy' on youtube, he has some how too videos that are very helpful.

 

[Bitza]

Well just to report that I have persevered with my fag paper, slowly slowly, adjust try out adjust kinda approach, and have had a positive improvement, although I do still have issues when holding 3000 ish rpm at low speeds.
For anyone thinking of resetting their throttle stops, my advice is to work on one cylinder at a time, and to start with the butterfly too closed making it much too rich. 1/4 turns of the stop screws make a significant difference. Finally adjust the balance screw after every adjustment.