I have swapped main jets on my Keihins, and running is good, shes got good acceleration and pulls well. Problem is when I come to a stop, clutch goes in and revs hang at 2000 for just under 10 secs slowly dropping down to 1000-1200, if I rev it a bit it can jump up and hang again also hunting revs a little. Is this too lean?
My SS did that..................there were three things necessary. 1) I reduced the tickover slightly, which helped it drop back immediately..........It ticks over at 1000-1100 rpm. 2) I made sure the rubber twistgrip cover wasn't dragging against the twistgrip housing..........I got caught out with that when trying to balance the carbs. 3) If it is hunting, try each pilot screw one at a time and say 1/2 turn out more, ie richer (return the first one to where it was before doing the second)..........Pilot screw settings aren't necessarily equal.
Ok , throttle moves freely, and cant lower idle too much or it stalls. Al I will try the fuel screws but they dont seem to make much difference when Ive moved them previously:weary: Im going to try a larger slow fuel jet. Gotta do what I can before I take it to dyno to set it up.
Possibly, its quite difficult to sort the balance, involves taking the top off them and when they are set they should be fixed. It could well be out though.....
Thats what happens when you fit FCRs, Ian.................the BDSTs are bad enough to get right, but the FCRs take quite a lot of setting up.
I can't add much to what's already been said, except the obvious - you've got a touch of free play on the outer cable when the throttle is shut? I'm not sure its worth the expense ( and buggeration) of changing pilot jets - mine ticks over ok-ish, but was quite rich, and adjusting the fuel screws made no difference at all (could screw them all the way in, and the tickover never altered!). Went from the standard 60 jet down to 55's then down to 52, with no difference to tickover - the only difference is the 52's get rid of a low speed hesitation when cold, but just make it harder to start. I've just accepted that tickover isn't FCR's strong point. Slow speed running isn't a dyno issue though? Sent from my P01M using Tapatalk
I never did get the Mikunis on my SS perfect. I never did manage to stop them hanging onto revs, as you describe either, although I did get them rather better than yours seem to be. A Morgantune carb balancer was a huge help. The columns are right next each other, so very easy to compare, which I found to be a big advantage over vacuum gauges. They should help you see what's going on right through the rev range.
I appreciate all the input. I know that they are race carbs and that the idle is rough at best, this I have accepted. I am not happy with the engine sitting so high though when I come to a stop. Something can be done to improve this as the rest of the range appears pretty good. I actually have a carbtune but thought the balancing was done with a drill bit underneath the slides and therefor not with a conventional balancing method? I went down to a 52 jet and it was gutless untill past 1/4 throttle, back up to a 60 and as I have a full Sil system and open airbox with K and N I am thinking the flow is perhaps a fair bit higher than these were originally set up for. I have upped the main to a 165 and this has improved things in the upper range. Might even try one up from that. Next will be to measure the slide height and use a carbtune for flow, then change the slow fuel to a 65. Will report back any improvements/decreased performance.
Have you checked out what the workshop manual has to say about carb tuning.? It's for the Mikunis of course but makes interesting reading. I think it might be useful to try the carbtune at various throttle openings to see where you are balance wise. Are you not supposed to use a co meter to set up the mixture screws?
When I pre-balanced my Mikunis, I used 0.75mm stainless lockwire..........that was to have them as closed as possible before fitting them and then adjusting balance............If it wasn't for my dragging twistgrip rubber confusing things they would have been as near as dammit spot on. With my Guzzi Le Mans I did it without the engine running doing it by eye and watched each cable pull the slides, adjusting each cable accordingly.......I had both cables slack and gradually tweaked them until they just started to move the slides..........
Going on a bit this one, Ian....are you thinking of going to see a pro about it? You have more stamina for the tinkering than I ever will. But I'd be down at a specialist workshop by now.
Yeah, still at it. I have certainly improved things, I just dont want to admit defeat and spend £££ for someone else to do it. I have already learnt so much about the internal of my bike Im beginning to understand carbs a bit. I'd rather do it myself where I can.
Have you checked for an air leak, split intake rubbers/rubbers not seated properly, that sort of thing?, hanging revs is often a symptom of the engine getting air from where it shouldn't
Back to basics Ian...........Tell me what your overall set-up is to save me reading the disjointed thread bits and I'll see what I can think of............
to check for an air leak spray carb cleaner around manifolds with engine on tickover revs should rise when spray is sucked in should help pin point air leak if there is one
