850 sputters upon acceleration????

I fixed the popping on deceleration problem with my commando by tightening up and sealing carbs to manifold but created another . My 74 850 Commando has had the intake polished and possibly widened by the previous owner?? When I pulled my carbs off last week to seal the mating surfaces better I decided to raise my two needles by one notch. They were both on the bottom notch and I raised them to the middle. Now the engine is behaving badly upon moderate acceleration in 2nd and 3rd gear. When I moderately accelerate in 2nd and 3rd it stalls or stutters for a split second until rpms rise and the throttle is opened more to mid or full throttle. I pulled both spark plugs and inspected them. The insulators look to be a nice whiteish tan color but I did notice a black powder soot on the electrodes and outer rim to the threads that is exposed . It was not having this stalling issue before I changed the needle settings. Should I now move the needles back to the original positions(CLIP AT THE NEEDLES TOP NOTCH). I thought that since the intake ports were polished and possibly widened it could handle a little more fuel to air ratio?? was I wrong?? Do you think I may have created some other reason for the stalling besides moving the needle position??? Thanks for any advise--Mark Cigainero

what slides do you have
what airfilter
what needles
what cut-aways for spraytubes

Mark, you say you raised the needles by going from bottom to middle notch? That lowers the needle and weakens the mixture. You then ask if you should go back to the original '(CLIP AT THE NEEDLES TOP NOTCH)'. That is even weaker and not the same as your starting point (They were both on the bottom notch and I raised them to the middle) ?? I'm confused but it sounds like a weak mixture in transition from pilot to cutaway to needle jet. Definitely check the spray tubes but if was running ok before go back to that setting....bottom notch?

if you are anywhere under 4000 altitude, put the needles back in the middle notches, the stock setting, you are too lean now?

It's impossible to diagnose without seeing so here goes. To rich and you are monentary fouling the plugs, it's more than possible your needle jets are rooted.
drop the needles again see if it improves
The outer rim of the plug gives you a good indication of mixture, it shouldn't be sooty

Sorry-- 850 Needles in TOP notch of needle

Sorry. The needle clip holders were originally clipped in the TOP notch of the needles and I moved the clip to the middle notch to make the mixture more rich . It was not stuttering before I moved the needle clips. Sorry for the confusion. Anyway I used a smalllll amount of gasket sealer inbetween the carbs and the manifolds and the manifolds to the heads to stop leakage causing popping upon deceleration. Popping stopped nicely but after moving the needles I started getting stuttering around early mid throttle range going from 2nd to 3rd at around 30mph. At full throttle with rpms up no stuttering. Is it now too rich?? Some black soot on outer rim of plug and metal part of electrode. Insulator was nice and whitish tan.

why didn't you see how it ran after reseating the manifold / carbs before you messed with the needle clips ? sounds like doing something that maybe wasn't required - i usually find that manifold leaks don't allow the bike to idle properly (low rpms) and require a very rich mixture to even get it to run if the leaks are real - are you sure the popping wasn't first by improper carb setting in the first place.....

If you moved the needles and it runs worse put them back. I agree with other poster that manifold leaks show up more as poor idle. I would look at exhaust system leaks inducing pops.

I cured the same (original) problem - popping on deceleration - with the same fix - an intake leak (quickly revealed by spraying WD-40 around the intakes) that required new gaskets.

Raising your needles (lowering the clips) may have caused a richness problem - either because the needles in the new position are too rich, OR because they didn't quite seat properly after you changed the clip position - I had this happen on my wife's Triumph a while ago, after I had the needles out to shim the clips. The needle somewhow went in off-angle and hung up, causing the jet essentially to be "too open" all the time - which was a problem in the RPM range where the needle operates, and went away at high RPMs where the needle would be fully or nearly fully raised anyway.

Good luck.

LOOSE JETS WERE THE PROBLEM!!!!!!

Again thanks for all the tech answers. I learned a lot. My problem turned out to be 2 totally loose jets that had fallen down in the bowl. I rebuilt both carbs one year ago so I never suspected jets would be the problem. Guess I did not tighten them enough. Scared to strip out the Pot metal or Pewter Amals are made out of I guess??? Inexperience got me bamboozled. I NEVER would have thought loose jets were the problem. One loose (But Two)??? Holy cow. How the Bloody Hell did that happen??? Anyway the reason I did not suspect loose jet as the problem is that it was running pretty damn good before I screwed with the needle setting and also replaced the throttle cable. I did however remember it had a little stutter before I began working on it but not enough to make me take notice and address it as a real problem????. I just did not think much of it till after I took it apart to fix the throttle cable and a MAJOR stuttering was happining at mid throttle. The clue was your responses that told me to CHECK THE CARBS AGAIN FULLY. I did it as a last resort. I haven't started it up yet but I am certain that was the problem. It has been raining here but will clear out tomorrow. I will road test tit then. Many Many thanks to all of you who responded. I will view the forums and try to help others with what I have learned..MODS & ROCKERS DALLAS TEXAS HERE I COME--------------Mark Cigainero

How'd they come loose? These things vibrate... :mrgreen: