[jack6251]

Hi guys,

2 things on my mind.

1st - RPM needle on rev counter "flickers" from a nice idle rpm of 1000 then when I leave throttle alone, it'll dip quite low and back. It's consistent but never low enough to stall. On occassion it will dip a little higher then back to the idle of 1000rpm, but certainly regular low dips, especially after a good rev of the throttle. When I've rev'd it'll return to idle rpm but will dip under the 1000 mark before climbing back to the 1000.

2nd - Upon going for it for a burst, really nailing the throttle and giving it "the beans" for a zoom, it begins to "jugub jugub vroom jug vroom" and kinda sound as though it hasn't enough fuel or something when opening the throttle for a burn. Fairly great when going steady though.

I know with these carbs they will tend to choke a little when suddenly opening the throttle, just wondering if I may need a larger jet with that prob.

So basically...

1st RPM needle dipping

2nd Choking/slight cutting when opening throttle for a burn down the road.

Any ideas would be appreciated.

Oh yeh, it does start much better after Seafoam, but these issues were there before and after Seafoam so maybe I don't have something set just right.

 

[Furball Zen]

The tach issue, isnt an issue, its normal.

At a certain temp, my Shadow would 'burp' for a split second if i cracked it too fast. It did this because the air was more dense at that moment, if i just rolled it normally it wouldnt happen.

So, it sounds like youre too lean on the intake side. But a recording of the sound would help better.

 

[jack6251]

The tach issue, isnt an issue, its normal.

At a certain temp, my Shadow would 'burp' for a split second if i cracked it too fast. It did this because the air was more dense at that moment, if i just rolled it normally it wouldnt happen.

So, it sounds like youre too lean on the intake side. But a recording of the sound would help better.

Ah ok thank you Furball!

Your lean suggestion would make sense actually, now I think about it I do have popping when throttling off.

I don't think I'll worry too much then about messing with anything tach related, the bike starts better after Seafoam afterall and it runs consistently apart from the dips.

I have a camera but the mic isn't too great, don't have a phone at the moment with recording things on. I think in future though I will try and video things, kinda helps all round I guess.

Tomorrow I'll turn the A/F screw in and tweak, I'll report back with updates

 

[Harryc]

Hey Jack, I am by no means an expert on 750's ( i have an 1100), but on my bikes carbs, turning the A/F screws in leans out the idle circuit (not enrich-ens it). So with decel pops I believe you'd want to back the A/F screws out a quarter turn each until the decel pops stop. The other direction would make it worse. If I am wrong someone with a 750 will speak up I am sure. Once you get it to stop I'd recommend reading the plugs to see how the fuel is burning. Light brown color = good. Anything else post a pic and we'll take a look. White ashey deposits = lean (mainly due to excessive heat). Dark or wet plugs = rich. The objective is to get all of your plugs burning light brown/tan.

 

[smilie]

Hey Jack, I am by no means an expert on 750's ( i have an 1100), but on my bikes carbs, turning the A/F screws in leans out the idle circuit (not enrich-ens it). So with decel pops I believe you'd want to back the A/F screws out a quarter turn each until the decel pops stop. The other direction would make it worse. If I am wrong someone with a 750 will speak up I am sure. Once you get it to stop I'd recommend reading the plugs to see how the fuel is burning. Light brown color = good. Anything else post a pic and we'll take a look. White ashey deposits = lean (mainly due to excessive heat). Dark or wet plugs = rich. The objective is to get all of your plugs burning light brown/tan.

^+1. Out to richen the mix.

 

[swifty2014]

I have a 1983 750 also but have only had it for a few months, so I am still learning.
But you may try pushing on some choke when you give it hard throttle to see if some enrichment is the answer.
Mine does a bit of erratic idle also if it is idling for some time. If it is sitting straight up it idles better but when on the side stand it changes= maybe a float level mismatch on the one carb.
I have aftermarket mufflers and have a lot of pop/backfire on decel and I think it may be from 2 separate pipes not being the original system, which had a large equalizing chamber between the pipes below the center stand area.
I remember in the old days guys would add dual exhaust to old cars and weld a crossover pipe to control much off the decel backfire.
It may not be your situation just a thought.
Mine runs petty good but your bike sure looks better !!! I'm jealous.

 

[jack6251]

Thank you for all the replies! Lots to consider and put me on right tracks.

Weather today isn't particularly good for riding, have ice, chills, wind and a lot of rain so will wait until better weather for a good inspection and tinker, then report back

 

[jack6251]

Update,

Tried all your advice and bike was much improved, thank you! I was definitley turning the screw wrong way for increased fuel flow as I was going off how my last bike was.

I've already mentioned in another thread, but gonna take the carbs off this week and get stuck in for an inpsection.