Surging while under enrichment

Bike has been running good, making little adjustments on the air /fuel mix screws to make sure they are not running too rich or too lean. Now im getting a constant surge up and down, up and down while the enrichment is on until the engine warms up. Any ideas ? Thanks.

 

Sorry this is a 82 xj 750 maxim

 

Stock jetting?

 

Yes sir everything stock.

 

Set mixture screws at 2.5 turns in other words lightly screw in till bottomed out. Then turn 2.5 turns out see if this helps . Do you have a colortune plug, it really is a cool item to use setting mixture.

 

I have done all that with the turns. Ive got the colortune plug and put all 4 in the bunson blue range. Im thinking i must have 1 or more too close to rich or lean setting.

 

I'm thinking that there may be an issue with the enrichment plungers. Were they removed and cleaned at some point?

 

Yes, carb cleaner and air. Im thinking i should have done the q-tip trick

 

That's along the lines of what I'm thinking. Since the enrichment circuits seem to be the only thing that affects the idle surging, it's wise to look at them very closely.

 

Will do, K. Thanks

 

Pull the carbs, remove float bowls clean the enrichment jet in bottom of the bowl. This is the usual cause of choke problems

 

Thats a good idea, since i moved to Arkansas ive changed gas brands

 

A change in brands won't cause a clog, but poor practices at an individual station could.

 

Thats true. My situation is the only station in town that sells non ethanol sales there own brand not a major brand

 

It came from the same refinery and the same blending depot as the other gas did. The days of independants being able to own and control their own supply are long gone.

 

surging with choke but not after warmed up sounds to me like one cylinder is blinking on and off.
1 put that screwdriver on the bench
2 get some new plugs
3 set the mixture in the garage after it's warmed up
4 go ride, take what you get while the choke is on
5 be happy
setting the mixture out on the road is like tuning a piano by ear

 

What do you mean by "blinking " polock ?

 

Kicking in/ kicking out/kicking in/kicking out....

 

Okay i understand, so 1 or maybe 2 or all 4 enriching circuits maybe blocked who knows until i get in there and look. Plugs are new less than 500 miles on them and look good, a little tanish brown with a dry black on the metal ring. Ill pull the carbs and clean again. Ill post the results when im done. I just dont know how i can do it with my screw driver sitting on the bench.

 

Screwdriver is a drink.....it's now sitting on your bench

 

My point exactly.

 

just for schlitz 'n giggles try turning enrichment off while this is happening

 

I have, she struggles to stay running.

 

Loose jet rolling around in a bowl?
Needle loosened from slide?
Develop a pinhole in a diaphragm?
Beanie caps clogged?

Etc....

 

but it runs good when warmed up

 

Yes sir, idle is normal after warmed up and throttle blip (and) return is good.

 

Hi Jeff,
Old thread but new question...."enrichment jet in the bottom of the bowl"(im lost).
The bowl as I understand it has 2 holes(bottom drain) and a tiny hole on the lip of the bowl that receives a
long thin tube from the carb(this one is a bear to clean and I confirmed it was clean by shining a flashlight into the base of bowl and saw a pinhole of light(after lots of poking cleaning and cursing)).
I still get hi revs on choked startup,but am thinking I have to go back, pull the carbs and reclean the Pilot jet? I also have the issue of it started up ok with 1/2 choke, let idle for 2 min...then tried to apply throttle and she died.
Keep in mind to I started it after sitting in garage for 3 mos.

 

Also throttle mechanical response is snappy,no hangups

 

I could be wrong here so bear with me, but as I understand it's normal for the rpms to be high after starting on enrichment. You just keep backing the enrichment lever off until she's warm enough to idle without the extra fuel from the enrichment circuit. I'm no carb guru, or guru in general for that matter. If you're having trouble with a warm idle then I'd suspect an issue in the pilot circuit. I would also suspect that if your sync and colortune(tune, pilot mix screws) are off far enough that it may exacerbate certain issues. I'm sure an actual guru will be along shortly

 

Thanks for replying. I was actually surprised how nicely it idled(1100) after I pulled her down from the revving 4k rpms. My choke is sensitive it's like choke open or choke closed, in a very small range of adjustment(say 1/4") , …..but then I got excited and said isn't this nice, touched the throttle to gradually increase rpms and it just died.

 

the carb bowl has a enrichment well in it the brass tube slides in the wall of the carb bowl it draws fuel up from holes that are in the bottom of carb bowl. if you spray cleaner down into the tube well it should spray out the hole in the bottom of the bowl.

when choke is used as bike warms up rpm increases above idle setting, it should or can rev quite high. if you break your throttle cable you can use the choke to limp home or someplace safe to fix it

warm bike up for another minute

 

Hah, well I have been using the choke most of my rides! I keep it a little open so it doesn't die at stop signs, at least until I have it running right. Usually when I sprayed the cleaner in the hole...it would come back out and try to give me a bath. It would be cool to see a diagram of the direction of that port ...I just keep poking around with guitar wire until it's clear...but I can see how that port can get gummed up fast. I guess the ethanol is the problem. Other forum member said he adds 50/50 Murphys/Stabil(8oz) to a tank o gas......Another guy said try 50/50 carb cleaner/acetone(just the bowls), while another used seafoam in the bowls only(run, let sit overnight, drain, reapply and drain again. Honestly ...I don't think anything but mechanical cleaning gets that bowl line clean. If you stick a wire in there, it doesn't come out the other side(like jet cleaning, one has to check to see that pinhole, AND see the carb cleaner come shooting out in the 9ft stream, well away from your face, or your helper. : > I will be draining and pulling the bowls just to see what has happened over 6 mos, with 93 Octane gas.
Did you see my shim measurements??

 

Shim diagram

https://drive.google.com/file/d/1VeU-hZIrop3qZSaCOpsDpddpXovgUgqy/view

 

looks like you can swap 2 of the 270 shims

 

i don't either. but if that jet were plugged the choke on that carb wouldn't have any effect, it's plugged.
if i start my 750 and go 1/2 mile to the first stop sign it stutters pulling out, by the next stop, 1.5 miles farther it's good. it takes these a while to warm completely up. try opening the mixture screws about 1/8 turn and see what that does.

 

I just installed the shims Chacal sent me.
I then seated mixture screws 1-3 to 2.75 turns( to start). Mixture screw 4 seems to have some kind of brass plug, should that come out
QUOTE="Polock, post: 617882, member: 782"]i don't either. but if that jet were plugged the choke on that carb wouldn't have any effect, it's plugged.
if i start my 750 and go 1/2 mile to the first stop sign it stutters pulling out, by the next stop, 1.5 miles farther it's good. it takes these a while to warm completely up. try opening the mixture screws about 1/8 turn and see what that does.[/QUOTE]

 

I was thinking that too, but I have heard 2 diff stories..1) shims get worn and thinner, so change them
2) shims dont get worn, its the valve seats that wear, so one can swap them(re-use)... but what the hell change them anyway?

 

Do you think 2.75 turns is a good start? Or, now that I corrected the valve shims, should I go back n start with 2.5, and adjust accordingly?

 

2.75 is where i start from. the valves might change your mixture a wee bit but there's no way to tell, that's down to splitting hairs.
if everything else is right, a lean mixture will give you a stutter when you open the throttle. you really need to ride it to get it dialed in.
they can act perfect in the garage but when you put a load on them with the clutch, the stutter can come back, need more fuel

 

Sounds good, and thank you.