Carburetor cough

Tfrank59 · November 02, 2018, 11:50:01 AM

Spark plugs are hard to get out at least the rear one is. I put in new NGK's when I first bought the bike which was about 19,000 miles ago so maybe I'll change them over

rob f · November 02, 2018, 09:30:43 AM

Gotta throw in my 2 cents ( 3 cents Canadian) again.
I would tend to lean to what Troll has said about mixture. I have a Harley carb conversion on my Virago and works great except the intake spitting when cold and just off idle when warm. Almost got it worked out by enriching the idle mix and adjusting the pumper.
Now.... having said that I would not rule out the sparkplugs. On that same virago I had repeated sparkplug misfiring on startup and as it warmed up it came around. Fixed that problem by throwing out the NGK plugs and going with autolites.
Not saying that you should do the same but if your plugs have any age and you say you think you are running rich maybe change them out. Maybe you have alot of carbon build up on them and when cold may have a dirty spark untill some heat burns them cleaner.
I have been fooled before, hunting down a carb issue and then turning out to be plugs. Plugs are cheap but kinda a bitch to get out on Drifters. Maybe start there and eliminate that aspect before attacking the carb.
Rob

Tfrank59 · November 01, 2018, 09:48:36 AM

Quote from: Troll on November 01, 2018, 07:51:10 AM
Hotter spark plugs do not make the engine run hotter. The distance from the firing tip is longer than the "colder" plugs. This causes the firing tip to retain more heat to help burn off any deposits. Yours is strictly a mixture issue. V-2's are notorious for this kind of problem, ask anyone who's owned a carbed H-D (provided they are honest and trustworthy).

OK thanks Troll, that helps. I think I had the same mistaken notion about spark plugs on a different thread and you set me straight there too. Stuff is sometimes slow to sink into my skull

Troll · November 01, 2018, 07:51:10 AM

Quote from: Tfrank59 on November 01, 2018, 01:40:02 AM
Well just a quick update, yesterday I rode for an hour or so and it was pretty cold it was in the upper forties I guess and at the start of the ride even though I warmed the bike up a few minutes it really was coughing but then after she got warmed up fully she quit, so the coughing or burping whatever you want to call it is closely related to the ambient temperature outside. I'm curious if maybe running hotter spark plugs or something would help?

Hotter spark plugs do not make the engine run hotter. The distance from the firing tip is longer than the "colder" plugs. This causes the firing tip to retain more heat to help burn off any deposits. Yours is strictly a mixture issue. V-2's are notorious for this kind of problem, ask anyone who's owned a carbed H-D (provided they are honest and trustworthy).

Tfrank59 · November 01, 2018, 01:40:02 AM

Well just a quick update, yesterday I rode for an hour or so and it was pretty cold it was in the upper forties I guess and at the start of the ride even though I warmed the bike up a few minutes it really was coughing but then after she got warmed up fully she quit, so the coughing or burping whatever you want to call it is closely related to the ambient temperature outside. I'm curious if maybe running hotter spark plugs or something would help?

mittico68 · October 23, 2018, 01:45:20 AM

Quote from: Texasdrifter on October 22, 2018, 21:31:29 PM
Mine has been heavily modified. The stock exhaust is gutted.
Everything outside the carb inlet was removed and I fabricated a plate to adapt and S&S Super teardrop Air cleaner kit with a Indian Gilroy cover. Removed the dual throttle cables and installed a Nash internal throttle.

It would be great to get some more infos about those mods...

Texasdrifter · October 22, 2018, 21:31:29 PM

Mine has been heavily modified. The stock exhaust is gutted.
Everything outside the carb inlet was removed and I fabricated a plate to adapt and S&S Super teardrop Air cleaner kit with a Indian Gilroy cover. Removed the dual throttle cables and installed a Nash internal throttle.
Used a 6 Sigma Racing Jet kit that was ordered specifically for the mods. I only run 93 octane.
Runs great, picked up a big bump in power in mid to high RPM and very infrequent burping only when hot after a high speed long run off idle it may burp but not all the time and never cuts out. I have the carb adjusted about as good as its going to get. Not sure if the burp be totally eliminated without replacing with an aftermarket carb. But that gets much more involved.

Tfrank59 · October 19, 2018, 20:59:39 PM

Rob, when I did the re-jet I followed suggestions to drill an extra 1/8" hole in the slide for more air, and per Dynojet's instructions backed the air screw out to 3 1/2 turns. I also put the e-clip in the middle setting, per someone's suggestion. I rode over a 100 miles yesterday (lots of it in the city), and she only coughed once, when I was going home after work at night in the cold (engine not fully warm). I agree carbs are a pain, so I'm not going to mess with it more at this point. I put in the corn-o-hol free gas last tankful, and I'll get some Seafoam and run that through her as well.

rob f · October 19, 2018, 10:19:49 AM

Just re-reading your posts and come up with another thought. Your one post sounds like a lean mix and the other sounds rich. Got me thinking about carbs and you may have both scenarios with your bike.
I am am a few notches under an expert so you may want to verify my so called facts . Anyone else fell free to correct me.
Most carbs have 3-4 circuits operating at different times. Judging by your description of stumbling just off of idle, I still say a lean mix which is controlled by the idle mix circuit. During a dyno jet install, you are instructed to drill out the plug covering the idle mix screw and then turn the screw out to 3-3.5 turns thus making the mix richer( made a big difference on my bike)
You also say that your bike seems to be running rich which would be caused during the acceleration or wide open circuit which is controlled by the needle clip position and the main jet size.
Can't remember but i think that these carbs are pumper style and not sure if adjustable or not. This circuit gives an extra pulse of fuel when you crack the throttle.( could be the culprit also)
My Virago acts just like your drifter and adjusting the idle mix and pumper got rid of that. My drifter after the dynojet kit still is anemic at wide open but better at idle to 3/4 throttle. Had it apart 3 times now and had enough of pissing around with jets ( this season anyway)
Carbs are a pain in the ass and they drive me insane. Fuel injection,way more dependable but a little more tecky with all the sensors and what not.
R

Tfrank59 · October 15, 2018, 12:16:34 PM

Rob, my air box is not modified but I have done the dynojet kit and my exhaust is modified. I think it's actually a little too rich based on the way it runs and that I get this black soot coming out of the exhaust when it's cold. There are other things that lead me to believe it's not lean mainly because when I got the bike it was totally anemic and the jet kit cured that. Actually my motor runs perfectly but it does that cough thing every now and again which is more of an annoyance than anything else. As for bad gas that's a possibility of course and my last tankful I put in the ethanol free high test so we'll see if that improves things. I fill up with that like every third or fourth tankful, and especially in the cold months. I will also run some seafoam through it per one suggestion

rob f · October 15, 2018, 10:43:38 AM

Something I found out recently playing with around with my carb, was some info from Mr Google. If your bike spits back through the airbox, the fuel mix is too lean. If it backfires through the exhaust it is too rich. Sounds like yours is too lean because it is worse cold.
I have been dicking around with my carb half the summer to gain more power. I installed a dyno jet kit and gained a tad bit. I was looking at Grampsizing the airbox but was not comfortable with the irreversable butchering of the box. Instead i invented a ram air system that had only one small screw hole drilled into the air box. Took her out for a ride and was spitting and stumbling in higher gears everytime i cracked the throttle. Came home and removed the ram air system and problem disappeared. Too much air in the fuel mix.
I am guessing that your bike is modified with different pipes,carb jets and grampsized air box? Has this problem showed up out of the blue or have you just done a recent mod? If it is outta the blue then the seafoam trick may work as you may have a plugged jet. How about water in your fuel? Could cause the same thing. If your airbox is modified, try duct taping up some of the opening and see if your problem goes away. Not a permanent fix but just a verification that it is a lean mix problem.
Rob

Pilgrim · October 15, 2018, 09:11:25 AM

Add a big dose of SeaFoam to a full tank of gas and run it out..it will clean your fuel system. May help.
Search seafoam in the search box and see results others have had.

mittico68 · October 15, 2018, 02:26:46 AM

I'm not a carb guru. And I can't help ya out.
All I can say is that sometimes it occurs to my bike, too, but it's when I try to give full throttle with the engine still cold...
Or when I try to accelerate even though the bike is ridin' at really low rpm's, in 4th or 5th gear.

Tfrank59 · October 14, 2018, 17:53:20 PM

Hey does anybody have like when you give it gas sometimes at an idle the thing will spit and cough for a second? And it doesn't matter if it's cold or hot but it's more apt to do it when it's cold of course. It's kind of embarrassing cuz I actually had the thing cut out on me a couple of times at an intersection when that happened. It doesn't happen that often maybe once in a 2-hour ride. You carburetor gurus what do you say? Is it a fuel-air mixture thing? I've had other bikes do it too like Honda one lungers and I never really figured out why it does it just had to live with it