stalling when warm, black smoke on startup

[psyguy]

well, anything's better than nothing when you wanna ride...

but ideally you would have it in this order:

1. adjust valves
2. sync carbs
3. adjust mixture
4. check sync

[azr]

More carb problems

ok....what the heck? I went to adjust the fuel and air mixture screws and then all of a sudden this weird knock/pop noise appears. I can feel it when I'm holding onto the carb or air box. There doesn't seem to be any rhythm to it and I can improve it or worsen it by adjusting the fuel mixture screw. Is this the cylinder in the carb bottoming out?? I've pulled the carbs off the bike (again.....). I had a couple of fuel leaks coming from the float bowl cover screws and it was odd but when I went out this morning there was fuel on several of the fuel mixture screws. This was ongoing throughout my adjustments, not much but a bit. I put new o-rings on all of them. My only guess is they are not sealing.

[azr]

Ok, no more fuel leaks, not that I can see anyways. But..the popping noise continues. I redid the bench sych and felt I got it bang on this time. I started her up and tried to adjust the air and fuel mixture with not much success. It's running rough at idle. It seems to hold at 1000, then all of a sudden it pops and drops RPM, sometimes enough to stall. I have not done a carb synch as my synchronized is not here yet. I'm just wondering if that is why I can't get the air and fuel mixture screw to work properly? On the #3 and #2 carbs there isn't really any difference on adjustments to either one. On the #4 and #1 carbs the fuel makes a small difference (it is almost completely set in) and the air mixture makes a large difference in RPM when doing it by the best idle method. It may not be running that great, but it is running and I'm learning lots. Any thoughts on all this??

[psyguy]

if it does idle, that's probably as good as it gets without the valve adjustment and the vacuum sync

[Thomas Kenny]

Before you pull anything down, put half a can of Seafoam in a full tank of gas and run it through the carburetors and see if it clears up your problem. It may not work but sometimes does. If it works you will save yourself a bunch of work. You can get it at NAPA and other auto parts stores. :-) Tom

[azr]

finished

So she's all back together. I did wind up doing a valve adjustment and 4 valves were too tight. It was a really easy job with the zap strap trick, they worked GREAT. I synched the carbs with my Carbtune, they are pretty good but when I had the carbtune hooked up the cylinders would bounce more than I think they are supposed to (I'm thinking I have a vacuum leak somewhere). I went for a long awaited ride and she is running great, except for when I am sitting at idle and go to give it gas she stalls unless I feather it a bit. I notice that when I had the carbtune attached. When I gave it a bit of gas the cylinders would go right to the bottom then quickly shoot up. I am thinking maybe I have a lean mixture? Thanks again for all the help so far. I couldn't have done all this work with out everyone's help.

[alke46]

Lesson to be learned from this is never take for granted what the PO tells you about the bike. He is just looking to get rid of it. Apologies go out to all of the honest ones, but for sure be skeptical of MOST of the sellers.

When I bought mine in August, the PO made it sound way too good to be true and you know what they say about that. Within a week of owning the bike I figured out he lied about just about everything on the bike so I took it upon myself to treat it as a bike in dire need of a tune up and found 5 of the 8 valves needed adjustment. One set of points looked like new ones while the other set was shot and gapped incorrectly. And on and on and on. It is finally coming around and as soon as the carbtune arrives later this week, I think she will be running good enough to scare the crap out of me when overtwisting the throttle.

Good to hear you finally got yours running so much better. Now you know better days are ahead.

[alke46]

Valve shims are no longer a pricey subject. In fact there is a member here that has a very nice exchange program for shims. He is Ghostgs1. Give him a try.
Also there is a salvage yard in Lubbock, Texas that sells them for $4 each. Phone # is (806) 745-4447. Another source is lloydrivers1964@yahoo.com phone # (952) 334-5838. Apple Valley, Mn. and he sells them for $2.50 ea.
Good luck

[skidMarkNZ]

Clean you carbs, replace your plugs check your plug leads are tight..... replace your air filter....

then try again...

Don't adjust the idle until it is warm.

[Pacman]

So she's all back together. I did wind up doing a valve adjustment and 4 valves were too tight. It was a really easy job with the zap strap trick, they worked GREAT. I synched the carbs with my Carbtune, they are pretty good but when I had the carbtune hooked up the cylinders would bounce more than I think they are supposed to (I'm thinking I have a vacuum leak somewhere). I went for a long awaited ride and she is running great, except for when I am sitting at idle and go to give it gas she stalls unless I feather it a bit. I notice that when I had the carbtune attached. When I gave it a bit of gas the cylinders would go right to the bottom then quickly shoot up. I am thinking maybe I have a lean mixture? Thanks again for all the help so far. I couldn't have done all this work with out everyone's help.

The carbsync will bounce some. That is normal. Also, the carb sync is measuring the vacuum in the intake manifold and when you open the throttle this vacuum does go down. That is normal as well.

The popping/thumping that you could feel from the carb body/intake is a sign of a lean mixture.

AZR, sounds like it is getting there. Did you set the mixture screws on the bottom of the carbs near the intake manifolds by best idle? The period right off idle is fed from these. I suggest turning each of these screws out another 1/8-1/4 turn.

Also, my '79(s) benefited greatly from raising the needles up one notch. However, this does involve pulling the carbs again and taking the throttle rod out and pulling all four needles and readjusting the vaccum sync. Maybe something to do in the spring.

Chris

[redscott33]

Just adding my ten cents worth.

How many turns have you wound out the pilot air screw? I know the book says 1½ turns as per most other carby's but I recently rebuilt mine and suffered popping and a rough idle. My best position was 3/4 out from full in. That's about as far in as you want to go but I was lucky and the 3/4 mark nailed it for me. I was running out of adjustment! Anyway, I completely agree with Pacman that you have a lean mixture. I went for a ride with a screw driver and continuously adjusted the screws every 500 meters or so. That helped to speed up the adjustments a bit.

Scott.

[Pacman]

Good catch, I forgot to ask about the idle air screws. Mine are all right around 3/4 turns as well.

Chris

Just adding my ten cents worth.

How many turns have you wound out the pilot air screw? I know the book says 1½ turns as per most other carby's but I recently rebuilt mine and suffered popping and a rough idle. My best position was 3/4 out from full in. That's about as far in as you want to go but I was lucky and the 3/4 mark nailed it for me. I was running out of adjustment! Anyway, I completely agree with Pacman that you have a lean mixture. I went for a ride with a screw driver and continuously adjusted the screws every 500 meters or so. That helped to speed up the adjustments a bit.

Scott.

[azr]

My air screws are anywhere from 3/4 out to 1 full turn out. The fuel mixture screws are anywhere from 1/8th out (I had to punch #2 out as the tip was JAMBED in there, and I mean JAMBED), to 5/8-3/4. All the mixture screws were set by the 'best idle' method. I've thought about buying a plugtune but have heard mixed results about them. I've thought about adjusting the mixture screws out a bit more while riding it but how do you know which one to adjust? or do you just do them all the same amount? I haven't tried the plug pull method yet (it seems too time consuming really). I pulled the airfilter and squeezed a bit more oil out of it (I used a bit too much obviously). Everything in there 'seems' pretty tight.

[Pacman]

Some guys I know here in KC use the ColorTune and they swear by it. I have seen and ridden bikes before and after they have used the ColorTune on them and it definitely made a difference.

Chris

My air screws are anywhere from 3/4 out to 1 full turn out. The fuel mixture screws are anywhere from 1/8th out (I had to punch #2 out as the tip was JAMBED in there, and I mean JAMBED), to 5/8-3/4. All the mixture screws were set by the 'best idle' method. I've thought about buying a plugtune but have heard mixed results about them. I've thought about adjusting the mixture screws out a bit more while riding it but how do you know which one to adjust? or do you just do them all the same amount? I haven't tried the plug pull method yet (it seems too time consuming really). I pulled the airfilter and squeezed a bit more oil out of it (I used a bit too much obviously). Everything in there 'seems' pretty tight.

[azr]

fixed

So I go into the timing again and this time check the points with a multitester. Turns out I am getting power to both points at the same time. So there is a short somewhere. I trace it as far as the harness going towards the tach/speedo and figure this could get ugly so I just unplug the two wires white and black and yellow and hook them directly to the coils by splicing them with the two orange wire from the coils and WHAMO!!! no back firing, no bogging, she ran and pulled like I've never seen her before. If I ever get ambitious I will trace down the actual short..maybe.