Carb Sycnh Woes

[DMPLATT]

My first ever Carb Synch. Actually it went alright, except the center adjuster was a muther. I finally got to use my Motion Pro Mercury stix.
Here's what I did.
Warmed bike, hooked up hoses, set idle to ~ 1700 Rpm's. TRIED to set air mixture screws on each for best idle. On #4 it was really hard, so I went in (BIke tried to die) came out 3 1/2 turns. Messed around there a bit until it SEEMED like the highest idle.

Carbs were pretty far out on the mercury. I adjust the 3 screws, but in the meantime the lines filled with condensation. THe mercury started seperating. I tried to get them as close as possible, but it was kinda hard to tell. I do know they are a lot closer than they were. :?
After it cools down (I burned my self enough ), I'll take it all off and see how she runs.

I guess what I'll do is run it for a couple days and check plugs and adjust mixture by plug color? Any ideas on this?

[KEITH KRAUSE]

The condensation is a problem usually because it took a long time to set the carbs. As soon as the bike is stopped and re-started, the mercury gets condensation in it.
I always have two large fans on the motor and can set the carbs quickly, so I never have to turn off the motor for cooling. I realize this was your first synch job and these things happen.
If you get condensation in the future, you can usually get it all out or most of it, by quickly slipping the effected cylinder hose off the manifold/carb adapter and re-connecting while the bike is idling. You'll see the mercury drop quickly and jump back up, hopefully without much or any condensation. It can take a few tries.
A little condensation is easy to allow for and still determine how the levels would be without any gaps.
As for plug reads, you'll get uneven reads if the synch levels are beyond spec's. The levels should all be within about 3/4" from the highest to the lowest level, or closer, to avoid mixture problems and funny plug reads. So be sure of your vacuum levels first, before adjusting the mixture screws in an attempt to get all 4 plugs looking the same. The ignition timing and valve clearances need to be good before a carb synch too. The mixture screw/high idle method should be done before and after the carb synch is done.
If the levels are good and the mixture screws are set for the highest idle, the plugs/performance should be good, as long as everything else is up to spec' and you haven't made other mod's.

[DMPLATT]

Thanks Keith.

The Synch seemed to have helped a bit. When I got this bike in June, it didn't want to idle without the choke until it was at just about operating temp. Today after about 3 to 5 minutes of choke, it seemed to idle ok. It also didn't change much after it got warm.
However, I seemed to have more vibration at certain RPM ranges. I could really feel it in my feet.
So, I guess I'm doing it again soon.
3 questions. Is there a Nifty little tool for the lock nuts on the carb adjusters? They are a b$itch with a small 8 mm wrench.
Also, the mixture screws. Am I correct in that it's air mixture? In other words. If I turn it IN it will Richen the mixture, if I turn it OUT it will lean the mixture?
Also, I only adjusted the mixture BEFORE I did the synch. Not after also. It was really hard to tell on #3 &4. I mean on #1 and # I would turn it and it would take a few seconds I could tell, however it seemed there was quite a range where the highest RPM stayed. On #3 & 4 it wasn't that easy. Actually I couldn't hardle tell. Should I watch the mercury instead of by ear?
Any help here is appreciated.

Another thing, I'm trying to keep the RPM's at ~1750 as the manual states, do I HAVE to re-adjust AFTER every little adjustment? I mean when I adjusted the mixture screw on # 1, the RPM jumped right up to about 2300. SHould I then stop and adjust the idle back down?

Thanks.

[earlfor]

Dave the mixture screws on the CV carbs meter an already combined stream of fuel AND air. (mixture) Turning in the screws reduces the flow or leans it. Out increases the flow or richens it.

More vibration means the synch is still out.

There is an adjustment tool that will make life a bit easier. On the Morgan carbtune site, there is a valve adjustment tool. It is a long blade screwdriver that fits into a long 8mm sleeve with a small wrench handle welded to the side of the sleeve. It allows you to set the screws and tighten/loosen the nuts with a single tool held in place as you make adjustments.

to start, I set the mixtures for apparent highest idle, but I dont fuss over it. Just quickly go back and forth until it seems to be about highest idle.
It usually takes me about a minute to make the preliminary set on all four carbs.

Then without trying to be particularly precise with the vacuums between the carbs, I quickly adjust back and forth on the throttle plates,always adjusting the carb that is farthest out. There is no numerical carb sequence or amount for each carb. At this stage, I do not tighten jamb nuts, I leave them loose. It should only take a minute or two to get all four carbs within a couple inches of each other. Up to this point, I dont pay much attention to rpm unless it goes over about 2500 in which case, I turn it down with the idle adjustment screw.

You will be matching vacuum to the #3 carb. It is the control carb. The throttle plate screws are for adjustment on the 1, 2 and 4 carb. There is no screw for the #3 carb.


Once the vacuums are within a couple of inches of each other, I still always adjust the carb that is farthest out. I lightly snug the jamb nuts about finger tight between adjustments and use the idle control screw to maintain a set rpm for all following adjustments. At this point, you will likely be working with adjustment of 1/8th turn or less and it will take a few seconds for any change to be noticed in the engine. Work slowly enough for the engine to adapt to the slight changes before going to the next adjustment.

Earl

Thanks Keith.

The Synch seemed to have helped a bit. When I got this bike in June, it didn't want to idle without the choke until it was at just about operating temp. Today after about 3 to 5 minutes of choke, it seemed to idle ok. It also didn't change much after it got warm.
However, I seemed to have more vibration at certain RPM ranges. I could really feel it in my feet.
So, I guess I'm doing it again soon.
3 questions. Is there a Nifty little tool for the lock nuts on the carb adjusters? They are a b$itch with a small 8 mm wrench.
Also, the mixture screws. Am I correct in that it's air mixture? In other words. If I turn it IN it will Richen the mixture, if I turn it OUT it will lean the mixture?
Also, I only adjusted the mixture BEFORE I did the synch. Not after also. It was really hard to tell on #3 &4. I mean on #1 and # I would turn it and it would take a few seconds I could tell, however it seemed there was quite a range where the highest RPM stayed. On #3 & 4 it wasn't that easy. Actually I couldn't hardle tell. Should I watch the mercury instead of by ear?
Any help here is appreciated.

Another thing, I'm trying to keep the RPM's at ~1750 as the manual states, do I HAVE to re-adjust AFTER every little adjustment? I mean when I adjusted the mixture screw on # 1, the RPM jumped right up to about 2300. SHould I then stop and adjust the idle back down?

Thanks.

[KEITH KRAUSE]

Earl answered your mixture screw function and tool question, etc. It does sound like you need to re-synch. I don't want you to think I deserted you, so I'll add:
When I synch the carbs, I warm it up first on the centerstand and then adjust the mixture screws for highest idle. Not perfect, just ballpark.
Yes, you should reset the idle to about 1,100 rpm's with the idle adjuster knob after setting each screw. Then hook up the tool and do your vacuum synch. Then adjust the screws again like you did the first time. This is being more precise and you may not even notice any significant changes to the screw settings the second time around. They certainly won't have to be turned much, if at all. If you wish, before turning them after the synch, make a temporary mark on each side of the screw slot and if you don't notice any rpm changes after slowly turning the screw a 1/2 turn or so, just put it back to the marks you made.
The 1,750 rpm suggestion is not that critical. I set the carbs around 2,500 to 3,000 rpm's. So if your manual says 1,750, just anything in that area will be fine. I find it much better to adjust the high vacuum level(s) DOWN to the lower levels to get things even. If you have a master carb, then you have to match it.

[DMPLATT]

Thanks guys. I will attempt it again this weekend. It is definately running better, just the vibration.
Thanks for clarifying the mixture screw. Makes sense now.

[Mr. Jiggles]

After synching my carbs the most notable difference was on the highway at approx 60mph (traffic). Vibration had dropped to the point that I'd often forget to shift from 4th to 5th.

As far as condensation goes, has anyone tried warming / heating the mercury before synching? I'd imagine that this should help.

[DMPLATT]

Thanks all.

I tried it again. I'll tell you what, what a bi$tch. One little microscopic twist and they ALL change. I got them all perfect and once I tried to tighten the Jam nut, boom - all change.

I ended up doing the 2 outside about 1" mercury above the 2 inside. That was the only way I could get them close. After all was tight, they were all with in 1/8". Ie... the 2 inside were within 1/8" and the 2 outside were within 1/8". And the outside was about 1" mercury above the inside. On the test ride, it seems pretty good. There is a small vibe - actually I think it's normal. Not like it was. 90mph in 3rd aint bad. :twisted:

As far as the mixture screw. Something must be wrong. On #3 & 4, I can tell an RPM difference when turned in, but once I get to a point turning them out, I get NO differnence in RPM's?

I guess, as I said before, I'll check Plug color after a while and adjust mixture that way.

OR

Earl, how much do you charge? I'm going to try and see Ron in a month or so, how bout I just pay you to do it.

[KEITH KRAUSE]

As far as the mixture screw. Something must be wrong. On #3 & 4, I can tell an RPM difference when turned in, but once I get to a point turning them out, I get NO differnence in RPM's?

Not sure what you're saying. If you're saying at some point the screws have no effect, that's normal. They only have a certain range.

[earlfor]

Good Job Dave. When you get to the point of "one microscopic little twist and they all change", youre getting real close. :-) :-) On the mixture screws, I think at about 4 turns out, they are wide open. Wide open plus two turns is still only wide open. LOL

On mixture screws. I turn them in until rpm drops off. Then slowly turn them out until rpm picks up. As soon as I reach a point where another 1/4 turn out makes no difference, I turn them back into to set to the rpm where the rise was most noticable. Set the screws to where the highest rpm first occurs, NOT to how many turns you can go past that point without being able to tell an rpm change. To put it another way, set them to the approach side of the curve, not the backside.

Earl

Thanks all.

I tried it again. I'll tell you what, what a bi$tch. One little microscopic twist and they ALL change. I got them all perfect and once I tried to tighten the Jam nut, boom - all change.

I ended up doing the 2 outside about 1" mercury above the 2 inside. That was the only way I could get them close. After all was tight, they were all with in 1/8". Ie... the 2 inside were within 1/8" and the 2 outside were within 1/8". And the outside was about 1" mercury above the inside. On the test ride, it seems pretty good. There is a small vibe - actually I think it's normal. Not like it was. 90mph in 3rd aint bad. :twisted:

As far as the mixture screw. Something must be wrong. On #3 & 4, I can tell an RPM difference when turned in, but once I get to a point turning them out, I get NO differnence in RPM's?

I guess, as I said before, I'll check Plug color after a while and adjust mixture that way.

OR

Earl, how much do you charge? I'm going to try and see Ron in a month or so, how bout I just pay you to do it.

[saaz]

Usually once you get to 2 turns out or so (to get it to run better), that means a next size up pilot jet is required. The pilot system is limited in its capacity to that of the air and pilot jets.

[DMPLATT]

On mixture screws. I turn them in until rpm drops off. Then slowly turn them out until rpm picks up. As soon as I reach a point where another 1/4 turn out makes no difference, I turn them back into to set to the rpm where the rise was most noticable. Set the screws to where the highest rpm first occurs, NOT to how many turns you can go past that point without being able to tell an rpm change. To put it another way, set them to the approach side of the curve, not the backside.

Thanks again Earl and Keith. That's it. I get to where the idle increases, then nothing more.

Thanks guys. That's all I think.

Cool. I might add, it's running better than since I've owned it.

Oh, and WOOO HOOOO

[earlfor]

Good going Dave. Its kind of nice when one runs like its supposed to isnt it? LOL BTW, it gets easier with a bit of practice. eh eh

Earl

Cool. I might add, it's running better than since I've owned it.

Oh, and WOOO HOOOO

[Anonymous]

carbs

One thing that keith mentioned and I think it is a must is a PAIR of GOOD FANS while working on it, I use a digial tac that clips on the spark plug wires so I get a good reading on rpm changes that you cannot pick up by ear so it takes more time, so the fans are more important to have, so to keep rpm changes from occuring do to temp changes, my bike will idle at 850 but I keep it at 1050, I also used a gas analizer to set the fuel screws, and they came out about a 1/8th turn more than the factory marks on the carbs, and the same on the air screws

[earlfor]

Re: carbs

I removed the stock tach on my 1150, made a carbon fiber faceplate/adapter and installed a digital tach in my instrument cluster a long time ago. :-) :-) Got tired of that errant stock thing. LOL

I dont think I want to spring for the bucks for exhaust gas analysis equipment in a home shop, but something a little less antediluvian than sniffing my bike's butt would be an improvement. :-) Since a rich or lean mixture changes the exhaust gas temperature, I have wondered in an EGT would be worthwhile for tuning purposes. They can be had switchable with multiple probes. Any thoughts?

Earl

One thing that keith mentioned and I think it is a must is a PAIR of GOOD FANS while working on it, I use a digial tac that clips on the spark plug wires so I get a good reading on rpm changes that you cannot pick up by ear so it takes more time, so the fans are more important to have, so to keep rpm changes from occuring do to temp changes, my bike will idle at 850 but I keep it at 1050, I also used a gas analizer to set the fuel screws, and they came out about a 1/8th turn more than the factory marks on the carbs, and the same on the air screws