Carb Sync Observations

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Paul Narramore
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Re: Carb Sync Observations

Post #31 by Paul Narramore » Tue Mar 22, 2016 1:26 pm

With my borrowed gauges, turning the adjusting screws makes no difference to the gauge need UNTIL the small valve is opened then closed. The needle then reads it's new setting. So I am noting the reading, opening/closing the screw, then opening the valve to see what the new reading is.

I shall heed the advice then have another go tomorrow (having removed the chrome trims which just get in the way). I am as certain as I can be that the O-ring are fine. The carbs themselves are from Old Fogey and have been reconditioned. With my eyesight and even using a torch, it's just a tad difficult to see what's what in there.
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BMW R100/7
1989 BMW R100GS-Paris Dakar
MZ ETZ250 Trials
1977 Honda GL1000 GoldWing

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robin1731
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Re: Carb Sync Observations

Post #32 by robin1731 » Tue Mar 22, 2016 2:06 pm

Paul Narramore wrote:snip............... A friend loaned me a set of four gauges, each with a small valve beneath each gauges which I presumed was an anti-flutter valve. They aren't.




That is exactly what they are for. You should not have to close them and open them to adjust the carbs. Set them so the needles don't "flutter" and leave them. If you have to go back and forth closing and opening them you aren't doing something right.
1975 GL1000 parts bike (parts for sale)
1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
and a rotation of various purchases
Randakk approved Carb Rebuilder

Paul Narramore
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Re: Carb Sync Observations

Post #33 by Paul Narramore » Tue Mar 22, 2016 7:02 pm

Well I've seen a YouTube video of someone balancing carbs without anti-flutter valves so tomorrow I'll leave the things open and see if that is an improvement, ta.
Present bikes -

BMW R100/7
1989 BMW R100GS-Paris Dakar
MZ ETZ250 Trials
1977 Honda GL1000 GoldWing

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Lucien Harpress
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Re: Carb Sync Observations

Post #34 by Lucien Harpress » Mon Mar 28, 2016 8:22 pm

Yup, the idea is not to close them all the way. The trick is to find a point where they are closed enough that the needle flutter goes away, but not so much that it locks in the reading (so you can still see the readings change as you adjust the sync screws).
1969 CT90- Needs some General Motor Work
1976 GL1000 (Yellow)- Minor Cosmetic Fixes, but a Good Daily Runner
1984 GL1200 Standard- Waiting on Saddlebags....
1980 KZ1300- Carbs Being Temperamental. Possible Charging Issue.
1972 CB750 Barn Find- Lots.

Paul Narramore
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Re: Carb Sync Observations

Post #35 by Paul Narramore » Tue Mar 29, 2016 5:41 am

Thanks Lucien. I shall have another go when the mood takes me.
Present bikes -

BMW R100/7
1989 BMW R100GS-Paris Dakar
MZ ETZ250 Trials
1977 Honda GL1000 GoldWing

rrockyrraccoon
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Re: Carb Sync Observations

Post #36 by rrockyrraccoon » Fri Jul 22, 2016 10:41 am

I had amazing luck with my homemade sync tool. Used 4 ten foot small diameter clear tubes gently zip tied to a 4 foot board. My tool is self calibrating as I only used a single bottle to hold the antifreeze used in place of mercury. kinda hard for it to be unequal if they all run off one bottle. To hook up to the intake manifold I use small delrin dowels that I threaded and tightly fitted to the hoses. Started up the bike after heating it up and connecting the sync. 1 and 3 were darn near each other 2 was about a foot off from that and 4 was about 4 inches off of 2. synced 2 to 4 then used 4 to bring 2&4 level with 1&3. After adjusting them they held within a inch of each other. Revved her up a few time and let go and they went right back to where they were synced. The sync took about 15mins after warm up (I guess I got really lucky). Hopped on the bike it idles smooth no chain sound anymore I rip the throttle and there is no more hesitation. Took it for a ride and it was like the bike wanted to leave me behind when I opened her up. :shock: Got home and had to glue on my left hand grip because it kept sliding down from holding on for dear life. Bikes FFAAASSSSTTTT now! :8) Spent maybe 10 bucks on everything I used to make my synchroniser.

EddieK
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Re: Carb Sync Observations

Post #37 by EddieK » Sat Sep 17, 2016 6:00 pm

So if #3 is the main carb (GL1000) is the butterfly set by the idle screw ? Also when you look into the carb and see the hole by the butterfly do you adjust it to show the whole hole, half hole or ? I'm having the idle go high and hang then fall and almost die. I think I'm chasing it around and may have #3 a little,too far open even though the sync gage show them all within 2Hg...right around 5+ Hg
1975 GL1000
'75 CB550, '72 CB350 and a '72 CL350

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Whiskerfish
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Re: Carb Sync Observations

Post #38 by Whiskerfish » Sat Sep 17, 2016 7:39 pm

This is the big list of possible causes.

http://www.randakksblog.com/lazy-slow-r ... high-idle/

From my experience the 2 most common causes of a hanging idle are over tight/ improper operation of the throttle cables or vacuum leaks. If it is changing behavior significantly after it warms up then odds are high you have vacuum leaks.

If it is dying after it drops down then odds are very high it is not idling on all 4.

Yes # 3 is the master set by the idle screw on the big bellcrank at the center of the carbs.
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robin1731
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Re: Carb Sync Observations

Post #39 by robin1731 » Sat Sep 17, 2016 10:12 pm

Whiskerfish wrote:snip.......................
If it is dying after it drops down then odds are very high it is not idling on all 4.


It can also be caused by having the idle screw out too far. Trying to compensate for the high idle you turn the screw out and then when it settles back down the throttle plates are pretty much completely closed. So it will die from lack of air.

.
1975 GL1000 parts bike (parts for sale)
1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
and a rotation of various purchases
Randakk approved Carb Rebuilder

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tlbranth
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Re: Carb Sync Observations

Post #40 by tlbranth » Fri Nov 24, 2017 9:52 pm

Back in the early 70's I built a set of 4 mercury manometers to synch the carbs on my '70 CB750. I bent the glass capillary tubing into a 'u' shape with a propane torch and assuming the id of the tubing remains constant (and I do), there's no calibration required. Originally, it was recommended to use surgical tubing to connect to the carbs. But that stuff costs a lot and deteriorates quickly. It was used because it had good damping qualities. But I'm now using drip-watering tubing which is cheap but quite rigid and there's no nasty fluttering. I think this is because of the inertia of mercury.
Mercury was easy to obtain back then - I have a bottle of it - but I think it's frowned upon now. I really like Rockyracoon's idea of using a common reservoir and wish I'd done that. There's no way to get a bad reading with that setup and no calibration would be required. And if your gauge is tall enough, I'll bet any fluid, pretty much, would work.
Terry

1999 GL1500 SE
2002 Honda VT750 "ACE"
1975 GL1000
1970 CB750

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salukispeed
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Re: Carb Sync Observations

Post #41 by salukispeed » Sat Nov 25, 2017 3:54 pm

I too use 4 of 28 inch clear rigid tubing from the aquarium store into a common reservoir of Mercury and proper sized vacuum tubing from the auto parts. No calibration and minimum flutter . I have used old "clean" idle jets in the vacuum tubing just above the clear tubes to reduce any flutter and trap any mercury from getting past if I get way over doing it with a rev. I don't want the mercury going thru the engine. I built them back in the early 70's and never had an issue except to replace the vacuum tubing because it gets stiff and brittle over time. But be careful as Mercury is very toxic and hard to clean up if spilled.
Honda 72 CL100 sold
74 CB750 K4 nice driver
1966 CA77/305 Dream nostalgic driver
84 GL1200I work in progress
1970 CT 70
1982 GL500 Interstate


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