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Author Topic: Vac Sunc issues  (Read 1043 times)

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Offline Duanob

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Vac Sunc issues
« on: March 29, 2011, 08:47:24 AM »
1976 CB550K 022A carbs.

I installed the typical 4 gauge vac sync tool and made sure there were no vac leaks and everything was tight and well connected. I couldn't get the bike to run right. It made it hard to read the gauges. At idle the gauge needles fluctuate wildy. At 3000 rpms I could get the needles to settle down in a certain location on the gauge but the engine would fluctuate wildy and spit and sputter. It was also running super hot. I burned my arm by accidently touching it it was so hot. Also I noticed when I changed one carb the other carb would self adjust making it hard to adjust two carbs at the same place on the gauge. After fighting with it, I got all 4 carbs kind of close. When I took the tool off the bike ran great. Do I have a defective tool? Anybody else have these kind of issues when trying to do a sync? BTW The 3000 mile tune up was done before the sync.

When a motor runs hot is it running too lean? Too rich? The timing is set pretty close to 1 - 4 and 2 - 3.
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"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
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2007 Moto Guzzi Breva 750ie
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Offline TwoTired

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Re: Vac Sunc issues
« Reply #1 on: March 29, 2011, 09:22:57 AM »
Doesn't your gauge set have damper valves to limit needle excursion?

Didn't you have a fan blowing on the motor for the extended idle period?
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Lloyd... (SOHC4 #11 Original Mail List)
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Offline Nortstudio

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Re: Vac Sunc issues
« Reply #2 on: March 29, 2011, 08:38:05 PM »
Quick question: if the temp is down in the 40s, will I still need a fan while sync'ing the carbs?  Might be tough to get a fan out to the curb....
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1976 CB550K...in progress
1975 CL360...eventually custom
2009 Husqvarna TE610

a blog about wrenching in Brooklyn, NY

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Offline TwoTired

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Re: Vac Sunc issues
« Reply #3 on: March 29, 2011, 10:43:32 PM »
Quote from: Nortstudio on March 29, 2011, 08:38:05 PM
Quick question: if the temp is down in the 40s, will I still need a fan while sync'ing the carbs?  Might be tough to get a fan out to the curb....

Not if you are fast.  You should still be able to put hand to valve cover.  And if it's 40, you might even enjoy that!  ;D

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Nortstudio

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Re: Vac Sunc issues
« Reply #4 on: March 30, 2011, 05:24:42 AM »
Thanks TT.  I am not sure how "fast" I will be, but the temps have been OK for curbside wrenching this past week, since the sun shines on my side of the block for the better part of the afternoon. 

This winter, as long as the sun has been shining, I have been good out there, with temps down into the low 30's.  But man, I can't wait for the Spring to finally kick in!
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1976 CB550K...in progress
1975 CL360...eventually custom
2009 Husqvarna TE610

a blog about wrenching in Brooklyn, NY

“Success is dependent on effort.”
~Sophocles

Offline Duanob

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Re: Vac Sunc issues
« Reply #5 on: March 30, 2011, 12:59:42 PM »
Quote from: TwoTired on March 29, 2011, 09:22:57 AM
Doesn't your gauge set have damper valves to limit needle excursion?

Didn't you have a fan blowing on the motor for the extended idle period?

Q1) I don't know, tell me more.

and

Q2) no. it was forties when I synced my carbs as well but the engine definitely ran hotter than normal while the guages were attached. After I pulled the gauges and started her up and let her idle, heat wasn't much of issue then.
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"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
2015 BMW F700GS
Another 1976 CB550K Cafe?

  __o
_- \_<,
(*) /' (*)

Offline TwoTired

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Re: Vac Sunc issues
« Reply #6 on: March 30, 2011, 01:20:50 PM »
The gauge set usually comes with an inline valve (thumb/finger operated) which restricts the air flow between gauge and manifold tap point.
These are tweaked to limit the needle excursion extremes so that a reading during strong idle pulses can be damped out.  If you don't have those, check an aquarium supply for air line valves.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Duanob

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Re: Vac Sunc issues
« Reply #7 on: March 30, 2011, 01:23:48 PM »
Quote from: TwoTired on March 30, 2011, 01:20:50 PM
The gauge set usually comes with an inline valve (thumb/finger operated) which restricts the air flow between gauge and manifold tap point.
These are tweaked to limit the needle excursion extremes so that a reading during strong idle pulses can be damped out.  If you don't have those, check an aquarium supply for air line valves.

Cheers,

Thanks TT, I know my set doesn't have any valves inline for sure.
Logged
"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
2015 BMW F700GS
Another 1976 CB550K Cafe?

  __o
_- \_<,
(*) /' (*)

Offline Nortstudio

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Re: Vac Sunc issues
« Reply #8 on: March 30, 2011, 01:42:19 PM »
My emgo system came with them. Little white pieces that have the knob to clamp down. Definitely needed on my sync, before that damping, they were bouncing all over the place.
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1976 CB550K...in progress
1975 CL360...eventually custom
2009 Husqvarna TE610

a blog about wrenching in Brooklyn, NY

“Success is dependent on effort.”
~Sophocles

Offline Duanob

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Re: Vac Sunc issues
« Reply #9 on: March 30, 2011, 01:48:21 PM »
Quote from: Nortstudio on March 30, 2011, 01:42:19 PM
My emgo system came with them. Little white pieces that have the knob to clamp down. Definitely needed on my sync, before that damping, they were bouncing all over the place.

**slap forhead/shrug shoulders** So that's what those little white plastic pieces are for. **kick self in arse**
Logged
"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
2015 BMW F700GS
Another 1976 CB550K Cafe?

  __o
_- \_<,
(*) /' (*)

Offline TwoTired

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Re: Vac Sunc issues
« Reply #10 on: March 30, 2011, 01:49:34 PM »
Quote from: Duanob on March 30, 2011, 01:48:21 PM
Quote from: Nortstudio on March 30, 2011, 01:42:19 PM
My emgo system came with them. Little white pieces that have the knob to clamp down. Definitely needed on my sync, before that damping, they were bouncing all over the place.

**slap forhead/shrug shoulders** So that's what those little white plastic pieces are for. **kick self in arse**

LOL
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Nortstudio

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Re: Vac Sunc issues
« Reply #11 on: March 30, 2011, 02:02:54 PM »
Fixing SOHCs one small, seemingly insignificant knob at a time :)
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1976 CB550K...in progress
1975 CL360...eventually custom
2009 Husqvarna TE610

a blog about wrenching in Brooklyn, NY

“Success is dependent on effort.”
~Sophocles

Offline Duanob

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Re: Vac Sunc issues
« Reply #12 on: March 31, 2011, 12:49:30 PM »
Quote from: Nortstudio on March 30, 2011, 02:02:54 PM
Fixing SOHCs one small, seemingly insignificant knob at a time :)

LOL you should use that for you sig line, it's perfect!
Logged
"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
2015 BMW F700GS
Another 1976 CB550K Cafe?

  __o
_- \_<,
(*) /' (*)
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