Author Topic: Bike won't start with carb sync gauge attached  (Read 897 times)

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Offline Texas Ty

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Bike won't start with carb sync gauge attached
« on: December 20, 2014, 11:59:53 AM »
Background info:

Freshly rebuilt (top end) '76 550. I can get the bike to start and hold a rough idle after a bench sync, but with the gauges attached it doesn't seem to want to fire.

Ignition timing was set with a test light and is spot on. Compression reads good across the board.

I bought the gauges from Dime City, maybe it was a mistake to cheap out? My suspicion is a vacuum leak with the brass adapters attached.

Anyone had this problem before?

Thanks


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Offline guitarkev66

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Re: Bike won't start with carb sync gauge attached
« Reply #1 on: December 20, 2014, 12:02:31 PM »
do they have the rubber o rings on the brass adapters?
1970 K0 CB750 JDM Blue
1972 K2 cb750 Gold
1970 K0 cb750 Blue
1970 K0 cb750 gold
1970 K0 cb750 red
1971 K1 cb750 gold

Offline Texas Ty

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Re: Bike won't start with carb sync gauge attached
« Reply #2 on: December 20, 2014, 12:14:41 PM »
They do. However when I screw the adapters in it does not seem like the o rings are engaging if that makes sense. They sort of walk up the adapter instead of being fully compressed and sealing. 


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Offline guitarkev66

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Re: Bike won't start with carb sync gauge attached
« Reply #3 on: December 20, 2014, 12:19:36 PM »
Can you take a pic?
1970 K0 CB750 JDM Blue
1972 K2 cb750 Gold
1970 K0 cb750 Blue
1970 K0 cb750 gold
1970 K0 cb750 red
1971 K1 cb750 gold

Offline Steve_K

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Re: Bike won't start with carb sync gauge attached
« Reply #4 on: December 20, 2014, 02:03:17 PM »
Maybe the o rings need to be closer to the end.  I mean, adjust the nut on the brass tube so the o rings are tight on the carbs.  That keeps the engine from getting too much air making it lean.
Steve
Steve_K

76 CB 550, 73CB750, 86 GSX-R750, 16 Slingshot
Old rides:305 Honda, CL350, 74 CB550
 05 SV1000S, 88 CBR600,92 VFR, 88 Hawk GT, 96 Ducati 900SS, 98 Kaw ZX6R, SV650

Offline guitarkev66

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Re: Bike won't start with carb sync gauge attached
« Reply #5 on: December 20, 2014, 03:08:03 PM »
Maybe the o rings need to be closer to the end.  I mean, adjust the nut on the brass tube so the o rings are tight on the carbs.  That keeps the engine from getting too much air making it lean.
Steve

+1
1970 K0 CB750 JDM Blue
1972 K2 cb750 Gold
1970 K0 cb750 Blue
1970 K0 cb750 gold
1970 K0 cb750 red
1971 K1 cb750 gold

Offline Texas Ty

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Re: Bike won't start with carb sync gauge attached
« Reply #6 on: December 20, 2014, 03:57:18 PM »
Steve_K, these adapters don't have nuts like the Honda ones.

I ended up solving it by putting some slightly smaller o rings on the brass fittings. What a pain!

Anyway all is solved. Thanks for the help fellas!


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