Sync issue


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Bigun58
Posts: 7
Joined: Fri Jan 19, 2018 4:23 pm
Location: Hitchcock Texas
Motorcycle: 1984 GL1200 Interstate

Sync issue

Post by Bigun58 » Tue Mar 13, 2018 12:04 am



Hey guys, help and ideas needed. Rebuilt carbs on my new to me 84 interstate with Randaak kits and manual, fixed the engine stop as soon as the throttle was touched. My issue is when syncing carbs #4 vac reading changes as soon as engine warms up, 2nd from left in pic, I synced 1 3 2 to each other but am stumped as to 4s reading, seems to run pretty good, haven't rode much as I haven't registered it yet. Idles good, throttle responsive, I checked compression seems good #1 & 3-165psi #2 &4 -175psi. Plugs read slightly rich, changing to new plugs tomorrow to get a fresh read. Swaped 4 & 2 gauge and problem follows. Any ideas greatly appreciated[attachment=1]Sync.jpg
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Aussie81Interstate
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Re: Sync issue

Post by Aussie81Interstate » Tue Mar 13, 2018 2:20 am

stuck vacuum slide on #4

DaveO430
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Re: Sync issue

Post by DaveO430 » Tue Mar 13, 2018 5:38 am

#4 is the base carb on a 1200, you synch all the others to it. The slides have nothing to do with synching the carbs. You could do it with the slides removed.

Bigun58
Posts: 7
Joined: Fri Jan 19, 2018 4:23 pm
Location: Hitchcock Texas
Motorcycle: 1984 GL1200 Interstate

Re: Sync issue

Post by Bigun58 » Tue Mar 13, 2018 10:13 am

Thanks for replies, unable to adjust to match the reading on #4, will keep trying, seems strange to me that vacuum would increase immediately upon warm up, when I touch throttle 4's reading is close to other 3 carbs

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julimike54
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Re: Sync issue

Post by julimike54 » Tue Mar 13, 2018 10:51 am

Have you double checked for intake vacuum leaks? The sync is utilizing vacuum and if you have a leak it will throw the readings out of wack.
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WingAdmin
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Re: Sync issue

Post by WingAdmin » Tue Mar 13, 2018 10:52 am

Bigun58 wrote:
Tue Mar 13, 2018 10:13 am
Thanks for replies, unable to adjust to match the reading on #4, will keep trying, seems strange to me that vacuum would increase immediately upon warm up, when I touch throttle 4's reading is close to other 3 carbs
You know that the engine should be fully warmed up before you try to sync the carbs, right? Disregard carb balance readings from when the engine is cold - only when it is fully warmed up should you then take readings and make necessary adjustments.

DaveO430
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Re: Sync issue

Post by DaveO430 » Tue Mar 13, 2018 2:56 pm

Bigun58 wrote:
Tue Mar 13, 2018 10:13 am
Thanks for replies, unable to adjust to match the reading on #4, will keep trying, seems strange to me that vacuum would increase immediately upon warm up, when I touch throttle 4's reading is close to other 3 carbs
Your #4 is too far closed. Turn the base idle screw in, it will increase the idle speed and lower that vacuum reading, then adjust the others to it to bring the idle back down. You will probably have to readjust the idle speed during the process.

Bigun58
Posts: 7
Joined: Fri Jan 19, 2018 4:23 pm
Location: Hitchcock Texas
Motorcycle: 1984 GL1200 Interstate

Re: Sync issue

Post by Bigun58 » Tue Mar 13, 2018 6:40 pm

Appreciate the instruction, didn't adjust carbs till at temp and fan cycled once, just noticed #4 read close to others when cold, reading changes to what's in the pic within a couple minutes. Will try the idle adjust to get a better read on 4 and will triple check vacuum for leaks. Thanks again Dave and W.A.will reply with any results.

Bigun58
Posts: 7
Joined: Fri Jan 19, 2018 4:23 pm
Location: Hitchcock Texas
Motorcycle: 1984 GL1200 Interstate

Re: Sync issue

Post by Bigun58 » Mon Mar 19, 2018 9:21 pm

Sync success! Thanks Dave0430 for pointing me in the right direction. Only thought it ran pretty good before, purrs very nice now. On to timing belts then in the wind. :D Thanks again.



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