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Author Topic: cb360 carb sync question... (crazypj?)  (Read 676 times)

Offline timdhawk

  • Posts: 203
cb360 carb sync question... (crazypj?)
« on: Jul 26, 2017, 19:26:15 »
I have my synchronizer hooked up and both needles read nearly identical at idle... problem is its in the red zone that says "late valve timing or leak at intake manifold or heat riser".


I have heard this area only applies to cars and it doesn't really matter where the needles are as long as they read the same. any truth to this?
My carbs were rebuilt by crazypj so I know they're good. Air screws are out 1 1/2 turns and I've triple checked my timing...
78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Offline Sonreir

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Re: cb360 carb sync question... (crazypj?)
« Reply #1 on: Jul 26, 2017, 19:29:49 »
Where the needles are at idle does matter. It should be around 17 inches of Hg.

You sure you have the gauge hooked up correctly? It's almost impossible to get a reading that low at idle. The bike wouldn't even run as there wouldn't be enough vacuum through the carbs to even draw fuel.
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Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #2 on: Jul 26, 2017, 20:42:07 »
Where the needles are at idle does matter. It should be around 17 inches of Hg.

You sure you have the gauge hooked up correctly? It's almost impossible to get a reading that low at idle. The bike wouldn't even run as there wouldn't be enough vacuum through the carbs to even draw fuel.

That's a stock photo off the interweb... mine actually reads somewhere around 6-8 in the vacuum red!!!! I'll get a pic/video of mine doing it in a minute...
78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #3 on: Jul 26, 2017, 20:51:06 »
Here's my connections and a vid: (I hope)



Sent from my SM-G920V using Tapatalk

78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Offline Sonreir

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Re: cb360 carb sync question... (crazypj?)
« Reply #4 on: Jul 26, 2017, 20:54:54 »
Here... check this out:
Sparck Moto - http://www.sparckmoto.com

Audaces fortuna iuvat.

1977 Honda CJ360 - Café SOS - Stage One™, Café SOS - Stage Two™
1976 Puch Maxi - APuchalypse Now
Suzi T500 Cobra Resto

Custom Gauge Graphics
Custom Wiring Harnesses

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Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #5 on: Jul 26, 2017, 20:58:46 »
Ok.. well, I can't figure out how to get the video of it so here's a still shot from the video. It idles around 2 to 3 in the vacuum and we'll go all the way down to 10 when I give it throttle.

Sent from my SM-G920V using Tapatalk

78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #6 on: Jul 26, 2017, 21:02:31 »
Here... check this out:

I actually watched that video whom trying to figure out why I was sucking so much.... literally!

Sent from my SM-G920V using Tapatalk

78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Offline Sonreir

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Re: cb360 carb sync question... (crazypj?)
« Reply #7 on: Jul 26, 2017, 21:17:16 »
Ok.. well, I can't figure out how to get the video of it so here's a still shot from the video. It idles around 2 to 3 in the vacuum and we'll go all the way down to 10 when I give it throttle.

It should be the opposite. Engines pull more vacuum at idle than they do with the throttle open.
Sparck Moto - http://www.sparckmoto.com

Audaces fortuna iuvat.

1977 Honda CJ360 - Café SOS - Stage One™, Café SOS - Stage Two™
1976 Puch Maxi - APuchalypse Now
Suzi T500 Cobra Resto

Custom Gauge Graphics
Custom Wiring Harnesses

DTT Red, White, and/or Black 360 Club - Better than those Blue guys

Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #8 on: Jul 26, 2017, 21:33:54 »
It should be the opposite. Engines pull more vacuum at idle than they do with the throttle open.

Exactly my thoughts! So... Any idea what the hell is going on?
78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.


Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #10 on: Jul 27, 2017, 00:11:52 »
ok, heres the video:


78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.

Online irk miller

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Re: cb360 carb sync question... (crazypj?)
« Reply #11 on: Jul 27, 2017, 01:47:43 »
If you're between 6 and 9 on the gauges idling at 1200rpm, you're golden.  You want to be within 2cmHg between the left and right carb, which the pic and vid seems to show.

Offline Sonreir

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Re: cb360 carb sync question... (crazypj?)
« Reply #12 on: Jul 27, 2017, 02:32:33 »
According to the FSM, vacuum is 16 - 24 cmHg @ 1200 rpm.  That's 6 - 9 inHG. 

Looks like I remembered the number correctly, but not the units.
Sparck Moto - http://www.sparckmoto.com

Audaces fortuna iuvat.

1977 Honda CJ360 - Café SOS - Stage One™, Café SOS - Stage Two™
1976 Puch Maxi - APuchalypse Now
Suzi T500 Cobra Resto

Custom Gauge Graphics
Custom Wiring Harnesses

DTT Red, White, and/or Black 360 Club - Better than those Blue guys

Offline timdhawk

  • Posts: 203
Re: cb360 carb sync question... (crazypj?)
« Reply #13 on: Jul 28, 2017, 11:48:59 »
ok, so I'm good then? thought I was going crazy...

Thanx
78 CB750 café - DONE!
Build Thread: http://www.dotheton.com/forum/index.php?topic=34145.msg369206#msg369206
74 CB360 café for wife - in process.


Offline CrabsAndCylinders

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Re: cb360 carb sync question... (crazypj?)
« Reply #15 on: Jul 28, 2017, 15:14:27 »
Bike is good but you may still be crazy. 
« Last Edit: Jul 28, 2017, 15:17:54 by CrabsAndCylinders »
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Offline crazypj

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Re: cb360 carb sync question... (crazypj?)
« Reply #16 on: Jul 30, 2017, 16:00:24 »
Idle speed needs to be around 1200 rpm, actual vacuum readings don't matter but will be anywhere from 10~20 cm/hg
Fit restrictors into lines (use around 75~80 main jets, vac adapters are 1/16" if I made them)
It's a good idea to SLOWLY increase rpm to around 4,000 to make sure vacuum stays more or less equal and advancer is working properly (shows all settings are equal, timing, tappets, etc)
« Last Edit: Jul 30, 2017, 16:03:18 by crazypj »
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