cb360 carb sync question... (crazypj?)

T

timdhawk

Been Around the Block
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...
 
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.
 
Sonreir™ said:
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.
Click to expand...

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...
 
Here's my connections and a vid: (I hope)
443489b97fda94a87c3b0f27398967b5.jpg
2e29fbd9b857fa123a595e0038d2b2d2.jpg



Sent from my SM-G920V using Tapatalk
 
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.
85a4004df7a8a717e2192087fb1ffce9.jpg


Sent from my SM-G920V using Tapatalk
 
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Sonreir said:
Here... check this out:
https://www.youtube.com/watch?v=TAhhMMnfN7Q
Click to expand...
I actually watched that video whom trying to figure out why I was sucking so much.... literally!

Sent from my SM-G920V using Tapatalk
 
timdhawk said:
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.
Click to expand...

It should be the opposite. Engines pull more vacuum at idle than they do with the throttle open.
 
Sonreir™ said:
It should be the opposite. Engines pull more vacuum at idle than they do with the throttle open.
Click to expand...

Exactly my thoughts! So... Any idea what the hell is going on?
 
According to the FSM, vacuum is 16 - 24 cmHg @ 1200 rpm. That's 6 - 9 inHG.
 

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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.
 
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)
 
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