Author Topic: Carb Balance Problems  (Read 242 times)

cvincer

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Carb Balance Problems
« on: March 19, 2019, 01:16:46 AM »
Bike is an Australasin 16R...83 Carb (small round air-filter on front carb) with flapper box.

Pros = starts easily, idles well, goes so so.

Cons = black sooty plugs shows running rich (float height ok & mixture screws never touched in the last 17 years)
            lots of 'popping' on the overrun
            frequent hesitation when going at a steady speed (have tried changing the TCI + all resistances as per OEM)
            poor fuel consumption.

No improvement after checking out the electrics & giving the carbs a good clean..........about 3 years since I balanced the carbs (home made manometer), so decided to balance again.

With warm engine idling at 1200rpm, petcock on prime, YICS removed & ports blocked off (83 carbs have the sync rod obscured by YICS) I connected the manometer & pressed the button.

Had to switch off almost immediately as the manometer ATF fluid was in danger of being sucked into the front cylinder.  Adjusted the sync rod several times but with the same result.   Out of interest removed the sync rod completely & pressed the button....with the same result  (ATF almost sucked into front cylinder).

Anyone any ideas why the front cylinder is sucking so hard (or would if I didnít switch off) the ATF fluid into the front cylinder?

I've never had this problem during other balances in the last 17 years.


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« Last Edit: March 19, 2019, 01:18:53 AM by cvincer »

Prophet Of Doom

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Re: Carb Balance Problems
« Reply #1 on: March 19, 2019, 03:46:10 AM »
If one cylinder is not firing, then you'll get massive vacuum differences

jefferson

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Re: Carb Balance Problems
« Reply #2 on: March 19, 2019, 11:46:05 AM »
The throttle blade on that cyl sounds like it is shut to the point of even being closed. It might be best to do a visual check and get the throttle blades both open about the same amount or just adjust the sync. rod so that carb is open some. Once you get it open so it's not trying to suck in atf you should be able to do a fine adjustment from there.

cvincer

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Re: Carb Balance Problems
« Reply #3 on: March 23, 2019, 08:32:52 PM »

So several afternoons spent without resolving the problem, ended up balancing by  'ear'.

Plug colour light grey,  'popping' on overrun stopped,  accelerates hard ....but still hesitation when going at a steady speed & occasionally whilst accelerating (no the tacho does not flutter & I cut the black/yellow wire long ago).

Re-installled the YICS & the hesitation has stopped, but it does not accelerate quite as hard.

Plan B =  make up a set of  82  carbs & see what happens.

Thanks for the replies

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