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carb balancing


Davy1100

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Posted

not done this in about 15 years so as im old i ve forgot has anyone got a link or advice its for a gsxr 1100 k just bought new balancing guages from m an p the £30 ones its got 4 tubes 2 long 2 short am i right in thinkin i dont need to use these and just push the rubber hoses onto the tubes on the carb tops the kit comes with t pieces with a valve on them not sure what these are for any help or advice would be a big help cheers http://www.Eblag.co.uk/itm/MOTORCYCLE-CAR-TOOLS-CARBURETTOR-CARB-BALANCER-VACUUM-GAUGES-GAUGE-2-4-CYLINDER-/231720318112?hash=item35f39 this is the kit 

  • Like 2
Posted

The valve is a dampener that reduces the vacuum pulse and steadies the needles on the gauges. Otherwise the pulse causes the gauge needles to flick back and forth without a reading.

First thing is first you should ensure the gauges are calibrated correctly. DO this by connecting one gauge at a time to the same vacuum take of on the bike. This way you can make sure that the gauges are all giving the same reading on a single source.Use the the little valve taps to adjust the dampening so the needles are steady but dont over tighten them or you will close the valve and get no vacuum signal.  After that you can go ahead and connect them to the separate vacuum outlets safe in the knowledge that the readings will be accurate.

Make sure the engine is nice an hot.  Set an elevated tick-over of 1500 revs and balance. After balance as you rev the engine the needles should rise and fall to  to same points.

  • Like 4
Posted

cheers Katanamangler am i right in thinking theres 3 screws 1 on left does 1 an 2 carb the 1 in the middles balances all 4 carbs together and the screw on the right does 3 and 4 

Posted

As Captain Chaos says mate do your valves first. When you're balancing the carbs balance carbs 1&2 then balance 3&4 finally balance 1&2 with 3&4 using the screw in the middle.

  • Like 3
Posted

If they are anything like all the ones I have done,

No 2 carb is the "base" and can't be adjusted as such. The left screw is for matching No1 to No2. The right screw is for matching 3 and 4. The middle screw is for matching the left pair (No 1+2 ) and right pair (No 3 +4) to each other. You'll also need some way of supplying fuel with the tank removed, an old 2 stroke oil tank does the job nicely.  

  • Like 2
Posted

so the middle screw does nt do 2 an 3 it levels the 4 carbs 

To a point, it's more that it levels out the two banks of carbs. I've been using a super-duper led Vacuummate carb balancer for years and can see what happens when you balance the middle screw the first time. Now 1 and 2 will out of balance and the same with 3 and 4. You have to go back and repeat balancing the screws till you manage to fine tune the balance. I usually do it 3 times to get bang on. 

If I'm rebuilding carbs I always screw out all the balancing screws till they just about touching their base plates. Then when I go to balance I start with number 1+2 screw (base side) and the 3=4 screw then middle screw. By loosening the screws to start with, you know you can only go clockwise to have an affect on you reading. It saves a lot of going turning back and forth with a screwdriver not knowing whats doing what. ;)

  • Like 2
Posted

You'll also find that even the slightest pressure on the screws will affect the readings so,what you thought was spot on turns out to be wrong after you've blipped the throttle. Don't worry, you'll get the hang of it. 

  • Like 3
Posted

usually I adjust the valves first, then with the carbs off the bike I balance them visually, so that all the throttles are opened equally. Then 9 times out of 10 it's idling correctly and only needs adjusting a bit with the mixture screws. I don't use vacuum gauges.

If it's still not running as it should, there's something wrong somewhere, like compression low on one (or more) cilinder(s) or the pilot circuit on (one of) the carbs not working properly.

 

  • Like 2
Posted

thanks everyone its comin back to me now i remember the fiddly screws an the slightest pressure sets them off i stripped the carbs fully and replaced all seals an cleaned all the jets so just this to do an should be running sweet 

  • 5 years later...
Posted

I know this is an old thread... but comes in really handy. 

Got my ´89 1100 almost perfectly sync´d, but then cylinder #1 got no fuel, and was not working, so decided to do it again, and took the "total uscrew" path. I tried to sync carbs again, but there is no way in which I can get a smooth idle now.

Is there a way to get a starting point for sync´ing while carbs are on the bike? 

Question #2: There is one carb seeping fuel from the drain plug. How can I regulate the float height with the carbs on the bike? Is there any reference I can use..

Yes... you know by now... I completely dislike getting the carbs out!ç

Cheers!

 

Posted
Just now, Carlitox33 said:

I know this is an old thread... but comes in really handy. 

Got my ´89 1100 almost perfectly sync´d, but then cylinder #1 got no fuel, and was not working, so decided to do it again, and took the "total uscrew" path. I tried to sync carbs again, but there is no way in which I can get a smooth idle now.

Is there a way to get a starting point for sync´ing while carbs are on the bike? 

Question #2: There is one carb seeping fuel from the drain plug. How can I regulate the float height with the carbs on the bike? Is there any reference I can use..

Yes... you know by now... I completely dislike getting the carbs out!ç

Cheers!

 

Actually, I can pretty much sync #1 with #2 and #3 with #4... but then I get to the center bolt to get both groups balanced, and my idle goes down like crazy

Posted
35 minutes ago, Carlitox33 said:

I know this is an old thread... but comes in really handy. 

Got my ´89 1100 almost perfectly sync´d, but then cylinder #1 got no fuel, and was not working, so decided to do it again, and took the "total uscrew" path. I tried to sync carbs again, but there is no way in which I can get a smooth idle now.

Is there a way to get a starting point for sync´ing while carbs are on the bike? 

Question #2: There is one carb seeping fuel from the drain plug. How can I regulate the float height with the carbs on the bike? Is there any reference I can use..

Yes... you know by now... I completely dislike getting the carbs out!ç

Cheers!

 

i think a carb strip is in order, if you are not getting fuel to one carb you will never get them balanced 

Posted (edited)

My guess is you're going to have to remove the carbs, bench sync, then replace and balance as described above. Bench syncing involves faffing around with the adjuster screws as described above but making sure all the butterflies open the same amount. A thin bit of wire enables this with additional careful use of the idle adjuster. Don't forget to back off the idle adjuster before re-fitting the bank. If you're lucky the bike will run perfectly after a bench sync and no further action is required. This is a major bonus if the bike is aircooled and has BS carbs, which have locknuts on the adjuster screws rather than springs: a major pain in the arse when balancing.

Obviously you'll have to first fix why carb 1 isn't getting any fuel. It's simply a toilet cistern in minature so my guess is the needle valve is sticking due to a bit of cack.

Edited by Dezza
Posted

Thank you guys. The carbs have already been stripped and new orings and  float valves have been installed. The carb losing fuel was a result of the balancing exercise... it´s a real pain, as they were almost perfectly balanced already.

Yep... I guess I´ll have to get them out of the bike again... :-(

Posted

Balancing idle mixtures / running should have no effect on float valve sealing ie. leaking or cylinders not getting fuel (unless the screw is completely closed!) If it is, then they aren't balanced! Looks to me as if another strip / clean / rebuild is required?

  • 1 month later...
Posted (edited)

Beware shite needle float valves, many non oem leak badly

Fit mikuni or wemoto valves, then set up a remote tank hooked to your carbs on a bench to make sure no leaks

Ive seen new valves leak at 40 mins under load like this

 

To reset float heights alter the tab the valve hangs on. Best to youtube different ways of doing it, ideal to have a manual for correct float height 

 

However if it wasn't wrong before it cant move on its own ... 99% of leaks come from cheap after market needle float valves, always the same problem 

Edited by wsn03
  • Like 2

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