Carb balancing with vac gauges

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Greenbat
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Re: Carb balancing with vac gauges

Unread post by Greenbat » Sat Aug 22, 2009 5:52 pm

Tom-Think I read it in CB mag. I'll have a look when I get home Tuesday

The Mighty Gusset

Re: Carb balancing with vac gauges

Unread post by The Mighty Gusset » Sat Aug 22, 2009 7:22 pm

Nah !
Nobody balances their carbs every 500 miles !

5000 miles maybe ?

Having said that, high frequency vibration does tend to loosen nuts and bolts and things on the 400/4, so it's probably worth bunging a drop of loctite on the adjusters.

Oh, and a blob of paint, or tippex so that you know where the spot-on setting is/was.

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sfb
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Re: Carb balancing with vac gauges

Unread post by sfb » Sat Aug 22, 2009 7:46 pm

I used to balance the W650 carbs every 3000ish miles - as do most other W owners, I think.

Triton Thrasher
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Re: Carb balancing with vac gauges

Unread post by Triton Thrasher » Sat Aug 22, 2009 8:41 pm

I could see a ramshackle Brit twin carb setup, such as late 650 Bonnie, going out of synch before 500 miles, though it should settle down after a few twiddles.

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Hooli
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Re: Carb balancing with vac gauges

Unread post by Hooli » Sat Aug 22, 2009 8:44 pm

i've never balanced the throttle bodies on 14 & shes on 41k now, they work exactly the same as jap carbs so need balancing the same.
i used to balance stroppy's everytime i put them back on :lol:
Classics ain't built in Metric

Coxy
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Re: Carb balancing with vac gauges

Unread post by Coxy » Fri Sep 04, 2009 3:29 pm

Loctite is too strong on such small screws as carb balance screws,what I have found to work great is simply to use one of those car paint touchup paint sticks that have a small inbuilt brush.this is in fact what the Japanese factories used from new usually in Yellow.Just dab it on the nut and thread or if spring loaded style the brush allows you to coat the thread thru the springs without a total strip.
For those with or without Vacuum gauges with the spring loaded style adjusters find the master carb that the others all adjust to, fully back off the idle adjustment so the butterfly is seated closed.
As you push the other butterflies home to seal against the carburetor bore and so align themselves with the master butterfly you will push against the spring on the sync adjuster,then simply adjust the screw up to take up the evident slack in the adjuster,if you go too far you will see the master butterfly move off the carburettor bore exposing an air gap.It may help somewhat to have a light source behind the closed butterflt valves as this will make it easily evident when the butterfly plate is no longer seated corectly
Test run and if happy with the result use paint as above to make sure the screw adjuster doesn't vibrate loose.
It is amazing just how well you can sync multi carb setups without expensive equipment when you carefully study the working principal of the design and do the basic mechanical sync first,remember with Vacuum gauges you can also be compensating for valve clearances or poor ring seal or leaking inlet manifolds as well, not just adjusting the Carb's.
Rule of thumb make sure the mechanical sync is as close as possible before trusting vacuum gauges as they can and do lie at times because they can not differentiate as to what component is affective the vacuum signal strength.
Using this method has the added advantage of also potentially isolating other potential issues you may not be aware you have.

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Pict
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Re: Carb balancing with vac gauges

Unread post by Pict » Fri Sep 04, 2009 4:00 pm

Coxy wrote:Loctite is too strong on such small screws as carb balance screws



Woah Coxy - there are several hundred 'Loctites' and one of them will be perfect for carb balance screws, get an application book ( it is a little spiral bound thing) from your stockist. It's a revelation.

Coxy
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Re: Carb balancing with vac gauges

Unread post by Coxy » Sun Sep 06, 2009 11:10 am

I was sponsored by loctite with my rally car in the past and having remembered uncrating new Kawasaki H1's and AJS Stormers and Commandos, I am speaking from real world experience,All Loctite products work as an aneobolic compound and the major difference between the grades is actually the temperature rating at which they return to a liquid state.
The actual required torque to remove a loctited fastener after achieving breakfree from the applied fastener tension is between 5~10 NM and this is a figure normally applied to a 6mm(1/4") size threaded fastener.
Most carby adjusting screws are between 3~4 mm and therefore the required torque would be too much.
Whilst Loctite will return to a liquid state when heated I do not believe it prudent to do so with Carburettors,again from experience as when working on BMW's the ammount of heat you need to apply to liquify the loctite so as not to destroy the threads in the alloy is ridiculous,in the order of 5~15 minutes with a 2400 watt heat gun.
Loctite like many things has it's areas of use but this is not one of them as I have seen too many damaged screws in this area ocer the years because some factories made that mistake,paint or even nail polish works just fine,after all this is not something for permenant assembly but does on occasion need to be worked on and adjusted.

The Mighty Gusset

Re: Carb balancing with vac gauges

Unread post by The Mighty Gusset » Sun Sep 06, 2009 11:31 am

Coxy, no-one is actually suggesting using Loctite on carb adjuster 'screws' !

The screw and locknut adjusters on the tops of 400/4 carbs are part of a mechanical linkage that sets the slide heights.
they sit on top of the carb, rather than being an internal brass screw
A small blob of Loctite on those threads is absolutely fine.

Please people, don't go glueing your air screws into your carbs !

Coxy
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Location: Sydney Australia

Re: Carb balancing with vac gauges

Unread post by Coxy » Sun Sep 06, 2009 12:17 pm

The adjuster screws I am refering to are actually steel fine threaded screws usually with a slotted head and I have seen many of these with one side broken off because someone did loctite them,as for the brass mixture screws if everything is as per factory the only issue with those is seizing occasionally.Loctite is a great product used with thought as appropriate but sometimes even the factories go overboard,over a decade working with Hinkley Triumphs and BMW Aprillia bikes led to the conclusion BMW only made motorcycles to keep their cable Tie and Loctite divisions in business. Cheers Steve

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