More Carb confusion

[dave]

I’ve got another carburettor question; I’ve not got to the bottom of that last one, but I’m going to stick a picture up when I get hold of a camera.

Now to this one, I’ve been given a carb synchroniser, but it doesn’t have the instructions with it so I just want to check I’m doing it right.

I understand the general principle but the kit came with some shut off taps which fit within the pipeline, would I be right in thinking these are used to dampen the needle because when they are fully open the reading oscillates so much it’s impossible to get a useful reading. When the tap is slowly closed the needle gets continuously steadier until it stops when it is shut off. This seems to be the obvious way to use the kit but I’m just curious if doing this will give me a true reading.

Also I’m assuming that the scale on the vacuum part of the gauge is mm of mercury, can someone confirm this. If it is then by bike’s well out as I was getting a reading on the first try of 275 and from memory it said in the Haynes manual it should be quite a bit lower.

The type of gauge I’m using is the one with the diala mounted on a blue metal back plate with Carburettor Synchnonizer witter accros the top, the one their is loads on on ebay

Cheers

[CD]

I tried one of these an couldn't get a relaible reading but others like them so maybe its just me.
However, I was forced to try the age old method of listening to the intake his on the carbs through a rubber hose. It really works. The carbs are set in pairs so you hold the tube end against carb1 and then move it to carb 2 keeping the tube in the same relative position on each carb. Adjust the balance until both hiss sounds are the same strength. Repeat for carbs 3 and 4 and then for the central adjuster that sets the 2 pairs.

[2old2boogie]

I have'nt done this for some time. Last bike I balanced the carbs on was a CBX750F, shows how long ago it was.

But....from memory. You're right about the dampers for the oscillating
needles. Damp them down till they are each reading the same.

One carb will be sealed. No adjustment possible. You adjust the other 3 carbs to this.

Hopefully someone who has done this job recently will be along shortly.

[alpaholic]

dave said:

This seems to be the obvious way to use the kit but I’m just curious if doing this will give me a true reading.

That's right, use the know to damp it. (Obviously don't seal it right off!)

You really need your haynes to explain how to do the job *if* they need adjusting. If they don't it's self explanitory.

[An X-Member]

The valves are for damping the gauges, you need to close the valve until the needles just oscillates slightly, if you close them off to much you will not get a true reading.

Connect the vacuum gauges to the carbs and adjust carbs 1 & 2 until they are reading the same, then adjust 3 & 4 until they read the same.
then adjust 1&2 & 3&4 so they all read the same, Don't worry too much about a slight deviation between the carbs as you will never get them perfect.

To calibrate the gauges plug 1st gauge onto carb 1 and note where the needle reads, then plug gauge 2 onto carb 1 and adjust the gauge until it reads the same as gauge 1 did, do the same with gauge 3 & 4.
You can adjust the needles position by turning the small screw at the bottom of the gauge, just unscrew the plastic cover to get to it.

Take no notice of what the manual says it should be, I've never had one yet that pulled to the manuals reading.
All you need to do is get them all reading the same, or as close as you can.

[dave]

Thanks for the input. Did it last night and there is a definite difference. I’d say the most noticeable thing is the reduction in vibration, which is good because the bike was trying to shake its self to bits. Also it seems to be running smother, which is all good.

El_Bandito, cheers for the mention of calibrating the gauges, I probably wouldn’t even have thought of it.

Dave