Carb Tune

[Wayne1960]

guys got myself a carb tune and set up yesterday. wasn't that bad but had to play!!!!!!!!!!!!!
now I've lost the settings and bike runs like crap.
can anyone help to get the idle set back up without taking cams off and then use the carb tune again?

[kev edwards]

I think you need to elaborate on what you've actually done then let us know what's happened and what you now think needs doing, I live in Walderslade and have a set of vac gauges if that's of any use.

[Wayne1960]

hi Kev

Ok i set the carbs up when i rebuilt the bike. Set the throttle gap to 2mm.
bike was running ok but its a hobby and i wanted it to be better.
purchased a Carbtune Pro
Set it all up and when i started the bike the balance wasn't that bad but needed adjusting.
set about adjusting and it went from ok to bad.
The main problem was that the tubes got near the engine and started melting, i didn't realize and was merrily trying to get the carbs to balance and they had come off the manifold.
also the grub screw adjusters sheered! the slots i mean.
bike ended up running like crap and coughing all over the place.

Going forward

Checked plugs OK
Checked compression OK little down on no 2
sorted out broken grub srews all good now
Took rubber boot off carb 1 and checked gap and adjusted to 2mm
Set all other carbs the same
Started bike and running but coughing, still popping and spluttering
Carbtune shows 3 and 4 a little high

Had to stop!!!!! neighbor moaning too noisy

So that's where i am untill next time.

[kev edwards]

Can I assume carbs have been stripped cleaned and float levels adjusted valve clearances and timing ok, whenever I do these I set the slide height with the carbs on the bench and always make sure the adjusting screw in the top of the carbs is always halfway, this gives scope to adjust both ways, the amount of times I've had no adjustment in one or the other direction on banks of carbs is countless.

[Wayne1960]

hi Kev yes assumed correct. so how do you set them up so its half way.
here's the question.

What should the gap be between the bottom of the carb and the bottom of the slide valve?
Is the gap measured on the engine side or the air box side?
Can i set 1 up from removing the rubber boot and set the rest up bu measuring down the carb to the top of the slide valve and then set up vacuum with carb tune.

[000zeds]

Wayne it is measured on the engine side and it is a very small notch on the bottom of the slide.

The clearance you need should be in the workshop manual.

[Wayne1960]

ok i have just had the rubber boot of no 1 carb and taken videos and pictures onside.
The bottom of the slide bore is flat and has no notch!
The bottom of the carb cylinder is also at the same level so whatever the gap at the front will be the same at the back.
the carbs are VM26 smooth bore i think!

[000zeds]

Standard Z900 VM26 are not smooth bores and you will have to take the crabs off to see the really very small notch at the bottom of the slide.

The engine side of the slide is flat and air intake side is curved.

Hope that helps

[Wayne1960]

Thanks for this. I'm seeing something different here.
I can put my finger into the carb with the valve up and I can't feel no notch and no curve. Worrying but they have been working.

[000zeds]

You won`t get your finger past the needle to feel the notch as it is only visible from the engine side.

Also you won`t see the curve on the slide if you have the throttle fully open and it is only a very slight curve.

I think you might have upset something.

[Wayne1960]

ok just had another look and did the following.

pushed a 2mm drill all the way through to the other side of the slide valve and gently lowered on to it.
pushed another 2mm drill into the back of the slide so the air side and it was loose.
so i should be able to adjust the slide from the back knowing it is larger.
so i read to use a piece of wire as a feeler gauge.
does that sound correct? and what size?

[000zeds]

Workshop manual should tell you what size piece of wire to use as gauge.
I used a very small drill bit but can`t remember size.

When you get all the slides level and all adjusters in the middle use your carb tune.

[Wayne1960]

Thanks for the advise.
I understand getting slides level and the gap but how do you get adjusters in the middle is there a technique for this.

[kev edwards]

to be honest Wayne they need to be taken off and set up on the bench, you will save on time and swearing.

[000zeds]

That is exactly what I did Kev