carb throttle adjustment

[02GF74]

well the carbs are off - wasn't so bad after all and it save me £££ not having to buy redex which would never have worked.

invewstigation and clean up revealed needle vavle on no. 1 stuck and bunged up and air corrector (little hole in screw on end of main jet) blocked on no. 2. Presumably both of these would have stopped the flow of fuel .

All is cleaned up and assembled - made a tiny needle file from a piece of wire and running a file over it to roughen the surface to remove the varnish from the little hole withtou removing metal.

The gap between throttle (cylinder thing that hold the needle) and the carb. body is about .7 mm on no. 3 and 4. but less on no. 1 and no gap on no. 2. (this was the stuck one).

Haynes manaul blabs about setting the distance and refers to some groove or something - can someone tell me how to do this? I'll probasbly set the gap to be like on 3. and 4. using a small drill to measure the gap.

Also to set the floats for fuel level, any tips on doing this (isn't there some special tool required)?

And finally how do I check the cold start jet things are clean? Are they easy to take apart?

[RALPHARAMA]

I hope the gap you refer to is the gap at the bottom of the throttle slide and the bottom of the choke (the big hole). If you're talking diameters then best you bin 'em

Getting them near enough is a good idea before putting them on the bike. They are adjusted from on top. When they're back on the bike, remove the carb top covers, attach a set of vacuum gauges to the vacuum take offs on the inlet rubbers. Run the previously warmed up engine on a high tick over and adjust the throttle heights, so that all the carbs show the same vacuum on each. Doesn't really matter what the reading is, so long as they're all the same. If you don't already have vacuum gauges and can't borrow any make sure you buy the manometer types rather than the dial style ones as they are much more accurate. The best sort are mercury manometers but thanks to health and safety they're as rare as rocking horse shit these days. I'm still looking for a mercury set myself, and have been for a long and fruitless time. John has a set I'm welcome to use any time, but I'd rather have my own.

Have fun

[Steve S]

The throttle valves are adjusted using the adjuster screws on the top linkage next to carb tops,by loosening the lock nut and turning the adjuster screw you can change the settings to get the measurement correct for the throttle valves using the notch cut into the throttle valve as the measuring point..6-.7mm or .024-.028 inch (old money) is stated for 900,s.
Its a good idea to get all the valves set up to the same measurement when the carbs are off,for one thing its easier and you are then starting with them all mechanically balanced at least.
Also dont forget to check your throttle stop clearances to ensure all the valves are able to fully open (Full throttle) and close as well (tick over).
Good luck.

Float levels i,ve never had to alter so maybe someone else can advise.

[Steve S]

Oh,forgot to say i use a filed down feeler gauge to measure the gaps but wire or a drill will do the job also.

[02GF74]

... you can change the settings to get the measurement correct for the throttle valves using the notch cut into the throttle valve as the measuring point..6-.7mm

cheers ...

is this the distance of the base of the throttle to the carb body? I am not quite clear about this

It is z1000 A1 if that makes any difference to the measurement; I guess it won't be a million miles out.

[Steve Cooke]

Underside of throttle slide to carb body = 0.7mm measured on the engine side and float height measured from carb body to top of float when carbs are inverted = 24 -26mm I set mine at 25mm and they were fine, these just give a manual set up for starters, once fitted as Ralph says you need to use vacuum gauges to sync. carbs with your engine.

[02GF74]

hmmmm, the haynes manual says there is a groove in the throttle - not in mine there isn't. a more careful look shows the carbs are slightly different (this is z900 manual with z1000 supplement) in that the air jet is in the side of the body - on mine it is underneath.

anyways, loads of messing about trying to set an even gap on all failed - 3 are adjusted to give a gap of .7 mm but then the last one is closef, adjusting that one to correct gap put the others out and so on .... and then one of the screws would bottom out or else other screws were too far out so the lock nut could not be done up!

so I thought what is the point of all of this? unless someone corrects me, it is to ensure that all 4 throttles are in the same position as the connecting rod is turned. (to be more accurate it is so the same air flow goes through each body which should be pretty close to throttle position, all things being equal).

I fitted the adjusters finger tight then adjusted the throttle idle knob so that there was a 0.7 mm gap and with some minor adjustments, was able to get all throttles to be the same. Undoing the knob left all the throttles in closed posistion - which sounds wrong according to the haynes but that may be the prupose of the groove. My reasoning is that this doesn't matter since the knob will be used to set the idle so all throttles will be partially open.

I also checked that the throttles were all fully open at the same time and they are more or less - I will have another measuing session tonight to see how close they are.

But put it this way, it was running reasonably well on just 2 cylinders along with the throttles being all out so this surely will have to be an improvement!

[Steve Cooke]

If your main throttle stop screw is too far in or out it will affect the amount of adjustment available on the individual throttle valves which you seem to have worked out, when set to .7mm you should have plenty of adjustment either way on the stop screw. Also you would be suprised at how much difference in the running of the engine there can be between the manually set up carbs and the carbs once they have been set up using the gauges, it is dependent on the condition of bores, rings, valves etc. As for your Haynes manual it is quite good for mopping up any spilt petrol whilst rebuilding your carbs and that's about it, try and find a genuine one if you can, failing that a Clymer one.