Having Trouble Starting From Cold????? - Carburettor- 28mm

[DogsbolloxofZ1B]

Having problem starting yours from cold? After all the effort that?s gone into my Z1B it was a right royal pain in the arse to start? and still maybe if these findings aren?t the root cause.

Before I start, I bought this Z1B as a non-runner from a mate who had left it standing for about 8 yrs, so I knew I was going to have a few problems. The carbs had been cleaned by Steve Smethurst, rebuilt with masses of NOS parts and I spent many hours cleaning & checking all the orifices?.. LOL

So if you have carb problems here?s a few things you need to check, some obvious but one certainly less so.

My saga:
On Tuesday , being pretty fed-up, I called Chris Rivett to discuss likely causes for my starting problems and for those of you who know me I?m not the sort of guy who asks for help very often (I?ve been around these bikes for 30+yrs & know it all, of course I would say that!) Chris gave me chapter & verse on the choke circuit, so much so that by the time I?d put the Mob down I?d forgotten most of it. I grabbed my tatty copy of the original workshop manual & read-up on how these carbs work. So, when starting from cold you must not open the throttle, this defeats the object! My bike would only run, reluctantly, by feathering the throttle and then only on 3 cylinders? don?t they all!

Finding No.1( Image 1 + 2)
Armed with a little more knowledge I stripped my carbs AGAIN and examined the chokes, choke ports & brass atomizer pipe and low and behold uncovered my first problem NO CHOKE JET in the atomiser pipe No.3 carb.
The first image (all blurry I?m afraid no David Bailey) shows the end of the atomiser pipe in which there should be a small jet (~1/64? diameter hole) and you?ll notice that mine is completely missing.. The second image is for comparison & shows this small hole in carb No.4.
I now need one of my fitters at work to make me a jet.



Finding No.2 (image 3)
I now turned to the float bowls themselves to test whether the hole that the choke atomiser goes into was clear, was it ####!! I found 3 out of 4 blocked, so by using a Pin-chuck I cleaned out the vertical & 45? holes with a
1mm drill so now fuel can be drawn into the choke tube.

Finding No.3
Again with carb No.3, in the hemi chamber alongside the choke tube are two holes that run parallel with the axis of the slide, one is slightly bigger than the other, one of these was blocked at its deepest point. I used a lot of release agent, strands of thin copper wire and tons of patience and finally cleaned this out too.

Hopefully I?ll have the carbs assembled early next week & ready to fire her up again. Fingers crossed.


Thanks to Chris.
DogsbolloxofZ1b.





(Edited by DogsbolloxofZ1B at 3:34 pm on Sep. 22, 2006)

[Rich]

Cellulose thinners works really well for cleaning carbs. My manual (Z1000 A1/2 etc) shows the starter jet in the float bowl casing.

[Mark O C]

That was one of the most interesting posts on carbs that I've read, but then I'm a sad git. learn something every day.

[DogsbolloxofZ1B]

Your welcome. Update next week.

[london calling]

What i can't understand is that if the carbs were cleaned and fitted with loads of NOS parts,why were they still blocked and had parts missing??
I always get my carbs ultra-sonically cleaned and have had no problems.

[DogsbolloxofZ1B]

Just to clarify, there were no missing parts. The brass choke tube isn't a serviceable part but in the end of it is a small jet (0.5mm hole) Looking closely at the way this is manufactured a small disc is pressed into the end of the tube, it maybe silver soldered in place but there are no tell-tale signs of this.

Mike

(Edited by DogsbolloxofZ1B at 8:57 pm on Sep. 24, 2006)

[london calling]

Hi Mike,i suppose when you think about it,you've got 30+ year old carbs that have probably had stale petrol sitting in them for many years so they've done well.
It's always the smallest,most awkward bits to get at that,that always seem to need attention.
Obviously when the bike looks as good as yours does,you also want it to start and go as well as possible also.

[Rich]

Does your tube have four little holes in the side of it as well as a press in(?) jet in the bottom? If so they may not be user servicable but they are user removable, put a drill chuck onto the tube and see if it will pull out, if it does there is one here with a jet in it for you. PM me you address and I will send it.
P.S. I wouldn't silver solder it you will probably melt the tube.

[DogsbolloxofZ1B]

Rich,
That's the one. I've sent you a pm earlier.

Mike

[Rich]

It's in the post and winding its' way to you by snail mail!

[DogsbolloxofZ1B]

Carbs all sorted now & runs lovely!!

Many thanx to Rich.

mike