Z1A Running Rough

[cottastaff46]

Hi there. This is my first time using the forum, as I've only recently joined after buying my dream bike, a 1974 Kawasaki Z1A. And herein lies the problem.
The bike would not fire on all cylinders or tick over. After having the carbs ultrasonically cleaned and the fitting of repair kits, plus a new Boyer Bransden electronic ignition (the old Neutronic ignition looked ropey) with coils/ plugs and air filter, the problem was found to be the cam timing was 1 tooth out!. This rectified, the bike, although running much better is still way off the pace. The throttle has to be coaxed from tick over up to around 3000 rpm, as opening the throttle quickly from tick over causes the engine to cut out. It is also very lumpy when cruising at 30mph in 3rd. The bike is now languishing in a local bike garage, as I have expended all of my ideas. The garage has dyno'd the bike and confirmed that at tick over it is running so lean that it will not plot on the electronic graph, and when revved to 5000rpm it runs so rich that it will not plot on the graph. Horsepower at the back wheel was a feeble 45 HP but says that this could easily be the result of the problem and not the cause. It has good compression on all cylinders and does not smoke. I would be grateful for any help, as at £37 a hour, investigating the source of my woes is rapidly depleting my funds.

[Pigford]

You need to check carbs for wear..... are they balanced ok - float levels good?

Needles & Needle Jets (emulsifier tubes) will wear over time and pilots - make sure they are correct sizes.

Is air filter good? You sure theres a good +12v getting to ignition (coils) whilst running? Are carb rubbers all good - no cracks/splits?

Borrowing a good set of carbs would be handy

[cottastaff46]

Needles and jets are new with the kits from Z power and so is the air filter. I set the float levels up and drained them off individually to check they had the same amounts in. According to the guy at the garage, the carbs are well balanced with gas analysis and temperature on each cylinder being reasonably the same. He also checked that the coils were earthed correctly and I was getting a good 12V.
Carb rubbers look to be in very good shape and are still very flexible. I removed the emulsion tubes when the carbs were ultrasonically cleaned, but can only confirm they did not look damaged or worn visually.

I agree, it would be good to have a set of proven carbs to put on the bike to eliminate a fuelling/ worn carb problem, but unfortunately I don't know anyone else with a set.

[garyd]

May not be an issue with your bike but 'back in the day' I helped a mate do a little work on his 1000A1. While reassembling the motor he managed to get the exhaust 1 tooth out. It ran O.K. ish but we found the problem and rectified it. But it always felt 'off' at low revs.

Turned out it had just touched the pistons with the valves so it was down on compression.

May not be the same but have you checked compression?

[Compo1955]

One way to check carb rubbers is to have the engine on tickover and spray brake cleaner onto the rubbers, if the tickover speed changes, this indicates an air leak at the rubbers. Either porous/cracked or loose clamps, or a poor seal between the inlet rubber/head.

[cottastaff46]

Compression on the cylinders was pretty well balanced at around 140-145psi.
I'll get the cam timing checked again as well as the carb rubbers.

There is a set of recon carbs on ebay at the minute but the float chambers look different. Mine have the hexagonal head drain plug directly at the bottom facing downward. The ones on ebay have a brass circular drain plug which has a screwdriver slot in it and faces nearly horizontal. Also, from the pictures, it looks as though he has 120 main jets fitted. Mine had 113's in it and that's what the repair kits came with.
I am increasingly confused!

[wilsonsjw11]

Your carbs are early Z1A
Regards
Steve

[Big Fluff]

Does the Boyer ignition you've fitted still use the Kawasaki centrifugal advance/retard mechanism?
If so, make sure that the cam/trigger advances and retards with the use of a strobe.
Additionally, in the past I've seen it where someone has fitted incorrect rated springs to the bob weights causing all sorts of serious running problems below full advance.
I would definitely check this first.

[zed1015]

Whereabouts in Lincolnshire are you ?

[cottastaff46]

Thanks for clearing that up Steve.
With regard to Big fluffs response, The Boyer ignition does use the centrifugal advance and retard mechanism and you are the second person to draw reference to the bob weights sticking. When the new ignition was fitted, the timing using the strobe seemed to be quite random and impossible to set up. I will enquire as to whether the springs are still readily available and purchase new ones if they are. Regards.

[PAULJAC47]

Hiya sorry to hear about troubles you are having few pointers.most modern bike shops dont have much idea about these old bikes if you cant plug it in to a Pc they seem lost.
1/Boyer ignitions are ok but the Dyna s used by most on here for the cost is by far the best if you couild not set up the boyer accurately may well be a prob,did you set at F and get full advance?.

2/What rating are your new coils and Ht leads and do they match the Boyer?check primary and secondary restitance with Ht leads att

3/If using Ngk plugs deposit in nearest bin and replace with Denso W24-ES

4/Is the valve timing set correctly.

5/Who rebuilt the carbs? is the needle set in middle slot, is the pilot screw set at approx 1 1/4 t0 1 1/2 tuns out from fully in this is what sets your idle rich/lean,i always use a Gunson colurtune to set this,have you set your float levels the manometer method works well for this.
6/When the carbs were cleaned were they stripped or just put whole in the bath? if the latter would suspect clogged air ways etc.
7/Have you ensured good flow of fuel,vent in tank filler cap clear.

8/Fom your post i would guess one or more carbs blockage ,wrong size jets,poor qaility rebuild kit,carbs set up wrong,bad carb rubbers ignition and or cam timing,hope this helps sure one of the lads local to you may help but if not send me a Pm and more than willing to have a chat...Cheers Paul J

[Mark Tiller]

set of carbs to try.... http://www.ebay.co.uk/itm/Suzuki-GS1000 ... 43c8744472

[steve bowdler]

Give Zed1015 your address he may be able to help , as he is asking , he can do great things check out his build in the projects section

[cottastaff46]

Have forwarded my address to Zed1015 who was very helpful.
Does anyone know if the carb bodies on the GS1000S (see link to ebay item above) are the same as the Z1A carbs? Please excuse my ignorance. Also, any comments on the Z1A/B carbs for sale on the same website?

[zed1015]

Gs1000s 28mm carbs are a different design to the z1a carbs.
They are similar to the later Z1R 28mm carbs but have a superior pilot circuit with additional fuel mixture screw.
They will work with your 900 engine but will not be original in appearance.