TOPIC:

hi again, cheers for all the assistance with my gearbox, going okay now - although 3rd occasionally slips, next problem is carbs, if i open them right up the engine cuts out, ive given them all a good clean (mains, starters, emulsion tubes, float valve etc) but im still haing this problem, so i dont seem to be able to rev much above 6000 rpm, any ideas ....

Maybe it is not the carbs:)

Are the coils the stock coils? If they are, the were weak when the bike was new. Just a thought.

Paul Sr.
kz1000g

hi again, my 1980 z1000 is an american import (im in cornwall, uk) it was converted from fuel injection to mikuni carbs and k&n type filters long before i got it, it had been sitting unused for about six years until i bought it last month, i am assured it was running correctly before it was garaged and that the fuel system was professionaly converted,
since i posted the carb question ive given them another really good clean and its revving a bit better now, if you open the carbs up in neutral it revs fine but as soon as your in gear and theres a load on the motor it really struggles if you open the slides up more than about 2/3rds, apart from that its got loads of torque but as you get around 6000 rpm and above it becomes hesitant - misses a bit then pulls hard again etc.
all cylinders seem to be running fairly evenly and are roughly balanced, and im prety sure the ignition system is ok, it just feels to me like a carb problem.
has anybody got the carb settings i.e jet sizes, float hight, pilot screw, and needle clip height for mikunis (no. on side is 33A 14), or any other ideas/info, thanks again- mat
p.s im using conical k&n type filters and a marshall 4 into 1 deeptone pipe. cheers

Do the K&N filters show enough use lend credibility to the assumption that it was, at one time, working properly with these filters and carbs in place?

FWIW the GS1000 I rescued was reving nicely on the stand and bogging on the street. This after a thorough cleaning of the carburetors. A combination of faults resulting from idleness and changes was discovered. The mechanical advance was not advancing, the main jets were too small for the aftermarket air filters, the spark was weak owing to leakage from cracked cables and spark jumping gap in broken boots. Addressing these moved the bogging up a bit in revs and gave it good top end with a big flat spot in the middle. A 2/3 mm of shim under the slide needles was the final tweak that made the midrange play nicely.

-Duck

you have mikuni 33mm smoothbores,it sounds like they may be a little lean try pulling the choke when it falters, if it helps, it is a lean condition if it dosen't help it may be ritch.

if its lean,lower the "e" clip one notch,go up one size on the main jets and try it again

it could be running on 3 cylinders if it will not rev above 6000,check the pipes to see if one is cold if so that sparkplug could be ritch/fouled,I have cleared fouled plugs by pulling that cap and holding it around an inch from the plug so it arcs while running

at any rate they will most times falter when snaped open from an idle with a stock 1000

I am adding an attachment from sudco which shows the stock jetting,note the gs1100 and the kz1000 has the same number but are tuned diferent.you may have the set that is tuned for the gs1100



just my .02

the attachment was to big and didn't load

Post edited by: craigpuckett, at: 2006/04/10 22:29

the k&n's do look well used and i trust the previous owner that the bike was (six years ago) running properly with this setup, all cylinders seem to be running fairly evenly and all pipes heat up equally, the mechanical advance is functioning, the spark doesnt look that strong on any cylinder but im used to working on 2 strokes so im probably just used to a stronger spark, opening the choke at any time other than when cold starting doesnt help issues, so yep maybee it is a bit rich- the wheels are off at the mo for powder coating, ill give the filters a good clean and try dropping the needles a notch when its back together and see what happens- although i am worried about ending up on the lean side, again if anybody has carb information i.e jet sizes and needle height etc please let me know. thanks again- any information however small greatly appreciated.

cant find any info on mikuni 33 mm carbs on the net- if anybody knows of the standard setup please let me know,
im running 4-1 marshall pipe and k&n type conical filters, cheers

here is the standard setup per Sudco

kz1000/1100 VM33-A14 main jet-127.5 air jet-1.2 pilot- 17.5 needle- 6DJ30-4th needle jet- 0.6
slide cutaway- 1.5 air screw- 3/4 out

if the slide cutaway is 2.0 they are for suzuki

Post edited by: craigpuckett, at: 2006/04/12 13:02

cheers for the carb details,
i would have thought with k&n filters and a marshall
4-1 system that the gas would be more freeflowing and probably require a larger mainjet, however the plugs are getting sooty so rapidly that i often have to clean them to get them sparking again - indicating an over rich mixture- im now thinking that maybee the carbs are not the main problem and maybee its the ignition system playing up when the engines under load, is it possible that a weak/intermitant spark could cause poor combustion and result in this kind of plug fouling?
also could this happen even though the bike seems to rev pretty well while its in neutral, any comments appreciated - cheers mat.