Bike running issues

[adamhearn]

I've had this problem for ages and it's meant that I've not been keen to use the bike. That in turn no doubt makes the problem worse It's a '94 L4 model that's standard.

My bike has been little used over the past few years (yeah I know!!). I didn't drain the carbs and also didn't know the fuel tap rubber had [again] split. So old fuel sitting in the carbs = blocked jets so I was told. I've stripped them a few times and cleaned with carb cleaner. They now look pretty clean - though to be honest they didn't look that bad previous to my interference.

I tried to put it all back together with the same settings and whilst the bike is running better than before, it's still really bad.

Starting - good, requires choke when cold
Tickover - seems almost OK, was told it's likely to be blocked pilot jets
Light load - poor. Anything below 5K revs it's really hesitant
Full throttle - variable. Sometimes it will scream as it should, others it will be hesitant like it's not being fuelled

I'm probably running with a poor mixture - I did adjust the mixture screws a little
I've not balanced the carbs as I don't have the tools or the capability - probably needs to be done?
I've not swapped out the fuel filter
I've not replaced the sparks - they look a little blacker than I'd expect

The bike garage I usually use isn't too keen on taking "an open ended carb adjustment job" - he's done it once before some years back and it was a real pain in the backside before the bike ran well.

Has anyone got any 'fit for dummys' guidance on how I should get my bike running well again? Failing that, is anyone based around Chippenham, Wilts and wouldn't mind lending me a hand for some beer money?

Thanks in advance!

[banner001]

i could help you, but im in coventry ~85 miles from you, so probably easier for you to come up here.

i have stripped, cleaned, and sold a few sets of carbs on ebay, all have been recieved in good working condition by their new owners, plus i have a set of carbtune pro II balancers here and access to a sonnicator - much better than carb cleaner!

under light load, does running with the choke on slightly make it better or worse? could also be duff HT leads, i take it all was well before it got garaged?

i could come to you but i would need petrol money, also i would not be able to bring the sonicator, ~170 miles works out at ~£24 in fuel (45mpg, £1.40/L).

from experience when my bike was really hessitant to 5k and it was down to the pilot settings, it was too rich, leaned it out by screwing the pilot air screw another 1/2 turn out and fitted k&n filter, now fuels a lot better but its lean above 7k so i have 97.5 and 100 mains here to test at some point.

if you can take it to a dyno place that will tell you a load about how the bike is currently fuelling, plus it makes for a good comparison before and after tinkering.

[adamhearn]

under light load, does running with the choke on slightly make it better or worse? could also be duff HT leads, i take it all was well before it got garaged?

It's been ages since it has been running well but yes, it was much better before being left to 'rot'.

i could come to you but i would need petrol money, also i would not be able to bring the sonicator, ~170 miles works out at ~£24 in fuel (45mpg, £1.40/L).

I couldn't expect or ask you to take that sort of journey! Paying for the travel costs would be the least I could do should that ever go ahead but I really think I need to try to eliminate things before hand. Perhaps the carbs need cleaning properly in your bath thing and maybe even some new o-rings and such.

from experience when my bike was really hessitant to 5k and it was down to the pilot settings

I could buy a new [standard] air filter as the current one is quite old (not done many miles mind you) and have a play with the pilot screws.

Thanks for the reply!

[banner001]

i do a full carb cleaning service for £25 minus parts...if you remove the main jets, the jet holder tube and the pilot jet i will do you a sonnication clean in acetone for £10+p&p.

also what is the condition of the fuel float needle, thats the small metal one with the rubber tip thats connected to the floats...if its damaged it will flood the carbs with fuel.

cant imagine that you need to replace the carb rubbers unless they are in a bad way/leaking.

i would suggest things to do:-
replace spark plugs - CR9EK or CR9EIX,
replace HT leads,
check coil resistances (need a multimeter),
replace fuel filter,
go for a ride, see if its any better, then either way go get a dyno run.

looking at ~£80 for all that.

[adamhearn]

i do a full carb cleaning service for £25 minus parts...if you remove the main jets, the jet holder tube and the pilot jet i will do you a sonnication clean in acetone for £10+p&p.

Thanks. Talking with friends they scowled at me when I said I used a wire brush strand to clean the jets. I was gentle but still felt scraping on the edge. Suggestion was that I may have changed the fueling myself with that action. Obviously a clean wouldn't correct that! Suggestions [buy new jets?] before cleaning?

also what is the condition of the fuel float needle, thats the small metal one with the rubber tip thats connected to the floats...if its damaged it will flood the carbs with fuel.

They looked OK - but then I haven't got a picture of what damage could look like on such a part.

cant imagine that you need to replace the carb rubbers unless they are in a bad way/leaking.

They don't look like they're in a bad way, bowl rubbers looked pretty flat but not seen any signs of fuel leakage. Hard to tell if rest of rubbers are OK/letting air past.

i would suggest things to do:-
replace spark plugs - CR9EK or CR9EIX,
replace HT leads,
check coil resistances (need a multimeter),
replace fuel filter,
go for a ride, see if its any better, then either way go get a dyno run.

looking at ~£80 for all that.

Will order plugs.
Will see if I can source leads - presume from Kawasaki or make your own?
Will check coils - have to find out how but have meter, can read!
Would a cheap fuel filter be fine? Difference of £4 vs £14?
Ditto for an air filter - £14 vs £33?
Dyno run - no idea if anyone is local'ish to me, will look.

Thanks in advance!

[banner001]

Your nearest dyno place might be Devizes (http://www.dynojet.co.uk/index.php/atcs ... alerid=166).

Yeah a wire brush can score brass easily, i would say new jets...what is marked on them? I have the same bike as yours and mine have K95 stamped on them, the Pilot jet should be K35 and the main jet holder shouldnt have anything stamped on it.

Jets can be bought from here (http://www.motorcycleproducts.co.uk/cat ... 8_423.html), if your jets say K95, then you need the (non-honda) 'Brass Jets Keihin 95' set, you can also buy bigger/smaller jets here (they come in increments of 2.5).

The float needle looks like this (http://www.newmotorcycleparts.com/image ... 43-001.jpg), the black plastic bit at the bottom (the pointed end) should have no damage/scoring/wear...if so it will need replacing (usually a kit with that needle and a fuel filter, possibly the carb gasket as well), if thats worn fuel can leak into the carb when its not supposed to.

HT leads, get 2m to be on the safe side, the same place that does jets does HT leads, i just got some from there and they are fine, cheap fuel filter is good, ive got one and it does the job no probs. Air filter you will be fine with a replacement foam one, if you go down the k&n route this will lean out your top end and as you dont really know what the fuelling is doing i would leave that for later.

Whilst you are in the engine guts would be a good idea to clean your coolant filter (on a lead coming from your carb heating circuit), then flush the coolant system, re-inspect the coolant filter and top up with fresh coolant.

Also it could probably do with the engine oil changing...cant imagine its in any good condition after so many years of inactivity...

[adamhearn]

Have purchased the 2 filters.

When I take it apart I'll look at the numbers on the jets. I'll also look at the float needles - though when I took them out whilst cleaning previously I didn't notice any issues of wear. When I know what I'll need I'll order some replacements and leads.

I'll grab some coolant and clean/flush/replace, thanks for the tip.

Yep, I'll be doing the oil and filter - Castrol Power 1 semi with an OEM filter.

Thanks for the reply.

[adamhearn]

The ZXR is in bits again! Carbs are apart and the jets as follows:

Cylinder 1 - Pilot: 35, Main: 88
Cylinder 2 - Pilot: 35, Main: 90
Cylinder 3 - Pilot: 35, Main: 90
Cylinder 4 - Pilot: 35, Main: 88

Looking at the manual they would seem to be the wrong size - I've not changed them myself but maybe the garage did it years ago when I had it looked at.

The float needles all look good with no obvious signs of damage.

I'll edit this post with a few pictures as soon as I can upload them.

[banner001]

as the middle cylinders run hotter than the two outside its not uncommon for you to have 88 and 90's in there.

95 are standard, but they came with everything from 88 to 100...still, you need to put it on a dyno, the main jet is only effective with wide open throttle, wont do anything at low revs...well not that much, midrange is controlled by the needle jet taper and other dimensions, shims etc...

a dyno will tell you a lot...

[adamhearn]

Images have been uploaded showing general cleanliness of carbs and a close up of a couple of bits

Carbs 1-4


Needle and main jet


General pics (dull)


Edited to provided thumbnails

[adamhearn]

The place you listed for the dyno is somewhere where a friend at work has had good experience with (albeit a number of years ago). I'll call them up tomorrow and ask what they could do for me.

Edit: Called; apparently no 'bike people' around today so have to call back Monday!

[adamhearn]

Sorry to keep posting! I pulled the plugs this evening and this is what they look like

Cylinders 1-4:


A couple of close-ups (3 & 4):


The plugs have been in the bike a while but not done many miles. I did clean them up last time I had the bike in bits and since then I've probably done 200 miles.

What wisdom do the plug oracles have to offer? Any thoughts on whether the colour/condition is good/bad.

Thanks in advance!

[adamhearn]

Further update is that I got a friend to look at them whilst they were apart and he said that the o-rings could be a problem. Being an SME he also extracted the 2 remaining fuel filter/needle jet holders as I was rounding out the screw heads and didn't dare continue. The needle jet holders weren't that clean either.

A carb repair kit (£13/carb) adds itself to the parts list which I'll finish fitting when the replacement screws turn up from Cradleys (sadly not held in stock). The o-rings I took out were like cardboard and the news ones soft; the needle jet holder was very shiny compared to the old one Rather stupidly I also split the fuel hose by not being careful enough when turning the tank to sit on the seat; such as life! Another part on order from Cradleys.

I checked out the leads, all seem OK. Sparks were given a good brush up with gaps rechecked. Will get some news ones if after putting it back together the problems continue.

[adamhearn]

Carb repair kit (o-rings, needle valve), new fuel filter and pipe (I split the original) installed.

1st attempt I had fuel pouring out of the 'overflow' outlet between 1&2. Stripped down again, light clean and back together. Saw a small hair across the o-ring on one of the fuel filters so perhaps this was this issue as putting them back I've no leak this time.

But, whilst it's not leaking it's not running correctly. What it's doing now is feel a little hesitant across the range of revs I tried (<8K). It also sometimes hangs at around 2-3K and is prone to stalling on light throttle from idle.

I'm pretty certain I've tightened the header rubber clips up correctly and the rest of the carbs have had new seals all round so I'm hoping no air leaks. The carbs haven't been balanced yet as I don't own any gauges though will have someone do that hopefully this coming week.

I've set the mixture screws to 1.75 turns out (manual is sorta vague I thought!). My L4 has 30mm carbs with 88, 90, 90, 88 main jets. Anyone have any ideas to try?

[banner001]

Carb repair kit (o-rings, needle valve), new fuel filter and pipe (I split the original) installed.

1st attempt I had fuel pouring out of the 'overflow' outlet between 1&2. Stripped down again, light clean and back together. Saw a small hair across the o-ring on one of the fuel filters so perhaps this was this issue as putting them back I've no leak this time.

But, whilst it's not leaking it's not running correctly. What it's doing now is feel a little hesitant across the range of revs I tried (<8K). It also sometimes hangs at around 2-3K and is prone to stalling on light throttle from idle.

I'm pretty certain I've tightened the header rubber clips up correctly and the rest of the carbs have had new seals all round so I'm hoping no air leaks. The carbs haven't been balanced yet as I don't own any gauges though will have someone do that hopefully this coming week.

I've set the mixture screws to 1.75 turns out (manual is sorta vague I thought!). My L4 has 30mm carbs with 88, 90, 90, 88 main jets. Anyone have any ideas to try?

ok, leaking fuel from the overflow means that you have either put the fuel needle in incorrectly so it wont seal, or your carb fuel filter o-ring is damaged, or (usually most likely) your fuel floats are too low...they should be at 11mm...yours were obviously the o-ring.

what were your air mixture screws set too before? sounds like you are rich in the pilot - low rpm range, back off each mixture screw 1/2 turn and see how the bike runs, then it will be a case of doing 1/4 turns in (richens mixture) or out (leans mixture) to get it spot on.

FYI i have 32mm carbs, de-snorkled airbox with k&n filter, 100 main jets, my mixture screws are set to 3-turns out, and i might nip them out another 1/4 turn next time i get the carbs out.