www.zxrworld.co.uk

Guys,

Please help. I cant figure this one out at all.

I got a ZXR400 L3 in a swap, apparent 'wiring problem'. I sorted the wiring and fired it up but it doesnt want to rev. I have done the following:

Changed the carbs, no difference
swapped with a known good loom, no difference
Changed head gasket, starts better but still doesnt want to rev
Replaced cam chain, not related but the tensioner was fully in
Checked the valve clearances, all about there (ish)
looked at head when doing gasket, looks okay but then I would spot a bad 'un anyway

When you first start if from cold it will rev (just) but as soon as you put it under load it will just die. The problem also gets worse as the engine heats up to the point where when you touch the throttle it just dies.

Any suggestions, anyone got a spare engine?

what happens with the choke at cold? do you have any choke on? if you do put it on does it die? Sounds like its far too rich. What size jets etc are in it?

thanks but I dont think thats it.

It needs choke to start and will die if choke is taken off too early (say 30 sec). Once warm it settles into a nice easy idle but just wont rev. Note I have changed the carbs anyway so the likelyhood of a mixture problem common to both sets is low.

The air filter is manky though but the bike is exactly the same even with the airbox removed.

I did notice carbon build up on one of the valves during the teardown. I have now compression tested the engine and found the no 2 cylinder is low on compression. Do you think a burnt valve seat could be at the route of this?

I give up. I'm going to get a replacement engine off ebay or go the whole hog and pay 300+ for something that will defo work from AMS.

Doing my nut in though!

M

Fuel filters all............... 6 of them ?

Fuel pump ?

Tank breather ?

Fuel tap ?

fuel pipe trapped ? correctly routed? and fitted right way round on fuel pump ?



Float heights ?

Ignition pick wiring OK ? the bit inside the casing can go brittle and break down

Spark plugs all ok?

HT leads all present and correct ? connections good?

Coils ?

And as ever how did the problem first appear ?
Did you or someone else perform some task or repair just before the problem started

Thanks Cargo,

Bike was a basket case brought to me so I know no prior history.

Not fuel, bike does it with fuel tank off, fed by temp fuel container (washing up liquid bottle). And also absolutely no difference with two different sets of carbs, so not float hieght.

Pick up wiring not brittle as there is a self lubricating thing going on from the timing cover (no gasket).

Coils...mmm....Coils....mmm these can break down with heat and revs!

Plugs look good though.

Will try coils and plugs cause they are cheap before I do anything else.

Ta.

Mark

You keep saying it isnt fuelling problems but thats what it is. Simple as that. If the bike starts then everything is working, the only variable to it working is when you open the throttle, which is connected to the carbs which control what? Thats right, the fuel. Its not impossible to have two crap carbs, Im currently sorting out carb problems on my girlfriends bike, been crap since we bought it and Ive never had the chance to do anything with it, Ive got 2 identical carbs. One came on the bike and one I bought off ebay, which i expect is the same situation as yourself. Now, I dont know who did what with either of them, and neither do you, even if you bought them brand spanking new they wouldnt be setup to run on your bike specifically because the same carbs are probably used on a range of engines other than Kawasaki.

Assuming you have no mods, such as ignition advancer, uprated air filter or race exhaust, then you will need to find the standard settings for the carbs and set them to those settings, take a look at the main jets and check they are not a different size to what they should be, check the pilot/air screw and see if thats different to the standard size, and then if thats all done then check the floats. Could be the tangs are too bent and not allowing enough fuel in to allow it to get passed idle. Just because a bike idles doesnt by any means mean that theres not a fuel problem. Only if it wont idle or burp at all is the problem elsewhere such as ignition etc.

For the bike to idle it only really relies on the idle screw and pilot jet whereas once you start to twist the throttle youve got roll off from pilot, main jet, needle jet, jet needle, jet needle position (upto 12 varient positions), diaphram, venturi vacuum (sync), float and emulsion tube to worry about. So as you can see, idling dont mean crap in the 'My carbs are fine' way of thinking.

I have to wonder if your asking for help or just posting to whinge about it. Do something constructive and start taking onboard what most of the forum members have told you already.

If no 2 cylinder is low on compression, does it make any difference if you take no 2 cyl ht lead off. I'd get that sorted if its major low as its probably blowing or the valves aren't seating right.

Thanks for your constructive critisism Jesta,

I am fully aware of how a CV carburetter works, thanks however for the lesson. At no point did I rule out carb internals, I simply said that the problem was still there with the tank removed (i.e not fuel pump/tank/filter) and there was 'ABSOLUTELY NO DIFFERENCE' in running on two independant sets of carbs from differing sources and backgrounds. In this life there is no such thing as a certainty but if it looks like a duck,walks like a duck and quacks like one, its probably a duck!!

The reason I got another set of carbs in the first instance is that the most obvious answer is carbs as you so rightly point out. I suspected the diaphrams at first as if these are perished or damaged the slides wont lift. but I have checked them out and are fine. I've also had the float bowls off and the carb internals - both sets - show no grit or varnishing. I didnt check the main jet size when in there so thank you for that suggestion and I will eliminate that from the list of suspects.

The reason for posting here is that this is a repository for information on this bike and a damn good one so I accept all suggestions including those from people who are convinced that the carbs are at fault.

In the interrim I'll get the compression problem sorted, change the coils (as helpfully suggested by Cargo) and see what happens. I am still open to any suggestions about what the problem could be INCLUDING known common issues on these bikes like carb slider wear etc. I have just got in contact with a local ZXR owner so I can get hold of a third set of carbs to make three sets of carbs with identical problems and will try this next.

I am trying to fix a bike, ride a bike, enjoy a bike, not whinge about anything. Thanks for your input, it is appreciated. Your technical advice is recieved gratefully even if your attitude and use of condesending prose irks.

Cheers mate.

Mark

Mark> My apologies if I was a little out of harmony, Id been awake for around 21 hours at time of posting and spent the entire day faffing around with my girlfriends carbs so was more than a little agitated with the whole world, then went on to make a 33hour day before passing out on the futon lol. There can be more than just the carb problems, especially your cyclinder problem which I managed to miss (probably due to over tiredness) valves gapping is also a known problem with any bike to make things run pretty crap even with good carb config, what mileage is the bike on currently?

I finally fixed my problems by drilling out the carb slides to 3.5mm in the needle slot and then fitting the standard needles from my zx6r as they are a much better profile, the bike runs helluva nippy now and handles superbly.

The purchase of a carb tune may help too, for the cost of having a garage due it (40/50quid) it cost me 62quid for the carbtune pro inc delivery, its 55 if you dont get the pouch/case/holder thingy but id well recommend it cos itll only get beaten up when not in use and youll only want it once a year. Took me 5mins to get the tank and air box off then another 5 to get all the carbs running perfect! Garage will charge you an hours work yet it takes 15 mins to get everything taken off, tuned and then put back together. Youll save yourself alot of money, its pretty blissful doing it yourself and knowing that its done right since so many garages are using old worn out ones, and then the mechanic can have a bad day and just not bother to get it all that accurate.

Not only that but you can do your friends bike for a tenner and youll be into profit in 2bikes time!

Theres some tech specs for the L (which Im assuming yours is from your name) on this site under the manuals section, has all the stuff your really really want for a bike but can never find, such as pilot screws out and main jet sizes!

Girlfriends bike is a L5 so if you wanna do what I did with the carb slides and Id recommend it to anyone here, then it should be ok for your bike too as there the same carbs.

James

Glad to hear you got your harmony back James. No issues at all mate. Thanks for the great advice.

I've got a viffer 750 streetfighter as well and that is doing about 20 to the gallon at the mo (mainly due to the fact I ride it in first and second with the front end airborne too much) but that could do with a balance as well so your economy tip is spot on. Even better, with the price of petrol these days if I get another 5mpg out of the VFR the vacuum gauges will pay for themselves in a couple of months anyway.

My engine is in bits (zxr400) at the mo so do you know how you can test to see if a valve is seating properly? Mileage is 55km (30 ish k miles) and I've picked up on here that that is head issue/cam chain time anyway so I think this is just par for the course.

TBH I am probably going to have to bite the bullet and get professional help. I'll take it down my local hospital (head cams, caps, shims etc) and get them to diagnose any probs and give a cost to check head is flat, fix, revalve and shim.

Once thats done I'll be right back for advice on carb set-up I'm sure.

I havent even ridden the thing yet so I'm hoping its all worth it.

Cheers, Mark

Lol, there not that great (cue argument) I bought mine when I passed a few years back, 19years old, cheap to insure, wanted the zx6r but it was 1200 for TPO insurance! glad I got the 400 in the end though cos it was a nice step up from my rs125 but not as stupidly powerful as the zx6r i ride now, I bought my girlfriend one after she passed her test for christmas last year as i figured it would be perfect height for her at 5' 4"ish, and it is, and not too powerful either (she got pretty scared just pullin out the driveway on the 6) got 130 out of mine, takes ages to get there, but its a pretty steady and easy ride, its the ideal commuter and perfect for first big bike.

Where about are you? If your anywhere near bristol theres a really really good bike shop, its awesome, its called fowlers and has every bike under the sun (except them horrible harley davidsons) and they do a toad hot deal on maintenance, pretty much everything checked, lubed and calibrated for 350ish fixed price, as for cam chain, when i sold mine the guy was whinging on about cam chain bein dead around that mileage, was bullocks, thing was fine and its just a way to get the price down, my 6 is on 43k and its the same cam chain in it since new (owned it for last 27k miles) and its fine, valve shims needed a few new ones last year (37k) If you can get 20k from a drive chain to your sprockets then a chain thats soaked 24/7 in good engine oil should see you to 50k

fowlers are toad, unless you want to order parts or buy leathers and drink coffee.

when i worked in bristol, i repaired and re-serviced half a dozen bikes that had been in to fowlers for full on services and come back running like shite.. some of the bodges were potentially lethal.. simple stuff, like .. ooh, finger tight rear axles with no split pin in it .. finger tight sparkplugs, loose sump plugs/oil filters, cracked plastics that werent when it went in, carbs further out of balance than when the bike was dropped off.. tried to charge a mate of mine over a grand to replace the "faulty" alternator on his daytona.. 2 months later after he'd extracted it from their clutches and refused to pay their £200 labour bill (for taking the seat off.. cos that all they'd done!) i fixed it for .. free.. it had a blown fuse !

i dont normally slag places off, and they "may" have changed, but i doubt it.. i was there doing some window shopping a few weeks ago and its still a lot of the same faces.

bristol kawasaki are far more knowledgable and thorough when it come's to carrying out work on bikes in bristol, and if its engine work (out of frame), Steve at piston broke is an oldskool engineering genius.

if its done 30k, fit a new camchain it WILL have stretched, i've done 2 this year, one on a bike with 31K, the other on a bike ive owned for 5 years and 50k miles which had the chain last replaced about 25k miles ago, when measured both chains were well past the service limit.

easiest way to see if you're losing compression because of the rings or a valve seat (and which one) is to connect a compressor t the spark plug hole using a compression tester adapter and pump it up a bit.. you'll hear and maybe feel the air leak out the inlet, exhaust, or crankcase..

if the heads already off, just fill the combustion chambers with petrol and see if any leaks past the valves ..

Jesta wrote: got 130 out of mine, takes ages to get there

it wasnt running right then.

Im pretty sure it was, 130 on a small engine, will get to 60quick enough but they have like 20torque and 60bhp, unless your gonna tell me they run at 90bhp at the wheel with a bit of polish? There not fast bikes, simple as that. If the 6r gets to 160 with 100 at the wheel and around 45 torque then how would something with roughly half that manage it? If you tell me the factory setup 6r's are not running right then your more than welcome to have a mess with mine and any bike I own in the future cos you must be some tuning god. According to wikipedia the zxr400 gets 135 top speed, but theyre obviously wrong, what with probably getting the info direct from kawasaki http://en.wikipedia.org/wiki/Kawasaki_ZXR400_(L_Model)

As for fowlers, tbh ive not had anything done by them, but i have not heard a bad thing about them from anyone else and they have been in business for decades, are the uks main importer for most stuff (so a friend, who used to work there as trainee mech said) they must be doin something right as theres only one fowlers in the world and its the biggest bike store ive ever seen. However, noted they may not be that great, thanks, but i dont know anywhere else i would take my bike for engine work, the places round here are sooo bad, never EVER go into FF Motorcycles in wincanton, theyre so shite, the owner/mechanic isnt even trained on vehicles, the place is a toad tip and when I had a tyre replaced by them I wandered back in to find the rim being thrown on the floor in anger cos he couldnt lever the tyre off. Never been back since, I do all the work I can myself as I honestly cant find a garage thats any good, from personal experience. Black Dragon MC's are apparently pretty good, do all the work on my girlfriends sisters bike, but then shes an idiot who collects bikes rather than rides them, sooooo.....?

im not trying to make out that they're rocket ships mate .. but the only time ive had one that would only do 130*, it was suffering fuel starvation, and to date ive had 3 H1's, an H2, an L4 ,2 ZX-4-G's and an L1 (but thats got a 6r engine in it) If it wont hit the redline in top on stock (15/45) gearing, its below par.

do all the work on my bikes myself, pretty much always have, recommend piston broke because the guy really knows his stuff, builds race engine's mainly.. i've not had anything done by him as such but used his workshop from time to time when i was in the trade and he had something we didnt. As for bristol kawasaki, i never had work done by them except getting a couple of tyres fitted, but used to get parts from there, and at least the guy behind the desk knew what he was talking about.

*not counting ones restricted to 180kph ..