bike runs bad after about 30 min.

[wisc]

Hi, I have to take my bike to get a tune up/shims checked. but before i did i thought i would ask here see if anyone can help me out to save a bit before i take it to the shop.

after about 30 minutes of riding (more-so at 100kph) the bike seems to start playing up. under heavy load it seems to be choking and there seems to be a flat spot when taking off from lights etc.

i think its running fairly rich, and is chewing the full tank in 190kms.

it has an exhaust and has been re-jetted with dynojets. I've only had it for a couple of months.

I know fuel expands when it gets hot so I'm assuming it has something to do with the fuel system...

its a zx9r 98(DEC) c2

any ideas on what steps to take?

[Rossi]

Check the breather from the tank first

[mike-s]

a quick check for the above is if you have a spare key. Take her out for a spin and wait for the symptoms to occur. When they do, open the tank and immediately close it, does it still have the same issue?

If so, your breather hose is blocked or the vent itself is stuffed.

If it doesn't fix it, i have to ask, what stage kit did they put in, and does the bike have *any* work on it aside from airfilter and can?

Do the problems specifically relate to load or do they reliably relate to degrees of throttle opening? and if so, what points on the throttle?

I'm asking this because this relates to what circuit(s) is(are) out, pilot, needle taper, needle straight and mains, each has a specific point it cuts in and out at, but is affected by and affects the circuit either side of it if it is out)

[wisc]

Thanks guys seems reasonable, will try the fuel opening after i get a spare key cut and go on a longer ride.

not sure what else has been touched, i know its got K&N air filters, dynojet jets and the exhaust, asides from that looks pretty standard.

not sure what jets its got in it as it was done before i got it.

I *think* its really happens when you snap the throttle a little sharper, like last night after hitting it pretty hard at a few sets of lights the last one i tried it sort of choked like its not breathing properly then it his power all of a sudden again....
usually when i open it up in sixth on the freeway and it has the problem it just keeps joking and accelerating slowly.

next ride i go on ill try to collect more info

thanks for the stuff so far.

[photomike666]

Is it running hot? What condition are the plugs in? How long after stopping does it take to be OK again? Have you got enough oil etc. It's usually something simple.

[FrogZ]

Ah the bueatiful kwaka vent, used to park my exes bike in the front room (mine was in the cold) and it used to wake me up at 3am when it got cold and started venting. Took a long time to track it down.

Other than that it sounds rich, both the description and the not til it heats up thing. What happens when you pull the choke on, MUCH worse I would think.
Any dynos around?
They should be able to do a quick cheap test run so you will KNOW....

[wisc]

Is it running hot? What condition are the plugs in? How long after stopping does it take to be OK again? Have you got enough oil etc. It's usually something simple.

on the gold cost this week for work so cant do much testing:(

Plugs looked pretty good, just did an oil change so that should be fine.
Usually takes about an hour maybe? Haven’t been playing round with it for that long so I could be completely wrong.

I think I tried the choke on and it was worse will check it again next long run i go for.

Going to Bendigo this weekend so it will be a great chance to test all the helpful ideas people have supplied.

Thanks

[kwakarider00]

I have the same model ZX9 and like you, suffer the exact same probs. I would suggest its a Carby Iceing problem, if you're in Southern States, as I am. The 99 or 00 Model I think, had a modification fitted as std and it was available as retrofit for 98/early 99 models, but of course, no longer avail.

Whats happening as I understand it, is that at constant throttle opening and constant load, ice is forming in Carby around jets and its only when the flow changes (accel or load up) that it clears it. If yours is like mine, it runs fine on warmer days and is only riding this time of year or early morning, that problem becomes aparent.

Fix - not sure yet. Brighton Kawasaki suggested some stuff for me to put in Radiator (haven't tried yet) and Race Replica suggested a line of tape around outter edge of Radiator fins, to increase running temp, this time of year.. As mine is pretty much a fair weather bike, the tape hasn't been fitted yet either, but I was thinking this is the cheapest and easiest to start with.

Give it a crack. I'd be interested in your findings..

Geoff in Melb.

[SocialSecurity]

after about 30 minutes of riding (more-so at 100kph) the bike seems to start playing up. under heavy load it seems to be choking and there seems to be a flat spot when taking off from lights etc.

ive had the exact same problem. turning the pilot screws in would help to an extent, but getting the mainjets, needles and float level set right first helps alot.

pretty classic sign of running too rich there... mention all the symptoms to the mechanic doing the tune up.

[mike-s]

do a search for dynojet and look for posts put up by myself (there are others, but i know i linked to uit at least once), theres a tuning guide linked in somewhere.

Basically it tells you to check mains first, then work your way down through looking at the needle height then the pilot screw, then the float levels. Each of these have a impact on the next to be checked, but not really much on the previous (i.e. mains affects needle height, but needle height doesnt affect mains/WOT, etc)

Besides i would have thought unless you were in the middle of jindabyne in mid winter, it'd take a lot less time than 30 mins to warm up. Perhaps 10 mins max.

But if its just off idle i agree, try turning the pilots in a half turn.

Remember, if the engine is cold and its fine then it goes to crap when warm, its running rich. Also if it runs piss poor when cold and goes great after a little while, its running lean.

Why? well when the carbs are cold and the fuel isn't being vapourised as effectively as when its up to operating temperature. Only part of the fuel is being burned, the rest is going out the exhaust. When its a bit lean, it'll be running v-lean until it warms up and its vapourising the fuel correctly. If its running rich, it'll run great until it all starts vapourising correctly.

A good compromise and one i thought they aimed for (well i do anyhow) is to get it to splutter a TINY bit for the first two to three mins, and then runs great afterwards. For me this means i've suited up and gone a max of maybe two km from home and am still babying it. Also remember this behaviour is better/worse depending on your location (brissie vs canberra f'rinstance) and the current season.

[SocialSecurity]

that would be this guide


what kind of pipe does it have? and is it a full system or just a slip on?


personally i would take the dynojet kit and throw it in the bin.... try and return the carb settings to stock and then see if it even needs a tune, should run fairly well with a slip on... also an idea to throw the K&N filter in the bin too, if you have the stocky then chuck that back in minus the steel mesh... as long as its clean and not over oiled it will flow just as well as anything else and present less of a tuning headache


see what your mechanic can do... there aint many out there that can make a 9 run perfectly thats for sure

failing that, grab a ivans or factory pro jetkit and follow the instructions, they give pretty good tech support too.

[mike-s]

i bought a dynojet kit, even with a full system the smallest jetkit and holes drilled in the airbox to lean it out that bit more it was still running around a 10:1 ratio. Good for snap crackle pop on the rolloff, but a couple HP short of its potential. used the dynojet kit needle spring, etc and the oem jet it behaved a lot better.

Even now i think i the main needles need to drop 1 notch, but given im tryin to sell the thing (the guy has been giving me no end of runaround due to screwups he has had at work) i cant really be arsed taking the tank off and dropping the needles now.

*sigh*

[SocialSecurity]

dynojet make some good jetkits, but certainly not for the ZX9R.

the factory or ivans is only a few bucks more, but you get a hell of a lot more for your money... and the results are there

[wisc]

Thanks guys that’s certainly given me heaps to play with before I take it in to get it looked at, cant wait to get back to sunny old Melbourne from this drizzly gold cost weather…. (Working not pleasure )
Actually cant wait to get back to get back on the bike and go for a nice cruse to Bendigo to help fault find…

It’s only a slip on micron exhaust. Found out last week that there where a few tiny holes in the exhaust pipe, so will probably trade it in for a system when I get a chance and the cash.

I didn’t think it would be ice as you’d think the bike would to hot for ice and id imagine it would happen earlier and ease up after I long ride, but I guess you never know with all the cold air flowing in.

[SocialSecurity]

if it starts to run really bad in stop go traffic, and starts to get really hard to get the bike off the line then its definately a mixture problem rather than icing... particularly in the pilot circuit