how to fix carb stumble on 2000+ 9r's?

[zed]

Great write-up and pictorial e1_ZX-9r, I'll have to give it a try in the spring.

[3cylinder]

Might try fuel mixture screws, carefully remove the factory seal and adjust. Mine were anywhere between 1/2 turn out to 1&1/2 out. I set mine all at 1 & 1/2. Really helped the bike.

[atleastitsnotaford]

1&1/2......hmm, maybe i need to go back into mine. supossedly it had a jet kit put in........but i have m,y doubts based on some other factors, but all mine were at 2&1/2 and mine is an absolute pain to start when cold, and will not run above idle untill about 113 degrees!

...........................? what are the stock jet sizes? and where was that pic of the top of the stock needle?

[e1_ZX-9r]

Thanks Zed!

"Atleastitsnotaford," I think your 9 would benefit from a carb and cylinder checkup. I hope too that you are using your choke/enrichener during cold starts.

To test, try starting it cold. When it's at its worst, turn it off and pull the spark plugs. I would imagine the tips should be black and wet, assuming the enrichener is dumping non-atomized gas in. Plug color can tell you a lot about how your bike is running.

There are lots of possible solutions, from valve float to leaking carburetor intake boots. Click on my e1_ZX-9r handle on the left and see my other posts. I've posted a bunch of info done to mine that might help you get your 9 straightened out.

BTW, to test if your intake boots are leaking, begin with the engine cold and a water hose near by. Start the bike and run small amounts of water over the tops of the intake boots & carbs, if the engine stalls or stumbles, you have an air leak between your carbs and cylinder intakes. Maybe simply a loose fastener.

[alfredo21]

The guy that had it before me said he put an ilegal exhaust it says texas on it. Very loud also said that something was done to the cam to make it go faster and that why it feels jerky. can you verify that. Also noitice like a sudden miss or kind of backfire, at times at low speeds 1st 2nd gear. The guy that owned before me said is because the bike had been modified and something done to the cam. That it was not meant for crusing but raising. Any imput on that.

[atleastitsnotaford]

illegal exhaust.........says texas.....very loud......prolly a D&D exhaust built in texas and known for being loud. violates most city ordinances for noise

i have "something done to the cam" in my car, and it doesn't have any jerkyness. sounds like its ****ed up when it's idling, then has a surge of power around 3k rpm, but no jerkyness.


e1...valve float......when starting? have checked for leaking carb boots. have checked lots and lots of stuff. i still think that when the original owner installed the jet kit, he did it himself, and did not do it right. something was left out, done wrong or something.....i have doubts that a jet kit was even used. he may have just messed with stuff in there till it ran better. i do use the enrichener, but it doesn't work right. bike won't start without it unless it's close to 100 degrees outside, and doesn't raise the idle speed any when its on......... bike also dies if you touch the throttle before its warmed up. i could swear i remember seeing 038 on one of the jets in there. if these bikes needed a bigger idle jet to begin with, and i've got a muzzy exhaust and k&n filter i would think i surely would benefit from a larger idle jet?

[e1_ZX-9r]

Ford, I'm guessing you have a C, E, or F model if you see a #38 pilot jet. The jet needles & mains are all over the map for the B, C, E & F, so there's no single answer for everyone (what are the stock jet sizes?). What year is your bike? I think rejet kits come with #40s.

Assuming all other engine maintenance is correct & the engine is sound, you might be best off just buying a used set of carbs for your model on eBay. I saw one lucky bastard pick a set up for $15, but they normally run $150+. Still cheaper than taking it to the shop, plus you'll have more jets and replacement parts for the future. Yeah, I know, valve float while idling sounds stupid, but if they've never been adjusted, like mine were getting by 7,500 miles, the cam will just drag the entire rotation and hold the valves open.

For reference, if yours is an E1/2 you can see all the stock carb settings, along with how mine is configured and driving impressions here on my profile.

[atleastitsnotaford]

sorry bout that. I thought i'd put my bike in my profile, but i guess i missed that one. it's a 2000 zx900e1

as for taking it to the shop........not unless they can do it cheaper than i would charge, or if i don't have the proper equipment like a tire balancer, and (as for right now) a chain riveter.it's cheaper to pay the shop to replace my chain/sprockets while they're doing my tire than it is for me to buy the rivet tool, so i'll pay them for that, but most work, i do myself.

the carbs on it are fine (everything intact) if one were cracked or had stripped threads, yeah i'd opt for a used set, but they just need tweaking. i think the "jet kit" the original owner put in was just backing out the fuel mixture screw till it quit popping.

[e1_ZX-9r]

I don't really need them now that my ZX-9r's CVRD carbs are tuned, but for $75 shipped, I couldn't resist. There seems to be carb sets there, from a bike that's being parted out, about every other week in this price range; one expires tomorrow. For those of you with carb troubles, poorly tuned carbs, or just wanting spare parts (like me) to compliment your current set, eBay's a great resource. Sincerely, Mr. parts hog.
Keepin her on the road has never been so easy.

[atleastitsnotaford]

got my head open yesterday, no surprise all but 2 valves were out of adjustment............surprise all but 1 are only off by one shim size. I thought it would have been much farther than that.

lucky though I only need to buy 10 new shims after reusing some on other valves.
weather permitting I'll be riding it this weekend, I'll let keep you posted

[rileydeed]

OK mine's fixed. To try to make a long story short as possible, I cleaned the carbs, adjusted the valves (all a little tight before adjustment), put in size 40 pilot jets, set mixture screws at 2 turns, and did the four degree advance. One thing at at time in that order. Each thing helped a little. After the pilot jets it was almost perfect, with just a tiny flutter between 3800 and 4200 rpm. The four degree advance fixed that and it runs better than ever. If I had to do it all over I would have started with the advance. Also from everything I've read, it sounds like the Factory Pro jet kit (which comes with size 40 pilot jets) or the Ivans might be the best way to go. They are more expensive than the Dynojet (which is what mine had in it when I bought the bike), but I've seen a fair amount of negative feedback about the Dynojet kit for the 2000 and 2001 ZX9s.

[HPM]

Okies, I've had a good read fella's so I will just summarise what I intend to do:

I have a 10/2000 ZX9R - I assume is an E1. I have a Jardine pipe which I assume has not had the carbs jetted accordingly.

I have "lag" on the early rpm stage, fine other than that.

I will remove the carbs and check the idle jet #, will also record the main jet # - if they differ from your posts - I'll come back to the forum.

If all the same - ie #38 and #160-165, I'll up the idle to #40. Then replace all items and test run.

Sound fair?

[rileydeed]

Originally Posted by HPM

Okies, I've had a good read fella's so I will just summarise what I intend to do:

I have a 10/2000 ZX9R - I assume is an E1. I have a Jardine pipe which I assume has not had the carbs jetted accordingly.

I have "lag" on the early rpm stage, fine other than that.

I will remove the carbs and check the idle jet #, will also record the main jet # - if they differ from your posts - I'll come back to the forum.

If all the same - ie #38 and #160-165, I'll up the idle to #40. Then replace all items and test run.

Sound fair?

While you have them apart, it's probably a good idea to have look at the needles. If they don't have grooves then it hasn't had a jet kit installed and you may want to add a shim under it as outlined by E1 or spend the money for a jet kit. I do think the 40 pilot jet was helpful on mine, but mine had a Dynojet kit done before I got it and my problem wasn't quite the same as the classic carb stumble. BTW the pilot jet is a model N424-74C size 40.

[HPM]

Cheers, your advice has helped me a little - pilot jet is a #38 on mine. I am swapping over tonight and will road test at the weekend. I'll post up the improvement if any.

[o2bazx9]

hey when you put your carb caps back on if you cant get the slides to seat properly use a little bit of vaseline in the groove to help hold it in. i took my carbs apart close to 15 times trying to find out why it wouldnt rev under load! turns out that the slides didnt seat properly under the caps. worked on them for 3 hours a day for 3 weeks turns out it was that simple

[HPM]

Thanks guys, in the end, I've cleaned the carbs - left jets all stock standard (no kit installed), balanced them with the air box on (manual says take it off) and now I have smooth grunt all the way from 2000+. Maybe I'm lucky?

[HPM]

^^^Nup - scratch that, went crap arse again - I may have to do the Ivan's Kit.

[rileydeed]

From all the research I've done I would go with the Ivan's too. I've even considered tearing mine down and upgradeing to Ivan's even though mine is running pretty good.
Anyway good luck.

I've heard that parts of Australia have some pretty fun roads. What's it like in your area?

[e1_ZX-9r]

Sorry about being a post whore here - Riley, great work finding the #40 pilot jet size and sharing.

My project is complete. 899cc mostly stock Cali 2000 ZX-9r, main jets lowered 4%, not the 8% Kawi recommends for operation above 4,000.' Wish I would have started with the carburetor synchronization first. I am positively nuts about riding my bike now. It feels like a new bike, through and through. Easy starting, great performance, 52 MPG - 240+ miles between fill-ups , awesome sound; couldn't ask for a better fit.

You can find my bike's historical information on my gallery profile linked at the bottom, but here's how I would rank getting my carbs dialed in:
Carburetor modification ranking (w/K&N, Supertrapp exhaust, elevation 4,500'), before & after
1) set idle mixture screws. Stock (see profile bottom)- poor idle, mod- 1 5/8 turns out, ideal when combined with #2
2) synchronize carbs. Stock- extreme surging, mod- w/o #3, only between 3K-3.5K and even then mostly unnoticeable. Easiest starting & best throttle response to date. Best results come after completing #1, 3 & 6
3) shim jet needle up 0.8mm. Stock- extreme surging from 2.5K-4.5K RPM, mod- 0.8mm ideal. Excellent torque and surge prevention. Other non-Supertrapp exhausts may need more shim.
4) tune main jets. Stock- excessively rich, mod- dropped two sizes (4.2%) to improve throttle response
5) Supertrapp discs & throttle response. Mod- 6-8 discs for stock/neutered like feel & high MPG, 9 ideal, 9-10 for superior torque & horsepower
6) float height. Stock- off, but good, mod- 4mm hard starting, 5mm ideal
7) K&N air filter must be saturated with K&N oil and/or 10/40 motor oil. Excess oil must be drained off, for best results.

[HPM]

Originally Posted by rileydeed

From all the research I've done I would go with the Ivan's too. I've even considered tearing mine down and upgradeing to Ivan's even though mine is running pretty good.
Anyway good luck.

I've heard that parts of Australia have some pretty fun roads. What's it like in your area?

Yes we are spoilt here, great weather - blue skies no clouds even 30 degrees celcius, dry warm roads....