ZX 9 still running rough.

[Dunn-y]

Basically since I bought my ZX9 it has had a rough idle and has ran rough at low rpms.

I have had the valves checked and adjusted. Carbs cleaned and balanced, twice. All mixture screws have been adjusted per the manual and there are no noticeable split or cracked hoses anywhere. Plugs have been changed, so has oil / air filters, oil and the battery checks out but it still runs rough to the point that cruising at anything below 40 - 50mph is almost unrideable.

I'm ready to give up on this bike now as I have no idea where else to look? My next option is simply to buy / borrow another set of carbs to see if that cures the problem to help[ narrow down what the cause is.

Any ideas on where to start looking would be very much appreciated. Thanks

[Ninthbike]

Basically since I bought my ZX9 it has had a rough idle and has ran rough at low rpms.

I have had the valves checked and adjusted. Carbs cleaned and balanced, twice. All mixture screws have been adjusted per the manual and there are no noticeable split or cracked hoses anywhere. Plugs have been changed, so has oil / air filters, oil and the battery checks out but it still runs rough to the point that cruising at anything below 40 - 50mph is almost unrideable.

I'm ready to give up on this bike now as I have no idea where else to look? My next option is simply to buy / borrow another set of carbs to see if that cures the problem to help[ narrow down what the cause is.

Any ideas on where to start looking would be very much appreciated. Thanks


You have done all of the obvious things. My next step would be the plug caps/HT leads as any short here could cause rough running which may disappear as more fuel is delivered. After that would be coils. Good luck.

[wideguy]

Check for vacuum leaks around the carb mounting boots?

[Dunn-y]

The rubbers look good, no noticeable cracks and look like they are sealing properly. Will have to check the coils next.

Anything else I can check? It's only at constant throttle below 4000rpm and idles rough. Give it more throttle and it just pulls smoothly, no hesitation or spluttering.

[SV650Racer]

Sounds like the pilot jets are still blocked or the emmulsion tubes are worn.

Ideally run it on a dyno and you will soon see if its fuel or electrical.

[atassiedevil]

Get some carb/brake cleaner or easy start too, spray it around the carbs/inlet area. If it's an air leak, revs will rise. This will eliminate that possiblity straight away.

[Dunn-y]

I sprayed some carb cleaner around the carb boots when it was idling and there was no noticeable change in the revs so I don't think it's a leak there.

What I have noticed is that if I rev it slightly, maybe to 3 - 4000rpm the revs drop below idle then raise back up. The mixture screws were set to 2 turns out which is what was recommended. They are now 1.5 turns out and it still does it. Not sure if this could help narrow down what the problem is.

I'm due a valve clearance check now (4000 miles since they were last changed) so I might as well just strip everything off it and triple check all hoses for cracks or splits and give everything another clean.

Never checked valves before so this should be interesting.

Not sure if relevant but I also loosened the bolts for the TPS and with the idle at 2000rpm there was no change in the idle speed when I moved the TPS to different positions. Reset it back to how it was now but I thought adjusting the TPS would have some effect on the idle speed.

[Red Herring]

Blocked/gummed up pilot jets seem to be getting more and more common place, especially if the bike has been sat for any period of time. It took me three attempts to clear some recently on a 600 Hornet. You need to do more than just remove them and blow through with lung power. Soak the passage ways for several minutes in carb cleaner and if you can pull a wire out of a wire brush they make quite effective "agitators" that you can use to prod gently inside, and then give it a proper blast through in both directions with compressed air. Don't forget to do the same with the emulsion tubes but be careful with the wire as some have a "cross" in the middle of the tube.

[yorkie_chris]

What I have noticed is that if I rev it slightly, maybe to 3 - 4000rpm the revs drop below idle then raise back up. The mixture screws were set to 2 turns out which is what was recommended. They are now 1.5 turns out and it still does it. Not sure if this could help narrow down what the problem is.

That is usually a sign of rich running. Sticky chokes or incorrect float heights.

[Dunn-y]

After riding it again today it does feel and sound as though it is misfiring / stumbling.

Will give all the jets and carbs a good soak over the weekend and adjust the float heights. Don't think it's the choke but I'll double check that as well.

Thanks for all your suggestions. I'll let you know how it all goes. :D

[yorkie_chris]

Don't soak the floats in carb cleaner and be careful of rubber parts

[Dunn-y]

Thanks for the heads up.

[Bibio]

Sounds like the pilot jets are still blocked or the emmulsion tubes are worn.

check your plugs to see what condition they are in. put a fresh set of plugs in and if all is well then starts to run rough again then it's the emulsion tubes/needles are worn.

[Dunn-y]

How can I tell if the needles / emulsion tubes are worn?

[Sid Squid]

Take the diapragms and slides out of the carbs and examine the needles carefully, there will undoubtedly be some polished areas on them, but if they're visibly worn you should be able to see it. The tubes should be perfectly round but if there's wear there will ovaling on the side of the tube toward the engine. Unless it has high mileage or if Dynojet needles, (otherwise known as "carburettor files"), have been fitted, the the symptoms you're describing wouldn't make me suspect these parts initially.

[yorkie_chris]

I don't think the zx9 was one of the worst culprits for emulsion tube gouging, they cause a boggy slobbery rich feeling as a transitional thing when coming up from idle to midrange if worn.

[Dunn-y]

Mine pulls like a train as soon as you give it more than 1/10 throttle but for cruising around at 30mph and even 40mph it's a joke. Going to pick up some washers to shim the needles and may even get a +4 ignition advancer as well depending on funds but only after the essentials have been done and it's running smooth, or at least as smooth as a 9 can low down.

Forgot to mention. It's the E1 I've got which apparently has pretty sensitive carbs.

[yorkie_chris]

Is it surging at all? That's generally a strong sign of lean running like blocked pilot circuits.

[rb8989]

Ultrasonic clean the carbs? Not too expensive or if they can be separated I will do it for a fiver.

I find with a good cleaning solution the ultrasonic cleans really well, it is in fact why I bought my unit, set time temp and timer, go have a tea and come back to clean carbs, blow through with air and at least you know youve got everything.


Also good for engine parts before you put them in an engine..

Anyway, maybe ask the guys at redmonkey?

[Dunn-y]

Is it surging at all? That's generally a strong sign of lean running like blocked pilot circuits.

I think surging is probably the best way to describe it. It's like riding a kangeroo. But if I then blip the throttle, it revs up fine but then it will dip down below normal idle speed before returning to 1000 - 1400rpm. (Yes, the idle is that rough)

[Dunn-y]

Got most of the fairings stripped off. Now does anyone know a good way to remove seized bolts? I can't get the right side fairing, belly pan or tail off due to seized bolts. Doesn't help that they were already pretty much rounded off from the last owner.

After removing the nose and all the ram-air ducts I found some of the worst wiring I have ever seen. Whoever fitted the gear indicator and heated grips obviously didn't know how to do it properly. They have spliced the heated grips and gear indicator into the front headlight wiring and clocks by using glue from a glue gun to bind them together and then didn't even cover them over with tape. So I've removed the gear indicator and the wiring from the heated grips and will repair the damage this week.

This is how far I got before I packed everything away today.

http://forums.sv650.org/picture.php?albumid=816&pictureid=7478

I'm thinking of getting some new indicators as well as I've somehow lost the plastic cover off one of the front indicators. May also replace the rear tail light with an LED one depending on how much they are.

[Dunn-y]

I've managed to get the lower fairings off now by removing the mounting brackets which hold them to the engine case.

The bolts holding the fairing to the brackets are rounded off and possibly seized. What would be the best way to remove them? I would have normally thought heat but that would damage the fairing.

I've also got a seized cross head bolt on the tail which just won't budge and I can't get any grip on it as it was so chewed up from whoever last tried removing it that I'm just chewing it up even more.

http://forums.sv650.org/picture.php?albumid=816&pictureid=7479

Any tips on how to remove these would be appreciated. Thanks

[maviczap]

Drill the head off it carefully, once you've got the fairing off, grab the stub with some grips, but treat the stub to some Plus Gaz

[Dunn-y]

Thanks. I'll give that a go tomorrow.

[Sid Squid]

Get a flat head punch about 1/4" and carefully reform the head of the screw. The action of whacking the end can help in shocking the screw free, and if you're careful you can make the screwdriver fit in the screw much better.