Running On 3 Cylinders, In Need Of Help?

[mr ninja]

Hi guys, can anyone cast some knowledge to my problem.

My ZX7R was running sweet as a nut having had the valves recently checked & shimmed and a factory pro jet kit installed. Then a few weeks later firing it up I noticed after coming off the choke and letting it idle for a while it then cuts onto 3 cyclinders, would say after about 7 to 8 minutes.

The cyclinder is No1 which is the culprit.

I have changed the plugs for new NGK Irridiums, have a spark from all HT leads, swapped the coils 1-4 & 2-3, have new fuel. I also have a clean air mod and checked over any air leaks which all checks out without fault. I can't do a compression check atm as I need a reducer to fit the thread

For a while it runs great and revs cleanly for the first few minutes then cuts onto 3, after a couple of minutes on 3 you can smell petrol from the end can.

Can a coil break down when it gets hotter?

Is it likely to be fuel related, stuck float, blocked jet etc?

Help aprreciated.

[BudgetBoy]

Yes coils break down when hot.

If you can smell fuel from the end can i would say you have no/weak spark on the cylinder.

Change coil for a new one.

Swapping the coils over will just move the problem to another cylinder, so it wont help.

[mr ninja]

Ok, so it is possible for a twin pack coil to break down on one side, just some people say that both cylinders like 1-4 would go down?

[V6Jon]

I would have thought if one coil was firing two plugs it would run on two if the coil was failing, but can't say I have seen the 7's setup, maybe it is the HT lead that is breaking down ?

[BudgetBoy]

Answer is YES..They just break down and give a weak or no spark to the plug/plugs.

If you have a multimeter you can test them?(hot & cold) if you get stuck in the meantime im sure someone will tell you how to do the below.

I'm off to my workshop now to do an engine but here are the specs for you.

Primary resistance is 2.3-3.5 ohms

Secondary resistance is 12000-18000 ohms

Firing order on your bike is 1-2-4-3

[Gregorious77]

If you have had the carbs apart, could it be something to do with those?

I have had the needle come unclipped on my 6r before.

Not sure if the carbs are the same but the needle is held into the slide by a push fit plug and spring on top, if this pops off the needle can move independently of the slide and will give the same symptoms that you describe.

Easy to check. Take the airbox off, stick your finger in the carb and open the slide, see if the needle can be moved up and down.

[mr ninja]

Thanks for all the replys, I'm convinced it's the coil & not a fueling issue. It surely wouldn't run for 8 minutes pefectly then cut onto 3 if it was fuel, the spark does look weak, the needle checked out ok when I have had the airbox off and I have swapped all the HT leads etc to no effect. I have just bought a 1&4 coil off eGay so will soon find out I guess.

[mr ninja]

I would have thought if one coil was firing two plugs it would run on two if the coil was failing, but can't say I have seen the 7's setup, maybe it is the HT lead that is breaking down ?

No, they are twin pack coils, 1 pack for 2 plugs but they have each side to them.

[mr ninja]

Put a new coil on and the problem is still there. Well it's beat me, time to call a professional me thinks...

[BudgetBoy]

Put a new coil on and the problem is still there. Well it's beat me, time to call a professional me thinks...

Dont give up.. This is how you learn.

Carbs you say are ok

New coil now fitted (i gathered you tested the old one with a multimeter)

New plugs

Provided you coils,HT leads,Caps are in spec (make sure the caps are fully home on the plug btw,listen for the clicks) then all you have left on that side is Pick up coil & battery

Ask yourself how old it the battery? Can you load test it? Is the charging circuit working (14.2-14.8volts+ at 4000rpm) battery at standstill 12.6 volts MIN.

Your Pick up coil resistance should be 375-565 ohms & the contact gap should be 0.4-0.6mm

Also make sure the pilot screws are 2.25 turns out as well.Were your carbs balanced when the factory jets were fitted?

[lorenzo]

Dont give up.. This is how you learn.

Words of wisdom.

[RonniB]

How about a clogged float valve, 8 min is what you run on the carbs alone, then it doesn't fill fast enough?

And for the sake of elimination, do a compression test (i just identified a wrecked engine by comp test, gives peace of mind)

[mr ninja]

Dont give up.. This is how you learn.

Carbs you say are ok

New coil now fitted (i gathered you tested the old one with a multimeter)

New plugs

Provided you coils,HT leads,Caps are in spec (make sure the caps are fully home on the plug btw,listen for the clicks) then all you have left on that side is Pick up coil & battery

Ask yourself how old it the battery? Can you load test it? Is the charging circuit working (14.2-14.8volts+ at 4000rpm) battery at standstill 12.6 volts MIN.

Your Pick up coil resistance should be 375-565 ohms & the contact gap should be 0.4-0.6mm

Also make sure the pilot screws are 2.25 turns out as well.Were your carbs balanced when the factory jets were fitted?

I went for a new coil as the possible quick fix as I picked up one cheap. I was convinced that it must be that. The plugs are brand new, the Yuasa battery is brand new. I have swapped the HT leads all around but still the No1 cyclinder fails after warming up. I have not delved into the carbs yet apart from checking the needle seating correctly.

What I don't get is the last time I rode it having had the valves checked & shimed and the carbs fitted with a Factory pro jet kit and carb balance, it was perfect, making loads of power and idled & revved superbly. I put it back in the garage went out a few weeks later then this??

Trying to be as accurate as possible, it starts on the choke easy, take the choke off after a minute and it idles ok, start gently revving it to warm her up, no problem then it cuts on 3 and if you leave running it then seems worse where it sounds like a bag of nails (2 cyclinders?) and will not rev at all stuck on 1,300 rpm with slight throttle, let go of the throttle and it dies, stops.

So maybe it is a fueling issue or worse? I havn't got the right size adaptor to fit my compression tester.

[mr ninja]

Also one other thing to note is I have a clean air mod, common to 7R owners. When I fitted the new coil today and wanted to check that the airbox was sealing correctly I noticed that there was fuel in the hose that connects to the top/front of the airbox???

[lorenzo]

Flooded carb on the one cylinder from a stick open float, fuel burping back up through the carbs? Total guess. Was the fuel properly fuelly, ie clear petrol, or could it have been oily blow by stuff from the crank cases etc?

[BudgetBoy]

MMMMM.

Are you 100% sure you have replaced the correct coil? Without testing anything with a multimeter you are guessing.

As lorenzo says it could be a stuck float..My zx6r had a main jet fall out and caused the same thing.i ruled out electrical with my multimeter and went to the carbs.

Mark the new coil with a marker pen. Then try the other two coils one after another and see if the fault is still there. This is just to rule these out.For all you know you could have taken off the good coil and the faulty one is still there.(Buy yourself a mulitmeter and you will save yourself hassle & money)

After this i would be inclined to whip the carbs off and open the float bowls.the float could be sticking in the open position so overfuelling the cylinder.

If this is the case then your exhaust could have fuel in it.So please be careful when running it.

Stick with it mate you are getting there.. And when you fix it you will be sooooo happy..Thats the buzz i get when fixing things.

[mr ninja]

No it was clear petrol, just been searching the phrase fuel in the airbox and the answer is sticking float or blocked jets, needle valve etc. As BudgetBoy said that's how you learn so I guess I should take the carbs off and inspect, I'll start by tapping the float bowl and see if I have any joy before wipping them off.

[mr ninja]

Thanks BudgetBoy, you are keeping me going . Yes the coils I have tested and do have a multi meter and they did check out ok. Please let it be a sticking float !!

[BudgetBoy]

Thanks BudgetBoy, you are keeping me going . Yes the coils I have tested and do have a multi meter and they did check out ok. Please let it be a sticking float !!

Not a problem mate, glad to help.

well looks like you have dialed it down then.. carbs next..

[mr ninja]

Well I'm not 100% sure but I guess it's the next logical thing.

[BudgetBoy]

Well I'm not 100% sure but I guess it's the next logical thing.

Diagnosing over the internet is hard..But we try..try looking at it on how much money you are saving!!

heres a tip for you before you take the carbs off.

Tap the carbs before you start it. Then when its running for say 2-4 mins tap it again. If the problem don't happen you have a sticky float. (remove and repair)

if it still happens you will have to remove the carbs to check the float heights,and for damage to the floats & float valve damage.

if the float or float valve is not returning to its proper level (and valve seating properly) then fuel will continue to flow. But we had to rule out the ignition side as a weak/no spark will do the same/similar.

Your doing ok mate..

[mr ninja]

Thanks mate, you've been a great help. I will try the wooden hammer tap to start with and as you suggest take them apart if no joy. Taking the float bowls off, how will I know if the float is working correctly or sticking as there will be no fuel in there?

Also the needle valve, I need to take the top off the carb and extract the valve with bull nose pliers? Do I need to check the 'o' ring, clip on valve etc and clean? But again putting it back together is there anyway to check other than a full re-assemble and starting the bike back up?

Thanks for you patience BudgetBoy but my experience has always been 2-strokes, 4-strokes I have always used a qualified mechy and steered clear.

[BudgetBoy]

Thanks mate, you've been a great help. I will try the wooden hammer tap to start with and as you suggest take them apart if no joy. Taking the float bowls off, how will I know if the float is working correctly or sticking as there will be no fuel in there?

Also the needle valve, I need to take the top off the carb and extract the valve with bull nose pliers? Do I need to check the 'o' ring, clip on valve etc and clean? But again putting it back together is there anyway to check other than a full re-assemble and starting the bike back up?

Thanks for you patience BudgetBoy but my experience has always been 2-strokes, 4-strokes I have always used a qualified mechy and steered clear.

As soon as you open the carb float bowl it will be full of fuel,so do this over a tub. Once open have a look at them as sometimes it is obvious which one it is. Whilst you have these upside down the sticky one might show itself.If not carefully lift each one and let it go you might see the binding.

next step is to take out the FLOAT valves. (Note the nice sharp point)

Check there is no wear on the valve or seat (inside the carb) any damage at all need to be fixed.

Lift out the needle valves and make sure there is no wear on them.Should be nice and smooth..

Once you have done all that you need to set the float height or make sure they are in spec.

Then put the carbs back together and set the fuel levels (this can take time) as it is normally +/- 1mm from a point on the carb.

Once that is all done bench balance the carbs, this will get it quite close (good enough for running)

then put them back on your bike and see how she runs.

if you have a glass jar you can empty each float bowl (via the drain screw) and measure how much each one has.The HIGH one would be the sticking one. Because the fuel is not shutting off.

If you get stuck "ASK" that what this part of the forum is for mate.

[mr ninja]

Thanks mate !!

[Evilchicken0]

Have a look at the float bowl gasket too. they can get flattened if the bowls are on / off quite a lot

[mr ninja]

As soon as you open the carb float bowl it will be full of fuel,so do this over a tub. Once open have a look at them as sometimes it is obvious which one it is. Whilst you have these upside down the sticky one might show itself.If not carefully lift each one and let it go you might see the binding.

next step is to take out the FLOAT valves. (Note the nice sharp point)

Check there is no wear on the valve or seat (inside the carb) any damage at all need to be fixed.

Lift out the needle valves and make sure there is no wear on them.Should be nice and smooth..

Once you have done all that you need to set the float height or make sure they are in spec.

Then put the carbs back together and set the fuel levels (this can take time) as it is normally +/- 1mm from a point on the carb.

Once that is all done bench balance the carbs, this will get it quite close (good enough for running)

then put them back on your bike and see how she runs.

if you have a glass jar you can empty each float bowl (via the drain screw) and measure how much each one has.The HIGH one would be the sticking one. Because the fuel is not shutting off.

If you get stuck "ASK" that what this part of the forum is for mate.

Well I stripped the carbs apart, cleaned the jets with carb cleaner, I did get a bit of black oily stuff from the pilot jet, also re-set the float height which was 17.5 to 15.5 (factory Pro settings) got it back together and a big improvement, so far staying on 4 cyclinders, although a little fluffy if left on idle for a while but one quick rev then ok. Must admit a bit nervous but now more confident. I think I will take them off again and clean them all thoroughly and set all float heights as I only concentrated on the first, carb No1.

One thing to note I noticed that the rubber 'o' ring that sits under the rubber bell mouth/ velocity stack is stretched and not seating correctly in the groove, I guess I should replace this (vacum leak possibly)?

[BudgetBoy]

Glad you are getting there now.. bet you feel pleased with yourself.But you should really clean ALL the carbs the same way you done number 1.

Any suspected damaged part IMO you should replace.If its just an o ring replace it.. it can only help matters.

nearly there,.

[mr ninja]

Glad you are getting there now.. bet you feel pleased with yourself.But you should really clean ALL the carbs the same way you done number 1.

Any suspected damaged part IMO you should replace.If its just an o ring replace it.. it can only help matters.

nearly there,.

Hmmm well I was, just been out again because I wanted to fit a new starter relay, that works perfectly however it's starting to play up again (arggghhh), not as bad as it was but if left a while on idle the revs drop off and then eventually stalls, still believe it's flooding, Also checking the spy glass the oil level is above maximum, would this be because I now have fuel mixed with the oil from all the countless times I have been trying to sort this problem.

I got to be honest I can't face taking it all apart again, it's got to the point where it's driving me nuts. It needs an MOT so they might as well fix the damn thing, cause all I want to do is ride !!!!!

[BudgetBoy]

Hmmm well I was, just been out again because I wanted to fit a new starter relay, that works perfectly however it's starting to play up again (arggghhh), not as bad as it was but if left a while on idle the revs drop off and then eventually stalls, still believe it's flooding, Also checking the spy glass the oil level is above maximum, would this be because I now have fuel mixed with the oil from all the countless times I have been trying to sort this problem.

I got to be honest I can't face taking it all apart again, it's got to the point where it's driving me nuts. It needs an MOT so they might as well fix the damn thing, cause all I want to do is ride !!!!!

Dont quit.

If you did not clean ALL of the main jets,idle jets etc then there is the problem.Just cleaning 1 will not solve it mate.If you were closer you could have dropped the bike off at mine.I would have done it for you like i did BigKingys bike (see in this we trust section). I would even take it to get the mot so it was all done for you ready to ride home.

have another go but do the carbs properly mate..Its running better than it did so the bike it telling you "Carbs".

Clean them.

[mr ninja]

Dont quit.

If you did not clean ALL of the main jets,idle jets etc then there is the problem.Just cleaning 1 will not solve it mate.If you were closer you could have dropped the bike off at mine.I would have done it for you like i did BigKingys bike (see in this we trust section). I would even take it to get the mot so it was all done for you ready to ride home.

have another go but do the carbs properly mate..Its running better than it did so the bike it telling you "Carbs".

Clean them.

Just for you lol I will give it one more attempt tomorrow by stripping everything down for cleaning & re-setting. I just did that carb because that's the cylinder that is giving the problems.

Why would I have petrol in the sump though? Thanks for all your help by the way.