FZR 600 cylinder 4 not firing? :S [Problem solved!]

[Rncv]

Hi all,

Recently i picked up my first big bike a fzr600.

I was told it was running perfectly, but when i got there turns out its only firing on 3/4 cylinders.

I have taken the fairings and tank off, and know its the 4th cylinder thats not firing.

Ive taken the plug out and check the spark against the head and it seems the ht lead/plug works okay.

Iv'e changed the plug from 3 to 4 and still it doesn't fire.

The problem is it fires sometimes as it gets warm (not hot)

Anyone have any ideas? could it be the coil pack even if the spark sparks?

im at a lost end :S

all help is appreciated thanks!

Edit: Blocked pilot jet on the 4th carb.
____________________
Current: 01' Bandit 600, 92' Goose 350
Previous: Lots!

[Frost]

A spark isn't just a spark. Under compression it can weaken the spark to the point where it won't be strong enough. Swapping the coils over should eliminate them as the fault. It could also be the plug cap, so try swapping those over and see if the problem follows it.
Have you tried turning the engine over with the plug out to make sure the cylinder isn't full of fuel or oil?
Spitting on the exhaust headers will show you how hot things are.

It might be a carb issue, at very least i'd drain them and check the float hights. There's a little screw on the under side of the float bowl for draining them and checking the fuel level.

https://www.bbburma.net/FujiFotos/FloatHeight/DSCF2434.jpg

Other possibilities are:
Blocked jet
Choke problem
Carb not seated properly
Carb sync
Timing
Compression

Those last 2 are the sods to fix so it's best to try everything else first.

[Rncv]

what coils can i switch over? can i swap 1 with 4? does it make a difference with the timing?

i have ran the engine over with the plug out and all is clean.

can i check the float hight without taking the carb apart?

the carb intake is cracked, but taped up until the new set arrives.

will check over the things either tomorrow or friday.
____________________
Current: 01' Bandit 600, 92' Goose 350
Previous: Lots!

[P.]

Could be a plug fault. Swap plug 3 and 4, use spit or a water bottle to see which pipes are getting hot.

A taped up intake could still let air in. But better than being open.

You have to take the carbs apart to check float height.

[weasley]

I had this EXACT fault on my Thundercat; it was a duff plug cap. You can take them off the HT lead by simply unscrewing them and they can be tested with a multimeter. I replaced it and have had no problems since.
____________________
Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[Rncv]

[Frost]

[jjdugen]

I rebuilt an FZR this time last year. Had exactly this problem. Checked and double checked the lot. Turned out to be the rubber gasket that seals the 'emulsion tube block'. I'll explain.
Take off the float bowl on no. 4 carb. You will see the main and pilot jet holder. This is held in place by a nut. Undo this and take the block out. You can poke through the jet holders while you are there. You will see a black rubber type sealing gasket in the block. Check it for tears or pinches and make sure it hasn't become flat or hard. If it has, a QUICK dip in thinners and an immediate wash in soapy water will fatten it up again.
No.4 carb is the one that empties and drys when the bike is on the sidestand for any length of time and is the one that usually gives the most trouble.
____________________
The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
Try Soi 23 on Amazon for a good read.... Self promotion? Moi?

[Rncv]

UPDATE]

Taken the carbs off and cleaned them all.

Intake rubber for cylinder 4 is split all the way around, Have a new set waiting.

Will assemble the bike today as yesterday I forgot my keys and couldn't get the seat off DOH!

Will update you again asap.
____________________
Current: 01' Bandit 600, 92' Goose 350
Previous: Lots!

[bwprice100]

.
Check the 3 basics.

Spark
Fuel
Compression

Are they happening and at the right time, if so should run.

Brian
____________________
www.eBolt.co.uk www.ToolRoomChucks.co.uk
My bikes 1956 BMW R26 250cc, !981 BMW R80 (was a TIC ex plod), 1994 R100RT, sold my 1981 Yam XS 250

[jjdugen]

bwprice100. And just how many 20 year old bikes have you tried bringing back to life?
____________________
The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
Try Soi 23 on Amazon for a good read.... Self promotion? Moi?

[bwprice100]

[Rncv]

[bwprice100]

[Rncv]

[Kickstart]

Hi

Coil would likely affect 2 cylinders, although the HT lead, cap and plug would only affect one.

Fueling could affect it on one cylinder easily. However I would be inclined to believe it would normally work at either decent revs / load or at idle (as they are very different fuel circuits) if the float bowl has sufficient fuel.

I would suggest checking the valve clearances on that cylinder. Clearances on the tight side (which is what normally results from wear on shimmed valve engines) will result in low compression, and might well get worse as the engine warms up (ie, the steel valves expands more than the surrounding alloy head).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Rncv]

Update for you all;

i took the carbs off again to clean them. I was messing around and i had a can of carb cleaner and was spraying around to see what is unblocked/blocked and noticed when i spray carb cleaner down the idle jet it sprays out of what seems to be the pilot air jet. its blocked for the 4th carb but not any others...

my question is;

would this cause the 4th cylinder not to fire? and how do I unblock it?

many thanks.
____________________
Current: 01' Bandit 600, 92' Goose 350
Previous: Lots!

[P.]

Get some thin needle usually found in the mothers sewing box and poke them through.

Leave them to soak in petrol or brake cleaner and blow them out again

[Rncv]

[Kickstart]

Hi

Not sure from the top of my head on removing them on the FZR, but probably.

Be careful with poking anything down the jets. They are accurately made to tight tolerances and easily damaged. If you do need to do so then try and use something made from a softer metal than the jets so it can't easily damage them (ie, maybe some copper wire)

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Rncv]