Author Topic: intermittant misfire (Read 15752 times)

wildchild74 · « **on:** 15 February 2015, 10:00:44 pm »

Hi folks got a bit of a problem on my 98 fazer 600 with 40000 miles on it....its developed a misfire when warm over last couple of weeks but bear in mind I can only get out on it on weekend for an hour or two and its kept outside under cover....now when I start it on full chock it struggles abit but starts and the first time it happened it sounded like a diesel so I touched the downpipes and no2 was warm so I took caps off n refitted them and it ran fine then last week went out on it Friday and Saturday only slight misfire at low revs ok over 3.5k but went out Sunday it was a right bag of nails and touched pipes again and no3 was warm so I put new plugs in today and it really struggled to start but when I did it was really smooth till it warmed up then slightly missing again but I had to out so couldn't do anymore.... Any suggestions thanks
Gaz

wildchild74 · « **Reply #1 on:** 16 February 2015, 04:13:24 pm »

Bump anyone
Gaz

Paulfzs · « **Reply #2 on:** 16 February 2015, 04:23:59 pm »

give carbs a clean and take it for a real ride, give it some beans

wildchild74 · « **Reply #3 on:** 16 February 2015, 05:13:48 pm »

I drained down the carbs and put full bottle of redex in a couple of litres of fuel and run it again then again after changing plugs then just been out to test the battery with a multimeter n thats ok n when it was chugging away if felt the pipe and i could hold no4 but others were red hot couldnt touch them im wondering now coilpacks and leads???

Paulfzs · « **Reply #4 on:** 16 February 2015, 05:22:32 pm »

is it sparking ok?

just flushing carbs may not fix the problem, but it may well just need to see the redline.

my fzs was sat up for a few weeks recently and only ran on 2 cylinders it needed a bit of throttle to sort it and it has been fine ever since.

wildchild74 · « **Reply #5 on:** 16 February 2015, 05:37:12 pm »

Dont know if it means anything but there is a slight backfire/popping noise but it has got a race can on
Gaz

Rev Chris · « **Reply #6 on:** 16 February 2015, 06:42:28 pm »

[size=19px !important]Profi Fuel Max - Fuel system & carburetor cleaner[/size][size=21px !important][/size]Great product. Purchased for my Yamaha FZS 600 Fazer (1999). It had been running very roughly (low revs, inconsistent tickover, low speed running, hesitation etc) since purchase in the spring of 2014. Did all the usual stuff - new plugs, checked plug caps,coils etc (all within spec) even purchased new TPS (ouch!) but problem remained. It was during a conversation with a mechanic that I found out that regular unleaded petrol had up to 10% Ethanol in it. Apparently it goes off after a month and leaves a residue particularly in the pilot jets (hence the poor low speed running). The bike was due to go into the garage for a carb cleaning session (about 2 hours labour ~£100). Read about Profi fuel so decided to give it a try. Took a third of the can (90mls) to the garage and filled up with Shell Vmax (less ethanol content) and filled the tank. Pleasantly surprised - running really well after 20 miles; by 50 miles engine is as sweet as a nut! Perfect low speed running, no hesitation and constant tickover. This product also stops the water content in the fuel rusting the tank during winter storage. If you are laying up your bike for the winter its probably better to drain the tank and run the carbs dry and fill up with fresh fuel next Spring. In summary - if you are experiencing poor running give this product a try first, rather than last - you could save a great deal of cash on unnecessary parts and labour costs.[/size][size=21px !important][/color]

noggythenog · « **Reply #7 on:** 16 February 2015, 06:49:03 pm »

Wait until it's pitch black & not pissing with rain.

Have some paience & start up the bike and look at the top of the leads where they go into the plugs........look for very small, arcing lightning bolts, take a while to sit and look or even ask someone else to look from the other side at the same time.

If you've been pulling plugs on and off then id also make sure that the leads and caps are screwed into each other and not just squashed up making a crap contact.

If you see any arcing then snip off the ends of the leads where the arcing is and screwback to the caps, the arcing might occur at the same time as a subtle change in the revs.

Worth a check anyway.

unfazed · « **Reply #8 on:** 16 February 2015, 07:56:57 pm »

Take the plug caps off the plugs, pull off the plug caps. Cut a half inch off the ends of the leads, now with the boots rolled back screw the leads back on the cap. Fill the top of the plug cap around the lead with vaseline, push the boots back on. Put the caps back on the plugs As long as there is no corrosion in the cap that should sort it.

Did it to mine a few years ago, never had a problem since.

wildchild74 · « **Reply #9 on:** 16 February 2015, 09:21:12 pm »

Quote from: Rev Chris on 16 February 2015, 06:42:28 pm

[size=19px !important]Profi Fuel Max - Fuel system & carburetor cleaner[/size][size=21px !important][/size]Great product. Purchased for my Yamaha FZS 600 Fazer (1999). It had been running very roughly (low revs, inconsistent tickover, low speed running, hesitation etc) since purchase in the spring of 2014. Did all the usual stuff - new plugs, checked plug caps,coils etc (all within spec) even purchased new TPS (ouch!) but problem remained. It was during a conversation with a mechanic that I found out that regular unleaded petrol had up to 10% Ethanol in it. Apparently it goes off after a month and leaves a residue particularly in the pilot jets (hence the poor low speed running). The bike was due to go into the garage for a carb cleaning session (about 2 hours labour ~£100). Read about Profi fuel so decided to give it a try. Took a third of the can (90mls) to the garage and filled up with Shell Vmax (less ethanol content) and filled the tank. Pleasantly surprised - running really well after 20 miles; by 50 miles engine is as sweet as a nut! Perfect low speed running, no hesitation and constant tickover. This product also stops the water content in the fuel rusting the tank during winter storage. If you are laying up your bike for the winter its probably better to drain the tank and run the carbs dry and fill up with fresh fuel next Spring.
In summary - if you are experiencing poor running give this product a try first, rather than last - you could save a great deal of cash on unnecessary parts and labour costs.[/size][size=21px !important][/color]

Hi m8 thanks for that but the only fuel I use is esso premium as it apparently got no ethanol so no moisture build up as I don't use it everyday but I will look into that stuff ta m8
Gaz

wildchild74 · « **Reply #10 on:** 16 February 2015, 10:00:51 pm »

Does anyone know where i can get this stuff from uk although i do wanna give it a try. But although im no expert or mechanic but i dont think its fuel more electrical as every time it misses its a different cylinder each time
Gaz

wildchild74 · « **Reply #11 on:** 17 February 2015, 04:32:18 pm »

Looking at these plug cap arnt oem as these are straight not 45° bends so the lead bit coming out of the cap is always bent so im hoping that is the problem and going to bike shop tomorrow and getting 1.5 metres of lead and 4 new caps hopefully 45° bends
Gaz

noggythenog · « **Reply #12 on:** 17 February 2015, 05:59:27 pm »

Quote from: wildchild74 on 17 February 2015, 04:32:18 pm

Looking at these plug cap arnt oem as these are straight not 45° bends so the lead bit coming out of the cap is always bent so im hoping that is the problem and going to bike shop tomorrow and getting 1.5 metres of lead and 4 new caps hopefully 45° bends
Gaz

If you try what me & unfazed suggest above then it might save you the bother.

Just unscrew the lead from each cap &snip off the ends....i dunno maybe 10-15mm, screw the lead back to the cap & see if it makes a difference. Nothing to lose if it doesnt work but if it does then at least you know.

unfazed · « **Reply #13 on:** 17 February 2015, 06:11:34 pm »

Noggy, we can only suggest, if they wish to spend money first????

Considering the fact you cannot remove the leads from the coils I am not sure what he is thinking of doing.

The straight NGK are the usual replacement, but the same issue applies as with the original caps, the leads loosen

noggythenog · « **Reply #14 on:** 17 February 2015, 06:44:08 pm »

Quote from: unfazed on 17 February 2015, 06:11:34 pm

Noggy, we can only suggest, if they wish to spend money first????

Considering the fact you cannot remove the leads from the coils I am not sure what he is thinking of doing.

The straight NGK are the usual replacement, but the same issue applies as with the original caps, the leads loosen

I actually dont know much but i learn every year & i remember having a similar problem & an old wise foccer (red98) suggesting the same.

Right enough it was arcing and i did the trimming the leads & hey presto quite satisfying.

red98 · « **Reply #15 on:** 17 February 2015, 07:12:17 pm »

Lol.....well iam old so your half right noggy

.......yes, as suggested check the plug caps/leads in the dark, look out for sparks jumping across from plug caps/leads to engine , leads can go hard and brittle with age and are sealed to the coils so trimming the ends to get a good connection is the best solution and if wont cost you anything....a good place to start

wildchild74 · « **Reply #16 on:** 17 February 2015, 09:52:07 pm »

Quote from: noggythenog on 17 February 2015, 05:59:27 pm

Quote from: wildchild74 on 17 February 2015, 04:32:18 pm
Looking at these plug cap arnt oem as these are straight not 45° bends so the lead bit coming out of the cap is always bent so im hoping that is the problem and going to bike shop tomorrow and getting 1.5 metres of lead and 4 new caps hopefully 45° bends
Gaz

If you try what me & unfazed suggest above then it might save you the bother.

Just unscrew the lead from each cap &snip off the ends....i dunno maybe 10-15mm, screw the lead back to the cap & see if it makes a difference. Nothing to lose if it doesnt work but if it does then at least you know.

Thanks lads i will try that tomorrow... and i just thought they may be cheap replacements and the chap in the bike shop told me that i could put new leads into coils but as i said im no expert or mechanics but i am a quick learner but once again thanks for all your input
Gaz

Jules-C · « **Reply #17 on:** 18 February 2015, 04:54:13 pm »

Quote from: wildchild74 on 16 February 2015, 05:37:12 pm

Dont know if it means anything but there is a slight backfire/popping noise but it has got a race can on
Gaz

Since the fuel going to cylinder 4 isn't getting burnt in the cylinder it is burning when it meets the hot gases from the other cylinders where the pipes join giving the backfire/popping noises.

Have you tried swapping the spark plug from cylinder 4 to another cylinder to check it's not just a duff plug?

wildchild74 · « **Reply #18 on:** 23 February 2015, 06:25:00 pm »

Hi folks just a little update tried trimming leads...no change so i won oem coils n leads on ebay came today and fitted them.....missing all over the shop so took them of 1 by 1 and screwed leads in to the caps fired it up n no misfire at all took it out for 10 mins and all it does now is when coming down the gears it sounds like theres a slight misfire but to be honest carbs prob need balancing and its still running the additive thru so not worried about at the mo so thanks for all your input lads
Gaz

unfazed · « **Reply #19 on:** 23 February 2015, 07:05:08 pm »

It mostly likely that the cap internals are corroded or the carbon resistor in the cap has gone higher resistance.

Out of curiosity and if you have time, remove the old caps and looking into to them, you will see a slot for a screwdriver. Unscrew it and out will fall, the piece you unscrewed, a carbon resistor, a tiny brass washer and a spring. A very high possibility that there is corrosion in there somewhere and if not the resistor is knackered.

I have swapped the resistors with the 5Kohm resistors ones from old NGK spark plugs, (these are wire wound and more reliable) cleaned up the corrosion on the spring and the internal part of the cap, dumped the tiny washer (they break half the time). Requires a bit more pressure to reinstall as the NGK resistor is a little longer than the carbon one. Put them all back together and works fine.

Have not heard of a fazer coil pack up yet.

wildchild74 · « **Reply #20 on:** 23 February 2015, 07:54:40 pm »

I will try that unfazed wondered what those slots were for cheers bud
Gaz

wildchild74 · « **Reply #21 on:** 27 February 2015, 06:30:06 pm »

Quote from: wildchild74 on 23 February 2015, 07:54:40 pm

I will try that unfazed wondered what those slots were for cheers bud
Gaz

Hi there i done that on the old ngk ones and they were clean but i then tried it on the one on the bike and the risister isnt too bad but one end of the spring was really corroded so i quickly cleaned them up with sandpaper but not had time to start it but will tomorrow.... are the risisters in the ngk one better than oem ones....many thanks
Gaz

unfazed · « **Reply #22 on:** 27 February 2015, 07:05:13 pm »

The resistors in the NGK one are wire wound whereas the Yamaha OEM ones are Carbon.

The carbon ones are cheaper to manufacture, but their resistance values can vary by 20%.
The wire wound ones are more accurate, normally within 5%.

The carbon type age badly and the resistance rises as they get older and coupled with corrosion it plays havoc with the spark, causing misfires, poor starting and all sorts of other issues

Be sure to clean the brass piece deep in the cap also. I usually spray the inside of the cap with WD40 before reassembly

If you put back the original caps with the NGK resistors pack the top of the cap with vaseline before replacing the rubber boot, no more water ingress.

wildchild74 · « **Reply #23 on:** 27 February 2015, 08:07:01 pm »

Will deffo try that tomorrow after getting the car remapped in the morning n let you know how it goes cheers buddy
Gaz

sgpwwg · « **Reply #24 on:** 28 February 2015, 07:22:49 am »

Hi There I have all the issues you've had I changed coils, caps, plugs and air filter. I cleaned the carbs, tried redex, the lot. My 98 fazer (88,000 miles) would be ok for s few days then misfire and you get one or two cold downpipes. After cleaning the carbs myself I noticed that diaphragm rubbers on the top of the carbs where slack, I replaced them from a set I had as a spare and the bike was back to normal. No misfire, perfect again. Hope this maybe of use.