Engine misfiring at low throttle openings

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Litening

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Hi, I obtained my first Yamaha last year and I am now a devoted fan. I have a 2010 FZ1S and it is a very impressive machine but last time out it began misfiring as though I was running out of gas, the fuel gauge was flashing, but after filling up the misfire remained. Give it a handful of throttle and it's fine, off like a shot but at low speed it misfires. Not being terribly familiar with modern technology on bikes, I'd be grateful for any ideas as to what may be the cause.
 
There’s a YouTube vid by AndyCamMan , regarding kinked fuel line . I thought it was just his , just got this 2007 FZ1 S , set out to do TBS , lo and behold it was kinked . Haven’t been out to try mine out yet , still work in progress, but mine was “bogging down “ at low revs . The pics are the kinked fuel pipe with the outer tube cut off . The connections for tank and fuel rail are re - used using 6mm I.D. and 12mm O.D. fuel pipe shown . It might not be the prob . Hope it sheds some light .BDF1DE34-1A59-47ED-BC6D-E1151C267D97.jpegBAEA1242-59A6-49B5-A005-3185AF5667A2.jpeg
 
Old Deek said:
There’s a YouTube vid by AndyCamMan , regarding kinked fuel line . I thought it was just his , just got this 2007 FZ1 S , set out to do TBS , lo and behold it was kinked . Haven’t been out to try mine out yet , still work in progress, but mine was “bogging down “ at low revs . The pics are the kinked fuel pipe with the outer tube cut off . The connections for tank and fuel rail are re - used using 6mm I.D. and 12mm O.D. fuel pipe shown . It might not be the prob . Hope it sheds some light .View attachment 28004View attachment 28005
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A kinked fuel hose will almost always show more pronounced problems with increasing throttle since the gas will be more restricted by the hose as the gas delivery needs to increase. I have seen this problem first hand on several bikes and they always bogged down trying to accelerate.
 
jwarden said:
Not necessarily. I have worked on bikes that these problems were masked by giving lots of throttle.
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A good first step is to remove the spark plugs. If one is fouled it's indicative of a problem with that cylinder. It could be a bad plug but more likely a problem with the injector or coil. Injectors can get clogged and not deliver enough gas but I have many times had injectors leak from not fully closing due to gunk. A leaky injector definitely exhibits the problems more at idle and low speed because there's too much fuel. Once the throttle is opened to the point that the gas needed is a large percentage of the total (leak is a small percentage) then the leaky injector doesn't come into play much. To diagnose the coil it is easiest to swap in a new one. The other way is to swap another coil into the cylinder with the previously fouled spark plug and see if the problem follows the suspected bad coil to the new cylinder location.

Good luck!
 
Cheers for that , done the fuel pipe anyway as I was under there , I’ll go on to the plugs etc once I get the bike on the road again . Just got this bike new to the fz1 , had a Fazer 1000 2003 , that had a missing cylinder firing at low idle once revved it went . It was a faulty spark plug cap with the screw inside slack on the spring inside , when revved the power jumped the gap . With the ex-up removed on my FZ1 and a Delkivik link pipe and end can installed , would that give low end bad response , do zi need a re map .
 
Old Deek said:
Cheers for that , done the fuel pipe anyway as I was under there , I’ll go on to the plugs etc once I get the bike on the road again . Just got this bike new to the fz1 , had a Fazer 1000 2003 , that had a missing cylinder firing at low idle once revved it went . It was a faulty spark plug cap with the screw inside slack on the spring inside , when revved the power jumped the gap . With the ex-up removed on my FZ1 and a Delkivik link pipe and end can installed , would that give low end bad response , do zi need a re map .
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Definitely good to fix the kinked fuel hose. I changed mine to the normal rubber flex fuel hose. Even those can kink if not put in carefully but will return to shape at least unlike the plastic one from the factory.
 
I literally just went through this EXACT problem. Bite the bullet and buy a new set of plugs and try that first. Then get an multimeter and check the resistance of the primary and secondary coils on each ignition coil pack. If it is a bad coil for the love of christ buy an OEM coil from yamaha. ECUs are espensive.
 
Blaintrain360 said:
I literally just went through this EXACT problem. Bite the bullet and buy a new set of plugs and try that first. Then get an multimeter and check the resistance of the primary and secondary coils on each ignition coil pack. If it is a bad coil for the love of christ buy an OEM coil from yamaha. ECUs are espensive.
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Thanks Blaintrain360, I am presently waiting for my new plugs and other service items, to arrive. I checked the coils just as you suggested and apart from them all having a primary reading slightly above that stated in the manual, they are all the same readings, which would seem to indicate they are serviceable. Thanks for your input.
 
When I removed the plugs the left hand one had some corrosion on the outside although the plug itself was a good colour and looked the same as the others, the coil was also very dirty but the resistances checked out OK. According to the computer diagnostics the injectors are also OK. I've now fitted the new plugs and cleaned everything carefully. I took it for a test ride today and I'm happy to report that it ran very well with no misfire or hesitation at low revs so I presume the dirty plug/coil on no 1 cylinder was the culprit. Many thanks for your interest and suggestions.
 
Litening said:
When I removed the plugs the left hand one had some corrosion on the outside although the plug itself was a good colour and looked the same as the others, the coil was also very dirty but the resistances checked out OK. According to the computer diagnostics the injectors are also OK. I've now fitted the new plugs and cleaned everything carefully. I took it for a test ride today and I'm happy to report that it ran very well with no misfire or hesitation at low revs so I presume the dirty plug/coil on no 1 cylinder was the culprit. Many thanks for your interest and suggestions.
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Glad it's running good again!
 
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