Bikes misfires

Garrydymond

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Jan 1, 2016
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Mexico City
I am on a trip from Mexico to The Great Lakes A few days ago the bike started to misfire just of idle. It happens at about 2,500 rpm. I changed the plugs before I left home about 3,500 miles ago. It hasn’t rained on the trip. Before I crossed the border I guess I got some bad gas. I filled up with Shell on the US side and the problem went away. This problem occurred when I ran the tank low. Today I took the tank and air box off to make sure everything was tightened down which it was. I ran a bottle of Sea Foam 3 tanks of gas a it did seem to get a little
Any ideas? It is more of an annoyance than a big problem.
 

Cycledude

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Rib lake wi
I would be wondering if possibly you messed something up during the plug change but since you have already checked that stuff I don’t know what to think, hopefully it doesn’t leave you sitting somewhere.
 

Nikolajsen

"Keep it simple"
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Does it happen when constant on 2500 rpm? or maybe during accelration? or deacceleration?
Or maybe all 3:eek:.
Missing ignition? coil?
Does the gas pump sound "normal" when you turn the key?
 

Garrydymond

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Mexico City
Does it happen when constant on 2500 rpm? or maybe during accelration? or deacceleration?
Or maybe all 3:eek:.
Missing ignition? coil?
Does the gas pump sound "normal" when you turn the key?
Fuel pump sounds normal. Basically it misses when pulling away off idle.
I am a a Tamaha dealer now and they will hook it up to a PC.
 

Garrydymond

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The Yamaha dealer told me that they couldn’t it because it is a Mexican/European model. Live with it till you get home was there advise.
It only misfires under acceleration in 1st and 2nd gear.
I will be at a friends house on Sunday so may buy new plugs and replace them to see if it makes a difference.
 

Don in Lodi

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You can pretty easily use an Ohm meter on the coils. Check between the two pins and write it down. Check between each pin and the plug tower and write it down. If one coil reads way out of range of the others you have a failure. Something greater than say a ten percent difference.
 

Garrydymond

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I took it into a Yamaha dealer who took the air box off and cleaned the throttle bodies. It made very little or no difference.
I will replace the spark plugs on Sunday even though they only have about 6,000 miles. I will also try to test the coils as that sounds fairly simple. I will also inspect all the hoses but din’t really know where the vacuum ones are.
It runs well above 3,000 rpm and fuel economy is not suffering.
I still have a long trip ahead of me and this problem is a little annoying. It was, however, put into perspective this morning when a deer ran across the road in front of me. A little misfire is nothing compared to almost hitting a deer. I had never seen one running and saw it out of the corner of my eye and thought it was a big dog. They can certainly move and this one was head down arse up and no fooling around.
 

LostDonkey

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Jun 24, 2019
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Perth, Western Australia
Hi Garry, I did read that your bike has not really been wet but I thought I'd share with you my experience from something very similar that used to occur on my ST Gen 1, (I've now got a Gen2 and this is no longer an issue). Overtime I would get moisture buildup within the coil pack connected to plug 1. (Far left plug when sitting on the bike). Mostly from riding in the rain and washing the bike. The moisture would result in the plug shorting and a miss-fire occurring at low revs. Similar to what you found, at higher revs the issue would go away. It could be this and if so, it could be that the rubber seal on the coil pack may not be seated correctly.
The vacuum hose is the one that is connected from the bottom of the airbox to the top of the head, about 12mm in dia.
Good luck with those deer, we have roos and emus to dodge.
 

SilverBullet

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I took it into a Yamaha dealer who took the air box off and cleaned the throttle bodies. It made very little or no difference.
I will replace the spark plugs on Sunday even though they only have about 6,000 miles...
Curious why you didn't replace the plugs at the dealer? If the airbox was already off you were 95% of the way to the plugs already.

I routinely change plugs at ~30K miles. Even then plugs were always still good. But once I did start getting a misfire 5K miles after plug change and it progressively got worse until bike would barely idle after 8.5K miles. Found one plug bad with an intermittent open, replaced and all good.
 

Nig5

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Jan 9, 2015
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Norfolk UK
I had to have all of the stick coils replaced at 40,000 miles, corroded to hell despite regular servicing, two completely ruined, other two on the way out, bike was a bugger to start and misfired below 3,000 rpm, just a thought!
 

RCinNC

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The left side coil stick (the one that's on the downside when you put the bike on the sidestand) seems to be the one that's most affected by moisture. There are several threads on here I'm aware of where guys have documented coil sticks that have swelled and corroded to the point that they couldn't easily be removed from the head. It wouldn't surprise me at all if a corroded coil stick starts to create a misfire. Part of the problem is the steel sleeve around the coil stick, and there's a post I read somewhere that an S10 owner just removed the sleeves from the coil sticks and that significantly reduced the corrosion issue. I never removed the sleeves on mine; I think they make it easier to push the coil stick down onto the plug to firmly seat it. I've gotten into the habit of putting a bead of Belray high temp grease on the inside of the cap on the coil stick where it meets the cylinder head. It helps to seal against water intrusion. Some on here have used O-Rings to seal the sticks; I bought a bag of them, but I haven't tried this method yet. I always use dielectric grease on the coil stick boot, and I've even put anti seize on the outside of the exposed parts of the plug (not the insulator or the electrode, just the flats) to try and slow any corrosion down.
 

Nikolajsen

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Just a wild guess....
Try to disable the TCS, but be carefull;)
(due to the fact that it only appears in low gear)
 
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