bad idle/ hesitant throttle response

[mvagogo]

Hi all i seem to have a problem with my t12. over the last few weeks the bike has been ideling low around 1000rpm and has been backfiring more than usual when you shut the throttle. anyways today on start up the bike started fine and when the engine warmed and the tickover slowed the engine is wanting to stumble and almost stall like when you get a bike wet, also upon acceleration at low revs theres like a misfire and then it seems to clear out at higher revs but still doesn't feel right almost like its on one cylinder and then onto two. bike has 50k on it I did the plugs and filter at 40 k any help much appreciated. theres no fault codes showing on the dash.

 

[~TABASCO~]

I would start with making sure the Throttle bodies are synced correctly. Sounds (just from this little info) that maybe one of the screws is "off"......

 

[Sierra1]

How old is that gas? And have ridden in heavy rain recently?

 

[magic]

Were the UK bikes covered under the wiring harness recall? Sounds like the exact symptoms that the recall covered.

 

[mvagogo]

I would start with making sure the Throttle bodies are synced correctly. Sounds (just from this little info) that maybe one of the screws is "off"......
bike ran fine yesterday apart from low idle and backfire on decal i will give it a try though

How old is that gas? And have ridden in heavy rain recently?
new gas a few days ago]

Were the UK bikes covered under the wiring harness recall? Sounds like the exact symptoms that the recall covered.
Its a gen 1 so i dont think they had the problem. i checked yamaha and it said no recall for my model.

Iwill lift the tank and check the coils tomorrow they looked good 10k ago though.

 

[mvagogo]

shit cant do multiquote

 

[magic]

Actually the Gen 1 bikes were covered under this recall, in the U.S. anyway.

 

[StefanOnHisS10]

Sounds like it needs a TB sync to me. You could measure the resistance on the coils. My Yamy dealer told that they can fail over time if they get a lot of water.

 

[mvagogo]

Spoke with someone today who has owned a t12 and does a fair bit of work on them and he thinks it could be the coil sticks causing the misfire by them arking out so in the morning i will check the resistance as per the video above, and while i am under the tank i will do the TPS clean if this brings nothing up i will get a synch tool and do the throttle bodies.
Thanks for the replies and any more help is welcome.

 

[Squibb]

Sounds like a plan.

If ridden in finest Yorkshire rain, then I suspect water ingress down the coil sticks.

However, when checking the TB sync, make sure the TB port plug is in good condition - they tend to deteriorate with age & can leak.

Keep us posted.

 

[mvagogo]

Had a check of the coil sticks today and the primary coil resistance is below spec in all four. the ohm reading should be between 1.19 and 1.61 and they were reading 1.4 and 1.5 so maybe this is the problem the secondary resistance was in spec , i checked the pipe work around the TBS and all is fine and worked the throttle mechanism on the TBS to clean it asper another thread on slow speed bad running.
can the primary ohm reading being low create these problems as the manual says replace if not between the specs.?

 

[mvagogo]

If ridden in finest Yorkshire rain, then I suspect water ingress down the coil sticks.

Hi mate coil sticks were dry and i ride in all weather but i do have a fender extender.

 

[Squibb]

Seems it's not the coils, at least when measured cold - I wonder what is happening when they get hot though?

It may be worth checking the exhaust header temperatures after a run, with an IR gun, to see if you can identify the cylinder that is lagging/misfiring. Could it be a burnt valve - do you know when the clearances were last checked?

 

[mvagogo]

The valves have not been checked as up until a couple of days ago was fine, still returning 60+ to a gallon and no starting issues. will the coils still work properly reading under the lower spec?

 

[jbrown]

I don't know what type of meter was used, but low ohm measurements on an inexpensive DVM aren't accurate enough to call a 1.5 ohm measurement out of spec.

 

[StefanOnHisS10]

the ohm reading should be between 1.19 and 1.61 and they were reading 1.4 and 1.5

Seems perfect to me.

 

[mvagogo]

I get it now so 1.4 is in spec but on further inspection coil no1 and 2 have rust on the metal sleeve so i dont know if this makes a difference?
I see in the vid he has primary of 1.9.

 

[mvagogo]

Bikes fixed today. I put some new tour max/mitsubishi coils in today spark plugs and air filter and she's like new again, its surprising how bad your bike can be running and you just ride round it without noticing. f

 

[StefanOnHisS10]

You changed all 4 coils? That’s expensive! But glad she’s okay again.

 

[Sierra1]

Bikes fixed today. I put some new tour max/mitsubishi coils in today spark plugs and air filter and she's like new again, its surprising how bad your bike can be running and you just ride round it without noticing. f

Your weather doesn't help the matter.