Misfiring under load - help please!!

[Popell]

I have searched and read many threads re batteries/TPS etc but have failed to find symptoms that match mine.

Just returned from 2,200 miles round France during which we got hailed on, snowed on and generally drenched......also dropped the bike onto its RHS at a hairpin at standstill when the car in front stopped and I discovered my right leg was too short to compensate for the camber on the inside of the bend!!

I mention my mishap simply because I didn't have the misfire previous to that.
Bikes starts fine, all electrics seem good, will rev out on light to medium throttle even in gear.
However, if I fully open throttle as in overtaking/coming off bend then I started to get an almighty hiccough then it would rev - the hesitation did not occur immediately as I opened the throttle but seemed to occur at just below 3000rpm.
Unfortunately the problem is getting worse and there are now multiple hesitations as it revs up - still in gear.

Makes overtaking a bit hit or miss

Considered water in the tank
unlikey to be bad fuel as I have been through rather a lot of it
Washed bike yesterday and the problem was as bad as before.
Will pull the plugs and see if there is anything obvious.

How do I check for good operation of coils?, TPS?

Any help much appreciated, thank you

 

[Pukmeister]

Home diagnostics for TPS etc (after checking all the simple and obvious) requires a GS911 and a laptop. Not sure you need to do that just yet:

Could be worth fitting new spark plugs as one of them may have cracked the ceramic during the drop? Available online for a few quid each rather than rip-off dealer prices, you need four. New plugs will transform the engine anyway so worth it.

The symptoms you describe sounds like a weak spark under load as the cylinder pressures rise. Light throttle won't cause it but heavy throttle will. Either plug or coil related.

Also check your lower coils, takes five minutes to remove them and inspect. I've had two lower coils fail over the years, oddly both RH cylinder. the last one had burst apart and was obvious once removed from the bike. Use a multimeter to measure primary and secondary resistances, can't remember what they are but a search on here should find the info.

Good luck with it.

 

[Pukmeister]

For measuring coil resistance, primary (low tension) is easy across the small connector. Secondary (high tension) is measured between the part that touches the spark plug centre electrode cap and the metal body of the coil IIRC. You will only measure a resistance one way as a diode is fitted so try reversing the test leads if nothing measured. I think it is 0.4KOhms as I recall, someone on here will know for sure.

No location on your profile, if you are anywhere near Fareham you are welcome to drop by for a check with my GS911, I also have an old coil and spare plugs you could try.

 

[Popell]

Thanks for the replies so far, I have a multimeter so will be able to measure primary and secondary-will have a search for absolute values if any of the four measure different.
Will check plugs, have changed them once - perhaps 8k ago, should have mentioned that bike now has 17k on it now and I did oil, valves and TB balance before I went to France.

No-one suspecting that I have done more damage than scratched engine cover when I 'dismounted' (I'd be happy if it wasn't linked)

 

[Popell]

No location on your profile, if you are anywhere near Fareham you are welcome to drop by for a check with my GS911, I also have an old coil and spare plugs you could try.

Thanks Mr P, I am in Yorkshire so thank you for your very kind offer, I'll check the things you mention.

 

[trainman]

does sound like a coil or plug but also lambda sensor may have taken a knock, there have been cases of internal damage as I believe these types have an internal heater which can break, there are some 2nd hand ones on eaby for about £30

worth a look if the coil and plug prove ok,

 

[Pukmeister]

I had a Lambda heater fail, would cause it to run shit and stutter across the rev range (mine did anyways).

 

[Magnet]

Had something similar on my 800GS - very unsettling. Always on hard acceleration and got worse to the point where the engine actually stopped and had to be restarted several times. Happened 3 times in 3 days on the Borders Bash. Not good if you happen to be overtaking or in lane 3 at the time

This fault coincided with some intermittent issues with the side-stand switch. This has now been replaced (and was found to be faulty) and the stalling issue has not re-occurred. Don't know if it's actually cured but so far so good...

 

[Popell]

Thanks again, will hope to find the cause with the plugs, but also check the side stand switch- if only to eliminate it as the cause, should be able to check with the multimeter.

 

[Popell]

I had a Lambda heater fail, would cause it to run shit and stutter across the rev range (mine did anyways).

Any idea if a fubar'd lambda sensor would show up as funny coloured plugs?

 

[Bob Jeffries]

Had the problem on my old 1150 twin spark during a tour around Scotland a few years ago, it was just one of the little connectors on one of the coil packs had partially come loose, worth a quick check.

 

[trainman]

Any idea if a fubar'd lambda sensor would show up as funny coloured plugs?

in a word yes, as it works out the fuel/air ratio a duff one is either going to give one extreme or the other (lean or rich, am not sure which and will depend I guess on exact fault with sensor), as well as electrical faults they can be affected by contamination of the sensor head, I am not sure if the bike falling over may cause this some how but someone may come along and advise further? if the coils and plugs are ok its worth having the lambda's out and compare one sides appearance to the other (have a look at the ebay used photos as well for an idea), compare the heater resistance readings side to side as well, not sure how you go about testing the sensor output as the thing needs to be hot to work and connected to the bike I would think (which makes getting a test lead on tricky)

 

[Pukmeister]

When my RH lambda failed, it ran very rich. I also ended up with a failed lower RH coil which I swapped with a mates bike in Glasgow to get me home and ordered him a replacement from Motorrad Central. The bike ran like shit, used loads of fuel and the RH spark plugs were heavily fouled. My GS911 reported the Lambda heater was faulty with a fault code, a Lambda trace showed the suspect Lambda probe Voltage all over the place.

By unbolting and swapping the Lambdas I could change the plug fouling from RH to LH cylinder, hence I knew it was definitely a defective part.

A replacement NTK Lambda was about £70 on eBay IIRC (compared to the same part in a very expensive box from BMW at twice the cost.)

 

[duckspeed]

Have a look inside the TPS plug for water...........

 

[Pukmeister]

Good call, forgot about the TPS plug.

 

[Steptoe]

I have searched and read many threads re batteries/TPS etc but have failed to find symptoms that match mine.

Just returned from 2,200 miles round France during which we got hailed on, snowed on and generally drenched......also dropped the bike onto its RHS at a hairpin at standstill when the car in front stopped and I discovered my right leg was too short to compensate for the camber on the inside of the bend!!

I mention my mishap simply because I didn't have the misfire previous to that.
Bikes starts fine, all electrics seem good, will rev out on light to medium throttle even in gear.
However, if I fully open throttle as in overtaking/coming off bend then I started to get an almighty hiccough then it would rev - the hesitation did not occur immediately as I opened the throttle but seemed to occur at just below 3000rpm.
Unfortunately the problem is getting worse and there are now multiple hesitations as it revs up - still in gear.

Makes overtaking a bit hit or miss

Considered water in the tank
unlikey to be bad fuel as I have been through rather a lot of it
Washed bike yesterday and the problem was as bad as before.
Will pull the plugs and see if there is anything obvious.

How do I check for good operation of coils?, TPS?

Any help much appreciated, thank you

Quick check for coil problems.
Unplug the coil leads on both the left and right lowers and see if the bike runs on just the main coils.... then do the same test with the mains, i.e. unplug the connectors to the left and right main coils and see how the bike runs on just the lower coils.

 

[alex_rsa]

My money is on the secondary coil. A broken secondary coil is annoying a broken main coil is downright dangerous!

You can accelerate slowly if the secondary coil is broken and it should not misfire too much, if the main coil is broken it turns into a popping farting beast.

Similar advice to Steptoe. It will actually start on 1 working coil, so disconnect 3 and try and start it. Do not run in for more than a few moments as you are throwing unburnt fuel down the exhaust. If it starts try the next coil.

When you have found the culprit swap the coil left to right cylinder to make sure it is the coil and not the wiring.

This should not take more than 5 minutes

 

[Popell]

OK, I've pulled the plugs and photod them
RH Top Plug

RH Lower

RH Lambda Sensor

LH Top

LH Lower

 

[Popell]

Will try later to sort out how to post(done it before so it can't be rocket science!)
Basically all plugs looked pretty light/white in colour, no obvious cracks and pretty similar to each other.
This would tend to make me think that there is a problem outside of the LH/RH specific bits.

Not sure where the tps plug is (nor indeed the TPS!), will try a tank of decent fuel(although the problem has been over a number of tankfuls already)

Will try the suggestions re disconnecting the lower coils then the upper ones - any benefit from trying top left and bottom right, then top right bottom left?

Put contact cleaner in all connections I could find around both sides of the engine.

I have an Accellerator module on it so the lean running causing white plugs is even more of a mystery.
Has anyone ever experienced one going wrong and sending the mixture the other way?

Going to order some iridium plugs even though current ones probably 8k old

Thanks again for all the suggestions

 

[Pukmeister]

Your TPS is in front of your left toes when sat on the bike, follow the air inlet pipe out of the air box. Before it gets to the LH throttle body or LH cylinder head you'll find your TPS.