Vibration - misfire??

[leftofcentre]

Evening
I have recently just finished servicing my new 57 GS but its now apparent that i have some vibes at motorway speeds.

The vibration is engine related and i was wondering if it was something to do with the new plugs i fitted - possibly a slight misfire?

So i did a test drive removing each of the "head-end" plugs in turn to see if that would make a difference.

To my suprise the plugs underneath the heads misfire terribly when under load. Is this normal? It almost seems like the ecu cuts them out over a certain rev range??

Anyway, satisfied that its not the plugs i am now wondering what else it could be. There is definately a flat spot in 6th gear at around 70-85mph (on a test track )

Any ideas? Maybe the throttles req balancing? Valve clearances? - Yet to do.

 

[Pukmeister]

Inspect the coils, especially the lowers, for signs of corrosion or damage.

Check spark plugs are tight.

Reset the TPS.

Recheck valve clearances and rebalance throttle bodies.

Try some fresh fuel.

 

[TeaPig]

All of the above for sure, plus check the coils are properly pushed onto the plugs.

Any chance you cracked a plug when you fitted them, or dropped one and closed up the gap?

 

[vikingiii]

Evening
I have recently just finished servicing my new 57 GS but its now apparent that i have some vibes at motorway speeds.

The vibration is engine related and i was wondering if it was something to do with the new plugs i fitted - possibly a slight misfire?

So i did a test drive removing each of the "head-end" plugs in turn to see if that would make a difference.

To my suprise the plugs underneath the heads misfire terribly when under load. Is this normal? It almost seems like the ecu cuts them out over a certain rev range??

Anyway, satisfied that its not the plugs i am now wondering what else it could be. There is definately a flat spot in 6th gear at around 70-85mph (on a test track )

Any ideas? Maybe the throttles req balancing? Valve clearances? - Yet to do.

I would not run the engine without the main plugs (center plugs), especially not when loading the engine. The aux plugs are designed to "misfire", or to be out of phase when they are not neded. See text below which is from BMW's R 1200GS press release from 2004 (I'm sure there are even better explanations) http://www.r1200gs.info/pressrelease.html.

By the way, how did you do it?

Featured in all BMW Boxers since 2003 (with the exception of the 850cc power units), dual ignition has been further modified and improved on the R1200GS. The auxiliary spark plug is now arranged at the outer edge of the cylinder, the ignition timing of both plugs being freely programmable as a function of load and engine speed in order to further optimise running smoothness, emission management, and fuel economy. Referred to as "phase shift", this adjustment process is maintained consistently all the way from part load to full load.

In practice, this means different ignition timing points on both spark plugs in defined control map areas. When approaching full load, where dual ignition no longer provides any benefits, the phase shift effect is so large that the spark crosses over on the auxiliary plug in the expansion cycle (60 degrees at TDC). For all practical purposes this corresponds to single ignition on the central spark plug under full load.

 

[ianran]

I had a horrible miss fire intermittantly on a twin spark 1150. Previous service gorilla had broken the connector where the lead plugs into the stick coil resulting in a dodgy connection. Possible fault, mind if it didnt do it before he service, I would check that all has gone back as it should. Favourites are connectors and leads also the throttle cables at the the engine end.

 

[leftofcentre]

Well i completed at 300mile trip two-up to Brighton yesterday to see if the vibes/misfire would settle.

The bike runs superbly and pulls like a train all the way upto 4000revs in any gear. Once over that it would still appear to be missing badly.

Acceleration through the gears to 65-70mph is fine (aprox 4000revs), but any faster than that and the speed increase rate is mediocre. A definate power loss after 4k revs. Vibes are appaling too but disapear completely below 4k. Bizarre.

V dissapointed with fuel consumption aswel. At a steady 80mph cruise she did about 180miles on a tank before Fuel warning came on. My last bike - 1998 ZZR1100 with carbs did better than that and was heavier and revved harder!

Ive order some Irradium plugs to rule out them as an issue. Am wondering about the Coils now. If they were to blame then surely the problem would be apparent all the time and not just over 4k? Do i really want to spend £280? Tried measuring Resistance as per the Haynes but couldnt get a proper reading or my head around the different scales on my multimeter (Nothings ever simple huh!)

£6600 spent and am a bit deflated to be honest

 

[Magwych]

Evening
I have recently just finished servicing my new 57 GS but its now apparent that i have some vibes at motorway speeds.
.

There could be a clue here ...

Did you remove the air filter intake? It is easy to dislodge the cable for the right-hand throttle, causing it to get trapped. This will put the throttles out of balnce, but would have the most impact over 4,000 RPM. Steppers, Lambda sensors etc work below 4,000 RPM, above that bodies out of synch will probably cause vibration issues and poor fuel consumption.

Did you try balancing them yourself using a vaccum guage? You need to either park the steppers using a GS911 tool, or balance them at over 4,000 RPM ...

Plenty of threads here and on ADVRider will show good ideas for balancing the throttle bodies and throw up a whole new world of worthy debate on what is the best way to do this


The easiest thing to check is your righ-thand throttle cable though, check that you do have some free play at the throttle body. If not the cable is probably pinched up or mis-routed somehere around the air intake tube ...

 

[Wapping]

There could be a clue here ...

...

Could be. But no, not least at the OP's doorstep it seems.

From another thread:

I havent really done a full service yet as the garage i purchased it from did one apart from changing the plugs as they didnt have a thin walled socket to get em out with.

All ive done really is just changed the plugs and linked up a GS911

One might though suspect his hand in there somewhere So, good tips, just the same.

 

[Magwych]

Good catch Sir Wapping !

Guess the lack of suitable tools also implies a non BMUU garage - they too could have fallen foul of the dear old trapped throttle cable or even tried to balance the throttles at idle without parking the steppers first.

I see the OP has a GS911, so at least he can do the balance at idle properly. Assuming he has , or can blag, a suitabel vaccum guage.....

 

[leftofcentre]

Any particular reason why the OP is being talked about in the 3rd person?

 

[Wapping]

Well, it would be difficult for a third party to correct Magwych's misunderstanding of the service work you have performed yourself, in the first or second person, would it not?

Evening
I have recently just finished servicing my new 57 GS but its now apparent that i have some vibes at motorway speeds.

Which prompted:

There could be a clue here ...

...

A third party addressing Magwych's misunderstanding with:

"I did not service it" or "You did not service it" (First and second person) would not make much sense, would it?

Other than making a mistake over who it was that did the servicing work, Magwych's reply (offering ideas of things to check) was addressed to you in the second person singular, quite correctly.

His second post was addressed to someone other than you (albeit you were its subject) requiring Magwych to refer to you in the third person, singular. Again, quite correctly.

 

[leftofcentre]

There could be a clue here ...

Did you remove the air filter intake? It is easy to dislodge the cable for the right-hand throttle, causing it to get trapped. This will put the throttles out of balnce, but would have the most impact over 4,000 RPM. Steppers, Lambda sensors etc work below 4,000 RPM, above that bodies out of synch will probably cause vibration issues and poor fuel consumption.

The easiest thing to check is your righ-thand throttle cable though, check that you do have some free play at the throttle body. If not the cable is probably pinched up or mis-routed somehere around the air intake tube ...

Alas, the cables are not at fault. Just awaiting the new Coils & plugs now....

 

[alex_rsa]

Sounds like a coil. i had one fail, it started under load but got progressively worse over a week or 2.

Biggest problem was working out which coil, tried all sorts of combinations and would ride up the road only for it to appear/dissapear. Also tried a new plug.

In the end I disconnected all the coils except one and started the bike. It will start quite happily on 1 working plug (don't ride it anywhere), after going through 3 of the plug/coil combinations the bike would not start - this is the dud coil.

Just to double check try the same spark plug with another coil and it should start.

Sounds fiddly but it takes 2 minutes.


Alex

 

[TeaPig]

OK, so it worked fine before you did the service and changed the plugs? Now it doesn't.

The blurb from BMW says the ignition system uses a fancy combination of both center and side plugs depending on rpm

Your bike goes funny above 4000 rpm...

I'm pretty sure there are similar posts on the 1150 pages that point to a failed coil (as alex-rsa suggests), in your case the one suppling the spark to one of the 'main' plugs. The assumption being that the secondary spark isn't utilised or is redundant above 4000 rpm and in your case the main plug isn't firing properly or at all to take you beyond.

It's unlikely to be a coincidence that the failure happened after you changed the plugs though. Alex's coil check is a very good place to start

 

[leftofcentre]

Sounds like a coil. i had one fail, it started under load but got progressively worse over a week or 2.

Biggest problem was working out which coil, tried all sorts of combinations and would ride up the road only for it to appear/dissapear. Also tried a new plug.

In the end I disconnected all the coils except one and started the bike. It will start quite happily on 1 working plug (don't ride it anywhere), after going through 3 of the plug/coil combinations the bike would not start - this is the dud coil.

Alex

I am inclined to agree with the Coil theory. No need to mess about though as ive gone and bought the lot brand new! Well the two mains anyway and the aux's 2nd hand from Motorworks with 6mnth warranty!

Fingers crossed!!

 

[leftofcentre]

UPDATE - Well the new coild and iridium Plugs arrived today.

Engine is much smoother but still a bit hesitant around 4-4.5k rpm.

I think it maybe more of a vibes issue rather than misfiring.

Just waiting for my new balancer to arrive. One i have isnt that good.

I have some spare Coils in good nick if anybody interested?? PM me

Cheers

Andy