Burnt out valves

Paul Wakefield

Well-known member
UKGSer Subscriber
Jan 6, 2002
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Just had a rather depressing visit to Hughendens.

Went up here for them to cure backfiring (I thought it was a leaky exhaust) and, because bike didn't feel right, to balance the throttle bodies (Why didn't I do it myself? - well, incompetence, lazines, mechanical illiteracy; delete all, some or none as appropriate).

Turns out Right hand cylinder compression is way down. Until they have had the head off, the firm diagnosis is awaited but they are nearly sure it is a burnt out valve. They have already had 2 GSs in which had both gone at the 25,000 mile mark - exactly my mileage. The only hope is that apparently the butterfly makes a lot of noise when this problem is developing and mine doesn't - Fingers crossed.

Not looking forward to an expensive (as the bike is well out of warranty) and lengthy job. No doubt, if diagnosis is confirmed, conversations will be had with BMW. In the meantime, has anybody else had this problem? If so, what was the outcome (costs, BMW discuaaions, etc.)?

Paul, who's been doing the servicing? if a valve has burnt out at this milage I would suspect the valve clearences were not correct... this will cause premature valve failure.
My previous GS1150 ate two exhaust valves at different times, one on each cylinder. It was like riding a very heavy one-pot 600cc bike.

The first went at 7,000 miles and when stripped down (under warranty) a chunk of the valve edge was missing. BMW could not explain what had happened.

Seven months later at 13,000 miles (and out of warranty) it did the same thing to a valve on the other side. I couldn't believe it.

It was fixed for nothing - BMW could hardly do otherwise considering the bike's history. Again no-one seemed able to explain what had caused it.

It went on to do 24,000 without further trouble before I sold it.

Make sure you are not suffering something similar.

Hughenden's have always done the servicing. Despite comments elsewhere on the site, I've had a very good service from them over the last 13 years & some reasonably high mileages so I would be surprised if they got it wrong. Not to say they didn't of course ! :)

Heated Grips,

Your description of a missing bit of valve edge exactly matches Hughenden's description of previous probelms. Sounds like this may be a relatively common fault.

I'll let you know more when they've had the opportunity to look at it properly.

Mmmmm, just wondering if this problem has anything to do with running weak? Have those of you who had valve problems fitted anything like an aftermarket pipe, K&N, etc. ???

no my bike was completely standard both times it broke. However... thinking about it, both times it had been serviced about six or so weeks earlier, at Sawbridgeworth. I never suspcted any connection between the two events before - doh!

I've since gone back to using Wollaston BMW as my dealer.
Well, I had the cat removed in August since when it has only done about 4k miles. Standard pipe remained. Interesting.

I was on one of the early Off Road courses where quite a few attended from BMW and they recommended removing the cat so presumably didn't expect it to cause any problems.

This thread is going to get VERY INTRERESTING as sooooo many of you riders are out there with the Remus etc and cat removed and I wonder what the mixture is doing in the cyclinders with these mods. Those on the list that have been on rolling roads have been told ??? that the mixture is very lean with the CAT and the Remus etc fitted. Any feedback from other riders that have reached this mileage or is there a collective need for valves from a lot of people at about 25k who run aftermarket pipes etc.
I'm probably going to sound very dull saying this but, surely as long as you have a serviceable lambda probe connected, the 'closed loop' design will ensure that the mixture remains correct.....

Having a Dyno........

I'm taking CC II to a local dealer next week to have a run on a Dyno.

I've got the 'Y' piece, Race Can, K&N Filter set up with the Sensor in place.

I'll report back if anyone wants to know what the result is without a Techclusion or Chip tweaking things.


If I remember correctly, when Steve Rose was with RiDE mag, riding a long-term GS, he had it dyno'd when the Y and race can were fitted, and the fuelling was a supposedly spot-on 13% mixture, better than the stock set-up.
Scurrell, you are dead right, I remember that article as well. But MikeO, I could be wrong here, and usually I am but.... The motronic runs both open and closed loops.

Closed loop is running at tickover and at very light throttle openings. As soon as you open the throttle more than a smidgin it defaults to open loop which is reading the map on the chip. Therefore (and once again I am assuming) it just feeds in what the chip tells it. I need someone to convince me that the system auto-compensates mixture everywhere. Both open and closed loops.

This is the bit that has me both confused and concerned. I assumed the sytem would auto-compensate but fitting the Techlusion R259 leads me to believe it doesnt. Or, if it does its not enough. I am delighted with the way my bike runs now and I am almost convinced that most of the reasons why I felt my bike should run better were mixture related. ie borderline weak.

Does that make sense:confused:

Agree with Panzer;

The motronic system only supplies fuel according to the chip's map at anything other than cruise, and unless you have a re-mapped chip, altering the way the engine breathes will affect the mixture. ( i.e. unless you have gone the other way and put a cork up the exhaust, the preformance mods such as Remus etc. will make the bike run lean!) The better the engine breathes, the leaner the mixture.

The probe is only used for the "Closed Loop" phase of the running which is the idle/cruise mode. Not sure though at what point the system switch from closed to open loop control.

Hence the design of the Techlusion gizmo's to allow more fuel or the BB Power chips.

The chip option allows several maps for differing states if tune switched via a code plug whilst the Techlusion method allows tuning of the individual engine.

(Take your pick, I went for the Techlusion. V. impressed.)

In conclusion, engine performance mods without the fueling changes being made = real chance of engine damage due to lean mixture & overheating. Prob. exagerating the dangers but can't make things any better in an already lean running engine.

Does my rambling make sense?

Cheers, Rick.
Yes, but... my dealer was happy to put a Y-piece and K&N on my new (600 miles) bike and also wanted to flog me a Remus, but lack of cash ruled that out.

They assured me that all the bits would not affect my warranty. So naive question, if putting them all on weakens the mixture to an unacceptable degree, aren't they shooting themselves in the foot?

I fitted K&N, ypiece and end can.

Got it dynoed.

It was running lean. not sure if it ran lean before.

thats why i fitted the techlusion.

I talked about this last year on this site, and warned about burning the valves.

Much of which was poo pooed.

Permission to say i told you so yet ?


Mind you, the header pipes on my current bike have turned a deeper colour than on the previous GS, and the effect goes much further down them.

Signs of leaner (ie hotter) running? Oh lor, what have I done?
Valve gaps I reckon

I think it will be the valve gaps.

Indeed I know of a bike serviced in your area that had 0 gaps. Coincidence ? Pure conjecture of course but it will cause it and it has been known for serviced bikes to have 0 gap.

OK I'll leave now before the gagging order appears.
burnt valves??

I have been running my GS for about six months now with no filter in the airbox and a length of flexible ducting sealed on the inlet snorkel. This is then fed around to the right of the tank and up to the space where the ABS stuff should be if it was fitted. On the end of this ducting I have sealed on a K&N performance filter for a Vauxhall cavalier turbo (not sure what year). There is very little in the way of air restriction and I have been thrashing the bike mercylessly since. As far as I know my valves are fine and the plugs look ok as well. I have a remus Y fitted and a less restrictive exhaust (half inch steel bar banged down the standard can a few times, ahem). I can therefore only conclude that the motronic system is controlling properly. Dunno, my mechanic friend says the mixture is spot on at 4000 revs although it has a very rough idle.

Bike has covered 20000 miles and has a full history (and was standard) up to 16000 miles. Maybe I just got a good'un.

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