Burnt out exhaust valves

[Steptoe]

Strange world.

I've had three bikes in over a short period of time with burnt exhaust valves. All 1150 models.

The latest bike had both exhaust valves burnt out on the L/H cylinder. How do both get burnt out at the same time , when one gets burnt, the engine doesn't run, so in theory it can't then burn out the other valve.

All the bikes were standard, no aftermarket exhausts etc.

But the strangest thing !!!!!! All the bikes have been silver, 2 RT's and an RS.

Thinking about it, over the years i've never had a GS in with burnt valves !!!. Perhaps not having a fairing they get more cylinder cooling .

 

[AndyT]

Strange world.

I've had three bikes in over a short period of time with burnt exhaust valves. All 1150 models.

The latest bike had both exhaust valves burnt out on the L/H cylinder. How do both get burnt out at the same time , when one gets burnt, the engine doesn't run, so in theory it can't then burn out the other valve.

All the bikes were standard, no aftermarket exhausts etc.

But the strangest thing !!!!!! All the bikes have been silver, 2 RT's and an RS.

Thinking about it, over the years i've never had a GS in with burnt valves !!!. Perhaps not having a fairing they get more cylinder cooling .

Is there a similar stamp in the service book?? I say that as my 1150 has incredibly noisey tappets and has just been serviced by John Clarks up here in Scotland. My lasy GS went in to them for a service and came out with really noisy tappets and I suspect it is the same mechanic (but of course may be wrong).

 

[squid]

Strange world.

I've had three bikes in over a short period of time with burnt exhaust valves. All 1150 models.

The latest bike had both exhaust valves burnt out on the L/H cylinder. How do both get burnt out at the same time , when one gets burnt, the engine doesn't run, so in theory it can't then burn out the other valve.

All the bikes were standard, no aftermarket exhausts etc.

But the strangest thing !!!!!! All the bikes have been silver, 2 RT's and an RS.

Thinking about it, over the years i've never had a GS in with burnt valves !!!. Perhaps not having a fairing they get more cylinder cooling .

I sometimes wonder if the protection people bolt all over their bikes could effect the cooling?

 

[cookie]

i blame the tyres.

 

[Steve]

i blame the tyres.

More likely Tarkas' oil advice.

 

[ianboydsnr]

Is there a similar stamp in the service book?? I say that as my 1150 has incredibly noisey tappets and has just been serviced by John Clarks up here in Scotland. My lasy GS went in to them for a service and came out with really noisy tappets and I suspect it is the same mechanic (but of course may be wrong).

surely its tappets to tight that causes burnt valves and to slack causes to much noise

 

[AndyT]

surely its tappets to tight that causes burnt valves and to slack causes to much noise

Your spot on - thats why I'm not overly concerned at the noise but prefer them to be correct.

 

[Posh Pete]

A little slack is better - for a change?

With regard to oilhead tappet clearances at least. Or so I've heard.

 

[(RIP) Bin Ridin]

Sounds like incorrectly set tappets, maybe exh set same as inlet, 0.15mm instead of 0.3mm?

 

[Steptoe]

Sounds like incorrectly set tappets, maybe exh set same as inlet, 0.15mm instead of 0.3mm?

I checked the clearences before taking the head off. They were spot on.

 

[Shep]

Its quite common for exhaust valves to burn if there is an issue with cooling, either insufficient coolant flow (either air, oil or water whatever is used) or due to to a hot running engine (weak mixture, poor fuel and air leaks)

Strange to have two fail on the same cylinder, but that may have been down to poor mechanical sympathy from the rider, you know "ooo that sounds rough, no worries I have a service due in 2000miles they can check it then"

Shep

 

[Yoda]

Steppers - curiosity question. Were they all on the left hand side?

 

[Steptoe]

Steppers - curiosity question. Were they all on the left hand side?

This bike (RS,60K miles) was on the left.

The other bikes were both RT's , one on the left (16K miles) and the other bike was on the right (45Kmiles).

It's the K1100 bikes that a chronic valve weakness , almost all (95%) the burnt valves happen on number two cylinder

 

[Yoda]

Ta - I'd just wondered if there was evidence of a pattern on the oilheads.

 

[Blackal]

For both valves to burn through - my guess as to the cause would be "afterburning".

If your spark timing on that cylinder is late, the burn process tends to continue into the exhaust-opening phase - causing valves to burn.

Or - If it is a twin spark model, and one plug fails for an extended period - causing a delay in ignition????

Worth a check

Al

 

[Jaws]

Hhmmm interesting that info..
I have had a pain in thebum problem for a few days now ( see a n other thread ) and today changed the plugs.. What came out scared the pants off me.. The bloody things were as white as KKK members washing line !!

Must admit I am running a Y piece and a K and N ( both fitted by previous owner ) and am now seriously considering refitting the cat to try and richen it up a bit ( the K and N will proly go too as in all honesty I see little point in fitting the darned things ! They are more trouble than they are worth. )