Cylinder bore damage

[Brewers Whoop]

'99 R1100GS, 53K miles. Recently lost power and developed a knock from the right hand cylinder, whilst riding on motorway. I'd checked engine oil level before starting journey (by leaving up-to-temperature machine on centre stand for 5 minutes after switching off, and then checking window. Level was just above centre of window, where I aim to keep it). After onset of symptoms, I checked again and oil level was below window after journey of only 300 miles. Compression test showed 160psi in left cylinder, 90psi in right.

After a couple of fruitless sessions spent checking valve clearances and rocker/cam assembly and cam-chain tensioner, I pulled the head this evening. Saw visible damage to the bore, so pulled the cylinder. The top ring is seized in it's groove, and there is damage in the form of heavy scuff marks to the piston and to the cylinder wall. The cylinder damage can be clearly felt by running finger up and down the bore.

Question 1 is this: Can oilhead cylinders be refinished, or would it make more sense to look for either good secondhand or even (gulp) new parts.

Question 2: The right hand piston is definitely dead. Am I right in assuming I will have to buy pistons (and, presumably, cylinders if refinishing is not possible or not recommended) for both sides, or is there any chance I could get away with replacing only the right?

Oh yeah, and while taking exhaust off to pull head, I sheared an exhaust stud. Intemperate language was used....

As to the cause, the machine is fairly new to me and came with Remus Revolution, Y-piece, K&N air filter, no cat., no motronic coding plug and standard 'chip'. Although I have never heard it pinking, it does pop on the overrun. I have been a bit uncomfortable with the idea it may have been running too lean, and it looks as if I may be paying the penalty for not taking the trouble to check it out. And to compound this, I found a split in the rubber throttle body stub that I am guessing may have allowed air to be drawn into the right hand cylinder, compounding a potentially already lean condition.

Sorry to bang on at such length. Advice/experience/opinion much appreciated.

 

[cookie]

sounds like you need a new cylinder and piston.

cylinder walls are nicasil (afaik on an 1100) and though you might find someone to redo it, i i think you'll find it's not worth the grief.

doing one side would be ok if you were sure you were getting identical parts (piston weight) to existing.

 

[Tsiklonaut]

For precise oil level inspection, you have to put warm-engined bike on the side-stand for 5-15 minutes, so the oil flows out of the radiator, then on the center-stand and also inspect after 15 minutes or so after puting on the centerstand.

If puting directly on the center stand, you have inaccuracy of approx half of the inspection window (showing less then there is).

Does your bike have a lambda sensor? (you should see the wires going into the exhaust pipe beneath the gearbox) Lambda sensor should equalize some part for the fuel-air mixture (up to approx 3K rpms where the engine is in the open loop, or so I'm told).

Running both free flowing racing exhaust and a free flowing K&N filter can make the mixture extremely lean, especially if there's no lambda to compensate anything. Stock EFI mapping isn't made for such a free flowing (=more air) stuff on both ends IMHO.

Best way to check the throttle body's rubber mount leaks by spraying WD-40 on them while the engine is warm and running - soon the exhaust will start to smoke if the rubber parts suck the oil in, if so happends = leaky rubber you ought to replace. If nothing happends, no smoke, it's OK.

Bore and piston and rings: if you can get a set of s/h cheap would be nice, so they have an even-wear. If not, as Cookie sayes: replacing only one is a good start too.

Good luck!

 

[Flipfly]

They all run lean, unless tinkered with, and that in itself rarely causes an issue.

Have you always had the bike? I always change the oil at 3k and filter every 6k (I use cheap oil but replace regularly, IMHO better than spending alot on expensive oil and using it until it's knackered).

You should really ride the bike to get it warm, then check the oil, better than just leaving it standing to warm.

Do you use the centre stand or the side stand? Obviously the oil tends to drain to the left when on the side stand, therefore starving the right hand side.

Always use the centre stand wherever possible.

I would make sure that oil is flowing around like it should do and replace broken bits with secondhand parts. Changing them for new would mean doing both sides as otherwise the left side will be well run in a right would be all brand new. The cost of new would be horrendous to.

 

[Steptoe]

Bolt it back together and stick it on ebay

 

[Flipfly]

Bolt it back together and stick it on ebay

Being the Guru that you are, I'm assuming that this would be the best course of action

 

[Brewers Whoop]

Thanks Guys. E-bay option did pass fleetingly through my mind!

To answer a couple of questions:

I always check oil after bike is at normal temperature after being ridden, not by letting it tickover on centrestand. But hadn't come across the leaving it on sidestand for 5 minutes thing before. I'll be doing that in future.

I use the centrestand whenever possible, although the trouble happened on my way home from the Red Marley hillclimb, where the bike had been left on the sidestand for a few hours.

However, I dont think oil starvation is the primary issue - I suspect the quicker-than-normal drop in oil level I discovered after the 'incident' was a result of the damage, rather than the main cause.

Going to see if I can find a decent second hand cylinder and piston, to match those I have taken off. May take some doing!

Thanks again for advice

Alan

 

[John Armstrong]

First thoughts for the bits are, in no particular order:

James Sherlock: http://www.devonbmw.co.uk/

Motobins: http://www.motobins.co.uk/

Motorworks: http://www.motorworks.co.uk/

 

[Brewers Whoop]

Next question!

Is there a customary place where the piston size and weight markings are located? Haynes says they are on the piston crown. I've carefully cleaned the carbon off the top with a plastic-type pan scourer, but can't see any markings at all other than the cast-in letters and numbers on the underneath of the piston.

Cylinder is marked 'B', so if Haynes is correct, presumably the piston must be a B or an AB. Haynes also says that piston should be marked with a weight code + or -, unless it is standard weight in which case there is no weight code marking.

As I'm hoping to get away with just buying one cylinder and piston, I'm guessing correct identification is fairly crucial.

As ever, advice/experience/opinion much appreciated.

Alan

 

[Backmarker]

I put Remus/Y piece/K&N etc on at 20k, and yes it backfires on the overun, but it has now done 90k - I doubt this is the cause.
The split in the throttle body rubber is something well outside my experience, but would worry me.

The oil measuring thingy is a bit of a red herring in this case, as failing to put it on the side stand first merely means that what you thought was 'half way' up the sight glass was probably somewhere between half way up and all the way up. So you had more oil in than you thought at the start rather than less.

Although obviously not being privy to any info about the bike/owner history and how long you've had it etc I wonder whether you bought the bike with an existing problem. This 'diagnosis' is based purely on the basis that many people respect and value Steptoes advice (me included). Maybe the previous owner did too?

 

[Brewers Whoop]

Ok, since posting last message I have spoken to CW Motorcycles. It seems the piston ID marks are sometimes scribed but also often just painted onto the piston crown. Sounds like I probably cleaned them off when removing the carbon deposits.

Ah, the joys of uninformed mechanical floundering.

CWs advice is that it would be best to replace both pistons, as even they would not be absolutely certain of correct ID of a bare piston. They also advised me to be wary of fitting secondhand pistons.

What are other peoples views on secondhand pistons? Steptoe, if you're reading this thread I'd much appreciate your opinion on this.

Thanks

Alan

 

[Flipfly]

A good secondhand piston would be fine, but alot cheaper than new

Let's face it, why spend money when you don't have to

 

[speeder]

James Sherlock=secondhand piston and barrell=end of problem

 

[Brewers Whoop]

Tried the triumvirate of sellers of used BMW bits. Motobins and Sherlocks haven't got a barrel and cylinder in stock.

Motorworks have got items in stock, but advise that it's unlikely that secondhand piston and barrel will have come from same engine.

I'm a bit lairy about putting 'non-related' used pistons in the secondhand barrel from Motorworks and also in the undamaged barrel on my 50K miler.

 

[Flipfly]

Tried the triumvirate of sellers of used BMW bits. Motobins and Sherlocks haven't got a barrel and cylinder in stock.

Motorworks have got items in stock, but advise that it's unlikely that secondhand piston and barrel will have come from same engine.

I'm a bit lairy about putting 'non-related' used pistons in the secondhand barrel from Motorworks and also in the undamaged barrel on my 50K miler.

If St.eptoe can't help ya then try Germany. 100's of good bit there and hopefully at a good price (although euro may put pay to that ).

I've seen whole short motors go for a few hundred quid so worth a look. Do a search for used bmw motorcycle parts in Germany

 

[Tsiklonaut]

http://www.ebay.de

Search in 4 separate searches to get the most effective parts list out:

R 1100 GS

R1100 GS

R 1100GS

R1100GS

 

[ktmmark]

My bike won't run on side stand it has a cut out switch