Oil on spark plug.

Macflurry · 11-07-2018, 11:27 PM

Evening guys.

I'm having a bit of an issue with one of my plugs coming up covered in oil and subsequently making my bike (M900) run like a dog!!

When I got the bike and set up the carbs I noticed one of the plugs was heavily covered in oil which was causing the bike to pop and bog when revv'd. I also noticed metal filings in the oil when I dropped it to remove the oil filter.

Cleaned them both up and it ran great in the garage while setting the carbs up. Just before taking it out, the bike ran out of fuel while it was ticking over (rust blocking fuel from the tank) and ran like crap when more fuel was put in. De-rusted the tank and cleaned everything out, including the carb's. When setting them up I noticed that it was still running rough, checked the plugs and the same one was fouled up just from time running in the garage.

Put a fresh set of plugs on and everything was great. But after a minutes just checking the carbs were set up I had started getting a small amount of oil on the one plug.

Doesn't show it up too well but just so you can see the state changes as it goes.

Took the bike out for two hours, three days ago, parked it up in the garage and then went to look at it today before going out again. Checked the oil and the plugs before setting out. On the two hour run the oil had dropped from 3/4 of the way up from Min to Max down to about 1/4 and the same plug had a coating of oil. It was only a thin film of oil all over the electrode which looked more ingrained than stuck to it and made it look anodised shiny black.

Gave it a quick clean and rode it into town to pick up some more spark plugs as backups. As soon as I set off it was popping through the rev's. As I got to town it had eased up so I thought that maybe what was left on the plug had burned off. Went from Frome to Glastonbury and about half way there it started getting worse again. Left it parked up and swapped the plug for one of the new ones after getting some lunch. Once again, same plug covered in oil. This pic is just short of 3 hours use and had a quick clean about an hour previous.

Fresh plug in and it runs great... for 20 minutes.

So then, what's the best way to track down oil leaks into the chambers?

A quick google said to carry out a leak down test and listen for air leaking into the crank case for piston rings or into the head if it's valve seals. But I thought I would ask if there were any common issues to look into first before I started looking too deep into things?

Any advice on this is appreciated as I can see it being the head of at a minimum or full rebuild if it's the rings.

Nasher · 12-07-2018, 07:16 AM

Unfortunately as you’ve suggested the oil could be coming from several sources:

Above from the valve seals
Below from worn bores or incorrectly fitted/worn rings.
Sideways from a head to barrel issue. Our engines have no head gasket but do have ‘O’ rings at the joint with oil passing through them.

My first instinct was that it was valve seals, but It sounds like you are using quite a bit of Oil and that could point at either of the other two.

Which cylinder is it that the fouled plug comes from?

A compression and/or leak-down test will establish if the rings and bores are worn, but only if the valves themselves are sealing properly on their seats.
I honestly don't believe you'll hear air escaping and establish where the problem is.
Have you checked the valve clearances?

If it was mine I’d be whipping the heads off to have a look at the ‘O’ rings and give the heads a quick refresh.
The only special tool you’ll need is one to torque down the head nuts afterwards.
The vertical one is a faff but achievable I’m told without removing the frame on a Monster.
I’ve only done it with an engine on the bench.

Inspecting the joint faces will immediately tell you if you have a leak.

With the heads off it’s an easy job to change all the valve seals, and a look at the wear ridge at the top of the bore will give you an indication of bore wear cylinder to cylinder.
The valve shims and seals are far easier to do with the heads on the bench so it’s worth doing them after lapping in the valves.

I’m not actually sure if the barrels will come off with the frame in place, but again if it were mine I’d whip them off, hone the bores and put new rings in.

If you don’t want to lift the barrels, once the heads are refreshed and back on the engine, spinning it up and doing a compression and/or leak-down test will establish the condition of the rings and bores.

Good luck

Nasher

Macflurry · 12-07-2018, 08:42 AM

Awesome, thanks for that Nasher. That gives me a logical direction to go in.

It is the vertical one that fouls up. Had to be the tricky one didn't it!! lol

I'll grab a set of seals and start taking the head off for a better look and then go from there. So far I've not checked anything other than the plugs and how much oil it was getting through. As this kind of fault is new territory for me I thought I'd ask some advice before taking myself off on a tangent.

mickj · 12-07-2018, 09:36 AM

I'd be more concerned with the amount of hair your magnetic sump plug has grown, they look like shavings to me suggesting a more serious problem inside the engine.

Dukedesmo · 12-07-2018, 01:22 PM

Quote:

Originally Posted by mjgt

I'd be more concerned with the amount of hair your magnetic sump plug has grown, they look like shavings to me suggesting a more serious problem inside the engine.

Agreed, I had similar. Turned out to be a knackered bearing on the clutch/transmission shaft.

Dukedesmo · 12-07-2018, 01:25 PM

Quote:

Originally Posted by Nasher

I’m not actually sure if the barrels will come off with the frame in place, but again if it were mine I’d whip them off, hone the bores and put new rings in.

They do, no problem (I've done it on both Monster and 916). It's the SS models that you can't get the rear head off in the frame.

Macflurry · 12-07-2018, 02:28 PM

Looks like I’ll have to bite the bullet and just strip it. I had hoped to get some use out if it for a month or two before doing anything too major but it looks like I may as well get stuck in and just get it done.

Thanks again for the help.

Darkness · 12-07-2018, 05:48 PM

While you are in there, check the studs holding the heads and barrels in place aren’t still the original brittle ones. They had a nasty habit of snapping at the root of the threaded bits.

http://www.ukmonster.co.uk/monster/s...highlight=stud

Macflurry · 12-07-2018, 06:58 PM

All good stuff. Anything like this to look for is a massive bonus, thank you!!

Macflurry · 29-03-2019, 08:17 PM

Hi guys, I've finally got around to the point where I can follow this up now.

Since my last post in August I've gone through quite a bit trying to get this running properly and although it is much better it isn't quite right yet.

From where I left off above:

1. I swapped the valve seals and checked the shim clearances. Clearances were well out but put it back together with the new seals to see if it improved but it didn't.

2. Stripped off the heads and swapped out all my shims as the tolerances were well out, found that one of the front valves was very slightly bent. It still sealed properly but can't have been healthy. Also found that the little oilway stud hadn't been seated properly previously and had dented itself into the barrel so it didn't locate all the way down. Fixed all this and it ran better but still heavily fouled the rear plug.

3. Removed the heads and barrels, found a shattered oil ring in the rear piston. This will account for all the metal around the sump plug. Gapped the new oil ring, put it back together and it ran even worse than before. It bellowed smoke out the back and spat oil out of the exhaust joints!! As it was worse than previous but now actually had an oil ring that lead me first to the oil seals I had swapped. Bought a new set and fitted them which sorted all of the smoke and oil coming out the back. Looks like I had nicked one of the seals slightly when fitting them and even a tiny bit of damage caused a LOT of oil to get through.

4. Ran a compression test, adjusted the mixture again and sync'd the carbs. All was looking much better but not quite right still. On the road the clutch was slipping badly and when you went through the rev's the bike still pop's between 4-6k rev's. At this point moving house and fitting a kitchen halted progress for a couple of months.

5. Fitted new clutch plates and oil seals a couple of weeks ago and the bike mostly pulls like a train all the way through to the top end. It isn't hesitant but it still pops slightly in the mid range. You notice when trying to hold a constant speed and as well as hearing it you feel it through the bike. Took it for a blast to my brothers and pulled the plugs out where I saw the back one fouled up again quite heavily with carbon and oil. As I couldn't remember when I swapped it out last I just bought a new set and rode it from Redditch to Blakeney (about 60 miles). Took a look at the plug again today and it doesn't have a heavy build up of crap any more but it has a light coating of oil over it still...

Now at this point I'm running out of ideas. It is much better than it was and it is rideable now but I don't like doing things by halves and want to nail this down but I've swapped out everything I can think of so any suggestions are appreciated!!

From here all I can think to do is swap out the rear valve stem seals one more time in case there was an issue from fitting them. But as it has had a new oil ring, new valve seals, new shims, new o-rings, several sets of new plugs and lots of TLC I was hoping it would be sorted by now.

11-07-2018, 11:27 PM	#1
Macflurry Registered User Join Date: Mar 2018 Location: Blakeney Bike: M900 Posts: 134	Oil on spark plug. Evening guys. I'm having a bit of an issue with one of my plugs coming up covered in oil and subsequently making my bike (M900) run like a dog!! When I got the bike and set up the carbs I noticed one of the plugs was heavily covered in oil which was causing the bike to pop and bog when revv'd. I also noticed metal filings in the oil when I dropped it to remove the oil filter. Cleaned them both up and it ran great in the garage while setting the carbs up. Just before taking it out, the bike ran out of fuel while it was ticking over (rust blocking fuel from the tank) and ran like crap when more fuel was put in. De-rusted the tank and cleaned everything out, including the carb's. When setting them up I noticed that it was still running rough, checked the plugs and the same one was fouled up just from time running in the garage. Put a fresh set of plugs on and everything was great. But after a minutes just checking the carbs were set up I had started getting a small amount of oil on the one plug. Doesn't show it up too well but just so you can see the state changes as it goes. Took the bike out for two hours, three days ago, parked it up in the garage and then went to look at it today before going out again. Checked the oil and the plugs before setting out. On the two hour run the oil had dropped from 3/4 of the way up from Min to Max down to about 1/4 and the same plug had a coating of oil. It was only a thin film of oil all over the electrode which looked more ingrained than stuck to it and made it look anodised shiny black. Gave it a quick clean and rode it into town to pick up some more spark plugs as backups. As soon as I set off it was popping through the rev's. As I got to town it had eased up so I thought that maybe what was left on the plug had burned off. Went from Frome to Glastonbury and about half way there it started getting worse again. Left it parked up and swapped the plug for one of the new ones after getting some lunch. Once again, same plug covered in oil. This pic is just short of 3 hours use and had a quick clean about an hour previous. Fresh plug in and it runs great... for 20 minutes. So then, what's the best way to track down oil leaks into the chambers? A quick google said to carry out a leak down test and listen for air leaking into the crank case for piston rings or into the head if it's valve seals. But I thought I would ask if there were any common issues to look into first before I started looking too deep into things? Any advice on this is appreciated as I can see it being the head of at a minimum or full rebuild if it's the rings. Last edited by Macflurry; 11-07-2018 at 11:34 PM..

12-07-2018, 07:16 AM	#2
Nasher Registered User Join Date: Jul 2014 Location: Portsmouth Bike: M900 Posts: 1,510	Unfortunately as you’ve suggested the oil could be coming from several sources: Above from the valve seals Below from worn bores or incorrectly fitted/worn rings. Sideways from a head to barrel issue. Our engines have no head gasket but do have ‘O’ rings at the joint with oil passing through them. My first instinct was that it was valve seals, but It sounds like you are using quite a bit of Oil and that could point at either of the other two. Which cylinder is it that the fouled plug comes from? A compression and/or leak-down test will establish if the rings and bores are worn, but only if the valves themselves are sealing properly on their seats. I honestly don't believe you'll hear air escaping and establish where the problem is. Have you checked the valve clearances? If it was mine I’d be whipping the heads off to have a look at the ‘O’ rings and give the heads a quick refresh. The only special tool you’ll need is one to torque down the head nuts afterwards. The vertical one is a faff but achievable I’m told without removing the frame on a Monster. I’ve only done it with an engine on the bench. Inspecting the joint faces will immediately tell you if you have a leak. With the heads off it’s an easy job to change all the valve seals, and a look at the wear ridge at the top of the bore will give you an indication of bore wear cylinder to cylinder. The valve shims and seals are far easier to do with the heads on the bench so it’s worth doing them after lapping in the valves. I’m not actually sure if the barrels will come off with the frame in place, but again if it were mine I’d whip them off, hone the bores and put new rings in. If you don’t want to lift the barrels, once the heads are refreshed and back on the engine, spinning it up and doing a compression and/or leak-down test will establish the condition of the rings and bores. Good luck Nasher __________________ Heaven doesn't want me, and Hell is afraid I'll take over.

12-07-2018, 09:36 AM	#4
mickj Registered User Join Date: Jun 2018 Location: Clevedon Bike: M1200s Posts: 554	I'd be more concerned with the amount of hair your magnetic sump plug has grown, they look like shavings to me suggesting a more serious problem inside the engine. __________________ Keep the rubber side down. Mick

12-07-2018, 02:28 PM	#7
Macflurry Registered User Join Date: Mar 2018 Location: Blakeney Bike: M900 Posts: 134	Looks like I’ll have to bite the bullet and just strip it. I had hoped to get some use out if it for a month or two before doing anything too major but it looks like I may as well get stuck in and just get it done. Thanks again for the help. Last edited by Macflurry; 12-07-2018 at 04:08 PM..

12-07-2018, 05:48 PM	#8
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	While you are in there, check the studs holding the heads and barrels in place aren’t still the original brittle ones. They had a nasty habit of snapping at the root of the threaded bits. http://www.ukmonster.co.uk/monster/s...highlight=stud __________________ Original and Best since 1993 Last edited by Darkness; 12-07-2018 at 05:53 PM..

12-07-2018, 08:42 AM	#3
Macflurry Registered User Join Date: Mar 2018 Location: Blakeney Bike: M900 Posts: 134	Awesome, thanks for that Nasher. That gives me a logical direction to go in. It is the vertical one that fouls up. Had to be the tricky one didn't it!! lol I'll grab a set of seals and start taking the head off for a better look and then go from there. So far I've not checked anything other than the plugs and how much oil it was getting through. As this kind of fault is new territory for me I thought I'd ask some advice before taking myself off on a tangent.

12-07-2018, 06:58 PM	#9
Macflurry Registered User Join Date: Mar 2018 Location: Blakeney Bike: M900 Posts: 134	All good stuff. Anything like this to look for is a massive bonus, thank you!!

29-03-2019, 08:17 PM	#10
Macflurry Registered User Join Date: Mar 2018 Location: Blakeney Bike: M900 Posts: 134	Hi guys, I've finally got around to the point where I can follow this up now. Since my last post in August I've gone through quite a bit trying to get this running properly and although it is much better it isn't quite right yet. From where I left off above: 1. I swapped the valve seals and checked the shim clearances. Clearances were well out but put it back together with the new seals to see if it improved but it didn't. 2. Stripped off the heads and swapped out all my shims as the tolerances were well out, found that one of the front valves was very slightly bent. It still sealed properly but can't have been healthy. Also found that the little oilway stud hadn't been seated properly previously and had dented itself into the barrel so it didn't locate all the way down. Fixed all this and it ran better but still heavily fouled the rear plug. 3. Removed the heads and barrels, found a shattered oil ring in the rear piston. This will account for all the metal around the sump plug. Gapped the new oil ring, put it back together and it ran even worse than before. It bellowed smoke out the back and spat oil out of the exhaust joints!! As it was worse than previous but now actually had an oil ring that lead me first to the oil seals I had swapped. Bought a new set and fitted them which sorted all of the smoke and oil coming out the back. Looks like I had nicked one of the seals slightly when fitting them and even a tiny bit of damage caused a LOT of oil to get through. 4. Ran a compression test, adjusted the mixture again and sync'd the carbs. All was looking much better but not quite right still. On the road the clutch was slipping badly and when you went through the rev's the bike still pop's between 4-6k rev's. At this point moving house and fitting a kitchen halted progress for a couple of months. 5. Fitted new clutch plates and oil seals a couple of weeks ago and the bike mostly pulls like a train all the way through to the top end. It isn't hesitant but it still pops slightly in the mid range. You notice when trying to hold a constant speed and as well as hearing it you feel it through the bike. Took it for a blast to my brothers and pulled the plugs out where I saw the back one fouled up again quite heavily with carbon and oil. As I couldn't remember when I swapped it out last I just bought a new set and rode it from Redditch to Blakeney (about 60 miles). Took a look at the plug again today and it doesn't have a heavy build up of crap any more but it has a light coating of oil over it still... Now at this point I'm running out of ideas. It is much better than it was and it is rideable now but I don't like doing things by halves and want to nail this down but I've swapped out everything I can think of so any suggestions are appreciated!! From here all I can think to do is swap out the rear valve stem seals one more time in case there was an issue from fitting them. But as it has had a new oil ring, new valve seals, new shims, new o-rings, several sets of new plugs and lots of TLC I was hoping it would be sorted by now.