Plug fouling

[Grimreaper]

Hi folks, the left outer plug on my ELR Z1000R2 keeps fouling after sitting overnight. Any ideas what's causing it. Thanks Mike

[zed1015]

Oil fouling due to a leaking valve stem seal or flooding due to leaky carb float valve.
Pull the plug before starting and see if it smells of fuel or oil.
Chances are it's the stem seal.

[Grimreaper]

Excellent, thanks for the help.

[BJ81ZED]

Oil fouling due to a leaking valve stem seal or flooding due to leaky carb float valve.
Pull the plug before starting and see if it smells of fuel or oil.
Chances are it's the stem seal.

I seam to be having a similar problem with my left plug but no symptoms after being stood, it seems to happen on a long downhill with throttle closed (some big hills around here). Its happend three or four times now on my new 81 1100STA1. 3 times it has caused it to run on 3 cylinders. Once home the plug check reveals an oiled plug. Had a 40 mile run out on Tuesday, all OK apart from one quick misfire after a downhill section, fired it up yesterday in the drive, warmed the engine and then removed plug, sooty black, all others are spot on.

Is this likely to be a valve seal? Why would it only happen on one valve or cylinder. Is it likely rather the seals deteriorate on a 40 year old bike?

Is this a cams out job to fix and would it make sense to replace all 8 valve seals due to age? No idea if any have been replaced previously in the bikes life.

And lastly, is there anyone in my area that is trusted to do the job on an old bike? I live between Blackburn and Preston in Lancashire.

Happy Easter

[zed1015]

A closed throttle creates a depression in the cylinders which will pull oil down a worn stem seal.
Puffs of smoke from the exhaust on the over run are an indication of this.
The seals do degrade over time and they are all not forced to wear evenly so you can have one bad one and the rest still hanging on in there.
If they have never been changed they will need doing.
It can be done with the head in situ but it's tricky and you need a special rig to remove the valve collets and springs whilst pressurising the cylinders to keep the valves from dropping.
It really needs the head off as it will most likely benefit from a clean up of the valves etc.

[BJ81ZED]

Thanks ZED1015

I was rather hoping it could be a no jead off job. I do agree if it is then valve seats and everything done does make sense for the long run. Its expense that was not planned though and no idea what it would cost.

Need to find a reputable parson to do it though, before the weather gets warmer.

[chrisNI]

Buzzard is always a good bet but it would need posting down to him, also you’re best ringing him to see when he can do it as he’s pretty busy. If it’s not all mangled it should be a simple task for him so he might be able to slot it in.

[BJ81ZED]

Thanks Chris

While ordering the bits from Z Power I asked the guy there if they new anyone and he did recommend an individual much closer to home. However, I have since discovered that one of my steam friends used to work at a bike workshop, has had multiple bikes and is more than capable apparently so it is going that way and I can help out after work if bed be.

Gasket set arrived from Z Power and we have also done a compression test to discount any issues with the bores and all is well so we confirmed the cause is valve seals. Also balanced carbs while we where at it with my new manometer test equipment to test it out.

Just need to fix the dstsrt date with him as it s going to another local steam friend's shed, he has way more space there to work as first guy will be bringing his bike ramp too.

Updates to follow in due course

Brian