Not Another Oil-Fouled Plugs Post!

Yes, it is. and VERY unfortunately. but I won't be a witch with a capital B about it. I was hoping to avoid work like this. I thought my plugs were carbon fouled because it was all black and dry when I took them out (like the 6th pair).

BUT, i idled it for 6 or 7 minutes with brandy new plugs (just revved it a few times) and took them right out and it was wet black this time. @$&#$)$&!

So, I think I've done my reading. It could be piston rings or a poor valve seal. To answer the question before it is asked, it doesn't smoke at all even during idle.

So I have to pull the top-end off right? this will be new territory for me. any forewarnings? tips and tricks? things to watch out for?

should i replace the pistons and rings while i'm in there if i can find new ones?

will i be able to find the gaskets that i need? i didn't have much luck on ebay or Z1.

Any help would be appreciated guys. :sick:

If I read this post correctly, your spark plugs are fouled. They appear black/sooty. They are fouled?

If this is the case, the fouled plugs are caused by incomplete combustion. The reasons for incomplete combustion are most likely:

1. Poor compression. May be caused by rings not seated. The number 1 reason for poor compression is lack of valve clearance. Read the valve clearance article on my web site. It is intended for 900/1000 models but the principals will help you understand the reasoning. Use a gauge to check compression before deciding to rebuild an engine. Check valve clearances.

2. Ignition problems. Poor spark WILL cause poor combustion as will timing problems. First, the bike may just need to be tuned. Has the timing been set? Have new points/condensor been installed? Have new plug wires/caps been installed? Has the coil impedences been checked as old coils have their resistance creep up and deliver miserable spark. Has the voltage at the coil been checked? See the article on my web site for re-powering your coil to be sure it fires to its full potential.

3. Last, could the air filter be clogged? Could the float levels be off in the carbs? This will cause plug fouling.

If you want to rebuild the engine, that is great but I would look for the cause of the poor combustion before going further.

hey george,

yes, the plugs are Oil-Fouled. I thought they were carbon fouled but it must have just been dried oil from combustion?

i thought that if it was oil-fouling, then some of the causes you mentioned would be ruled out (air filter, ignition problems.

if oil is getting onto the plugs, isn't that definitely a problem with the rings or valve seals?

Also, just so I'm sure that I understand, if oil is getting past the rings, does that mean I must have poor compression and a compression test would show that?

thanks again guys.

Yes, do a compression test. It will show low compression if the rings are bad, or if the valves are not sealing properly. If the compression is low, put a little oil in the cylinder and test again. If the compression test then shows better, it is likely to be a problem with the rings. If the compression is still low it is probably a valve issue (carbon fouled, clearance, bent valve stem...)

Z1 does have engine gasket sets for the 750 B series (twin cylinder), it is just not listed online. I got a set from Jeff earlier this year for ~ $65.

good tips! figuring out what the problem is without pulling it apart will be nice. one question: how much oil do you consider "a little oil"? won't it all just burn off right away?

Well, I don't really know exactly how much, just enough to provide additional sealing around the rings. A quarter teaspoon? The compression test is done without the spark plugs, as that is where the compression tester goes. As this is the case, it won't burn off until the engine is run again.

Can ya tell I've never done a compression test before????? Well, I'm going to when I get home. Thanks!

Well, it was a crappy old compression tester I borrowed (the press and hold type) with cracked rubber around the end, so I don't know how accurate it was...

(also, my girlfriend was holding the guage against the engine for me so that may have contributed to the numbers to! she was getting freaked out and then one my clothes-pinned gas tank hoses popped open and the "helping me" thing was all over.)

...but the highest readings I got were mid ninties. One thing I read in the service manual (after the fact) was that you should do it on a hot bike and make sure both of the spark plugs are removed.

Question 1: Are these steps absolutely necessary. I'd imagine the metal in a hot bike would have expanded, making the compression chamber more tightly sealed.

Question 2: My starter is disconnected (previous owner said it grinded every time he tried to use it, haven't investigated or researched yet) so i have to kick it over for the test. is this sufficient??????

thanks guys.

Not necessary to test hot. Remove plugs. Get a GOOD QUALITY compression tester and place the tip in a plug hole. Have someone do this for you while you kick bike over several times. No sense doing things hapharzardly as it is a waste of time. Open throttle all the way while you kick else your readings will be low. Report back when you have done it this way and diagnosis can continue from there.

will do.