Oil foul spark plugs - KZ750 Twin 1976 (KZ750B)

Hi! I have the plug fouling issue on my Kawasaki KZ750 Twin 1976 (KZ750B, Z750B). The bike runs great and starts easy with the kickstart with new plugs but they get fouled quite quick. Maybe like 100km or something near that. More on the right cylinder than the left. Have ridden the bike for like 7000KM in maybe 5 years with a lot of plug changes:)

Have tried almost everything except oil seals and piston rings now. Really like the bike and I think it will be with me for the rest of my life.

- Dyna S ignition spot on installed.
- Dynatek coil
- Strong spark with new plugs.
- Valve clearance within specs.
- Former perfectly clean BS38.
- Now new VM34s with Jetting: 200 mains, 27.5 pilots, 159 P-8 needle jets, 6FJ6 jet needles, 2.0 slides, and 2.0 air jets..
- Pod filters.
- Shorty mufflers
- Have tried every spark plug from B6ES-B9ES and the Iridium BR7EIX (I think that was the name) with the same result.

Have not done compression- or leak test yet.

Is it hard to change the oil seals and piston rings? I have the shop manual and read it for a couple of years now:) Do you need the special tools or can you do it otherwise?

//Fredrik

Sorry. Did not mean to post 4 images. This is my first post here I think. I will learn how to post images:)

//F

Do you know the stock jet settings? 200 mains seem really high.

Chances are it's the valve guide seals. You can take the head off but be careful to not disturb the base gasket. Be sure all the carbon is out of the cylinders or it will scratch the walls.
Steve

Valve guide seals. On my 750 twin, they would fail about every 12 years average (city riding) and start fouling plugs. Some new VITON seals should fix it.

As previous speakers says, renew the valve guide seals.
They do the hardest job of all seals in the engine. and loosen her flexibility and sealing properties by hardening through the heat.
VITON seals are the best you can buy.
Michael

Thanks Boyntyhunter/Scirocco!

I have the service manual who says that I need the special tool for valve jobs. Do you have it or do you manage to change valve seals wo that special tool?

//Fredrik

No eBay APP ID and/or Cert ID defined in Kunena configurationHello Shellsson

eBay is a good source for the right tools





This tool set include all you need, seal puller grip and remounting tabs for the seals
No need to remove the cylinder head for the valve seal job. In this tool set is a spark plug adapter to put compress air into
combustion chamber on TDC to prevent that the vale fall down into the cylinder or hit the piston.





Michael

Great Michael! Will order the tools asap.

//Fredrik

Shellsson wrote: Great Michael! Will order the tools asap.

//Fredrik

Verify the application. :blink:

Have made the oil seal upgrade now. Have not had time to test the bike yet but hopefully it will work!

Thanks Shellsson for the update 4 years later !!! Wow. Could be a record here.

Please let us know if the repair was successful and was it difficult do do without removing the head