Long time problem with one valve in cyl1? Pix

id4rox · 06-18-2007, 02:16 PM

Aloha all, I was referred here by someone at forumshawaii; said there were some real smart folk here that might know what my problem is!

I have an 88 zx-10. The bike has a bit of a problem at low speeds and low rpm; a slight hesitation that doesn't really affect the bike to make it a jolting ride or anything, but I have a distinct popping/ticking sound. Instead of doing a lip smack, do the tongue on the roof of the mouth. It sounds like pops of air. At higher RPMs the bike is smooth as butter and the problem isn't around.

The physicals: carb 1 gets coated with black gook that can be easily cleaned up with carb cleaner. After cleaning the carb it will get coated again within a day or two. The inside walls of cyl1 get black coating too. The top of a valve from what I can see gets a thick coating on it. The other valve(s) in the cylinder are clean as a whistle, and the other cylinders, carbs and valves are all clean as a whistle.

Since a picture is worth a thousand words, here's two pictures of the carbs to show you:
http://www.livefromhawaii.com/carbs/carbs1.jpg
http://www.livefromhawaii.com/carbs/carbs2.jpg

Here is a high res picture of the valve to show you what the valve looks like:
http://www.livefromhawaii.com/carbs/valve.jpg

Can anyone make any assertation or diagnosis of what is the likely problem with my bike? The bike runs OK, but I would be happier if I could remedy this problem.

When I bought it, cyl 1 wasn't firing because of a worn o-ring around the float valve seat; this was causing extreme fuel flooding in the cylinder and resulted in my getting 10mpg. I wonder if this problem with massive fuel flooding contributed to what I am experiencing now in some way? I don't think its a simple valve adjustment neccessity, since it's only the single valve and the rest are squeeky clean (but what do I know).

Aloha all

Veefer97 · 06-19-2007, 05:39 PM

Compession test is in order and will probably show a bad seal at the intake valve. While you have the compression tester hooked up use just the hose and pressurize the bad cylinder with air. Listen for air escaping through the carbs. My guess is a bad valve or a valve that is not sealing corectly. I beleive that the exhaust gases are escaping through the leaking valve at low RPM. Check your valve clearance as it may be too tight. The fuel flooding would score up the cylinders but the valves would not be harmed.

id4rox · 06-20-2007, 01:43 AM

Thank you for that detailed post, veefer.

I'll try to find someone with a compression tester and put it on my bike.

I think the problem in general is out of the scope of my abilities and something I would rather not try myself at this time, and a problem that I might need to shop around for shops to see what it might cost to fix.

User Name · 06-20-2007, 06:31 AM

If the compression test comes back good, it might be a bad valve seal. Is the other valve in that cylinder clean? Carbon deposits (if that valve isn't closing completely) are dry and dark gray, fuel/oil deposits are dark brown/black and wet/sticky. If the the other valve is clean, it's specific to that one valve and probably not a carb problem. A leaking valve seal wouldn't necessarily cause the popping/ticking, but it could cause the buildup you're getting.

gboezio · 06-20-2007, 07:46 AM

There a definite oil control problem, I suggest you a leakdown test, that way you'll know exactly where the air escape, witch valves, rings, even coolant. A compression test would work too, but you'll need to tear the engine apart to know what's wrong.
+1 on the valve guide, since the carb side is covered in oil, I suspect a guide to be worn.
As the hesitation issue and backfire (since your throttle plates are covered in soot) I suspect a low throttle lean out. Check your idle screws, count the number of turns and make sure it has the same as the others or the base setting. Take the carb bowl (easy, it's the lower pan of the carb) off and check the jets specially the pilot (small) and the needles for proper operation.
For a leakdown tester build, I made a detailed writeup here :
http://forums.bimmerforums.com/forum...d.php?t=680940

Veefer97 · 06-20-2007, 12:29 PM

Even if it is a oil control problem, valve guide seals or oil rings, there should be no dirt buildup on the carb buterfly. Air and fuel goes into and past the carb, very little goes against the flow of air. Oil would have to travel from valve through the carb and into the airbox in order to coat the carb buterfly. That discoloration is made my exhaust gases which are bypasing the valve seat. There still may be an oil control problem but it is not causing the symptoms in the picture of the carb. Intake valve guide seals show up on decelaration and startup as a puff of oil smoke, if they are bad enough they smoke all the time. Rings smoke all the time.