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Discussion Starter · #1 ·
Hey all, My first post. I have a 90 ZX750F Ninja with 30,000 miles on it and am adjusting my valves. I was able to adjust all except the 2 exhaust valves in the #4 cylinder. I could only back off the gap to the min. recommended clearance. Any idea why this is so? I was able to adjust all the other valves easily. Thanks, Bing
 

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Ahoy Bing and welcome.
First, check the possible causes that are cheap and easy:
~Are you 100% certain that #4 is at TDC when you're checking the clearance?
~Are you 100% certain that you're using the metric measurements given on your feeler gauge and that the blades aren't stuck together? Most feeler gauges in the US are given in inches, while our bikes' clearances are almost always given in millimeters.
Sorry if these sound like stupid questions, but I've made similar mistakes and have learned the hard way to check for the basic stuff before calling a machine shop for an appointment.

Next, these are the screw-type adjusters, right? If so, what happened when you attempted to loosen the adjuster screw more? If you cannot loosen it anymore, it sounds like these valve seats have reached the end of their service life. The only reason I can envision for the #4 exhaust valves having worn out more quickly than the others is additional heat. Possibly #4's carb was too lean for a period? How does the #4's sparkplug look compared to the others?
If this is the case, I've heard of some places that can add material to your valve seats and then re-cut them and the valves, but this would be almost as expensive as buying an all-new head; and certainly more expensive than searching every moto salvage yard in your state for a new head.

I hope it's one of the simple causes and I mean no offense when suggesting them. I can't believe that your valve seat would have worn so much after only 30,000 miles. I've got 32,000 miles on my '02 ZX9R and some of the valves still haven't required any adjustment at all.
Good luck and let us know how it goes!
-CCinC
 

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Discussion Starter · #3 ·
Calamarichris said:
Ahoy Bing and welcome.
First, check the possible causes that are cheap and easy:
~Are you 100% certain that #4 is at TDC when you're checking the clearance?
~Are you 100% certain that you're using the metric measurements given on your feeler gauge and that the blades aren't stuck together? Most feeler gauges in the US are given in inches, while our bikes' clearances are almost always given in millimeters.
Sorry if these sound like stupid questions, but I've made similar mistakes and have learned the hard way to check for the basic stuff before calling a machine shop for an appointment.

Next, these are the screw-type adjusters, right? If so, what happened when you attempted to loosen the adjuster screw more? If you cannot loosen it anymore, it sounds like these valve seats have reached the end of their service life. The only reason I can envision for the #4 exhaust valves having worn out more quickly than the others is additional heat. Possibly #4's carb was too lean for a period? How does the #4's sparkplug look compared to the others?
If this is the case, I've heard of some places that can add material to your valve seats and then re-cut them and the valves, but this would be almost as expensive as buying an all-new head; and certainly more expensive than searching every moto salvage yard in your state for a new head.

I hope it's one of the simple causes and I mean no offense when suggesting them. I can't believe that your valve seat would have worn so much after only 30,000 miles. I've got 32,000 miles on my '02 ZX9R and some of the valves still haven't required any adjustment at all.
Good luck and let us know how it goes!
-CCinC
Hey, Thanks for the reply. My cam is 180 degress from the lobe. My shop manual has both metric and inches on the recomended clearences. I do have the screw type adjusters with a locking nut. I backed the screw all the way out to just reach my minimum clearance. I will check my spark plug as I am going to replace them anyway and get back to you.I live in Calif. so that cylinder might be running lean cause of the smog requirements. I'm supposed to do valve adjustments every 6000 miles but last did it around 15000 cause the bike was running fine. It looks like a valve job is comming at my next adjustment time and I will do it in 6000 miles. It's a pain to get all the plastic off to get to the valves. Thanks for the info. Bing
 

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Discussion Starter · #4 ·
Hi again, You saved my life. You know how you said you make stupid simple mistakes.Well after I got home from work and after I made that next post I bought some new spark plugs and was going to gap them when I recalled that you said to look at the type of measurements(metric vs. US) welllll I had gapped all my valves to the us specs when I should of been in metric!!! What a dummy I am. And I thought I new what I was doing. Oh well, Now I get to regap my 16 valves again. Sometimes it pays to talk to others. Just think this is my first time in your forum and I got great results!! Thanks again. I'll let you know how it all turns out. You might have just saved me a valve job and lots of money. Bing
 

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I'm SO glad to hear that Bing! And don't feel stupid. It's not easy doing this stuff and there are so many little things you have to be so careful about. Over the years (and the many unsmart mistakes) I've learned that I can't have loud music playing or have ANY beer in the garage until the job is almost done and all that's left is to clean up.
The natural tendency is to rush because there are so many steps you have to go through to remove the plastic, hoses, carbs, headcover, etc.
I'm really happy it worked out. I'm in Carlsbad down by San Diego, so shoot me an email if you ever want to go for a ride:

my back yard

Take your time putting her back together and let us know how she's running when you fire her back up!
-Calamari Chris in Carlsbad, CA
[email protected]
 

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That would be one heck of a ride down from Pleasanton. He's almost by San Francisco. Great call on checking metric vs sae.
 

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True, but then he'd have an excuse to ride the :cool: Big Sur Highway :cool:.
My wife has made the trip from Diego to Francisco 3 times, and I rode all the way up there and back in one day once for a Babybutt. 1375 miles in 24 hours on my Superhawk.
Wife Lisa on :cool: Big Sur :cool:


And her first 500+ mile day back in '01:

-CCinC
 
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