G9 valve adjustment
 

Hey guys. I've never adjusted valves before and I think my G9 needs some TLC. Is that an easy task and do I need any special tools to do so?

Thanks
Scott

G9 valve adjustment
 

I’ve never done it but wait until CP241 sees this thread... he knows everything about gas Yamahas.

Re: G9 valve adjustment
 

I just did this on my G2 (Same/Similar engine) and it is relatively easy.

My recommendation is to get a new valve cover gasket or gasket making material. I tried to re-use the old one and it was broken. Had to wait a week or so for the new one to come in.

As far as tools, screws were Torx on mine, not sure if original. And a feeler gauge

Re: G9 valve adjustment
 

I use a small pair of vise grips and a 10mm wrench. Set them both at .004 while the engine is cold.

Re: G9 valve adjustment
 

This always seems to be a recurring question, so I will write up with pictures so hopefully anyone referencing adjusting valves on a G2/G9 (though it will carry over to any model) can find this thread.

This should be done on a cold engine. I always like to do a compression test before and after, if it's the first time I've done it on a motor just to see if it makes a difference. IF the motor has been neglected and adjustments have not been made, you'll usually notice a bump in compression. Sometimes I've even had motors with NO compression come back with perfect compression after a valve adjustment.

Pictures were taken using a spare cylinder head on a bench, but in the cart will not be any different. Disregard the dirt and funk on it, it's been in a bucket under my workbench for I'm not sure how long :lhmo:

1. Remove the spark plug 3 hoses on the valve cover (green boxes).

2. Remove the 4 bolts securing the valve cover. These use a 5mm Allen wrench or socket (red circles).

3. Remove the spark plug.

4. Insert a dowel rod (or long screwdriver) into the spark plug hole.

5. Using the primary clutch, turn it over by hand until the screwdriver is all the way up, just before it starts to go back down again. Look at both valves/rocker arms. They should be even, and should both be a little bit loose (can wiggle them up/down by hand). If one of the valves is not even, rotate the motor over by hand until the screwdriver is all the way up again.

6. Insert a .004 feeler gauge between the valve and the rocker. If it won't fit, the valve is too tight. If the feeler gauge slides in with no resistance, it's too loose.

7. Loosen the 10mm nut on the adjuster. Don't remove it, just break it loose so you can turn the nut with your fingers. (ignore the screw in the picture, this will come into play later).

8. Insert a .004 feeler gauge between the valve and the rocker arm. When you pull or push on it, there should be a little bit of drag... not "loose" but not so tight it binds either. It takes a little practice to get the "feel" of it, but once you have it right, you'll know. If you try to use a .006 feeler gauge, it should not fit. Tighter or loosen the adjuster, I use a wood screw with a square drive head. Fits on the adjuster perfectly (this is the screw in the picture). Tighten/loosen this screw while sliding the feeler gauge back and forth until you feel the light drag.

9. Once proper drag is achieved, hold the adjuster with the screw and tighten the lock nut with a 10mm wrench. Snug is good, don't overtighten it. You will need to hold the adjuster with the screw while tightening the nut or the adjuster will turn with the nut a little bit, tightening the adjustment.

10. Once adjustment nut is tight, recheck with a feeler gauge to make sure it is still right.

Then, turn the motor over by hand (rotate the primary clutch 2 revolutions for 1 complete engine revolution) and double check your valve adjustment with a feeler gauge to make sure it's still good. IF so, replace the valve cover gasket (I always like to use a light skim of permatex black on both sides of the gasket, but that's just me), reinstall the valve cover and take it for a drive.

Re: G9 valve adjustment
 

Also, Never try to reuse the old valve cover gasket, it will leak every time. Get your exacto knife scraper blade ready for this job, the gasket is almost always baked on to the head, it's a pain, and I have seen new guys "throw their hands up in disgust" over getting it clean enough (and I was once, or twice, that guy). Clean, clean, clean! And no junk you scraped off falling down in the head either, that's a task in itself. I usually stuff a portion of a plastic grocery bag in the rocker galley to collect the junk that tries to fall in, No "red rag lint" that way!

CP241, really good write-up on the process!

Re: G9 valve adjustment
 

Good idea with the bag. I use washcloths from walmart as rags, an 18 pack is like 3 bucks and they don't leave the red lint either :)

IF there's anything I've missed, please add. We always say "adjust the valves" but to a lot of folks that have never done it before, this is sort of a mystery. I often take for granted simple things like valve adjustments, timing belt, etc. because I've done so many. But to someone that hasn't, it can be a bit overwhelming. I'd like to be able to point them to one thread where they can read start to finish exactly what to do from a beginner standpoint without the confusion.

Re: G9 valve adjustment
 

CP241 you are the man to go to!! Thanks!!!! And what do correctly adjusted valves do for the engine? Runs smoother? Quieter? Just curious.

Thanks again for everyone's input.

Re: G9 valve adjustment
 

If the valves are too tight, they won't close and seal all the way like they are supposed to in the closed position. This will most noticeably cause loss of compression/power/etc.

IF they are too loose, they won't open as far as they are supposed to, and usually this isn't too noticeable. But loose valves will be much noisier than they should (clickity click) and will wear out the components faster (valves, seats, stem, etc). IF they get too loose you also risk the possibility of the push rod falling out.

Ultimately valve adjustment is also an extension of valve timing. Correctly adjusted valves will allow the engine to produce optimum power, run quieter, smoother, cooler, etc. Remember during compression the exhaust valve is closed. This allows the dissipation of the flame not only on the valve itself, but into the cylinder head. If the valve is too tight, not closing/seating correctly it can cause the valve to eventually burn out because it can't dissipate the heat into the cylinder head, so it absorbs it all by itself.


edit: just to add, valve adjustment will NOT have anything to do with engines smoking or not. Valve stem seals will cause the engine to smoke under certain conditions, but not the valves themselves (unless the stem has excessive wear and the seal cannot properly do its job... at which point you've probably got bigger issues to deal with than just a little smoke).

Re: G9 valve adjustment
 

Thanks again CP241. I have noticed the cart sounds like the engine is rattling so I assumed the valves probably have never been adjusted. I'll re-post after the adjustment to let you all know the results.