I am about to adjust the valves on my 05 Rubicon. It has over 5000 miles and hasn't been done since the first one when it was new. I'd say it is overdue.

Anyway, my question is do you have to take the fuel tank off to adjust the valves? Everybody I talked to said you have to take the fuel tank off but the service manual does not say anything about taking it off. Also is there anything else special I need besides feeler gauges?

 

I took the tank off when I adjusted the valves. You are way overdue and I have heard of serious problems when you do not adjust them regularly, but that may have been missing the initial adjustment the posters were talking about. Besides making it easier, you are able to inspect other things. I can't tell you what the clearances are because I think I remember seeing the 05 and up had a difference clearance than my 04. Maybe Gimp or another one of the Honda wrenches can help you out and shed some light on not adjusting the valves regularly and the problems they've seen because of it.

 

I didn't notice until you said that, but my book doesn't say to remove the tank either, though it says to remove the heat shield (below the tank).

Anyway, no I don't think you could do the valves very well without removing the tank. I think they forgot to mention that part.

When you've got the T in the window, make sure there is play in both rockers. If there isn't, it is because the valves are in overlap with the piston at TDC between exhaust and intake stroke, so you would need to rotate the motor another turn. When you check the valves, you want the piston TDC between compression and power stroke where the valves are fully closed and there is play on th rockers.

If valve clearance is too tight, it can hold a valve slightly off it's seat where it can leak and may also burn the valve, since they give off heat to the head when seated. I've usually only seen major warped valves on multi-piston engines, since on a single if one valve leaks pretty soon the motor won't run well or start.

Cam profiles are usually designed so that valves close as fast as possible without risking floating the valves at redline. At the very end of the valve's closing, though, the cam profile will decelerate the valve to set it on the seat. The valve and seat life would be short if the valve were allowed to slam into the seat at the valve's peak velocity.

Anyway, if the valve clearance is WAY too loose, you might be missing part of that decleration/set the valve down gently part of the cam profile.

 

I don't know about yours but where I adjust the valves on mine is right behind the spark plug and the spark plug is not under the fuel tank. Unless what I am looking at is not where you adjust the valves. I will try to put a pic on here to show you what I am talking about.

http://i170.photobucket.com/al...larke_017/100_0999.jpg

The valve adjustment hole is right below the black rubber piece, correct? So why would I have to take the fuel tank off to adjust them?

 

Also, do I have to replace the o-ring on the valve adjustment cap? Or if it is good shape, can it be reused?

 

Angler,

If you pull that rubber piece, I think you will find that you have access to the cap on the back of the head, but that the other cap on the front of the head is pretty much under the gas tank.

Seals on the valve inspection covers are reuseable if in good condition. I like to use Locktite Blue on the bolts for a little extra security and corrosion/seizure protection.

 

Is one of them the intake and the other the exhaust valves? Is it possible to do just the one below the seat?

 

First question: Exactly. The intake valves are under the cover at the rear of the head and the exhaust valves are under the cover at the front.

Second question: It would be possible to adjust just the intake valves, but that would be kind of pointless.

As long as you are messing with it, spend the extra 15 minutes or so to take the plastic gas tank cover off, then I think there's only like 2 bolts and a couple of rubber straps and the fuel line to take the gas tank off. Below that is a whiteish translucent plastic heat shield, that if I recall clips to the frame and may use a couple body clips.

 

Well I just got done adjusting the valves tonight. The valves were not that bad at all. On the intake valves, they only had to turn about a half a turn tighter or so. On the exhaust valves, only one needed to be adjusted and it was a little to tight. It took a few minutes to get the rockers in the right position where they had play in them. How much of a difference will I notice if any since they were not that bad?

It wasn't that hard of a job. Just getting to the valves was a pain. I got a question, on the flywheel you have to line the T mark up with the index mark. There is also an F mark, which is for the firing order, and there are two lines right above each other. What are the two lines for?

Thanks for all the help.

 

Glad you got it done. Did you actually turn it a half turn? That would be hugely off... Generally they will be off a couple thousandths at most, but then yours haven't been done for a long time. Did it show .006 intake and .009 exhaust in your owner's manual? Maybe the screw moved when you loosened the lock nut?

Anyhow, as long as you got the piston in the right stroke and got the valves at the specifed gap when you were done...

Since it's a single cylinder, it doesn't really have a firing order. The F and other marks are used with a timing light to verify spark timing.