Took me a day and a half to do but my first 20 hour valve adjustment is done. Everything you've read about removing the plastic is true and then some. And even though the manual doesn't specify to remove the white plastic engine cover I did anyway just to make the job a bit easier and to get a better look at the engine. What a PITA is was to remove! Luckily after removing the gas tank I was careful not to detach the pressurized fuel line and get sprayed in the face with gas. To remove the pressure requires running the engine after the tank is removed until it dies which I didn't do, just carefully removed the white plastic around the line.

So upon first examination I noticed the clearances were very tight on both the intake and exhaust. I didn't check them with a feeler gauge but you can bet they were a long way from the factory specs. (.015 intake, .023 exhaust)

I guess the tight valve clearances are normal on a new machine, I don't know but it sure made me wonder how hot the valves were getting before I adjusted them.

After adjusting the valves, slapping the plastic and gas tank back on I started the beast up. Now I can hear the valves clicking. Almost seems too loud but l guess not?

 

You didn't check them with feeler gauges?

Even an expert who does valve adjustments all day, every day, wouldn't be able to set them accurately by feel...

Use some Feeler Gauges!

Also, often when someone thinks the valves were tight, and then has a ticky engine, usually they have adjusted the valves with the cam in the wrong position.

When the T is in the window, the piston is at the top of it's stroke. If both rockers are tight (can't feel any play at all) then the piston is top dead center between exhaust and intake stroke, and there's no slack in the rockers because both intake and exhaust valves are slightly open during the overlap phase when the piston is TDC between exhaust and intake.

In that case, you would turn the crank another turn (360) until the T on the crarnk is back in the window. There should then be slack in both rockers, because both valves would be fully closed when the piston is top dead center between the compression and power stroke, and this is the position you want the engine in to adjust the valves.

If you try to set the valve gap when the piston is TDC between exhaust and intake, you will end up with them being set way looser than they are supposed to be, and the result will be a lot of valve noise.

 

Yes, I used feeler gauges and made sure the piston was at TDC, timing marks correct and both rockers had slack in them. Even observed the intake rise and then fall just before TDC.

I had also observed them between intake and exhaust stroke at TDC and with zero movement. (note this was covered in the factory service manual which I followed diligently as well)

They were both just very tight as set from the factory yet both had some play and with the engine idling prior to adjustment you could not detect any noise at all from the motor valve wise

So the question is does a correctly adjusted valve rocker exhibit zero noise or some noise?

 

I've got an idea, I'll upload a short video with sound of the engine running to YouTube tomorrow. Pictures are worth a thousand words but sound has no limit. I'll post the link here. My gut feeling is that they are ok, it's been a few dozen years since I've done a valve adjustment on a bike but it's been just long enough that I'm doubting myself. Ill let the video decide.

 

I don't know but I'll be watching this thread because I will have to do mine shortly.

 

A slight bit of valve noise would be normal with correctly adjusted valves.

It would be unusual for them to be too far off on the first check, though. I think my Foreman stayed pretty close to spec until it had over 1000 miles on it, when I tightened up the intake just a touch. My Rincon was slightly loose on the initial check, and hasn't changed since.

Also, if they are off, ususally they get looser as the valve tip, rocker and pivot and lifter wear. They can get tighter if the valve wears into the seat, but those are pretty hard parts. A Rubicon a while back was about a thousandth tight or so, but it was getting it's first check way overdue...

 

From the get go honda had a service bulletin out on their 420s having tight valves, up to a certain serial number. I was still finding valves tight on the first check up on units after the fact, but at least they would start. Not like the early ones though.
The first time on a 420 valve adjust will set you back quite a few hours. I have a system down to get them done in under an hour. I am not a big fan of the valve cover caps. They make the use of a normal feeler gauge near inaccurate feeling of the correct drag because of the bind angle of the straight feeler gauge blade against the head when inserted between the valve and rocker adjuster. I use the angled feeler gauges for a good feeling of the drag when checking or adjusting clearance.
Also be aware that Honda conciders a cold engine, 90 degrees as the lash is measured. When setting lash on a room temp engine the valves may end up loose after the engine warms up.

Just a few tips

----- Gimpster -----

 

I remember reading a post about some 420's with tight valves.

FWIW I have an early 2WD 07 model, perhaps it may have been one of the aforementioned? I'll call the Honda dealer on Monday and see what they say, they were very tight-lipped on what happened to the first 420 I had to return for the mystery oil problem so I may not get a straight answer from them.

 

<div class="FTQUOTE"><begin quote>Originally posted by: JeffinTD

A slight bit of valve noise would be normal with correctly adjusted valves.

Also, if they are off, usually they get looser as the valve tip, rocker and pivot and lifter wear. They can get tighter if the valve wears into the seat, but those are pretty hard parts. A Rubicon a while back was about a thousandth tight or so, but it was getting it's first check way overdue...</end quote></div>

I had read somewhere too that instead of getting looser the clearances became tighter and thus the valves became quieter as time went on.

Still in the few months I've had this machine any valve noise now seems strangely odd even though as you say a slight bit of valve noise would be normal.

Tomorrow I'll post a short video on Youtube and let the world be the judge.

 

Video of the engine running right after valve adjustment

engine running video