XR 400 valve adjustment

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#1
I'm planning on checking and adjusting my valve clearances on my
96 XR 400 very soon. I've got a feeler gauge, and a vague idea on how it's done, however, I'm wondering if any of you more experienced in valve adjustments can give me some tips, tricks and stuff to watch out for. Thanks a million.
 
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#2
The "feel" for adjusting valves is a learned thing.

To properly do it the first time, it would be really good if you had a friend who has done this and knows the feel for the right amount of drag on the feeler gauge. This way, he can adjust it, then let you see what the correct drag, too little drag, and too much drag feel like.

If this isn't possible, then the best way to describe it is you want to be able to feel the "pinch" of the tappet nut and the valve without feeling like you're marking the metal of the feeler gauge. If you're not sure, try to insert the next size larger - if it fits, it's too loose. Try the next size down, if you feel drag with it, then it's too tight.

Angled feeler gauges will make your life much easier with an RFVC. If you don't have them, you'll have to get them or bend the ones you do have.

Honda makes trick ones which are really easy to use (not as wide, nice handle), but they're spendy.

Also, if you have compressed air, blow off the area around the valve covers - dirt gets caught in the little depressions at the top of the head and has a nasty habit of falling in the engine while you're adjusting valves.

If you're really having a hard time getting the right "feel" - remember more clearance is better! Over-tightened valves are worse for an engine than loose ones.
 

Rodzilla

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#3
I find the trickiest thing for me finding true TDC. But once there it's a snap to do.

Rod
 

SFO

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#4
K&L or Motion Pro sell the angled feeler gauges that PJ describes along with a 2 piece tappet adjuster that allows you do this job with two hands instead of trying to hold a feeler gauge and two wrenches whilst feeling the tension on your screw tappets.(three handed wannabee nightmare)
The biggest bummer I have experienced is people over tightening these screw tappets.
Resulting in
a)stripped adjuster bolt heads
b)stripped rockers
c)cracked rockers
d)cracked adjuster bolts
My best advice would be to feel your hands. The short handles on the special tools are meant(I believe) to discourage overtightening.
 

Jon K.

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#5
I can't help it. . . .I am a glutton for punishment.
Neither feeler gauges nor TDC is required. Most rocker-type engines set on .002 intake and .003 exhaust. If you grab the rocker with your fingers and move it up and down, you can just feel .002, but you can't hear it ticking. If you can't feel it moving it's too tight. You can just hear .003. . . it ticks a little upon movement. If it goes clank clank clank. . .it's too loose. After doing about a million of these, I have a feel for it. Actually for a novice this may be more accurate that trying to read a feeler gauge for the first time. But then a novice might be better advised to watch a pro a couple of times to get a feel for it for himself.
TDC? TDC? We don't need no steenkin' TDC! Rotate the engine in the normal direction of rotation until the ex valve just starts to open. Set the intake. Continue rotation in the normal direction; the exhaust opens, the exhaust closes, the intake opens, the intake closes. Just as the intake closes. . .set the exhaust.
OK guys. . . . fire away!!!!:eek:
Oh yeah, do this on a cold engine. It is much easier on the fingers!
 
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#6
The only problem I see with this procedure is that it's easier to get it too tight, rather than too lose.

I'd rather take a few extra minutes and make sure it's right - i mean really, we're only talking a procedure we do every six months or so anyway, right?
 

SFO

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#7
WFO, the first time I saw someone do what you described I almost dropped a load in my pants.
I must confess that I do the same thing now. I do double check once in a while, and on a forked rocker I still use feeler gauges.
I was at a loss to describe this procedure and unwilling to endure the flaggelation at the hands of my peers.
 

mtngoat

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#8
There are some tips, tricks and traps. I suggest getting a manual and the right tools.

TDC can be tricky because it's easy to engage the auto-compression release, causing a bad exhaust valve adjustment (not something you run into on other valve adjustments).

The thin Motion Pro gauge is great because there's not much room for a full size gauge; bent or otherwise.

Beware though, my last Motion Pro broke off during an adjustment, leaving a piece precariously hanging in the adjustment area. I had to carefully extract it with forceps, hoping it wouldn't drop into the motor.

BTW, get the big socket for the valve caps. I took the short cut and used a crescent wrench. The caps are soft aluminum and have tight access. There easy to mess up.

There's more on this topic already posted. Do search on "XR4 valve adjustment" or try this link:

http://dirtrider.net/forums3/showthread.php?threadid=15315&highlight=valve+adjustment
 
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Jon K.

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#9
SFO; apparently I have gotten away with minimal flagellation (is that an intestinal disorder?) and must agree that forked rockers are a challenge. We still see a few on three-wheelers, and yes a feeler gauge is useful.
Rotating the engine as described was stolen from a Sig Erson cam book. It works on ALL engines!
Mtngoat; kickstart activated decompression releases shouldn't be a problem (don't turn the engine with the kickstarter!) and the new 450 Honda automatic system (I think) will crack the valve as the piston nears top. I would like to hear some discussion on this, however, as I am behind the curve on automatic decompression systems.
No, wait, the Honda uses a completely separate rocker to crack the valve and so shouldn't confuse the adjusting process. That one uses shims anyway!
 

mtngoat

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#10
For us "DIY amateur adjusters" here's more specifics of my practical experience on the auto-decompression:

The manual has a very good explanation of how to get TDC using access ports for turning the crank (not with the kickstarter) and seeing the alignment marks.

However, when approaching the alignment marks, I've noticed that the crank wants to reverse direction. If you let it, you run the risk of engaging the auto-decompression. If you overshoot and try to reverse direction; same problem. You have to go all the way around again. That little "under-documented/discussed" detail threw me off on my first try. Just my two yen.