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4Takt

Impending Valve Doom?

17 posts in this topic

My 650R seemed low on power, so I did a checkup today. I have about 4000 mostly off road miles on it. Last adjusted the valves about 500 miles ago.

Today I found the right exhaust valve had tigthened up so much I had to back out the adjusting screw a full two turns before I got any play. Now, with both ex valves adjusted for .02mm of free play, the right adjustment screw sticks out almost 2mm more than the left.

This can't be good, can I still ride and keep an eye on it, or is this the time to take the head off?

What do you think is going on here?

4Takt

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Run A compression test and compare it to stock spec. This should tell you a lot.

There are other tests but this one should tell you what you need to know.

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I'm sure you're aware but make sure you weren't on the wrong stroke when you checked them. Did all the valves have a tad bit of play in them prior to adjustment. If you did them 500 miles ago I can't see how it would tighten up that much, that fast. If it did maybe there's something more catastrophic going on in there.

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Since the only valve with problem is the right exhaust then I suspect that you allowed the motor to rotate slightly clockwise and had the automatic decompression feature open up the right exhaust valve. You can check real easy by just starting the bike up. If I am correct the bike will just barely run and will sound like hell. You will need to start over with the valve adjustment and be sure you do not go clockwise at all. You do not even need to be perfectly on the "T". Just do not go clockwise.

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oldturtle is on the right track, :applause: it is a common mistake to adjust the valves with the auto decompressor activated. The result is that the RH exhaust valve is too tight, no clearance, the fact that the adjuster is backed way out is a sure tip-off. Like he said, rotate the engine slowly counterclockwise when bringing up the "T" mark, don't let it go backwards.

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I agree with all this, I answered this on the Yahoo XR650R group an hour ago. The only problem is everyone is saying right hand side????? :applause:

The auto decompression opens the left valve but, everyone might be facing the bike? Left hand would be the side that your left hand holds the bars when you are sitting on the bike.

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I think you guys are right and I'm a moron. Shoulda took the stator cover off instead of going by feel. All other three valves had play, so I thought I was on the right stroke. I started the bike, and as predicted it chatters like hell, so obviously the valve is way too loose now.

BWB63, the valve in question is the right one, same side as the throttle. Hmm, that doesn't really make sense, as you say...

4Takt

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Hey,

It's easy to remove the left side cover. I turn the flywheel by hand (remove the spark plug). Check that all the tappets have play and then measure each with your feeler guages. If you have the kind that fold up into a pocket knife sized deal, remove the feelers you need for the whole tolerance range on the intake and exhaust valves. Bend each of them about 3/4" to 1" from the end at almost a 90 degree angle. After measuring each, go back around to TDC and check again for consistent results. Then adjust per specs. Go back around again and recheck, if consistent then you are good to go. All this redundancy takes time, but it's a heck of alot quicker and cheaper than needing a new valve/valve seat job. Good luck, check and re check and be patient.

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I think you guys are right and I'm a moron. Shoulda took the stator cover off instead of going by feel. All other three valves had play, so I thought I was on the right stroke. I started the bike, and as predicted it chatters like hell, so obviously the valve is way too loose now.

BWB63, the valve in question is the right one, same side as the throttle. Hmm, that doesn't really make sense, as you say...

4Takt

Hey don't kick yourself too hard. All of us have done this at one time or another. You think your being really careful and the flywheel only moves a hair almost indiscernible which engages the autodecompressor so when your done the valve is way loose and starts clattering.

Live and learn. :applause:

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There is really no need to remove the cover for TDC to adjust the valves.. Just pull the caps and slowly rotate the engine with the kickstarter until the valves for either intake or exhaust begin to open, continue to rotate thru open and to just a little after the point in which they close again.. Your on as flat a point of the cam as your gonna get.. You can verify by checking for clearance.. Do either intake or exhaust first, it doesn't matter then the other.. Start to finish it's a 15 minute job tops... :applause:

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I think you guys are right and I'm a moron. Shoulda took the stator cover off instead of going by feel. All other three valves had play, so I thought I was on the right stroke. I started the bike, and as predicted it chatters like hell, so obviously the valve is way too loose now.

BWB63, the valve in question is the right one, same side as the throttle. Hmm, that doesn't really make sense, as you say...

4Takt

Don't kick yourself too hard, how do you think we know this? :applause:

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4Takt,

I HAD this similar problem with my '95 650L at around the 14,000 mile mark (1998). I blame it on my Acerbis 6 gallon fuel tank , with it not giving proper air flow to the head.

What may be happening is that your valve seats are sinking into the head. This is why you keep having to adjust your valve tappet back to get it to the right clearance.

With mine, I was adjusting both of my exhaust valves back. A week later the bike would start running crummy. Hard to start. I'd pull the caps off of the valve cover, and find that I needed to adjust the exhaust valves back again.

To make a long story short: I bought a new head and installed it myself. Both of the exhaust valve seats literally fell out as soon as I removed the valves. I could see that the seats were pounding themselves further into the aluminum head.

Fourtunatelly, head replacement on the 650L is easy!!! :applause:

.

.

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There is really no need to remove the cover for TDC to adjust the valves.. Just pull the caps and slowly rotate the engine with the kickstarter until the valves for either intake or exhaust begin to open, continue to rotate thru open and to just a little after the point in which they close again.. Your on as flat a point of the cam as your gonna get.. You can verify by checking for clearance.. Do either intake or exhaust first, it doesn't matter then the other.. Start to finish it's a 15 minute job tops... :ride:

Interesting. Why not just do it the right way? :applause:

Adjusting valves

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If you set the valves from the bottom of the lobes you take the auto decompression system out of play and eliminate the possibility of this thread.

You can see the cam once the valve cover caps are off. The valve adjustment procedure was made to make it easier to understand but, it's hard for some to get the bike on the right TDC or they pass it or they pass it and turn the engine backwards. It would have been better for most if Honda would have just wrote the "valve adjusting procedure" the same as all the others.

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Yeah, when I first adj. my valves, I did that... I was thinking "Wow, this one valve sure is tight..."

Then I went to go start it and it went knock knock knock... I only ran it for a split second, and you could hear it right away. Took it back apart, and made sure I didn't go past TDC one bit. Re-spec'ed it, and it worked fine..

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