HELP! I might have Killed my Engine?

Okay, I ride my '90 XR600 HARD, on the street with street tires. I can't help it, I live minutes from one of the greatest concentrations of twistie roads in all of North America!

So I'm fairly new to the XR thing and I treat it like my old liquid cooled CBR. That is, I ride it hard and don't worry about much else. :D

Anyway, after a long hard day of riding (hot engine most of the day) the engine starts making a light tapping noise. I check my oil and sure enough it's 3/4 a quart low.

Well stupid me, I ride to the nearest gas station to buy oil. That's probably not the stupid part, but what is... is I rode HARD to the nearest gas station.

I filled it up with semi-synthetic which is what it had in it, then called it a day and rode the 75mph 15 mile trip back home.

When I got home, it was tapping again. LOUDLY!

I changed my oil tonight and started it up and it's still tapping, LOUD!

Seems to be coming from either the upper cylinder area where the cooling fins are, or from the bottom front area of the engine just below the header tubes.


Does anyone have any ideas? Or is this a tear-it-apart and figure it out type of thing?

How much would a complete rebuid cost me? Ballpark figure?


Its not the top end I'd worry about right at this moment....its the valve train. Not a whole lotta oil gets up around the cam and rockers in the first place, and running with almost half the oil capacity probably did a lot of harm. Tear it down and inspect things. Rocker arms aren't that expensive by themselves (around $30 maybe), but keep in mind you'd have to replace 8 of them!! Not to mention the cam.

I wish you luck.....things could get spendy.

Dear friend,

your XR seems to be needing some valve adjustment!

Beware of one thing: a french dirtmagazine warning refered the third gear breakage on stock 600 XRs in case of excessive road use of the bike...but I suppose that yours demultiplication isn´t the original and it's longer!!!In that case I think you shouln't worry.

Great rides and happy new year for you

JP :)

if you take the top off and need to replace anything do that then replace the piston and rings(or what ever is making your bike lose all of its oil.

Thanks for all the suggestions!

Well I took the XR over to my friends house and he adjusted the valves for me while I watched and learned.

one needed a bit of adjustment, one was perfect and two others REALLY were out of adjustment. I mean wiggly like.

After he put the bike back together I started it up and it ran PERFECT with no tapping at all. BUT.... about 30 minutes later some of the tapping came back. An hour or two later the tapping was actually loud again, though I can't hear anything at idle where as before it was very loud at idle.

Any suggestions?

Suggest all of the above: Really that bike has given you a lot of service and you have only had a friend adjust the valves once? If the top end is shot you sure can't blame Honda.

The piston and rings are cheap and the nykasyl cylinder probably won't need replacing but the valve parts on top may get pricy. Did you change out the old oil and check the filter and screen for metal particles? Probably not but that is a good place to start looking for serious wear and tear.

That old bike is not worth much on the used market so you really have to conseider how much it is worth to yourself before getting into a major rebuild.

I chased this problem on my 91 XR628. It kept eating the left Exhaust rocker. Ended up being the oil hose from the down-tube to the oil pump would crimp and starve the motor.

Did find that you could pull the offending rocker and run as a 3 valve motor to get home. (two days back to the truck in Baja)

Well thats a Honda for you. It's not broken until your home.

I herd XR600's making a loud tapping noise because of the decompression cam. I would check the valves again, your friend might not have tightened everything well enough. You can also take a valve cap off and start the bike to see if it's getting oil. It should make a mess.

If you pull the valve cover off inspect the top end and look for lack of oil damage. If your not getting oil the screens could be pluged.

How does your plug look? Is it all white? I wounder if it's pinging. I could here my bike pinging and making noise unless I ran 95+ octang when it's hot. This bugged me for years.

Thanks guys. Yes, I've put about 4K miles on it and beaten the crap out of it on the road.

Mostly because I was coming off a "real" street bike (4cyl CBR900RR) and didn't realize that keeping the revs up would kill the motor. Also thought it had about 4 quarts of oil instead of the 2.1 that it holds. :D

The decompression lever and stuff is no longer on the bike. The previous owner (who also beat the bike) took all that and bunches of other stuff off the bike to get it as light as possible. No battery, electric starter, tachometer, odometer, etc.

After riding all day today I can say that the noise is definately back. Though still not as loud as before.

I'm going to look at the valves again tonight. Does anyone know what the clearance is? My buddy did 4 and 5 for the clearance and after reading my manual I think that's wrong.

Do I still need to adjust the front right valve differently even though it's no longer setup as a decompression?

Thanks all! :)

Having had a few XR's that lost some oil I am going to guess that yours has scored the cam lobes and rockers. Good time to do the entire upper end and send the rockers and cams off to Mega Cycle to have them resurfaced and go for a more agressive grind. Your friend was close enough on the settings as those were what I ran on my cammed up xr's. Your adjustment is likely changing due to your wearing through the harder part of the cam and rocker. By the way,, as you are continuing riding you are sending lots of metal(the stuff off your cam and rockers is going somewhere) through the engine, so pull the pump off and clean it out along with anything else that catches things like that,,,(your clutch is a good example). Good news is that these engines seem to be able to take lots of metal. If you are in doubt, tear down and put in a Carillo rod,,it doesnt cost much more than OE. If you do that you might as well go for a big bore with 11 to 1 or so compression. It will go nicely with the cam regrind we just talked about. Now you will easily be able to take out that third gear that the man in an earlier post mentioned. But whatever,,,these things are lots of fun.

After riding about 100 miles since the valve adjustment, I tore it apart (easy to do it seems) and checked the clearances.

Of the two that were previously loose, the left front was loose again. The other was fine.

So I adjusted that one valve clearance and took it for a test ride.

Some of the tapping was gone, but for the most part it was still tapping pretty bad. :)

I can't afford a top end rebuild right now, much less a new cam.

Dont count out the possibility that when a timing cam chain is loose it tends to tap like real horribly. Consult someone who can listen and reconfirm any one of the many suggestions you have recieved. There are too many notes in the average Honda Opera....


Took the valve cover off tonight. The CAM looks GREAT! and FEELS okay. I felt the "tiniest" amount of wiggle at the end cam bearing. Sort of the same amout of wiggle that you feel at the valves are at TDC of the comression stroke.

The left front <larger> ROCKER or LIFTER is GONE! Absolutely worn THROUGH!

The other seven large and small rockers are fine!

So can I can just replace the one rocker without a problem or will that screw other things up?.

Anyone got a used one for sale, or know a place on the net that sells them? I can't find rockers for sale ANYWHERE on the net. :)

Yep, thats the rocker that gets oil last. I am suprised that the cam does not show damage also. If it really does not show galling then you might just be able to replace the one rocker. Although you thought it ran low on oil make sure its pumping oil when you put it back together. Loosen the oil line fitting at the cylinder head and it should have good oil flow, does make a mess.

Well, there was a pool of oil that drooped out when I removed the valve cover. I don't know how much that means, but the top end didn't have any odd coloring. I was told to look for a "gold" color and didn't find any on the caps or the walls.

Just bought a rocker... $42 at Honda.

Thanks for the help everyone, I'll give you an update when the rocker goes in. :)

If the noise went away for a while after a valve adjustment and the returned shortly after

returning the bike to service, I would suspect that you are having a problem with the valve

train. Something is wearing out causing the valve clearance to change rapidly. Sub rocker

arms are a problem on the RFVC motors, the adjuster screws actually drag across these

rocker arms and when it starts to wear the valve clearance will change rapidly. If I

remember correctly the sub rockers are about fifteen bucks each and can be sent out and

heat treated for twenty bucks each, the adjuster screws should be heat treated as well. Or

something else is going away in the valve train, one of the various rocker arm pins, the

valve cover itself, or it’s fixen to swallow a valve. Either way don’t run it any more until

you remove the valve cover and find out what is going on. A factory service manual will

help a great deal with top end service.

I failed to read all of the posts and see that you found the rocker problem. As I mentioned

you can get all of this stuff heat treated (harder) but is not necessarily a required process.

What is a must on the RFVC motor is fully synthetic oil to keep that monkey motion valve

train alive.

I had to rebuild my 91 600 many times before I got shot of it. It kept starving itself of oil. Seemed to air lock the oil pump after oil changes .I tried everything though. Oil coolers new lines the lot. I can't see how your cam isn't shot if the rocker was worn thru. Check the oil ways in the cam that they haven't blocked also .Good luck., THANKS! to all who helped me with advice and such!

I put the new rocker arm on last night and test rode it and it is running SUWEEET! Nice! :)

the engine seems "crisper"! and a bit more of a "cracklin" exhaust note!

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