Will a valve 're-seal' itself?....

[crazy steve]

Ok, here's an interesting question...

I got the motor out of my 'rebuild project' XJ and did a compression test. The numbers weren't very encouraging on the first try. I got 175, 90, 60, 175. The two outside holes checked nicely, not so good on the inner two. I checked the valve lash, and all but one were too tight, some down to less than .002". After changing the shims to get back within spec, the 90 psi cylinder came right up to match the two outside cylinders but the other only came up to 150.
All the plugs looked real good as far as no signs of burning oil, so I suspected maybe a valve issue. I sprayed some WD40 onto the exhaust valve and then that hole came up to 175 too. So it appears I have a very slightly burnt valve from being ran with insufficient clearance. So, what do you think the chances are that that valve will 'wear in' and get a better seal? I'm building this one for resale, so I want it 'right'; if I have to bite the bullet and pull the head to lap the valve, I'll do it. But I don't want to if I don't need to...

On a side note, this bike has about 49K miles on it, and I'll bet money the valves have never been adjusted. One exhaust valve (the only valve within spec no less) still had a 315 shim installed...

[BA80]

When I put this engine in mine out of a parts bike,after trashing a bearing in mine, it did the same thing when I checked the compression. It was kinda all over the place after sitting so long in the attic of Bob Jones garage.

I put it in intending to run it temporarily until I got my other engine squared away.

That thing runs better than the original EVER did and it's still in there.

Put it in and give it a shot. You might get lucky too, who knows.

[bikerphil]

Ride the bike for a while, then you should know pretty quick if there is an issue. Not that big of a deal to pop the head with the engine in the bike you know. JMO

[TopCatGr58]

Hey Steve,

WD40 is kinda thin, it could have easily and quickly dripped down around the rings, and helped them to seal better than perhaps the valve??

Hopefully the burnt stuff on the valve is fairly fresh carbon, and with running it a few hours at normal temps it might both smash and break the carbon from the surface of the valve/seat as well as burn it away??? I've read about folks using both Sea Foam in a FOG style application as well as just spritzing water into the intake to help break up and remove carbon build up, but I realize that it's for carbon on the top of the piston, not between the valve/seat...but might help?

I say run it few hours and then retest the comp....might get lucky!

T.C.

[ddragon63]

I've read about folks using both Sea Foam in a FOG style application as well as just spritzing water into the intake to help break up and remove carbon build up, but I realize that it's for carbon on the top of the piston, not between the valve/seat...but might help?

T.C.

I think Seamfoam should pay me every time I mention their products

get yourself a can of liquid seamfoam and an aerosol can of seamfoam deep creep... (I've made MANY skeptics into believers with this method) your gonna want a new oil filter and oil for after you done so get them too. and maybe some spark plugs.

put half the can of liquid seafoam in the gas tank with full tank of fuel. (stir it up real good) and put the other half of the can in the crank case oil....

Put bike on centerstand.... and run heat cycles... I like 10 minutes @ about 3,000 rpm, let idle down and shut off, let it sit and cool for about 5 minutes and repeat a few times.

before your last shut down let the motor get good and warm...fog the carbs with the aerosol @ idle until it stalls out... I've found 4 hoses to the sync ports plumbed to 1 hose works the best. the idea here is to pack seafoam in all of the cylinder and choke it out. so how ever you wanna do it is fine as long as you get it into all 4 cylinders. no let it sit for about 15 minutes. Make sure your in a well ventilated area because all your carbon deposits are about to come out the tail pipes

The deep creep will bubble all the carbon out of your combustion chambers.
The liquid in the oil will clean up any varnish in the engine, and the liquid in the tank will help clean the valves while you ride it the next 100 miles.

Do note that you are going to want to drain the seafoam soaked oil out of the crank case before riding it. Your clutch will not like it too much.

I've "fixed" many of motorcycle engines I thought had burnt valves this way... You would be amazed the carbon you'll push out of the motor...I also do this to them if they've been stored more than a year without running.
Hope this helps Buddy

[crazy steve]

...WD40 is kinda thin, it could have easily and quickly dripped down around the rings, and helped them to seal better than perhaps the valve??

I only sprayed a bit into the exhaust port with the valve closed, so there wasn't enough to get to the rings; it's definitely a valve problem. But I like the idea that it may only be some carbon deposits... I think I'll go for it...

I had to go down four shims sizes on both the inside exhaust valves, that's how tight they were. I might go down one more on the 'problem child' to allow for the 'cleaning'...

[crazy steve]

I'll give the Seafoam a try! The inside of the motor is really clean, so it appears it got regular oil changes with a quality oil at least. But there's definitely some carbon build-up in the exhaust ports....

[ddragon63]

I'll give the Seafoam a try! The inside of the motor is really clean, so it appears it got regular oil changes with a quality oil at least. But there's definitely some carbon build-up in the exhaust ports....

then I would forego the seafoam in th oil... put some in the gas and fog the motor. Don't stand behind it after

Make sure the motor is GOOD and hot before you fog it or the deep creep will creep right past the rings... you want it to vaporize. I no longer buy wd40 Seafoam deep creep works for everything

[motoman]

Specially if it has sat for any long period of time. Any lubrication that was left around ring land of piston would of got a bit gummy not allowing ring to flex. IMO, selling it, you would definitely want it right. Worth riding it some yourself if not in a super hurry to have to sell. Plus it will already be mounted in a built in stand if you gotta pull the head. Amounts to whatever YOU feel better doing. By the same token, selling it, would'nt want it coming back 6mo. later or sooner with an issue you had suspect of prior.

[jetmechmarty]

A little ATF in the gasoline removes carbon in a hurry. I go with BIKERPHIL. Run it.

ALTHOUGH...If it was me, there would be a very strong inclination to take it apart. I have a tendency to get carried away.

BTW, I got my SG showing 9500 miles. I have about 55000 now. I'm about to make the first adjustment, and it's still in spec, though just barely.

[bikerphil]

Steve, if you decide to fog the motor, be sure to take a video. Also don't forget to get the look on the neighbor's face.

[ViperRon]

My understanding is that the valves are designed to rotate during operation because of the swipe of the cam. In an engine that has set for some time you always battle oxidation or rust. The compression could be lost either by a sticking ring set or by minor rust or carbon on a valve or in a cylinder. So if the valve spins I can see were running it expecially with something like seafoam could clean this making it seat and if its a sticking set of rings it can also work its way free. Rings typically stick because of the first swipe across a slightly rusted or carboned cylinder forces that into the piston ring gap locking the ring till it breaks free. I'd run it and try sea foam trans fluid etc etc before I took it appart.

[Schming]

For internal cleaning of engines I have been using Auto RX for a couple years now with noticable results. It is a little costly but it works.

Here is the link:

http://www.auto-rx.com/motorcycles.shtml

I was skeptical and just went for it after reading the forum and seeing the testimonials on their site. I'll just say that my, bought used with 53,000 miles, '95 F150 now with 223,000 miles on her is getting the best gas milage ever, more throttle response, and the usual resonance in the 300 I6 is so subtle the antennae that wiggled about 1.5'' hardly moves 1/4'' now.

I'm not sellin' this stuff but I'm sold on it.

YMWV

[ViperRon]

with what is stated in last reply Auto RX may be the answer to clean slipping clutches that have been exposed to improper oil and engine treatments without having to pull and manually clean them.

[trbig]

Steve, do you have any way to do a leak-down test? Hook up air pressure to the cylinder. Hear it out the exhaust, it's the valve. Out of the breather by the back of the motor.. rings. If it's rings, I still wouldn't worry about it. With the other 3 cylinders good, the chances of one cylinder being a fluke is.. well.. a fluke. That could be the cylinder that sat with the intake valve open and exposed to air/humidity and got the cylinder wall/rings a little rusty.

As thin as WD-40 is, I don't see that filling/sealing any air gaps to increase your compresion much at all.. let alone 70-80+ points. I think you just got some rust or carbon wet and squishy or it loosened something up a bit. A burnt valve, and you won't get compression numbers like that.