'79 XS project by a mechanical newbie. (But hey, it was free)

[skids]

Bent valve will show no compression. Also, shim clearance will be larger than normal - like there might not be a shim that big!

[TopCatGr58]

Hey Stone,

In 2000 I did my rebuild of my bike/engine, complete Wiseco 1179cc little big bore kit, lapped valves, new seals, etc., put it all together. I had checked the valve clearances with the head OFF, but had put both cams in at the same time, didn't keep them synced, and rotated one, and then the other while on the bench. Unbeknownst to me at the time was that you couldn't do that, not enough clearance between valves that are sticking out/being depressed by the cams so that both the intake and exhaust valves will hit each other. I BENT a valve but didn't know it!

After getting it together, putting cams in, setting timing/chain, just for S&G I did a static compression test, and to my surprise, I had NO pressure in 1 cylinder! SO...I had to tear it all back down again. After removing the cams AGAIN, then the springs, I was able to spin the valve in the head and could THEN see the wobble it made due to it's bent state. Fortunately replacement valves were still available from Yamaha for the 81 model, replaced it, and did NOT put both cams in at the same time to check/set the clearance/shims. Rode it for some ~15 years before tearing the bike down to frame a last year to swap frames(had a bent one), and to do the Dremmel tranny fix AGAIN after some 25+K miles after the rebuild/Dremmel in 2000.

I did not pull the head, but did replace the cam chain this time. It's still running strong.

T.C.

[stoneairsoft]

On summer vacation right now. Giving it one last hurrah.
I have the cams off, head capped-bolts off, but can't maneuver the head off by hand. When my brother & I replaced the gasket we used a paper gasket PLUS non-hardening gasket sealer. *Sigh. I assume a rubber mallet could get it off, but I know those cooling fins are delicate...tips?

[stoneairsoft]

Never mind. I have the head off after some gentle tapping. I might as well continue prying out the "cylinder assembly" according the the pry points on the manual. However, I'm not sure what I should be looking for as far as damage goes. Any help?


I believe the valves are what I'm supposed to be looking at after having the timing off, correct? I shouldn't really need to take the cylinder assembly out, should I?

If so, do I need a valve compression tool to remove the the valves? I have new valve stem gaskets I could put on since I have the entire thing off.



Is there any way to put the correct shims in place without putting the head back on and the cams depressing them? I have them out now and if I have to do so, would rather make it easy on myself without the special depressor tool.

[Radioguylogs]

It's hard to see a bent valve, unless it's bent really badly.

I would have checked the compression in each cylinder before pulling the head.

If you didn't do that- no problem. You can use fluid to check for leaks on the bench.

I bought the valve compression tool from Part-N-More, and was glad I did. Some folks have made their own tool with a C-clamp and a ratchet socket.

New valve stem seals are a given (of course you would do it) once you have the head off. The seals are only about $2.00/each.

You can re-shim the valves on the bench. You could install the cams, check the clearances, then remove the cams and exchange the shims as needed. Careful though, I think TC warned us he bent a valve on the bench by rotating one cam when the other was in a unfavorable position. It might be safer to re-shim after you put the head on the engine.

If it were me, I would pull the jugs and re-hone them and put in new piston rings while I had come this far, but I know sometimes you have to cut off the job somewhere and get it done.

Others with more experience will chime in.

[stoneairsoft]

Thank you for the tips. I pulled the cam cover & realized the timing was off slightly. I didn't want to run it any more for fear of further damage.

It's hard to see a bent valve, unless it's bent really badly.

I would have checked the compression in each cylinder before pulling the head.

If you didn't do that- no problem. You can use fluid to check for leaks on the bench.

I bought the valve compression tool from Part-N-More, and was glad I did. Some folks have made their own tool with a C-clamp and a ratchet socket.

New valve stem seals are a given (of course you would do it) once you have the head off. The seals are only about $2.00/each.

You can re-shim the valves on the bench. You could install the cams, check the clearances, then remove the cams and exchange the shims as needed. Careful though, I think TC warned us he bent a valve on the bench by rotating one cam when the other was in a unfavorable position. It might be safer to re-shim after you put the head on the engine.

If it were me, I would pull the jugs and re-hone them and put in new piston rings while I had come this far, but I know sometimes you have to cut off the job somewhere and get it done.

Others with more experience will chime in.

[DiverRay]

Unless you have over 75K miles on the engine, I would NOT remove the barrels.
With the head off, and BEFORE you do anything to it, flip it upside down and put a little LIGHT oil into each combustion chamber. Fill them and leave it for a few hours. If the level has not moved, you should be OK with the valves.
Next is the valve stem seals. You can rent a tool to help remove the keepers from the valves. Keep the valves in order, DO NOT mix them up between locations!! If you buy an overhaul gasket set, it will have the new seals included.
To adjust valves on the bench, do only intake OR exhaust. Install one cam, measure clearance, adjust shims, and verify that all 4 valves are in spec. Remove that cam and do the same with the other cam. Remove that cam before you re-install the head.
To get things lined up, put the crank on the "T" mark, and with the cams aligned with the arrow and dots.
DO READ UP ON REASSEMBLY before you start it, so you have an idea of what order you need to do things. I have the Yamaha manual that I use.

[stoneairsoft]

Thanks Ray,

I just ordered a C-clamp style compressor from Amazon for $16. All the local auto parts stores carry the bigger spring tool that wouldn't work. I'll do your upside down oil test right now while I wait for the tool to come in. I already have the stem seals from my gasket kit.

The Odo has only 13k on it, so I won't tear it down further. Silly me, I didn't consider putting the cams in to do the clearance on the bench. Duh!

Unless you have over 75K miles on the engine, I would NOT remove the barrels.
With the head off, and BEFORE you do anything to it, flip it upside down and put a little LIGHT oil into each combustion chamber. Fill them and leave it for a few hours. If the level has not moved, you should be OK with the valves.
Next is the valve stem seals. You can rent a tool to help remove the keepers from the valves. Keep the valves in order, DO NOT mix them up between locations!! If you buy an overhaul gasket set, it will have the new seals included.
To adjust valves on the bench, do only intake OR exhaust. Install one cam, measure clearance, adjust shims, and verify that all 4 valves are in spec. Remove that cam and do the same with the other cam. Remove that cam before you re-install the head.
To get things lined up, put the crank on the "T" mark, and with the cams aligned with the arrow and dots.
DO READ UP ON REASSEMBLY before you start it, so you have an idea of what order you need to do things. I have the Yamaha manual that I use.

[skids]

Unless you have over 75K miles on the engine, I would NOT remove the barrels.
With the head off, and BEFORE you do anything to it, flip it upside down and put a little LIGHT oil into each combustion chamber. Fill them and leave it for a few hours. If the level has not moved, you should be OK with the valves.
Next is the valve stem seals. You can rent a tool to help remove the keepers from the valves. Keep the valves in order, DO NOT mix them up between locations!! If you buy an overhaul gasket set, it will have the new seals included.
To adjust valves on the bench, do only intake OR exhaust. Install one cam, measure clearance, adjust shims, and verify that all 4 valves are in spec. Remove that cam and do the same with the other cam. Remove that cam before you re-install the head.
To get things lined up, put the crank on the "T" mark, and with the cams aligned with the arrow and dots.
DO READ UP ON REASSEMBLY before you start it, so you have an idea of what order you need to do things. I have the Yamaha manual that I use.

Personally, if you have the head out, I would recondition the valves and seats with grinding compound. It is pretty easy to do. It might change the shim requirements somewhat. Don’t over do it! The ground surface might be between 1/16 to 1/8th inch max.

[DiverRay]

Personally, if you have the head out, I would recondition the valves and seats with grinding compound. It is pretty easy to do. It might change the shim requirements somewhat. Don’t over do it! The ground surface might be between 1/16 to 1/8th inch max.

With 13K on the odo, they probably don't need much. If you go to 1/16", you are in need of a new valve. 1/8" you would have a valve that is about 5mm too small in diameter!
If you feel the need to do something, just use the fine grit and make sure you have a 1-2mm seat/valve area. But again, if it was mine I would NOT do anything unless I saw something off.

[skids]

With 13K on the odo, they probably don't need much. If you go to 1/16", you are in need of a new valve. 1/8" you would have a valve that is about 5mm too small in diameter!
If you feel the need to do something, just use the fine grit and make sure you have a 1-2mm seat/valve area. But again, if it was mine I would NOT do anything unless I saw something off.

I shouldn't speak from memory like that... Yeah, 1/8" is excessive. P.S. 2mm is over 1/16". If you do have to replace a valve, do lap it with fine compound.

[stoneairsoft]

After 16 hours with the head upside down (I put the spark plugs back in), the oil level was maintained in all 4 "bowls". I'll post a pic in a bit. I'll proceed with the valve stem seals tomorrow when my compressor gets here & then reassemble? Hoping timing was the only issue with it...perhaps my hopes are too high.

[stoneairsoft]

Sorry for the repost. Missed my edit window for the picture descriptions

Oil level


A look at the crud on the cylinders (barrels?) 1-2 I realize it's in the opposite of TDC right now. I'll rotate it back before I reassemble

[TopCatGr58]

Hey Stone,

Congrats on NOT finding any bent valves. First little warning, see the valve clearance indents in the pistons, that means that the valves WILL protrude below the mating surface of the bottom of the head when the cams depress the valves open, and so IF you have the head flat on a bench, you "could" still bend a valve while rotating the 1 cam during the clearance check, so you'll want to be sure to support head with some pieces of wood that will NOT be in position to hit/press the valve heads while they are depressing towards the pistons.

Secondly , even though you have no leakage of the head/valves, with the evidence of the carbon buildup on the pistons, it's possible to have some carbon buildup on the valve seat/valve contact interface. And since you'll have the springs off, it will THEN be very easy to perform a "LIGHT" valve lapping to just clean up any small amount of carbon buildup/pitting on the valve seat/valve contact surfaces. If you're not sure what you're seeing, google valve lapping and images, there is a small grey line that forms on the seat and the valve during lapping, and they are talking about how wide that line should and shouldn't be, so doing just a small/light lapping to get the contact grey line to about 1/16"/ <2mm wide is what you want when you're done.

Next, I've read where folks have used a rag soaked in vinegar laid on the piston to break down the carbon, but vinegar is a mild acid and could still cause some rust to form on the cylinder surface and possibly on the rings if it drips down around the piston/rings. Alkali's can damage the aluminum piston and the outer cylinder jugs or head. So...a very flexible BRASS cup or wheel brush on a SLOW SPINNING drill may be the better route to remove the bulk of the carbon buildup.

Now with the engine sitting for so many years, carbon buildup, you may also have some around the rings. So after getting the engine back together and working, it could be good to use some Marvel Mystery Oil in the engine oil to help further purge gum/varnish from inside the engine, and can help loosen up stuck piston rings to help with the reseating /breakin of the engine.

Good Luck.

T.C.

[stoneairsoft]

Thank you all a thousand times. I feel the confidence coming back seeing that some of the MAJOR issues are (likely) ruled out. And I had it running clunkily last year, so I know the electrical stuff is at least operable and hopefully the transmission is still good and the 2nd gear issue won't pop up with so few miles. I'll take extra care when I place the cams back in this time. I thought we followed the repair manual before, but I'll double check since I'm doing it solo this time.

The depressions make sense, and the size difference in the depression makes sense with the valve clearance differences between intake and exhaust. I'll get some feeler gauges on sale at Harbor Freight today and be all ready for the valve removal and hopefully reassembly tomorrow.

Happy Independence Day!

Hey Stone,

Congrats on NOT finding any bent valves. First little warning, see the valve clearance indents in the pistons, that means that the valves WILL protrude below the mating surface of the bottom of the head when the cams depress the valves open, and so IF you have the head flat on a bench, you "could" still bend a valve while rotating the 1 cam during the clearance check, so you'll want to be sure to support head with some pieces of wood that will NOT be in position to hit/press the valve heads while they are depressing towards the pistons.

Secondly , even though you have no leakage of the head/valves, with the evidence of the carbon buildup on the pistons, it's possible to have some carbon buildup on the valve seat/valve contact interface. And since you'll have the springs off, it will THEN be very easy to perform a "LIGHT" valve lapping to just clean up any small amount of carbon buildup/pitting on the valve seat/valve contact surfaces. If you're not sure what you're seeing, google valve lapping and images, there is a small grey line that forms on the seat and the valve during lapping, and they are talking about how wide that line should and shouldn't be, so doing just a small/light lapping to get the contact grey line to about 1/16"/ <2mm wide is what you want when you're done.

Next, I've read where folks have used a rag soaked in vinegar laid on the piston to break down the carbon, but vinegar is a mild acid and could still cause some rust to form on the cylinder surface and possibly on the rings if it drips down around the piston/rings. Alkali's can damage the aluminum piston and the outer cylinder jugs or head. So...a very flexible BRASS cup or wheel brush on a SLOW SPINNING drill may be the better route to remove the bulk of the carbon buildup.

Now with the engine sitting for so many years, carbon buildup, you may also have some around the rings. So after getting the engine back together and working, it could be good to use some Marvel Mystery Oil in the engine oil to help further purge gum/varnish from inside the engine, and can help loosen up stuck piston rings to help with the reseating /breakin of the engine.

Good Luck.

T.C.