Author Topic: Valve job/head rebuild or no? (Read 4109 times)

BlindSight · « **on:** February 01, 2011, 07:21:38 am »

Finally got all of my parts in yesterday and going to start putting the bottom end back together. Wondering if I need to go ahead and rebuild the head and do some valve work while im at it or should I just clean them up and go with it? Doesn't seem to be any damage...just dirty.

Gordon · « **Reply #1 on:** February 01, 2011, 07:25:17 am »

No way to tell without more info.

fmctm1sw · « **Reply #2 on:** February 01, 2011, 07:34:28 am »

Do you have any idea what compression was like before? At a minimum, replace the valve stem seals...

BlindSight · « **Reply #3 on:** February 01, 2011, 07:36:40 am »

bike was sitting 23 years...#2 piston was stuck so couldn't get a compression test. have new valve seals in the gasket set I ordered...never done any valve work though.

MCRider · « **Reply #4 on:** February 01, 2011, 07:42:46 am »

I vote for valve stem seals, "lap" the valves in (search on it) or google it. And slap it back together and ride!

Gordon · « **Reply #5 on:** February 01, 2011, 07:44:05 am »

Do you have any restrictions, like time-frame or budget?

If it were me and I had plenty of time and wasn't on a tight budget I'd rebuild the entire top end just so I'd have a pretty much completely new engine to start off with. If I were on a budget I'd only replace the parts that really needed it. Either way I'd do the cam chain tensioner assembly.

BlindSight · « **Reply #6 on:** February 01, 2011, 12:22:04 pm »

by rebuilding the entire thing what do you advise? have new valve seals, should I do new seats/valves/springs as well? I noticed using the socket and hammer method for taking of the keepers but whats a good way to put them back on without the spring compressor?

fmctm1sw · « **Reply #7 on:** February 01, 2011, 12:23:59 pm »

Quote from: BlindSight on February 01, 2011, 12:22:04 pm

by rebuilding the entire thing what do you advise? have new valve seals, should I do new seats/valves/springs as well? I noticed using the socket and hammer method for taking of the keepers but whats a good way to put them back on without the spring compressor?

Some guys have fashioned tools out of C clamps and sockets and the like... There's pictures around here somewhere...

camelman · « **Reply #8 on:** February 01, 2011, 06:02:31 pm »

Blindsight,

As I remember, you had a stuck #2 on a CB500 or CB550. As long as you have it apart, I highly recommend replacing your valve guide seals and lapping the valves. It really does make a difference for power, smooth idling, even power band, possibly blowby past the valve guide seals, and a minor impact on oil consumption. These engines are pretty robust, and will run even if they are in a bad state of repair, but the more you prepare your engine now, the happier you will be down the road. It REALLY makes a difference to do it right from the start... trust me.

Regarding your cylinder head, pull the valves, pull the valve guide seals, lap the valves, replace the seals, and reinstall the valves. You will need a valve spring compressor (I recommend this one: http://www.amazon.com/Tusk-Valve-Spring-Compressor/dp/B0039L9GAC/ref=sr_1_11?ie=UTF8&qid=1296611378&sr=8-11), valve lapping compound, and a suction cup tool to grip the valve.

If you do not replace the valve guide seals, then you risk a lot of blowby going between the valve and valve guide and pressurizing your engine. The greater crankcase pressure won't really do much to the operation of the engine, but you will see greater smoke coming from the positive crankcase vent hose, which is pretty stinky and will make your pants smell. Your engine oil life will decrease too.

If you do not lap your valves to get a good seal on your intake valves, then you will lose some power (could be substantial), blow the charge back through your intake system (which will screw up idling, smoothness throughout the rpm range, and make the engine run pretty roughly no matter what you do).

If you do not lap your valves to get a good seal on your exhaust valves, then you will lose some power (could be substantial), and you will notice some rough idling.

This all adds up to a smooth running engine that doesn't die when you roll of the throttle, is easier to modulate power (especially nice when you are in traffic), and also an engine will not leave you smelling like poorly combusted 87 octane and eau de 10w-40.

Your engine will run if you don't do these things, but I can almost guarantee that you will be happier with your bike if you do.

Also, make sure you use a good sealant when you apply those rubber pucks on the cylinder head. Don't use RTV. Three-Bond works well.

Camelman

OldSchool_IsCool · « **Reply #9 on:** February 01, 2011, 07:59:41 pm »

To lap means to unbolt the head. unbolting the head means to unbolt the cylinders. Unbolting the cylinders means disturbing the base gasket. to replace the base gasket means pulling the cylinder block off the pistons.

Now the fun begins. What condition are the wrist pins and clips in? Are the pistons reusable? (some carbon is easily cleaned, but what about rust or jammed rings) Are the rings serviceable? (not broken, not seized, proper ring end gap). Are the cylinder walls in good shape? (pitted, scored, rusted). If you need to hone the bores, you need to then replace the rings with new. If you find the rings need replaced, then you need to hone the bores. Severe bore damage may mean reboring the cylinders (machine shop type work) which means new oversized pistons and oversized rings. Don't loose those barrel-shaped oil restrictors, they are tough to replace. Keep all valve hardware together with the valve from which it came. Also make sure the valve goes back into the same cylinder that it came from. Are the various blocks warped? Gasket surfaces in good shape? Be sure to back out the tappets and hold them back with rubber bands lest you jam one and bend things.

It's a slippery slope once you start, but if it needs to be done, then it needs to be done. But I gota say, there is a certain thrill that comes when you first start an engine knowing you were elbow deep in it just a few weeks ago!

BlindSight · « **Reply #10 on:** February 01, 2011, 09:18:06 pm »

Wow thanks for the detailed responses fellas...going to purchase that compressor and some more parts now that I had my paycheck clear and will go ahead and replace everything. I would hate to do more work than needed but I would hate to have to pull everything back apart because I should have done a little more work in the first place.

I just got done re-ringing the pistons, the pins are in great shape and going to re-use them and I went ahead and picked up new clips since they were only $8 for the set.

bryanj · « **Reply #11 on:** February 01, 2011, 09:30:19 pm »

You HAVE to use NEW clips avery time, and if its been stood that long you may find some valves corroded into the guides and not moving easily so take all out and clean up with a wire brush the lap in the seats

IT HELPS IF YOU TELL US WHAT THE BIKE IS

BlindSight · « **Reply #12 on:** February 01, 2011, 09:44:48 pm »

sorry its a 72 500/4. Have new valve guide seals that came with my gasket set so now just need a valve spring compressor, lapping stick and compound and just need to make sure the valves and seats are in good shape right? Whats the best chemical or way to clean them without damaging them?

OldSchool_IsCool · « **Reply #13 on:** February 02, 2011, 12:52:49 pm »

Quote from: BlindSight on February 01, 2011, 09:44:48 pm

so now just need a valve spring compressor, lapping stick and compound and just need to make sure the valves and seats are in good shape right?

My lapping method is to use a conical spring about an inch tall. Not a strong one, needs to be compressed with the fingers yet strong enough to hold the valve against the seat. Slip the valve into it's guide (remember to mate the valve to it's original cylinder!). Wrap 2 or three layers of electrical tape over the tail of the valve stem. Slide the conical spring over the valve stem with the wide side against the head. Using a T-handle from a tap set, clamp onto the electrical tape. This should compress the spring while giving you about a quarter to half inch to open the valve. Open the valve and apply a little lapping compound (I use Permatex). Slowly rotate the T-handle so as to evenly spread the compound. Now, spin the T-handle half a dozen rotations clockwise then half a dozen anti-clockwise. Apply more compound and repeat until you have a nice even dull gray band on the valve and on the seat.

Kanticoy · « **Reply #14 on:** February 02, 2011, 12:53:00 pm »

I like to soda blast mine. Really does make a world of difference in the cleaning process. Some of that carbon is damned near impossible to get off. My go to solvent for motor work (sans anything rubber) is Berryman's B-12 Chemtool. It is available in an aerosol can or a dip can. It leaves no residue like some of the cheaper cleaners. Also Purple Power is a great, cheap general degreaser. Both of these products like to eat skin

!

MCRider · « **Reply #15 on:** February 02, 2011, 01:02:38 pm »

Agree with the soda blast. Check "services offered" forum.
http://forums.sohc4.net/index.php?topic=79458.0

MRieck · « **Reply #16 on:** February 02, 2011, 03:07:15 pm »

Quote from: bryanj on February 01, 2011, 09:30:19 pm

You HAVE to use NEW clips avery time, and if its been stood that long you may find some valves corroded into the guides and not moving easily so take all out and clean up with a wire brush the lap in the seats

IT HELPS IF YOU TELL US WHAT THE BIKE IS

The seats can also be very corroded (especially on those that had an open valve). All the lapping in the world won't correct it

BlindSight · « **Reply #17 on:** February 03, 2011, 08:59:25 am »

Think I might make a cheap soda blast setup...read a bunch of posts about it but they don't seem to worry about cleaning up the part too much afterwards...I know with traditional bead or sandblasting you have to wash the heck out of the part afterwards...same rule apply for soda? What I found was just wash with warm water and blow dry with compressor, should I drop it in a tub of water or anything like that?

MCRider · « **Reply #18 on:** February 03, 2011, 10:47:38 am »

On a valve there are no nooks and crannies, its a simple rinse off in water cleanup. Well, same for everything, but if you do your head you'll get some wedged here and there, so some air or higher water pressure would be good. In my mind you could blast your valve seats, I'd use the lowest pressure your pickup will tolerate, and move up from there. But i can't imagine the soda hurting the seat like glass beads would. If you don't like that idea, and truthfully i haven't done it, leave the valve in place while blasting the combustion chambers. And if some is left behind it would dissolve in the oil, I think, where beads won't.

Come to think if it everybody uses glass beads on their heads, chambers and ports, so maybe they don't hurt the seats either? But the cleanup is more intense for sure.

TwoTired · « **Reply #19 on:** February 03, 2011, 11:05:41 am »

Fear leaving abrasives in the oil passageways of the head. Circulating oil will distribute it to places where increased friction is rather bad.

Kanticoy · « **Reply #20 on:** February 03, 2011, 11:06:10 am »

I know for a fact that soda will not hurt the seats. I do it all of the time pre-lapping.

BlindSight · « **Reply #21 on:** February 03, 2011, 02:20:28 pm »

Sweet thanks for the responses...hopefully the weather will clear up soon and I can get cracking on this. DIY soda blasting it is.

faux fiddy · « **Reply #22 on:** February 03, 2011, 05:01:50 pm »

Quote from: MCRider on February 01, 2011, 07:42:46 am

I vote for valve stem seals, "lap" the valves in (search on it) or google it. And slap it back together and ride!

+1 A little bit on insurance that you have made everything better.

Quote from: fmctm1sw on February 01, 2011, 12:23:59 pm

Quote from: BlindSight on February 01, 2011, 12:22:04 pm
by rebuilding the entire thing what do you advise? have new valve seals, should I do new seats/valves/springs as well? I noticed using the socket and hammer method for taking of the keepers but whats a good way to put them back on without the spring compressor?

Some guys have fashioned tools out of C clamps and sockets and the like... There's pictures around here somewhere...

Here's a piece I used that was around the shop. Note the slots in the side for installing keepers. An arbor press is handy if you can scare one up.

The thread is here:

http://forums.sohc4.net/index.php?topic=58702.msg654051#msg654051

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Author Topic: Valve job/head rebuild or no? (Read 4109 times)