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post #1 of 18 (permalink) Old 1-31-2017, 12:31 PM Thread Starter
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Cleaning Valve Seats -- Brass Only?

So I think I've read every top-end rebuild and refresh thread on these forums.

Points gleaned:

1) Rebore cyclinders & use 1/2 mm OS rings. endgap to .005". Knurl piston skirt.

2) Lap head & cylinders. Clean and repaint head gasket, one coat.

3) Lap in exhaust valves. Get new intake valves and re-cut valve seats.

4) Might as well degree cams.

After calling about eight different machine shops, no one in my area has the tools/interest on doing a small job on a small engine.

So it looks like I'm cleaning the valve seats by hand. I've used a brass brush to clean off most of the hardened carbon. There's still a layer clinging to the valve seat though that the brass cannot break free. A steel pick breaks it easily but I don't want to risk gouging or knicking the valve seat. Overnight solvent leaks past the valves so they definitely need work.

All this to ask: Will I trash my valve seats if I use a steel wire brush to clean the hardened carbon off? I realize this is not a proper rebuild and I won't make optimal power. This is just an after work hobby in my garage.

Many thanks.

Last edited by melon rancher; 1-31-2017 at 12:34 PM.
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post #2 of 18 (permalink) Old 1-31-2017, 1:50 PM
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Personally I won't do it but you can use a super fine steel wire to clean them.
Effective method I've used is a brass wire wheel in a Dremel type tool.
And seriously... some nitro bore solvent (used in firearm cleaning)
Believe me when I say there's tons of hard carbon build up on a dirty a** gun.

And if you do need to scrape any... take a piece of 1/4" copper plumbing pipe, cut it about 5" long, flatten one end and dress it.
Works quite well for scraping gaskets too... and the nice thing is that copper is softer than aluminum and other materials in the engine.
Not saying it can't scratch but it's less likely with copper.

If you're gonna lap the valves you can do it with a battery drill and a piece of tubing. Put some compound on the valve and drop it in head.
Piece of tubing on stem, drill bit of appropriate size in open end of tubing... chuck it up and pull light pressure on drill, reversing direction every few seconds.
You'll hear as the compound does its work. Grinding sound gets softer.
Reverse direction... Rinse, repeat.
Do a few times each way then CLEAN the hell out of it to remove compound.

O_E_M
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post #3 of 18 (permalink) Old 1-31-2017, 2:15 PM
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Might look on eBay for a vintage "ZIM" brand valve lapper. Small tool like a hand egg beater, but it reciprocates and advances the valve with each turn of the handle. Used with lapping compound, you should have excellent seats in little time.

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post #4 of 18 (permalink) Old 1-31-2017, 2:19 PM
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Quote:
Originally Posted by one_evil_monkey View Post
You'll hear as the compound does its work. Grinding sound gets softer.
Reverse direction... Rinse, repeat.
Do a few times each way then CLEAN the hell out of it to remove compound.

O_E_M
I've lapped a few valves at this point. O.E.M is right on the money, though to spin the valve, I used a manual valve lapping tool, which is just a small suction cup on the end of an 8-inch long wooden stick, can be had at any auto parts store for a few bucks. The end result is the same as the drill method, just slower.

It really doesn't take long for the lapping compound to do its work. Took maybe 10 seconds with the manual method to hear and feel it smooth out.

I've read something about not lapping the intakes or something, but when I lapped the valves for the top end I sent out to Snowdrift, I did all 8 valves and the valves and seats appeared as they should have. I didn't get too aggressive with it, didn't have to, just enough to smooth out any minor imperfection and carbon deposits.

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post #5 of 18 (permalink) Old 1-31-2017, 2:35 PM
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I've done my fair share of lapping... can't you tell? Haha

I just use the drill method because it's faster and if you're doing a bunch of valves sitting there with the manual one kinda sucks.
However, there's nothing wrong with the manual method and for a one time shot on an 8 valve head, you won't be there all day.

With the drill method it only takes about 5 seconds in one direction before the sound gets soft. Reverse direction with another 5 seconds, reverse direction with another 5.
And that's really all it takes.
The compound cuts pretty quick and remember that you don't need a ton of pressure.
Not like you're carving granite or anything. Haha

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post #6 of 18 (permalink) Old 1-31-2017, 3:38 PM
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Hey, hand lapping is the green solution! If it worked on 51mm sodium-filled, stellite-tipped Packard V8 valves, it will certainly work on 29mm EX micro-valves. Electricity? How do you think cavemen lapped their valves?

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post #7 of 18 (permalink) Old 1-31-2017, 3:44 PM Thread Starter
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Thanks all for the responses.

I think I'll stay away from any steel wire.

I lapped the head and cylinders last weekend so I've got a good idea of the sound and feel of fresh compound vs. lapped surfaces.

I'll lap the valves tonight with my drill. I suppose the lapping compound oughtta cut right through the carbon shit, eh? I was thinking I needed to get all the visible carbon off the seat before I did the lapping. If that doesn't work, I'll swing by a gun store and get some of the solvent you recommended O_E_M.

On the bright side, it looks like I won't be spending $50-$100 at any machine shop. I'm kinda done putting new money into this bike
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post #8 of 18 (permalink) Old 2-1-2017, 1:40 PM
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Hoppes #9 or similar will cut the carbon.

If you have some carbon on the seats I'd remove it BEFORE lapping in the valves.
Not that it technically matters but I've never liked doing it with it there.
Just makes me feel better to remove first, then lap.
Call it a personal preference.

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So easy a caveman.... Haha

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post #9 of 18 (permalink) Old 2-1-2017, 3:06 PM
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If you need to lap the valves or the seats your only kidding yourself. Because the valves are very thinly case hardened, any perceptable wear is as good as junk.
Cutting the seats wit the proper cutters and replacing the valves with new ,is the only repair.

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post #10 of 18 (permalink) Old 2-2-2017, 1:12 PM
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I will add that if the lapping cuts through the case hardening...
Lapping will smooth it out but they won't last.
They'll wear at a LOT faster rate and adjustments may become sooner.

Now, that being said...
I've lapped plenty of valves and they've lasted a right smart many a mile.
One example...
Actually have close to 10k on a set in a dinky scooter that started life as a 50cc.
New jug and piston, ported and polished original head... Lapped valves...
Different cam profile...
It's 100cc now, went from 1.9 bhp to almost 3... 10k miles and still strong.

But YMMV
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post #11 of 18 (permalink) Old 2-2-2017, 3:18 PM
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Note to melon rancher,
I have all the tools necessary to do a proper valve job on your EX. if you wish to have it done right you may contact me via email 'FOG

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post #12 of 18 (permalink) Old 2-2-2017, 5:33 PM Thread Starter
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Thanks for the responses.

FOG that is kind of you to offer your services to do a proper valve job. If I lived closer to you it's something I'd consider but with the cost of shipping & the cost of your services I can't justify it. I am out here in the Pacific Northwest.

Perceptible wear....hmm. I'll take my loupe home from work tonight to better check the valve seat condition. To the naked eye the intake seats actually look pretty clean. The exhausts are in worse shape. It looks like there are two beveled surfaces surrounding each valve. The smaller of the concentric circles being the actual valve seat, and the larger beveled circle being the area immediately outside the valve seat. That is where the carbon crud is stuck on really hard.

My macro photography skills leave a lot to be desired but here is a picture.


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post #13 of 18 (permalink) Old 2-2-2017, 6:35 PM
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the condition of the seat is not a important as the valves themselves. any ridge or groove in the valve is cause for discarding for the intakes ,the exhausts can be re cut then a light lapping to check that the seal is good is all.

O.E.M. Has suggested that a vigorous lapping to renew the seal is ok. My point of view is from a racers perspective that power production is tantamount. not simply 'RUNS OK"

A good valve job allows the valve seat to start flowing as soon as the valve breaks the seal as little as .001" any grooving on the valve can increase this amount to .01' or more. this can translate to a reduction of valve opening time and height. coupled with a too large a clearance setting can result in a massive loss of power. but it will "RUN OK".
Also on the valve itself, the area above and below the seal line can and does affect the flow too. keeping the valve clean and if allowed removing as much of the unsued portion can aide power production.

The sealing surface is critical for sure ,but the angles under and over the sealing surface are where the power is made. This is so important that stock racing rules prohibit anything but stock 3 angle valve seat cutting.

On my race bike engine ai redid the valves after every race to refresh the seats.

I submit the above for you entertainment and enlightenment not to say it is necessary
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Last edited by fog; 2-2-2017 at 6:39 PM.
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post #14 of 18 (permalink) Old 2-3-2017, 3:32 PM Thread Starter
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Consider me enlightened and entertained. Thank you for the technical explanation. I have a better understanding of both the "how" and the "why" regarding valves.

"Runs OK" is about where my sights are set on this engine. 27k miles, and as I saw you advise someone elsewhere, "I think that considering the Mileage on that engine (25k), The bottom end can't be far behind the top, and then your into big money. Just put it back together after the head work".

So that's the plan. Right now I'm just interested in having a spare engine in the garage to play around with and drop in a bike if needed. I appreciate the responses and advice.
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post #15 of 18 (permalink) Old 2-3-2017, 4:03 PM
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Absolutely FOG is correct...
There's big difference in doing "proper" for most power gain versus just getting a decent seal to run for street use.

Doing the way I do, it makes a seal and works fine for intended purpose but it does mess with the 3 angle stepped seat... losing a little bit of flow/power in the process.
Not enough to truly matter in the scheme of street use though.
At least not in my experience any way.

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post #16 of 18 (permalink) Old 2-3-2017, 8:14 PM
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The only place you can notice the diffrence in a good or so so valve job, is when you are pulling your competition down the front straight,or out digging him coming out of a corner.
I did this a lot

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post #17 of 18 (permalink) Old 3-20-2017, 12:14 PM
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FOG, you've stated before you would often lap valves during a race weekend. I would assume you were lapping stainless steel valves, since you do not recommend lapping stock valves? I read on another forum to NOT lap titanium valves and wonder your thoughts on that?

All new to this, and again thanks to the forum for the wealth of knowledge here.

Edit: Further search found this:
Engine rebuild
So it's possible to lap stock exhaust valves?

Last edited by vance; 3-20-2017 at 3:29 PM.
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post #18 of 18 (permalink) Old 3-20-2017, 6:22 PM
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Never during a race weekends but between them . Mostly to clean the back sides and recheck clearance, then just enough to clean the seal surface.
Do not lap stock valves unless they are new valves to just check the seal.

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