Valve Lapping: Did I do it right? [video]

[TwoManyXS1Bs]

I like the trick with the small spring, helps to get the valve off the seat.

Coupla adders:

The newer valves (after '73-'74) will have a stellite coating. Grinding of valve face and tips should be limited to no more than 0.005" (0.12mm) to avoid excessive reduction of the stellite layer.

A snippet of valve dimensions from a later manual:

 

[5twins]

Maybe I've just been lucky so far, but I have yet to have a seat grow beyond that 2mm width limit, and I've lapped some pretty bad ones. My measuring technique isn't high tech, I just hold a steel rule up to the seat. It's easy enough to see with the naked eye if it's too wide.

 

[Marlin72xs]

I like the trick with the small spring, helps to get the valve off the seat.

Coupla adders:

The newer valves (after '73-'74) will have a stellite coating. Grinding of valve face and tips should be limited to no more than 0.005" (0.12mm) to avoid excessive reduction of the stellite layer.
View attachment 114831

A snippet of valve dimensions from a later manual:

View attachment 114832

As always I appreciate your input 2m. I will comment with more info later, thanks.

 

[Marlin72xs]

Maybe I've just been lucky so far, but I have yet to have a seat grow beyond that 2mm width limit, and I've lapped some pretty bad ones. My measuring technique isn't high tech, I just hold a steel rule up to the seat. It's easy enough to see with the naked eye if it's too wide.

I'm probably unlucky, but I have 3 heads to choose from once I pull my 72 head. Will comment later, too many beers. Loaded Landsharks actually. Hey, it's Saturday night and it's gonna rain tomorrow. But I'm sure the guy who had this head over did it because the seats in the head are about as wide as the seats on the valves. 2 mm or more. I'll try to take some Picts.

 

[Marlin72xs]

And, 5twins, I also appreciate your input. Thanks.

 

[Marlin72xs]

I've done a few valve lapping jobs sporadically in the last 50 years or so. A 50's Briggs and Stratton, a 56 Hillman flathead 4, a Datsun B210 in the 80's. All were supervised by my father who was a Tool & Die engineer for Bendix Aviation. His job was to figure out how to machine mass produced or one of a kind parts for planes and satellites. I grew up with a basement full of drill presses, lathes, grinders, shapers, punch presses and milling machines. If we needed something he would just make it. Only wished I had 1/10th of his knowledge of tool sharpening and metallurgy. The milling machine would also have been handy, it was older than me and heavier than 2 Harleys, but my brother sold it. But I am about to get another lathe.
Enough history, and to note, I'm no expert by any means. I rely on past experiences and now I have you guys.

5twins, I'm just unlucky. Actually, this head was purchased from eBay by the guy I bought the 75 from. He assumed there was a head problem, and there was. I found a bent valve and another badly pitted.

Enough talk from me, I measured the seats and I get an average of .1" or 2.54mm. Check out some pics.

 

[Marlin72xs]

I like the trick with the small spring, helps to get the valve off the seat.

Coupla adders:

The newer valves (after '73-'74) will have a stellite coating. Grinding of valve face and tips should be limited to no more than 0.005" (0.12mm) to avoid excessive reduction of the stellite layer.
View attachment 114831

A snippet of valve dimensions from a later manual:

View attachment 114832

Uh-oh! I think i found something that u don't know. Just kidding of course. My XS1-B book also shows stellite on the valves. Fyi, the xs1-b book came with the 72, plus an addendum booklet for the starter and such.

 

[5twins]

Yes, it's pretty easy to see even with the naked eye that those seats got too wide, exhausts especially. The angled parts leading into the seats on both sides will need to be cut to narrow the seats back down.

 

[Marlin72xs]

Yep. Thank you. I'll wait to see which head is better when i pull mine. I'm curious though, have you ever tried those angle cutters from mikes or know any one that has?

 

[TwoManyXS1Bs]

... I'm curious though, have you ever tried those angle cutters from mikes or know any one that has?

I have the MikesXS seat cutter set. Haven't used it yet, but a review in here:

http://www.xs650.com/threads/review-of-some-parts-purchases-from-mikesxs.10849/page-3#post-267242

This may be of interest:

http://www.xs650.com/threads/how-to-determine-which-size-valve-guides-are-needed.27318/

Back in the ol' shop daze, we had 2 different seat cutting tools.

A powered Souix valve seat grinder, like this:


And factory Honda seat-cutting tools:


The powered grinder was great. The arbor was fitted and tightened into the guide, best accuracy and kept grindings out of the guide. Keep the stones dressed, great results. You could make up arbors and profile stones to your liking, custom angles and such. Gotta be careful, tho'. Can easily grind thru the seat, head, the table, floor, all the way to China. Use a very light touch, let the stones center on the arbor for best concentricity. Your best choice for hardened seats.

The hand-powered cutters were cheaper, but (*grunt*) a bit more work. Their arbors had to have a looser fit in the guides, so you could spin them. If you beared-down a bit too hard on them, the cutter would want to center on the existing seat, not on the guide center. And, if your turn/cut technique wasn't good, you'd sometimes get "chatter" marks. These don't work well on hardened seats, and can permanently dull the cutter. A real risk factor, since it's not easy to tell early on, on an unknown head, if the seat is cast iron, or hardened. The loose fit of arbor to guide could also let chips in there, risking the guide...

 

[Marlin72xs]

Yikes!