-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Lapping valve feedback
- Thread starter JE4570
- Start date
That's looking good. What you mostly want to look at is the seat in the head. That's what gets pitted mostly and those pits will appear as black specs if you haven't lapped enough yet. Lap again (or some more) until those black spec disappear or nearly do, then switch to the fine compound. They would come out eventually using just fine compound but it takes much, much longer. The coarse compound knocks them out of there much quicker and then the fine just puts a final, finer finish on the seats.
I'd say you're good. I use a combination of liquid (solvent, kerosene usually) in the combustion chamber and compressed air blown up into the port. Leaks show as streams of bubbles .....
You sometimes need to experiment with the blowgun position. Get it too close to the valve and you'll actually blow it open. It will appear to leak when it may not be.
You sometimes need to experiment with the blowgun position. Get it too close to the valve and you'll actually blow it open. It will appear to leak when it may not be.
One more quick concern... I double checked my work this morning and I found something worth bringing up. I may have a small problem here
Notice the light ring that formed on on of my exhaust valves. Is this enough to be concerned? It looks a lot worse in the photo than from the naked eye.
Should I be worried or just do the test that 5twins described to determine if it leaks?
Should I be worried or just do the test that 5twins described to determine if it leaks?
Yea thats what I was thinking I was just wanting to make sure. Its definitely not as bad from the naked eye. My phone’s camera has trouble focusing up close and it appears a lot larger and deeper on camera. I’ll try it as soon as I put em back together.
Not an XS but my engine builder just did this one for the guzzi today. I think yours looks good.
He had to recut the seat in the head then lapped in the valve.
He had to recut the seat in the head then lapped in the valve.
Hi again so I got my valves set.... i was able to produce bubbles on both exhaust valves, but I think I was just blowing the valves open. now I am left confused. Is it me or the valves? I used isopropyl alcohol as my solvent. Is there another test for determining leaks? I will have to do some reading up on this.
With the head upside down, you could fill the combustion chambers, or with it right side up fill the ports with liquid so the backs of the valves are covered, and let it sit a few hours or over night. Then look to see if any solvent has leaked past the valves. The compressed air trick just expedites the process, shows you immediately, but you kinda have to get a feel for it so you're not blowing the valves open.
Valves seal the combustion chamber during the compression and power strokes. Those pressures tend to force the valve (more) closed. At 4000rpm, a valve is asked to seal that chamber 2000 times every minute. Here's what I do... turn the head upside down and fill the combustion chamber with gas. Then count to 30 out loud and look in the intake and exhaust ports. If they're dry, you're good to go.
In operation that valve would have opened and closed a thousand times by the time you counted to 30.
You are doing this with the springs installed... aren't you?
In operation that valve would have opened and closed a thousand times by the time you counted to 30.
You are doing this with the springs installed... aren't you?
