Question on lapping valves

BillK · 07-13-2016, 09:05 PM

Jeff,
Harleys have very short valve guides and they never go in exactly concentric to the previous guide or the seat. You always have to recut the seat. Have you checked your pilot to see if maybe it isn't bent a little ? Put it in the guide and touch the seat. Then put some dykem on the seat, turn the pilot 180 degrees and touch the seat again. It should touch right up. If it doesn't your pilot could be bent.

You can do the same thing to check your valve grinder. Chuck a valve up and grind it, then turn it 180 degrees in the chuck and grind it again. It should touch right up.

I always lightly lap valves just to make sure they are hitting the seat all the way around. I use 320 grit lapping compound. If the seat and guide are concentric and your pilot isn't bent or flexing, you should be able to lap the valve in and see a pattern with very little pressure.

07-13-2016, 09:05 PM	#4
BillK Member Join Date: Nov 2005 Location: Waldorf Md Posts: 230 Likes: 12 Liked 30 Times in 17 Posts	Re: Question on lapping valves Jeff, Harleys have very short valve guides and they never go in exactly concentric to the previous guide or the seat. You always have to recut the seat. Have you checked your pilot to see if maybe it isn't bent a little ? Put it in the guide and touch the seat. Then put some dykem on the seat, turn the pilot 180 degrees and touch the seat again. It should touch right up. If it doesn't your pilot could be bent. You can do the same thing to check your valve grinder. Chuck a valve up and grind it, then turn it 180 degrees in the chuck and grind it again. It should touch right up. I always lightly lap valves just to make sure they are hitting the seat all the way around. I use 320 grit lapping compound. If the seat and guide are concentric and your pilot isn't bent or flexing, you should be able to lap the valve in and see a pattern with very little pressure. __________________ Bill Koustenis