damn this actually works! I used duct tape to secure the sandpaper to the valve but it does work! I currently have to use low grit to get out the big issues but it follows the contours even if there are multiple angles. Great fix without going to a machine shop

3:25 The sound that valve makes, when you push it in the guide is no good 😵‍💫

The best way to check the leakage is put the water on the head dome then spray the pressurized air on the port

Great idea!!! Thanks for sharing,👍 I have an old tractor with a peculiar problem where the valves wore themselves in to the head to a mushroom shape. No hardened seats in the head, just bare cast, but with new valves I will try this method and see if I can't increase the remaining surface area withought machining.

whoah!!!.....that's a neat trick to keep in the back of our minds....

I've done lapping compound many times. It just takes along time. What he's showing is basically a poor man's way of grinding seats without the stones or $300 to $400 machine. Sandpaper on the valve is like using a stone

Thank you so much for the technic, in fact i thought about it but wouldn't have the balls to do it without seeing your video, your awsome. Ps¹: i just used gasoline to remoove the litle patches and the glue, then the rest came out at the grinding by hand. Ps²: first i used 240 water paper because of the gap with the new valve guides (hand hammered) then 400 Peace

Permatex valve grinding compound is good

I usually put polishing compund instead of sandpaper. But your way works too

air molecules are smaller than water, I always use gas to check for leakage...

That’s a pretty inventive way of getting the job done.

Great idea, I need to cut seats to for larger valves, or at least move the seat area on the valve, only problem is the valve is 16mm , I'd like to go to 18/23mm, instead of 16/18mm, the sad part is the valves are seating on the smallest part of the valve possible, so it's more like 14.7-15mm with the rest of the valve shrouding it's self, either boring out the seats, to seat on the mid to outer portion of the valves, or grind off the valves making them smaller, doesn't normally make sense to go with smaller valves to improve flow, but the are at least 1mm in their own way, I'm used to 2"+ valves( 2.02 / 1.60" and such) the smallest seat cutter I found is 20mm, 30°/45°< I'd be happy with a cutter that would only do 45°, and do 16mm-18.5mm, 20would be better, I can get 20/23valves for this head, it's a small engine, and no revlimit, it still will not spin over 8500, it runs out of air, even with ported head, and larger intake and carb, exhaust! Even with a cam! It is severely under valved!! The ports are huge compared to the valve opening! I'd like to atleast swap to a 18mm exhaust, but 20mm would fit the 1" port better, the intake is also 25mm, and I want to go to a 26mm carb, the 7mm valve stems don't help either! A 5mm would help, with it but down to 4mm, the spring rate is kinda low, so a 7mm stem isn't needed, sorry to ramble, but I was thinking about brazing small pieces of a file to a old valve, similar to this sandpaper thing, if I had access ta machine shop, I could make a cutter I'm sure, with replaceable cutters, sorry again for the rambling, but the engine runs ok, with the small valves, and ported head, and opened up seat throat, I wish I had ground the valve diameter, about 1mmand back cut them a bit, it may had made another 1/4-1/2 HP, that's a lot when you are starting with about 3.2hp at 7500, I'd say, (guess) it is about 5-6hp now, I'm shooting for about 10-12hp at 9500-10k rpm, with 1.5" stroke it should do it!! After the valve upgrade, and increase the compression ratio to about 11:1 , it's about 9.5-9.8:1 now, about .3-.4 more than stock, unshrouding the valves in the chamber , reduced it slightly, but is a major improvement over stock, low lift flow should be greatly improved, next step is a bigger bore, big valves, and a stroker crank, nearly doubling displacement!! Rambling I know!!

Bro. 80 grit and try some oil to cut, like wd

great this what im looking for. thanks

Helpful- gives me some ideas to solve my problem on my BMW e30 head if I need to change some of the guides; the valve seats will then need some work.

Awsome. Cool fix.

😳 WOW!…. What a Fantastic Idea! I can see that this will work just fine. Your Exactly Correct that this will indeed save money on costly tools! I’ll get back to you on how well it worked out….. ✌️

This might have saved me a ton of money.

dont get it just go buy some lapping compound and save all the time of gluing paper to valves total loss

hmmmmm... This might just do the trick! I was using toothpaste to grind away the area (didn't feel like buying compound) but one valve seat was pretty damaged from rust. I gotta get some real grinding compound to redo the others, use that water trick, and see what I can get done!

What was your static compression after this trick?

Creative thinking.

Hey, do your seats not have 3 angles from the factory?

Thanks for the idea

what expensive tools are we talking about? grinding compound?

i like ur style

That port looks crude for a German 5 valve job!

Use gasoline after water gas will piss where water holds

Great idea. Gonna use it to remove the pits in mine.

terrific idea thanks

Can You Do This On A Small Engine 3.75 Briggs Stration

Did you try this in a cast iron head?!

Great

Looks like you should have got a new seat. They are not hard to replace

I thought I was the only one who tried this!! lol

That's a Yamaha head isn't it? R1 head?

kzfaq.info2W3A1_uD-yg?feature=shared. How I do it with a dremel tool

Lovely

That's so dumb the whole point in using valve grinding paste is so that it grinds the valve and the valve seat to the exact same size if you only grind the seat then they won't match up

Hack job

Why the quotes? Do you think they're not _really_ called valve seats?