Top end work

[DAM shop]

Are valve seats (90/110) heads something that can be replaced without machinery tools? Is this something 1 could do in a home shop with some basic tools? We flip a lot of trikes and our biggest hurdle is cylinder boring and reseating valves. The boring is simple enough we bring 3-4 cylinders and piston to our guy and have them bored slightly over stock specs that way we have some ready to bolt on. The heads on the other hand would be great to do on a bench in our home shop. Opinions?

[ATC King]

Are the seats that bad they can't be cut?

Even the old handheld seat grinders are kind of expensive. The modern seat cutters are pretty affordable.

I have no idea about the quality of this set, it's just something I found with a quick search.
https://www.patintc.com/valve-seat-cutters-carbide-tipped-fast-economical-valve-seat-restoration-sys

I've used similar on automobile engines. I don't think it could be much easier, especially if using new valves. These type cutters are hand use and work very quickly. Just got to see if you can find one with the right size guide and cutter.

[DAM shop]

Yeah I have no idea how that all works being we’ve always had new valves done by our machine guy. That kit looks pretty extensive for our application I suppose a talk with my machine guy the next time I see him would make most sense. I feel we are at this point in our flips that if we could do some bench head work ourselves we could save a bit of time and money. I’m guessing all one does is cut new valves into old seats? And at what point can you get away with a re grind ?

[kb0nly]

How bad are these valves that you are working on? Most of the ones i get just have your basic wear, some are bad enough they need cutting but most of the ones i have had i just got my valve lapping compound out and my cordless drill with suction cup adapter to spin the valve. A little oil on the valve stem so it doesn't damage the guide and spin it clockwise then counterclockwise and keep working the lapping compound in, i can lap them in for a good seal in no time. Now if they are really bad then i just get out my cheap valve seat cutters, i have a cheap set like this... Thats not the exact seller just one i could find quickly to show what i have.

https://www.ebay.com/itm/Valve-Seat-Reamer-Motorcycle-Valve-Repair-Displacement-Cutters-Valve-Tool-Set/184409306894?hash=item2aefa6b70e:g:r7MAAOSwtjdfIhL o

Came with the right size guide and its easy to use. For most with light wear or pitting the little grinding wheels will take care of it, if its really pitted or bad then use the cutters, but with either i follow up with lapping the valves afterwards for a good seal. Just how i was taught to do it back in high school shop class, and i have been doing it that way ever since, too long to mention and date myself... LOL

If the valves are not bent or badly beat up and the stems and guides are ok i just go through this process to clean them up, then i re-assemble with my cheap valve spring compressor, new stem seals, etc... After thats done i put in a spark plug and tighten it down and then flip the head over and fill the chamber with isopropyl alcohol to cover the valves right up to the edge as full as it will go, let it sit for an hour, some alcohol will evaporate, but as long as i am not seeing it coming out the exhaust or intake ports and i know the valves are sealing then thats good enough for me and it goes back together.

My current project, 82 200E, sat for 15 years, and when it sat it must have been sitting with the exhaust valve slightly open, compression test showed 145 psi which is at the bottom of the service range by the manual, figured it was cylinder but the bore looked ok and the rings weren't that bad either, but then i took apart the head, the exhaust valve was for sure leaking, no shiny wear line around the valve and seat like the intake valve, it was pitted and rusty. Cleaned the valve on the wire wheel then gave the valve seat a quick buzz with the cordless drill and the grinding head from that kit to get most of the rust and pitting gone, then i lapped it in with coarse compound until the valve and seat were cleaned up and free of rust and pitting and then switched to fine compound and buffed them to a mirror finish. The intake just needed the fine compound to clean it up a bit. I'm sure when this one goes back together the head will be great on it now. It don't take much, and unless its really really bad you don't need a machine shop to clean up these heads, just some basic tools, time, and practice.

[DAM shop]

That’s the answer I was looking for kb, thanks.

[ATC King]

To add a little bit, you've got to keep up the valve stem and installed spring height.

When material is removed from the valve/seat, the valve will ride higher.

Probably not a huge issue on something needing minimal material removed, but still something to know and measure.

A new pair of Japanese made valves is about $15. It's possible to grind or cut used valves, but with the low price, it's probably better to just go with new and not include that additional height change with a cut seat.


There used to be small engines shops in every little town, back in the side valve days. They managed to get by will very little major equipment and most of the work was by hand. These ATC engines aren't much different than that for stock rebuilds. With the information available online now, there's no reason a person can't do the same anymore in their garage.

[kb0nly]

That’s the answer I was looking for kb, thanks.

Welcome! And like the King added, yes height difference, forgot to mention that because normally you aren't removing enough material to cause an issue. A new set of valves are cheap, so definitely if you wanted you could put new valves in every one you work on, me personally, i'm cheap, if i can save $15 on a set of valves and put that into something else i will... LOL

But i evaluate every one, i have had a few that just had to have new valves, but far more of them were fine after a good lapping.

[kb0nly]

To add a little bit, you've got to keep up the valve stem and installed spring height.

When material is removed from the valve/seat, the valve will ride higher.

Probably not a huge issue on something needing minimal material removed, but still something to know and measure.

A new pair of Japanese made valves is about $15. It's possible to grind or cut used valves, but with the low price, it's probably better to just go with new and not include that additional height change with a cut seat.


There used to be small engines shops in every little town, back in the side valve days. They managed to get by will very little major equipment and most of the work was by hand. These ATC engines aren't much different than that for stock rebuilds. With the information available online now, there's no reason a person can't do the same anymore in their garage.

Ahh the good old days... when pretty much every town had an old guy that could rebuild your lawnmower and sharpen and balance the blades. I miss those days. Now i have all the tools to do everything myself, ironically some of my tools came from the local shops that closed down over the years.

[Dirtcrasher]

I'm about ready to drop the hammer on a valve grinding kit myself, I plan on 1 - 1.5k$.

Those India kits I have not heard the best about, maybe they're ok if you go slow, are gentle and don't do much work, I'd rather have a very good set if I'm gonna buy any.

People send me heads to replace the broken exhaust studs, and often the valves are beyond serviceable. Once you can hook a fingernail on the valve, you can't lap that out. So, I can't provide a full service without a valve cutter kit. Honda uses 32, 45 and 60 degree cutters, the 32 and 60 are just relief and can probably be off a hair.

I've even contemplated making my own cutters, just for Hondas to start. The best ones, Neway cutters, are expensive, but they are made from aluminum with replaceable cutters. I bet I can make the housing on my mill and lathe with a rotary table and some slitter wheels....