Author Topic: Machinist said "don't lap your valves" (Read 9790 times)

zabzob · « **on:** June 26, 2015, 09:44:22 AM »

Today I dropped my head off to have it run through a parts washer and blasted. The machinist asked what I was doing with it, and I told him I was going to lap the valves when I got it back. He said that you shouldn't lap your valves, as somehow the modern fuels react with leftover lapping compound that gets embedded in the metal. He showed me a valve with a massive ridge cut into it, supposedly only 600km after lapping the valves.

He wasn't force selling anything. He said after it's cleaned on Monday, I should give him a call and see where it's at. He'll do the valves and seats for me they're needed, for about $4/valve.

Anybody heard of something like this before, lapping causing problems?

70CB750 · « **Reply #1 on:** June 26, 2015, 09:48:46 AM »

Never.

754 · « **Reply #2 on:** June 26, 2015, 09:53:08 AM »

If there is a groove, from lapping, they probably. Lapped. A few too many laps...

lrutt · « **Reply #3 on:** June 26, 2015, 09:56:04 AM »

My first question would have been, what are the options?

Then laughed and went home, lapped them, cleaned good, and enjoyed the bike.

I have countless miles on bikes with lapped valves that have been running ethanol fuels.

If that bike had a ridge??? it was caused by improper cleaning, assembly, adjustment, or possible over lapped the valve and cut through the hardened surface.

We are talking just lapping and not cutting new seats and doing a full 3 angle valve job right?

dusterdude · « **Reply #4 on:** June 26, 2015, 10:36:12 AM »

Bull#$%*

Duanob · « **Reply #5 on:** June 26, 2015, 10:46:20 AM »

$4/valve? Go for it. If time is money, is your time worth the $64 for hours worth of work? Not mine!

zabzob · « **Reply #6 on:** June 26, 2015, 11:03:42 AM »

Normally, I'd think he's trying to rip me off... but he's not exactly hurting for work, and this isn't exactly a tonne of business for him. I'm going to think about it over the weekend. As @Duanob says, time is money. I have to move halfway across the country in about 6 weeks, so I'd like to get my bike back together and ride it before too long.

chewbacca5000 · « **Reply #7 on:** June 26, 2015, 11:22:10 AM »

Got to clean the carbon off somehow. That said if the valve and/or seat are pitted up no amount of lapping is going to help. Recut time. I lapped a head the other day and it cleaned up nicely. Lots of carbon on that head.

martin99 · « **Reply #8 on:** June 27, 2015, 12:51:24 AM »

Quote from: Duanob on June 26, 2015, 10:46:20 AM

$4/valve? Go for it. If time is money, is your time worth the $64 for hours worth of work? Not mine!

Yeah, sounds cheap enough but it really isn't a big deal lapping in valves, probably only take a few minutes each once you got going. Besides, I'd be wary going back to that fella - if he won't use grinding paste then what's he going to do? You might end up with an aggressive cut which will cause you problems down the line.

Deltarider · « **Reply #9 on:** June 27, 2015, 02:14:24 AM »

Actually, it's not the first time I've heard a specialist advising to refrain from lapping the valves. Forgot who it was and I'm not a pro on the subject.

trueblue · « **Reply #10 on:** June 27, 2015, 03:42:01 AM »

In workshops, lapping went out in the dark ages, if you are using quality machines it is a total waste of time. A serdi or similar will provide a far superior sealing surface than any lapping job. $4 per valve is cheap, as long as it is a proper job, which I would assume it is given the price, lesser methods take longer and hence cost more I wouldn't waste my time lapping at that price.

Also a serdi type job and valve grind will ensure your valve seat is perpendicular to the guide, the face on the valve is perpendicular to the stem, and above all the valves should all be the same height, which is something that won't happen with simply lapping the valves, and something most amateurs don't even know about.

The only thing worse than a lap job though is using neway cutters, they are total crap and anyone who tells you otherwise has no idea what they are talking about. They will create a chattered seat which will leak, unless they have been lapped to within an inch of their life, and valve heights will be all over the shop.

70CB750 · « **Reply #11 on:** June 27, 2015, 04:48:15 AM »

Gosh, I wonder if anybody told Neway that

trueblue · « **Reply #12 on:** June 27, 2015, 04:53:03 AM »

Quote from: 70CB750 on June 27, 2015, 04:48:15 AM

Gosh, I wonder if anybody told Neway that

I have had to repair too many #$%*ed up seats from "experts" using neway cutters they are the most overrated crap on the market.

hotdog · « **Reply #13 on:** June 27, 2015, 05:02:35 AM »

I have and use a neway set and have had good success with them at home and also in bikeshops - yes they require lapping...last time I looked though I couldn't afford a $30K serdi machine.
I wouldn't say I'm an "expert" either - but have worked professionally in bike shops and have run my own small business and have used neway cutters with success. Sure there are better systems out there, just not anywhere near where I live....
Wondering how you repaired the #$%*ed up seats..??

trueblue · « **Reply #14 on:** June 27, 2015, 05:35:00 AM »

Quote from: hotdog on June 27, 2015, 05:02:35 AM

I have and use a neway set and have had good success with them at home and also in bikeshops - yes they require lapping...last time I looked though I couldn't afford a $30K serdi machine.
I wouldn't say I'm an "expert" either - but have worked professionally in bike shops and have run my own small business and have used neway cutters with success. Sure there are better systems out there, just not anywhere near where I live....
Wondering how you repaired the #$%*ed up seats..??

With a serdi, which any good engine shop will have

70CB750 · « **Reply #15 on:** June 27, 2015, 08:08:59 AM »

Quote from: hotdog on June 27, 2015, 05:02:35 AM

I have and use a neway set and have had good success with them at home and also in bikeshops - yes they require lapping...last time I looked though I couldn't afford a $30K serdi machine.
I wouldn't say I'm an "expert" either - but have worked professionally in bike shops and have run my own small business and have used neway cutters with success. Sure there are better systems out there, just not anywhere near where I live....
Wondering how you repaired the #$%*ed up seats..??

I used them on the F3 engine I replaced guides on. The engine pulls like a train, happy with the Neway job.

MRieck · « **Reply #16 on:** June 28, 2015, 06:08:43 AM »

Quote from: trueblue on June 27, 2015, 05:35:00 AM

Quote from: hotdog on June 27, 2015, 05:02:35 AM
I have and use a neway set and have had good success with them at home and also in bikeshops - yes they require lapping...last time I looked though I couldn't afford a $30K serdi machine.
I wouldn't say I'm an "expert" either - but have worked professionally in bike shops and have run my own small business and have used neway cutters with success. Sure there are better systems out there, just not anywhere near where I live....
Wondering how you repaired the #$%*ed up seats..??

With a serdi, which any good engine shop will have

...or one of the newer CNC machines.The Serdi is a proven machine. Some people say no lapping after cutting the seat on the Serdi but the CB750 intake seats are so soft the need a quick lap to settle them down after cutting. The exhaust seats cut much better. I wouldn't lap a Ti valve but I you can use a steel valve to give the seat a quick lapping and then install the Ti valve.

jonda500 · « **Reply #17 on:** June 28, 2015, 06:12:35 AM »

An interesting topic I've heard so many different conflicting views on this that I don't personally have one.

I am definately not even close to an expert with any heads, let alone motorcycle heads.
So just for interest sake only, when I did an automotive mechanical engineering preapprenticeship course in the 80's we were taught - never to lap valves unless the seat was first recut and a new valve was fitted with the lapping being the final finishing of the sealing surfaces only, - and that by lapping old used valve/seat surfaces you would only succeed in removing embedded carbon from any pitting of the surfaces making the valve leak even worse...

Deltarider · « **Reply #18 on:** June 28, 2015, 06:38:56 AM »

70CB750, you thought it the right occasion to have that flag in your avatar? I personally think it shows bad taste and I remind you it's a rule in this forum to refrain from politics.

ekpent · « **Reply #19 on:** June 28, 2015, 07:19:31 AM »

Quote from: Deltarider on June 28, 2015, 06:38:56 AM

70CB750, you thought it the right occasion to have that flag in your avatar? I personally think it shows bad taste and I remind you it's a rule in this forum to refrain from politics.

Please don't start down that path with him and don't make it political. Be glad you don't have a Nazi flag hanging over there.

kmb69 · « **Reply #20 on:** June 28, 2015, 07:37:46 AM »

Quote from: ekpent on June 28, 2015, 07:19:31 AM

Quote from: Deltarider on June 28, 2015, 06:38:56 AM
70CB750, you thought it the right occasion to have that flag in your avatar? I personally think it shows bad taste and I remind you it's a rule in this forum to refrain from politics.
Please don't start down that path with him and don't make it political. Be glad you don't have a Nazi flag hanging over there.

+1. "Freedom of Speech" - bad taste or not.

Deltarider · « **Reply #21 on:** June 28, 2015, 07:44:10 AM »

Quote

+1. "Freedom of Speech" - bad taste or not.

But no one questions "Freedom of Speech" here. You're free to vomit as well.

kmb69 · « **Reply #22 on:** June 28, 2015, 09:52:38 AM »

Quote from: Deltarider on June 28, 2015, 07:44:10 AM

Quote
+1. "Freedom of Speech" - bad taste or not.
But no one questions "Freedom of Speech" here. You're free to vomit as well.

That's true. Knock yourself out!

It's history and the people that are making it a racial/political issue are pushing an agenda.
Just heard on the news yesterday, they are going after the American Flag now!

Sorry, got nothing to do with lapping valves.
I personally hate all valve lappers. They are all racists, homophobe, leftwing, rightwing bigots!

Deltarider · « **Reply #23 on:** June 28, 2015, 10:01:39 AM »

Quote

It's history and the people that are making it a racial/political issue are pushing an agenda.

Right so. Changing your avatar into that flag in these days shows you have an agenda. Can't argue with that.

kmb69 · « **Reply #24 on:** June 28, 2015, 10:15:08 AM »

Quote from: Deltarider on June 28, 2015, 10:01:39 AM

Quote
It's history and the people that are making it a racial/political issue are pushing an agenda.
Right so. Changing your avatar into that flag in these days shows you have an agenda. Can't argue with that.

Can't speak for Prokop, but I took it that he was protesting the "agenda".

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Author Topic: Machinist said "don't lap your valves" (Read 9790 times)