Lapping compound


44 replies to this topic
  • ToyMan

Posted August 28, 2006 - 07:10 AM

#1

I had to get the head resurfaced on my drz. When it was time for reinstalling the valves I went to buy some lapping compound. I had to goto 4 auto parts stores before I found any. At the last place -the clerk was actually excited to sell it to me. He said nobody every buys this stuff anymore. Is that true? Would the valves seat properly without it? Well, I used it anyway but I was curious as to what everyone else here does.

  • Noble

Posted August 28, 2006 - 07:28 AM

#2

Valves and seats are resurfaced with grinding stones. Or the valves are just replaced. Valves are rarely lapped in. The days of grinding valves by hand are gone.

  • NateTheGreat

Posted August 28, 2006 - 07:56 AM

#3

Yup cut the seats if required and throw in new valves.

  • ToyMan

Posted August 28, 2006 - 08:13 AM

#4

Is there any downside to using the lapping technique? I have already done it and put the valves back in.

  • smcdonn

Posted August 28, 2006 - 09:55 AM

#5

On titanium valves there is a huge downside to lapping in the valves. It wears through the nitride coating and the valves are shot in less than half the time. I am not sure what the DRZ's valves are made of but I'm sure you will be just fine as I am possitive they are not titanium. Just so you know. When I replace valves, I take the old valves and put some lapping compound on them and lap them in. This smoothes out the seats. Then take your new valves and drop them in. Cheers

  • MJBruns

Posted August 28, 2006 - 10:28 AM

#6

If you look even the factory manual says NOT to use it
Mike Bruns

  • Eddie Sisneros

Posted August 28, 2006 - 12:03 PM

#7

never use lapping compound on any modern motorcycle valves valves.they are coated.

  • ToyMan

Posted August 28, 2006 - 12:27 PM

#8

Thanks for the info - How would you proceed if you were me? I have already used the compound & put the head back together. How long do you think it would last as it is?

  • Pitbuell

Posted August 28, 2006 - 01:58 PM

#9

never use lapping compound on any modern motorcycle valves valves.they are coated.

the coating on the stem is important.
The coating on the seat area can be grind off without any problem,
valves with good stem surface can be reused and if there is a pitted surface
on the erea that touches the seat it can be grind smooth in a valve grinding machine.

No problem

  • ToyMan

Posted August 28, 2006 - 03:00 PM

#10

the coating on the stem is important.
The coating on the seat area can be grind off without any problem,
valves with good stem surface can be reused and if there is a pitted surface
on the erea that touches the seat it can be grind smooth in a valve grinding machine.

No problem


Okay - well we only did it on the valve seat. We definetly did not touch the valve stem. I guess we will run with it & see what happens.

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  • E.Marquez

Posted August 28, 2006 - 04:25 PM

#11

the coating on the stem is important.
The coating on the seat area can be grind off without any problem,
valves with good stem surface can be reused and if there is a pitted surface
on the erea that touches the seat it can be grind smooth in a valve grinding machine.

No problem

Umm, no... Not even close..Not sure where you get your info.. But as far as this application, and in general,, any coated valve.. It is a huge deal,, Lapping these valves ruins them.

  • Eddie Sisneros

Posted August 28, 2006 - 04:52 PM

#12

the coating on the stem is important.
The coating on the seat area can be grind off without any problem,
valves with good stem surface can be reused and if there is a pitted surface
on the erea that touches the seat it can be grind smooth in a valve grinding machine.

No problem


fraid not.please dont post things like this when you have no clue about the subject.

its not a buell.

the coating on the face of the valve is critical.

if you try to reface a japanese motorcyle valve it will last maybe one ride.

  • Eddie Sisneros

Posted August 28, 2006 - 04:54 PM

#13

Okay - well we only did it on the valve seat. We definetly did not touch the valve stem. I guess we will run with it & see what happens.


just depends if it went thru the coating or not.

keep your finger crossed and hope you got lucky.

you will know soon enough.

  • Pitbuell

Posted August 29, 2006 - 12:33 AM

#14

fraid not.please dont post things like this when you have no clue about the subject.

its not a buell.

the coating on the face of the valve is critical.

if you try to reface a japanese motorcyle valve it will last maybe one ride.

I know it's not a Buell and yes i got a clue but never to old to learn
so O.K. educate me.
what kind of base material is the valve of the DR-Z400
and what kind of coating is used on the stem and head ?

  • Eddie Sisneros

Posted August 29, 2006 - 03:04 AM

#15

its just a plain steel valve.stelite (sp) coating.this goes for th eoem ti valves as well.

intake valve opens and closes roughly 62 times a second at 11k rpm.

do you really want to take chances in the valve train?

there is no reason to use lapping compound.if the valve has a issue,its replaced.if the seat has a issue its recut.

  • Pitbuell

Posted August 29, 2006 - 04:54 AM

#16

its just a plain steel valve.stelite (sp) coating.this goes for th eoem ti valves as well.

intake valve opens and closes roughly 62 times a second at 11k rpm.

do you really want to take chances in the valve train?

there is no reason to use lapping compound.if the valve has a issue,its replaced.if the seat has a issue its recut.


Ti-valves are a different ballgame
most valves are a hardsteel/stainless base with a coating on the stem
the coating is for anti-wear purposes on the stem and lowering the friction
between the stem and guide
As there is a coating on the face it just ads protection but the base material
is hard enough.
(wear on older engines was on the seat not on the valves after lead was out)

take for example Manley or Kibblewhite, the both offer coating on the stem
but grind the face.

at 11.000rpm /2=5550/60=91.6 times
but most of us don't see 11.000rpm and if so it's a second or 2
most rpm probably used between 4500-8000 ?

i'm not out to disrespect or make a big yes and no game out of this
it's just not that exiting to lap your valves

  • Eddie Sisneros

Posted August 29, 2006 - 05:08 AM

#17

its cut and dry.the coating wearing off is one the reasons for the valve reccesion issues in modern 4 strokes.

lapping the valves is the same thing is as ingesting dirt thru the intake.

your just starting out with the coating worn off.

good valves (not kibblewhite,manley doesnt make valves for this app) are coated on the face.

im not sure you came upon your math,but the cams rotate at half the speed of the crank.not 1/4.

my original figure was out of my head based on 10-10.5 k rpm.

  • Pitbuell

Posted August 29, 2006 - 06:12 AM

#18

oops my mistake about the cam rotation :thumbsup:

anyway what brand valves are we talking about



never had a problem with kibblewhite

  • Eddie Sisneros

Posted August 29, 2006 - 07:08 AM

#19

we are talking oem in this case,but doesnt really matter.

any decent vlave is coated on the face.thats the only way they survive.

what your talking is true on cars and hd motors.way different valve train dymanics going on here.

good aftermarket valves?ferrea is the only real choice currently.even they can be improved upon.RHc actually sends ferreas out to be recoated.

  • mustangsvo85

Posted October 13, 2009 - 12:37 PM

#20

never use lapping compound on any modern motorcycle valves valves.they are coated.


you sir are mistaken, check the 450x service manual, it states you can use it on the stainless valves and it recommends it





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