Head Gasket

Got questions? We got answers....
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Head Gasket

Post by magilla »

Pulled my head off last week to send to RB. I was very happy to see that after ~3 seasons of riding the piston/cylinder/combustion chamber looked almost new. No carbon or spooge, nice cross-hatch on the cylinder.
Given that, I think I'll hold off on a new piston and just clean the KIPS up and re-assemble.

Question is, should I install a new head gasket, or re-use the one that's on there? I'm guessing theres some deformation when the head is torqued down.

Thanks!
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
User avatar
Indawoods
Creator and Founder
Creator and Founder
Posts: 9951
Joined: 09:59 am Jun 12 2003
Country:
Location: Midwest

Post by Indawoods »

You had crosshatch on a plated cylinder?
*** Administrator //***
****'95 KDX 200/****

"People ate cows a thousand years ago for the same reason we eat them now. Cause they are easy to catch.We're not savages,we're just lazy. A cheetah could taste like chocolate heroin. But will never know. Those bastards are fast!!! "
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

That's what it looked like.
Perhaps from it being honed prior to being re-plated?

When I did the top-end ~3 years ago the piston was cracked, and the plating was wearing off in places. I sent the cylinder to Fredette to clean it up and re-plate. It doesn't look much different now than I remember it looking when I re-installed it then.

*edit*
Lots of good info out there on this (the cylinder crosshatch, etc..) and after some further reading that's exactly what I'm seeing there.
Of course, now I'm back to wondering if I should just go ahead and at least put fresh rings in, and deglaze the cylinder.

Still curious about the head gasket though...
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

My kid's Yamie had cross-hatch looking marks in his as well.
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Post by KarlP »

I'd put new rings in after 3 years.
Of course that does mean pulling the cylinder. The base gasket won't stay in one piece like the head gasket does. A new base gasket comes in one of those top end gasket kits, Cometek (?) I think.

To directly answer your question, I've got a "used" head gasket in my bike now, no problem.

On the other hand, you can't clean up the KIPS without pulling the cylinder.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
KarlP wrote:I'd put new rings in after 3 years.
Of course that does mean pulling the cylinder. The base gasket won't stay in one piece like the head gasket does. A new base gasket comes in one of those top end gasket kits, Cometek (?) I think.

To directly answer your question, I've got a "used" head gasket in my bike now, no problem.

On the other hand, you can't clean up the KIPS without pulling the cylinder.

Thanks KarlP.

All very true. The more I think about it now, the more I'm thinking I should at least do rings. I bought a new piston, small-end bearing, and top-end gasket kit anticipating doing a top end. Perhaps I should just go ahead and do it.
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
User avatar
canyncarvr
Gold Member
Gold Member
Posts: 6943
Joined: 01:07 pm Nov 05 2004
Country: US
Location: The Mythical State of Jefferson

Post by canyncarvr »

What's the end gap on your 'old' rings?

And the new?

Piston-to-cylinder?

Just because the plating on the cylinder looks fine does NOT mean the piston has no wear. It does mean there hasn't been friction enough to leave marks. That's a good thing.

'Fer example: Your old rings are .015", your new rings are .010".

I'd change 'em anyway...but .015" is pretty big. Not over spec as I recall...but big.

If the piston is over .007"..it's time for a new one, ain't it?

Wiseco I presume?

Consider the source
Using a perceived level of knowledge to boost my self worth.
Non impediti ratione cogitationis

bike profile: !clicky!
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Post by KarlP »

All very true. The more I think about it now, the more I'm thinking I should at least do rings. I bought a new piston, small-end bearing, and top-end gasket kit anticipating doing a top end. Perhaps I should just go ahead and do it.

I'll tell you what, I'm Lazy. If you havent disturbed anything but the head, how about you just put the RB modified head on and give us a performance change report? My gut feeling is that the head does a LOT.

Do the whole rebuild later, after the report. :wink:
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
canyncarvr wrote:What's the end gap on your 'old' rings?

And the new?

Piston-to-cylinder?

Just because the plating on the cylinder looks fine does NOT mean the piston has no wear. It does mean there hasn't been friction enough to leave marks. That's a good thing.

'Fer example: Your old rings are .015", your new rings are .010".

I'd change 'em anyway...but .015" is pretty big. Not over spec as I recall...but big.

If the piston is over .007"..it's time for a new one, ain't it?

Wiseco I presume?
Hmmm...
I typed a response, but somehow it didn't post. Interesting.

Anyhow, yes, the current piston is a Wiseco, and the new one sitting on the shelf (actually in a box of parts) is a Wiseco as well. I haven't got it apart far enough to check ring gap and I haven't checked piston-to-cylinder gap either.
There are light scuff marks in the up-down direction, but not much.
I'll likely tear it down to inspect further this week, with time to actually rebuild/reassemble this coming weekend.
Last edited by magilla on 03:58 pm May 05 2008, edited 1 time in total.
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
KarlP wrote:
All very true. The more I think about it now, the more I'm thinking I should at least do rings. I bought a new piston, small-end bearing, and top-end gasket kit anticipating doing a top end. Perhaps I should just go ahead and do it.

I'll tell you what, I'm Lazy. If you havent disturbed anything but the head, how about you just put the RB modified head on and give us a performance change report? My gut feeling is that the head does a LOT.

Do the whole rebuild later, after the report. :wink:
Well, I actually just got an email from my girlfriend saying she'd just signed for a package from RB. Talk about fast, he got the package on Friday, and I got a notice from USPS that it had been shipped on Friday night, arrived today (Monday). :prayer:

Oh, and I went ahead and got the new AS carb as well as the head mod... :supz:

I would consider just bolting it all back together, but I have the engine out at the moment, making it really easy to do all this on the bench.
The reason for all this attention is actually that I'm almost finished building a KDX220/KX125 hybrid. All the modifications to make the engine fit in the chassis are done. I got the chassis back from the powder coaters last week, and will be installing all new chassis bearings this weekend. After doing all this work to build an essentially all-new motorcycle, doing the top-end (or at least rings and a KIPS cleaning) just seems like the right thing to do.
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
User avatar
Indawoods
Creator and Founder
Creator and Founder
Posts: 9951
Joined: 09:59 am Jun 12 2003
Country:
Location: Midwest

Post by Indawoods »

That's going to be rightous! :supz:
*** Administrator //***
****'95 KDX 200/****

"People ate cows a thousand years ago for the same reason we eat them now. Cause they are easy to catch.We're not savages,we're just lazy. A cheetah could taste like chocolate heroin. But will never know. Those bastards are fast!!! "
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
Indawoods wrote:That's going to be rightous! :supz:
I cannot tell you how excited I am to put it together and ride it!
Debut should be Memorial Day Weekend at Forest Hill near Auburn, CA.

DaveJ of Smart Performance Inc. has my suspension right now so that'll be fun to get back and play with too.
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
Little Jeff
Member
Posts: 136
Joined: 08:40 pm Feb 14 2008
Country:
Location: Tacoma, WA

Post by Little Jeff »

What is the ring gap supposed to be on a new set of rings, ideally?
Little Jeff
Riding with your buddies and an adventure, riding with certain individuals is an ordeal.
User avatar
kicknrocks
Member
Posts: 111
Joined: 07:11 pm Apr 16 2008
Country:
Location: Theory

Post by kicknrocks »

karlp,

I just rebuilt with the cometic gasket kit and the case/jug gasket was metal, just like the head.

be advised though, it doesn't come with the water spout gasket for the head, which you'll need after sending it out.
'01 KDX 220
Frisbee air box
RB Designs Carb
FMF Gnarly Woods
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Post by KarlP »

Ahh, there is a lot more to this story than just a head sent to RB.

Sounds like a new bike in the making!
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
kicknrocks wrote:karlp,

I just rebuilt with the cometic gasket kit and the case/jug gasket was metal, just like the head.

be advised though, it doesn't come with the water spout gasket for the head, which you'll need after sending it out.
Thanks for that note kicknrocks. I did notice that the water inlet elbow gasket wasn't in the kit and ordered one.
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
magilla
Supporting Member I
Supporting Member I
Posts: 49
Joined: 05:58 pm Nov 18 2004
Country:
Location: Rodeo, CA

Post by magilla »

>|<>QBB<
KarlP wrote:Ahh, there is a lot more to this story than just a head sent to RB.

Sounds like a new bike in the making!
Yeah, basically all new. I've had to stop short on a few things because I've already blown my budget, but I'll get to those few items a little later.

The RB modded head looks great, I didn't unwrap the RB modded AS carb yet, but I'm sure it's purdy too. :mrgreen:
Michael
00'/01' KX/KDX220R Hybrid
Fredette porting, RB AS carb & RB head, Wiseco, DFIII, Gnarly Rev, TC2, Smart Performance susp.
Mmm... Dirt...
User avatar
canyncarvr
Gold Member
Gold Member
Posts: 6943
Joined: 01:07 pm Nov 05 2004
Country: US
Location: The Mythical State of Jefferson

Post by canyncarvr »

>|<>QBB<
Little Jeff wrote:What is the ring gap supposed to be on a new set of rings, ideally?
Little Jeff
Feel free to redress if incorrect...but my rememories say .006-.013"

Doesn't generally matter..as it's not something you can do anything about short of replating.

It does give you an idea that something may be out of whack. If your brand new rings have a end-gap of .015"... something isn't right. That 'something' may be as simple as not having the ring square in the bore :wink: , still...something isn't right.

If you happen to measure .002"...yep! You guessed it...something isn't right!

Consider the source
Using a perceived level of knowledge to boost my self worth.
Non impediti ratione cogitationis

bike profile: !clicky!
User avatar
Jeb
Gold Member
Gold Member
Posts: 1894
Joined: 08:01 pm Jul 14 2006
Country:
Location: Cincinnati / Northern Kentucky

Post by Jeb »

Wiseco recommends about .004" per inch of bore size - minimum (for new rings). Your bore being 69mm bringing the minimum gap to .011" (0.8mm). If it's less than this you'll want to remove some material to make the ring gap wider. Go to their website for their recommendations on how to do that properly.

They also recommend that the upper ring have the larger ring gap (of the two rings) to "help reduce top ring flutter or lifting". I don't know what that means or why that's the case BTW.

I personally would not use ring gap to conclude bore tolerance - direct measurement of the bore is best.

A recent example: I installed new rings earlier this year and my bore measured well within tolerance yet my brand new Wiseco rings measured 0.014" and 0.015"

All of this stated and based on other comments made in this thread, I'd gather that Wiseco's specs & recommendations likely differ from OEM or other pistons. That's a guess . . .
"No farmer ever plowed a field by turning it over in his mind" -George E. Woodbury

CLICK FOR PICS!
User avatar
kicknrocks
Member
Posts: 111
Joined: 07:11 pm Apr 16 2008
Country:
Location: Theory

Post by kicknrocks »

I can picture where/why end gap occurs, but how do you measure it?
'01 KDX 220
Frisbee air box
RB Designs Carb
FMF Gnarly Woods
Post Reply