KX Guru Racing

Larry Wiechman

What was wrong with the piston?

Motorrad

Found the 2nd machining flaw in my wiseco piston.... (yep 2 in one piston)... not happy.. that was causing my ring seal issues..

What was wrong with the piston?

Issue #1 (can be found in here somewhere).. the wrist pin clip grooves were cut .040" too close together.. Easy fix back then... narrow wrist pin some more..

Issue #2.. noticed a tight spot in the top ring land.. kaw rider even noticed when he had it.. we shrugged it off as a Tight spot... no biggie with the rings I was running.. as it sorta cured it.... well 3 sets of rings later trying to get the rings to seat properly. I was showing blowby in just this area... so I looked harder... Hmmm the ring lands are cut like a twizzler Angled up on one side, angled down on the other tight spot in the middle.. Very VERY hard to notice... but they are.. Kind of like it walked in the cutting fixture a bit...

UGGG...

so now off to modify the 88mm piston... this thing is a PORKER..

so far, I have countersunk the wrist pin oil holes...

going to take soem weight out above the wrist pin hole today as well..

Oh... by the way.. Line2Line has my vote for coatings..

That piston has over 300miles on it.... all the coating is still there... at that rate... motor would never wear out. cool

Off to the races... will be back tomarrow night... (ugg have to ride the bloody 426 Yamaha 4t again...)

evil .................. http://www.extremeion.com/pdfs/Wrist_Pin.pdf ............ evil

alward25

How much does it weigh???

Motorrad

The titanium Pin?

bored the same as a wiseco pin.. (going on the safe side of life here). not pretty when wrist pins break......

so thats would be a pin with the following measuremetns.

19mm X 2.5" with a .140" wall thickness...

weighs..



wait for it.













wait for it...










50grams

piston back from getting coating done..

skirt coat is .0035" thick.. for a .0005 (yes I said half a thou) piston to wall clearance...

way the coating works, is on its "break in" it clearances itself to the "perfect fit".. then LASTS..

I had a hard time believing them also, but my last piston proved it worked...

and also Ceramic coated crown... (Gold color) for that extra "Bling"

Got my Jug back..


just went to check ring gap..

undecided Hmm the rings arnt supposed to have a negative gap (overlap themeselfs)... undecided

So I think to myself.. Okay. this is better than the "Grand Canyon" rings they put in the last 5 ring sets I had...

so I break out my bore guage..

Hmm

87.75mm okay so they blew it by .25mm to start... THATS 10 f**kING THOU!

why cant any one do good work anymore!?

Especially with a name like ERIC GORR.. If they dick up somthing as simple as making a Hole a specific size.. (by 10 fing thou) makes ya wonder how bad they would dick up other stuff..

Motorrad

Got my DLC coated Titanium wrist pin back in the mail today evil evil

went to snap an pic for ya.. and camera is dead... will get a pic up as soon as camera is charged

Larry Wiechman

I don't want to be a buzz kill, but I have a hard time believing that a Ti wrist pin will coexist with a needle bearing, regardless of coatings.

It works in 4-strokes that have a bushing or other plain bearing in the small end of the rod.
Lots of surface area to spread the load in that design.

A caged needle bearing offers only line contact, resulting in extreme load/area ratios.
The rolling element bearings need a hard, stable surface to be compatible. DLC is hard, but titaniun is not.

Motorrad

I too.. think the same thing larry..

I had a long conversation with the company that did the coating (not naming names, incase it doesnt work out) ... but they are one of the main titanium wrist pin supplyers (DLC coated)...

they said they do alot for guys running needle bearing setup, "drag race and hill climb guys".. he said they arnt having problems, BUT are rebuilding motors very often... so problems may not show, like a high milage motor like mine..

so I... for the sake of science.. have decided to give it a shot..

I ... NEEDLES TO SAY.. will be tearing top end off frequently to keep an eye on things...


but.. Im still on Your side of the fence Larry... undecided Very sceptical...

he also told me the wall thickness etc We are using is WAY WAY overkill..

Few pics... Trying not to give away any trade secrets, while giving you all good pictures... grin

Im not sure what he does to the kips parts... but WOW! Mine looked like s**t before I sent them to him..

YES I ran the piston over the buffer.. not him.. as well as my usual skirt mods...

After some cutting... grinding... drilling.... (wossener comes with oil "slots" not oil holes... I decided to add oil holes as well grin
done cutting on everything..

officially going together.

checked piston wall.... .004" exactly.

Ring end gap .016 top, .018 bottom

my thin Reed spacer is going in this time, (remember piston is closer to reeds now)...

Vforce 2 reeds (V3's are going to go on the wall of Shame)

NEW OEM small end bearing going in.

Clips, facing up... check
Ready to drop on...

I dont believe I ever have shared this one either...


the "Motorrad 2T ring compressor tool"

just slide the jug down, and it pushes the Zipties down ... cut zipties once jug is installed...

no fuss, no muss...

ZERO Deck Hight .... Ohhhh Yea.... always wanted to build a zero deck motor..