Pictures of the damage

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Mar 4, 2007

• #1

Here is the piston I scored, right over the exhaust bridge. The oil holes were not drilled in it and I will be changing the right side crankcase seal in an attempt to prevent this from happening again.

The scuffing continued up the cylinder above the exhaust bridge.

All of this is minor compared to my new problem, the plating has worn through just below the exhaust ports. The picture was taking in looking through the intake port and the bottom of the exhaust ports is visible.

I guess I'm going to run this as is until I can find a cylinder or can afford to have this one plated. I hope it doesn't cause any problems.

 

2

2 strokes for life

Member

Jan 3, 2007

1,860

0

• Mar 5, 2007

• #2

Thats some good scaring you got there.

 

A

adam728

Member

Aug 16, 2004

1,011

0

• Mar 5, 2007

• #3

Time for a replate, don't waste your time/money putting a piston/rings in a cylinder that looks like that.

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Mar 5, 2007

• Thread starter
• #4

None of those black lines are scoring, it's just glazed a little.

 

R

rmc_olderthandirt

~SPONSOR~

Apr 18, 2006

1,533

8

• Mar 5, 2007

• #5

What was the history of this piston?

Did you rebuild the top end, and put a piston in that didn't have the oil holes for the bridge? When I rebuilt my top end recently the piston came with instructions that basically said to drill the bridge oil holes if thery are needed.

It definatly looks like the holes were needed in you case....

Rod

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Mar 5, 2007

• Thread starter
• #6

The piston came with the bike, it has at least 40 hours on it. I pulled the cylinder about 10 hours prior and there was no damage to the piston. Within those 10 hours, it scored badly. I have a new piston on order, Wiseco.

I just got done with the inside micrometers, The cylinder is actually spec, but barely. I came up with 2.616 above and below the exhaust port, and 2.614 towards the bottom of the cylinder. Using the old piston, I measured the piston to wall clearance to be .005" while max is .004". I should be able to gain back that .001" with the new piston. I am going to keep hunting for a cylinder for the next week and if I don't get one, the bike is going back together with the new piston. My absolute maximum budget is $100. I need this bike together for Glamis on the 24th. Oh yeah, taper was .002" as well.

 

Last edited: Mar 5, 2007

S

snb73

Member

Nov 30, 2003

770

0

• Mar 5, 2007

• #7

Have the cylinder re-plated and install a new piston and rings.

Do it right the first time and fix it once.

http://www.forwardmotion.com.mx/nicomcylinder.html

http://www.uschrome.com/

 

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• Mar 6, 2007

• #8

Does anybody else think it is strange,that the top of the piston is scored worse than the skirt? Rings compressed around the piston is narrower than the skirt. I can't see in the pik plating chipped,I do see allot of flashing! I would bet you clean that cylinder good and because of the age,lightly hit it with a 00 ball hone ,drill some holes in the piston and ride the wheels off.

 

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• Mar 6, 2007

• #9

And the bridge relief,4 to 6 thousand,as always a manual should cover this.