Wrong size cylinder !

S

sherrif

Member

Jun 23, 2002

18

0

• Aug 16, 2002

• #1

Help guy's. I just sent my KX 250 H1 (1989 I think) engine in for a complete rebuild, mains, big ends, cylinder weld up and re-plate. The cylinder eventually comes back, the mechanic then finds out that the cylinder fitted to the bike is a '98, and is approx. 1mm larger ! So a new piston has been ordered, but what I need to know is will this combination be ok. I did run the bike for around a month before the rebuild (not very well, but that could have been the cracked crankcase, or the worn seals, or the shot bearings....I could go on !)
I look forward to you're comments....

 

R

RMXkid

Member

Jul 13, 2001

108

0

• Aug 17, 2002

• #2

I would think that is a little too big and it will slaap around

 

B

Buzz Bomb

Member

May 9, 2000

706

0

• Aug 17, 2002

• #3

If you just ordered a replate, they should have given you the same cylinder you sent them, not one off a completely different bike! Call the company you sent it to and ask them to do some explaining.

 

M

Moto Squid

~SPONSOR~

Jul 22, 2002

853

0

• Aug 17, 2002

• #4

a 98 cylinder fits on an 89 :think:

 

S

sherrif

Member

Jun 23, 2002

18

0

• Aug 17, 2002

• Thread starter
• #5

The correct size piston for the repaired cylinder will be fitted, so it won't slap around, but I was more concerned about the stroke, as if the bore is approx 1mm larger, and the stroke is the same, wouldn't the overall capacity be larger than 250cc ? Anyone know how to work out the capacity ?
It was the cylinder I sent them, it seems as if the previous owner was a bit of a bodger....

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

0

• Aug 17, 2002

• #6

This will be like putting a .040 over piston in. If I remember correctly you don't really need to worry about crazy compression until you get close to 2mm or .080". Worst case you will need to have the head machined a bit to reduce compression or double up on base gaskets.

 

marcusgunby

LIFETIME SPONSOR

Jan 9, 2000

6,450

2

• Aug 17, 2002

• #7

Im sure the 98 had a different powervalve design and the cylinder will not bolt up-can you post any pics of the engine?

 

S

sherrif

Member

Jun 23, 2002

18

0

• Aug 26, 2002

• Thread starter
• #8

Just thought I'd let you all know, just refitted my now overhauled engine, and it was worth the wait ! I thought it was quick before, but now OH MY GOD ! I ran it in gently for a while and gradually started using more revs, I still haven't had her wide open ! Can anyone tell me the standard gearing (1980 KX 250), as I seem to ge throwing gears in as fast as my foot can move, and I don't feel I'm travelling that fast in top gear.
Thanks in advance

 

D

Durt Cycler

Trial Subscriber

~SPONSOR~

Nov 13, 2001

1,173

0

• Aug 26, 2002

• #9

I am confused first it was a 98 cylinder on a 89 not it's a 1980? :confused:

 

David Trustrum

~SPONSOR~

Jan 25, 2001

1,396

0

• Aug 27, 2002

• #10

Finger trouble surely meant 90. Musthave.

Try looking at click here should find gearing there, View vehicle info/parts

 

Last edited: Aug 27, 2002

B

bigred455

"LET'S JUST RIDE"

LIFETIME SPONSOR

Sep 12, 2000

782

0

• Aug 27, 2002

• #11

He had to be talking about a 90 ,a 80 kx 250 was air cooled with no power valve.

 

S

sherrif

Member

Jun 23, 2002

18

0

• Aug 29, 2002

• Thread starter
• #12

Doh ! Yep it was an '89, I really shouldn't drink and type, it's not big, and it's not clever....