1983 KDX80 top end questions

Got questions? We got answers....
Post Reply
kljjr
Member
Posts: 4
Joined: 08:17 am Aug 30 2008
Country:

1983 KDX80 top end questions

Post by kljjr »

A few months back I bought my boy an 83 kdx 80. He rode it for a few weeks and it locked up. I was running pre-mix at 32:1. I ordered a new piston and rings for the top end. I tore the jug off and the old piston had a cracked skirt. I decided the few small parts missing from the skirt had to be in the bottom end. I split the casing and got the parts out. I put the bottom end back together and redone the top end. I can't get the thing to start now. I have spark and it's getting fuel. When I pull start it I can hear it firing, however if I give it some throttle while pull starting I can't hear it firing. I was wondering if there were any alignment marks (that may have affected the timing) I needed to pay attention to when putting the bottom end back together? I'm pretty sure I have the marks lined up on the stator and rotor.
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

No, there arent any marks on the crank, but there should be a key in the crank to hold the flywheel in alignment, then you need to align the stator with the mark on the flywheel with the piston at the spec called for in the manual. I never split a KDX 80, but 2 strokes are pretty similar. Wenn aligning the flywheel to the stator, make sure you're looking at the right mark on the flywheel. usually there are two, one bold one that shows where the key is, and a lighter one for the ignition setting.

Also check the reed cage for pieces of piston skirt, Probably too late now, but they like to get in there.

You did replace the crank seals while you had it apart, right?

No rag in the intake from when you had it apart? :lol:
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
kljjr
Member
Posts: 4
Joined: 08:17 am Aug 30 2008
Country:

Post by kljjr »

Ok I double checked everything. Got fuel and spark. Tried fuel in the spark plug hole with no luck. The keyway on the rotor shaft is in good shape and rotor has not slipped on the shaft. I'm kind of wondering about compression. My first kick with throttle open it goes to 50 psi within 4 kicks it is right around 120. I think I'm just in the acceptable range of compression after the 4th kick.

Any other thoughts?
User avatar
Indawoods
Creator and Founder
Creator and Founder
Posts: 9951
Joined: 09:59 am Jun 12 2003
Country:
Location: Midwest

Post by Indawoods »

A short?
*** 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!!! "
kljjr
Member
Posts: 4
Joined: 08:17 am Aug 30 2008
Country:

Post by kljjr »

No I don't thinnk it's a short. I have good spark. Does the compression sound alright to you? I was thinking the first kick should be more than 50 psi. I don't have that much experience troubleshooting.
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

50 psi sounds pretty low to me. I don't know that motor, but is there a gsaket between the cases or do you use Yamabond (or similar)? did you measure the bore to make sure the piston isn't supposed to be over sized? check your ring gap? You used a new base and head gasket and torqued to spec, right?
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
kljjr
Member
Posts: 4
Joined: 08:17 am Aug 30 2008
Country:

Post by kljjr »

I used a new gasket set when I put it back together. I didn't measure the bore though. I ordered the stock size piston. I will tear it down tomorrow and check my rings to make sure they didn't somehow get messed up when I put the head on. I'll also double check everything. Thanks for your help.
Post Reply