Author Topic: 88 kx500 crank play... options?  (Read 3515 times)

0 Members and 2 Guests are viewing this topic.

Offline idaho_nate

  • Newbie
  • *
  • Posts: 5
88 kx500 crank play... options?
« on: September 14, 2014, 11:31:48 AM »
I just bought a sf conversion with an '88 motor (was supposed to be '89 per seller but turns out to be '88) :x

Head gasket was leaking so I took the top end off and it is a bit of a mess.  Cylinder is cracked on the outside along a water jacket and repaired with what looks like jb weld, cylinder has been sleeved and the piston has obvious marks from something coming apart and then being reused...  On the plus side it has been ported by a reputable shop in the past.

The rod seems ok, has an IMS with no detectable play, but the whole crank moves side to side about .5mm in the cases.  I don't have a manual yet but am guessing this isn't normal for a KX and am fearing problems with crank journals or cases.  The seller claimed he put new bearings and seals in the bottom end but I am a little dubious at this point.   

I can't decide if it is worth it to split cases and fix or throw a new piston in and run til she blows and search for a 89-04 transplant in the mean time.  I hate to spend a bunch of money on the earlier motor if parts are going to be a problem or if the performance isn't as good as the later models.  I did find a pretty cheap '87 cylinder core which I believe will work but then I would have to get it ported, plated, etc.  I'm not sure how the 560 big bore works compared to stock bore but pricing wise ($660) it seems like a good deal if I have to get it ported and plated anyway.  I have plans for all of the usual mods (compression release, v force 2, 40 mm smartcarb w/heat, Powerdynamo ignition, etc) to be used in a snowbike application.  I have saved a little $ to get some of the goodies I need but hate to end up sinking it all in the motor.

Also, what is the real difference in the powervalve set up in the 88 vs 89 on?  I know visually the difference but as far as power, rideability, etc?  Looking for as much mid to top power as possible, while running on 93 and not being a time bomb. 

Needless to say, I am a little bummed and would appreciate advice on the best way to proceed?


Offline sandblaster

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,271
    • OEM-CYCLE QUALITY USED PARTS
Re: 88 kx500 crank play... options?
« Reply #1 on: September 14, 2014, 12:04:56 PM »
Can you post some pics of the bottom of your cylinder along with the intake?
If your crank halves are sliding back and forth easily it's time to take it apart and see whats happening.
Blowing up a engine is a lot more expensive then rebuilding it  :-D
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline idaho_nate

  • Newbie
  • *
  • Posts: 5
Re: 88 kx500 crank play... options?
« Reply #2 on: September 15, 2014, 04:41:02 PM »
Roger that.  I was hoping (wishing...) that some play was ok.  Pulled the motor last night but haven't torn it down yet.  Hopefully find some free time this weekend.

I took some pics, will work on getting them posted.  Started the parts collection process, so far have another cylinder on the way as well as another IMS rod.

Offline Foxx4Beaver

  • Hero Member
  • *****
  • Posts: 8,952
  • James Stewart DID NOT invent the scrub!!..JoJo
Re: 88 kx500 crank play... options?
« Reply #3 on: September 16, 2014, 08:12:36 AM »
Blowing up a engine is a lot more expensive then rebuilding it  :-D

I can't say that I agree. :-P
Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline sandblaster

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,271
    • OEM-CYCLE QUALITY USED PARTS
Re: 88 kx500 crank play... options?
« Reply #4 on: September 16, 2014, 09:05:05 AM »
Blowing up a engine is a lot more expensive then rebuilding it  :-D

I can't say that I agree. :-P

Ok...Ok... You win on that.....
For most "Normal" people rebuilding before a blow up is cheaper then rebuilding after it's blown up :lol:
« Last Edit: September 16, 2014, 09:07:47 AM by sandblaster »
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.

Offline Foxx4Beaver

  • Hero Member
  • *****
  • Posts: 8,952
  • James Stewart DID NOT invent the scrub!!..JoJo
Re: 88 kx500 crank play... options?
« Reply #5 on: September 16, 2014, 09:13:15 AM »
oh thank God...I was worried you might list me in the "Normal" category :-D 
Excuse me, ma'am...but you've got extremely nice legs!!!...what time do they open???                                                                                                               https://www.youtube.com/watch?v=n8tCgN3aryQ

Offline sandblaster

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8,271
    • OEM-CYCLE QUALITY USED PARTS
Re: 88 kx500 crank play... options?
« Reply #6 on: September 16, 2014, 10:47:08 AM »
Yeah... Normal just means average... Who here is average?  :-D
The four stroke engine: That's one stroke for producing power and three for wearing the engine out.