Maintenance & Technical > KX500 Original
1988 & older VS. 1989 - 2004 : Engine Performance | Output Shaft Nut | Swingarm
manco:
--- Quote from: manco on April 27, 2015, 04:29:10 AM ---
Another few questions I have are about the output drive shafts on the two motors. The 87 has the old lock nut style output shaft and the 98 has the newer snap ring to hold the front sprocket. The reason I ask about the output shafts is that my 87 is missing the obsolete drive sprocket lock nut. A custom nut could be made I am sure though I would rather purchase one if something is avaliabele. Is there a known readily available nut that can be purchased to fit the 87 output shaft? I am also wondering can the output shaft in the 87 be swapped with a snap ring output shaft from a newer motor?
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Here is my update on this M24x1 nut:
They are impossible to find. M24x1 is not a standard nut size. It is a custom thread found on a handfull of applications including flywheel puller threads, the honda stem mentioned in the above linked thread & yamaha YZ & WR stems from roughly the early ninties all the way up to current models. The aftermarket offers aluminum & titanium nuts for these stem nuts. The new and used market appears to offer steel versions of these nuts. I have opted to try a used Yamaha stem nut. The one I ordered appears to be steel. I will update on it when it arrives.
I did also check with hardware stores, looked online and checked with a custom nut maker. Only coarser thread M24 nuts could be found. M24x1.5 and M24x3 seem to be pretty common. There are M24x1 taps available for machinists. Most nut makers don't have these taps in there collection thus most nut makers won't be able to make m24x1 nuts. However since the taps are available all a custom nut maker needs to make the nut is to buy a $40 tap and get busy. Search google for m24x1 tap for more info.
manco:
--- Quote from: manco on April 27, 2015, 04:29:10 AM ---...I just aquired the 87 and haven't had a chance to take it out yet. When fired up in my shop the 87 seems to sound a bit meaner though. It could be the sound characteristics are that my 98 is running lean with an airbox, stock carb, Fatty pipe & a freshly packed FMF TurbineCore while the 87 is running rich with a Mikuni, no air box, a rag for an airfilter & a stock pipe with a performance silencer that needs repacked.
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I should also give an update on this. Turns out my excitement in aquiring an new to me 1987 KX500 muddled my head. I had the chance to fire up both my 1987 & 1998 side by side the other day. The 1987 runs great but the 1998 just crushed it even on the stand. It had just been a while since I had fired the 1998 up last fall. When I did yesterday the 1998 was clearly pissed off at being considered tamer then the 1987. When the 1998 roared to life I darn near wet my pants. The ground started vibrating, windows rattled, dogs barked and a child next door began crying. I tried to be cool putt putting around the block on the 1998 so as not to arouse the neighbors further. Unfortunately when I took off out of my driveway and rolled unto the throttle I forgot that I needed to be sitting with the gas tank cap under my butt when riding a KX500. Yep, I gently rolled unto the throttle and proceeded to wheelie right past my neighbors house. Oops. :roll:
yeomans:
The nut from a cr 80 output shaft will fit the 87. Same measurements, also try running the part number on ebay. I find them there sometimes.
The 86 and 87 output shafts are completely different lengths as well and different part numbers. Not sure how they compare in length to the 89-04 but ill have to check it out on my 91.
manco:
--- Quote from: yeomans on April 30, 2015, 03:48:30 AM ---The nut from a cr 80 output shaft will fit the 87. Same measurements, also try running the part number on ebay. I find them there sometimes.
The 86 and 87 output shafts are completely different lengths as well and different part numbers. Not sure how they compare in length to the 89-04 but ill have to check it out on my 91.
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Great info. Thanks for clarifications on shafts. I did notice the part numbers were different in schematics. Differing part numbers can be misleading sometimes though. There are quite a few differing number parts that are integchangable in various makes models years of bikes. The shaft looks similar but it is just a drawing of cousre but that dosen't mean much. I also noticed last night that newer output shafts have only snap rings between the gears on the shaft while the 1987 & older have snap rings & circlips. Mabe this effects the physical differences in shaft out design.
manco:
What about top end swap? Will the -1987 top end swap to a 1988-?
I am also thinking of messing with some power valves. Has anyone ever yanked the power valves out and run straight ports? I figured it would just kill some of the low rpm tune & give the bike an overall higher rpm power curve.
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