KX Riders

Maintenance & Technical => KX500 Original => Topic started by: scotscooby on January 21, 2007, 06:48:04 AM

Title: KX500 to 250 bottom end, help needed.
Post by: scotscooby on January 21, 2007, 06:48:04 AM

Hi to everyone I have just found this site and it looks great. I own a 1991 kx500 with 2002 kx250 front forks; billet triple clamps new talon wheels and plastics plus a lot more work to get it looking the dogs dangly bits. The bike looks great but there is a small problem the engine let me down during my last race the gearbox department is causing problems. Now the question is, is it possible to mate the barrel and head onto a KX250 bottom end and if so how much work is involved? :?

Title: Re: KX500 to 250 bottom end, help needed.
Post by: don46 on January 21, 2007, 12:03:38 PM

can't be done, K5 is way to big a bore to fit the cases and the the stroke on the 250 is to short. Fix the tranny on the K5 .

Title: Re: KX500 to 250 bottom end, help needed.
Post by: gowen on January 22, 2007, 03:15:17 AM

don46 is correct, can't be done. The porting in the crank would never line up.. The crank is smaller, the gears are crap compared to your 500.. Check ebay out for a lower crank. Your issue could be small, invest in a crank split tool and get to work. That's all I can say with what little info we have.. Post up some more info about your problem and maybe we can help get to the bottom of this.

Title: Re: KX500 to 250 bottom end, help needed.
Post by: scotscooby on January 22, 2007, 06:42:58 AM

Hi guys, its not a problem, just a thought. I will rebuild the K5. The 250 engines are easier to get than an engine for the K5. Well that is over here :roll: there is not a lot of spares to get most of my K5 stuff has come from the USA.  :-D If I could lay my hands on a late K5 engine I would be up for that rather than spend a lot of time and money doing up my old horse. But if needs must that is what I will do. Thanks for the information Guys.

Title: Re: KX500 to 250 bottom end, help needed.
Post by: hughes on January 26, 2007, 01:14:13 AM

Quote from: scotscooby on January 21, 2007, 06:48:04 AM

Hi to everyone I have just found this site and it looks great. I own a 1991 kx500 with 2002 kx250 front forks; billet triple clamps new talon wheels and plastics plus a lot more work to get it looking the dogs dangly bits. The bike looks great but there is a small problem the engine let me down during my last race the gearbox department is causing problems. Now the question is, is it possible to mate the barrel and head onto a KX250 bottom end and if so how much work is involved? :?

What issues are you having with the gear box?? Could be a bent shift fork, or a bent shift fork shaft.

Title: Re: KX500 to 250 bottom end, help needed.
Post by: JBKX on January 28, 2007, 12:26:54 PM

Here's a link to a KX500 top end to a Tecate-4 bottom end.

http://www.tecateconnection.com/ProjectKX500.htm (http://www.tecateconnection.com/ProjectKX500.htm)

It looks expensive and timely.

Title: Re: KX500 to 250 bottom end, help needed.
Post by: Danger4u2 on January 28, 2007, 12:34:41 PM

Cool link, Thanks