I live north of Los Angeles and yet I was born & raised in Maghull Merseyside.
I race vintage 2 stroke motorcycles in AHRMA which stands for American Historic Racing Motorcycle Association here in the US and I also ride track days at circuits like Laguna Seca.
The two bikes I have are a 1972 Yamaha Tr3 (Formula 500 class) & a bit of a mongrel I created & built that has all four Japanese manufactures Honda CB175 roller with Yamaha CT1 MX motor with Kawasaki ignition and a Suzuki clutch (GP 200 class)
My next project will be another creation for the Sound of Singles class AHRMA racing.
I bought a 94 Yamaha FZR600 (may have a different name in the UK) and a 87 KX500 2 stroke MX engine. The plan is to transplant the KX500 into the FZR600 with your help and input the vision is to develop a bike that gives me 100HP in a fairly modern road race chassis.
Time frame looking to get this on a track for trials by the end of February 2017. My local track is called Willow Springs which is about an 1-1/2 hrs from my house. In the US that's just around the corner.
Look forward to posting the progress and posing questions to you all
My plan is to post a specification and information I am gathering to come up with a plan to take a stock KX500 engine that was designed for 65HP and increase it to at least 85 to 100 HP. I would like to stay with the stock bore if possible
I'm not entirely sure this was the forum you intended to join but welcome anyway.
Initial thoughts are the KX500 is not really in a very low state of tune from the factory so finding another 30 brake or so could be difficult and certainly pricey if possible.
Secondly, we got the FZR, decent mid-weight bike of the time but not really the lightest rolling chassis either. If you've got it then fair enough but I'd have thought something like a Kwak KR1, Suzi RG/V, Yam TZ/R or Aprilla RS would be a better starting point for what you have in mind.
Black Widdas S.C. - Taking idiocy seriously since 1999.
KX500 aftermarket big bore kits can get you to 130HP granted with all the mods you are looking at $3,500
By removing the 4 stroke engine and replace it with a single cylinder MX engine the total dry weight will be significantly lighter. The FZR400 steel delta box frame with 17" wheels and upgraded suspension should make it a very stable track bike
Everything is always on a budget so my investment so far is $300 for complete bike & $250 for the engine.