Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: mini-thumper on April 10, 2010, 07:24:55 PM

Title: CB250RS Chassis + XBR500 motor = ?
Post by: mini-thumper on April 10, 2010, 07:24:55 PM

Anyone had any experience of, or thoughts on, marrying a CB250RS chassis with an XBR500 motor? Have read often about putting XL500 motors in the RS but they are almost akin to the Dodo these days!

Cheers
Boyd

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: themoudie on April 11, 2010, 09:30:43 AM

Aye Boyd,

Maybe this engine conversion might be the answer? Currently on Fleabay, (Lot: 130379035478) link follows: CBR300RS (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=130379035478&ssPageName=STRK:MEWAX:IT)

Fairing and paintwork are 'Naff' in my humble opinion ???, but the rest would be interesting. Starting might be a problem! :(

Off to play! ;D

Bye Bye, Bill.

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: SteveC#222 on April 11, 2010, 10:06:25 AM

If you still have the Winter2003 'Thumper' magazine, there is a big article on Steve H's CB500RS. He used the XL/FT500 engine.  I would have thought that size wise the XBR will be very similar as it's based on the XL. Your biggest problem will be how/where to fit the oil tank.  You might be able to rig something up where the air box sits and then use a K&N filter? It'll be an intersting bit of kit if you manage it!!

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: guest564 on April 11, 2010, 12:04:07 PM

I'm pretty sure that the XBR engine will be too big. There was a guy who raced a 300cc Yoshi converted RS back in the eighties, it was a very quick motor.

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: Steve H on April 11, 2010, 12:17:51 PM

Quote from: Rhinoman on April 11, 2010, 12:04:07 PM

I'm pretty sure that the XBR engine will be too big.

Is the RFVC head significantly taller than the earlier non-RFVC heads ?

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: SteveC#222 on April 11, 2010, 01:11:46 PM

As the engine is dry sump, wouldn't the the sump be shallower than a wet sump (XL/FT etc) engine? if so this should reduce the overall hight?  :-\

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: guest564 on April 15, 2010, 09:14:54 PM

I think the engine is a lot beefier all round, its a much stronger design than the old FT/XL500. I can take some measurements if you like.

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: paulp2655 on April 18, 2010, 02:56:13 PM

Inspite of the engineering issues, it does sound like a very good idea.

Title: Re: CB250RS Chassis + XBR500 motor = ?
Post by: el vencejo on April 18, 2010, 03:34:54 PM

I always like big motors in little chassis, sounds a worthwhile project  8)
The Euro VTR250 looks ideal for an aircooled 600/650 RFVC motor (when they've been around long enough to suit my locked wallet)  :D
The XBR 500 and Dominator-to-FMX 650 motors are almost identical externally; similar power but lots more torque on the big 'uns. Depends what lights your candle  ;)