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big bore

Started by bcguide, December 29, 2010, 11:45:09 PM

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bcguide

Ok it time I Drug my old bike out of the shed and rebuilt it
So what is the best big bore kit. Will an xjr cylinders work?
Do any of you have an lightlybused parts around

Scott

Pat Conlon

Hey Scott.  Yup, buy one of these:
http://cgi.ebay.com/ebaymotors/Legends-Race-Car-600-INEX-FJ1100-FJ1200-XJR1250-/180490850307?pt=Motorcycles_Parts_Accessories&hash=item2a0617d003

According to Curt Andrews, the Legends guys take these oem 1250 blocks off their new XJR motors because they need sleeved blocks for durability i.e. the Nikasil chromed bores go out of round with the WFO 10k rpm racing these guys do, night after night.
However, these blocks are just fine for street motorcycles, and in some ways superior.
Along with the added power from the bump in displacement, the Nikasil plated cylinder walls of the 1250 block sheds (transfers) heat better and has less friction than our sleeved blocks. Curt mentioned to me that he took a sleeved 1250cc motor dyno'ed it, then, using the same motor, installed a XJR1250 block with plated bores, and put it back on the dyno, and gained 9 hp.

Get some 79mm pistons of your choice, and some nifty XJR rods...You will have to have your oem case relieved to fit the XJR1250 block. No biggie.

Want Even More Power?
To further bump the displacement from 1250cc to 1350cc several folks bore out the XJR1250 block, install sleeves, and run 82mm pistons.

Have fun and bring your wallet....

Cheers!
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

bcguide

Thanks

Does the xjr bolt right on other than than milling the cases?

SCott


racerrad8

Quote from: bcguide on January 02, 2011, 09:43:07 AM
Thanks

Does the xjr bolt right on other than than milling the cases?

SCott



Yes, with the appropriate gaskets.

Randy - RPM
Randy - RPM

fj1250

I've got a cylinder with 1202cc pistons, very good condition.
Hone, re-ring and drop it right on.
$175 + shipping.
Mike C

fj1250

I'm going to have a set of 1250cc pistons for sale soon also.

Mike C