Big Bore Kit

Anybody have luck with the 818 kit, if so did you get a decent power increase.

 

Which kit specifically (there have been several over the years), and for which XJ?

 

I believe the OP is asling about the cruzinimage kit available on eBay.
http://www.ebay.com/itm/81-84-YAMAH...m21006e53eb:m:m3wV1BJ2P2VUe8UompBdRDg&vxp=mtr

I have never used the kit myself but from the reviews that I have seen I would not eliminate it as an option.
The Honda guys over on the sohc4 board like the kit, and I believe we had one of the OZ members use the kit in his bike with success.

Some things to note:
-This kit is +3mm bore. Equal to a 6th(?) over piston. The cylinder liners will be getting thin at that point.
-The pistons are not fully finished. There will still be minor casting flash and stress risers inside the piston that can be cleaned up. The pistons are usable as delivered though.

~Ghost

 

Both of those notes make me want to shy away from using that kit. Cleaning up new pistons I can somewhat deal with, but thin liners on an aircooled engine is asking for a very short service life. But then if it were just going to be a fun close-to-home bike that might not be a bad tradeoff.

I haven't seen it offered for a few years, but there used to be a kit that included oversized cylinders with thick liners. It required boring the upper case and using hylomar instead of the base o-rings (at least I think that was the case).

 

Wiseco had a kit with the liners. Haven't seen it in a long while.
You could also forget about the details and throw the 900 crank, rods, pistons, jugs, head on the 750 case.

~Ghost

 

Ok it's the ebay kit out of JAPAN 818 cc due the legal rights with 820 kit. Nice price already have it and spare jugs to waste for the try. Also picked up a oil cooled adapter to help with the heat. It is a short hop bike as it is my number 5. Am also doing a cam regrind and have beehive springs from a ebay seca 900

 

Yoshimura made the other kit I was thinking of ( I think).

 

I was looking at the 818 kit as well.
My 82 maxim is starting to get mile'd out, and I'm looking to rebuild. One of the main reasons I joined this forum.
The unbranded kit still available on eBay out of Japan.
But I wasn't worried about heat, just the thin cylinder is what made me want to back off.
Tuning it might be fun to.. But I have a spare jug, I might bite cause of the price.
But have no idea where a baseline for jetting it would be??