650L BIG Bore kits

Hi All,

I'm new here and have a question.

Anyone have any experiences with large bore kits for the 650 L? I'm looking at one done by an outfit called Kustom Kraft that has a sleeve and slug displacing 720 cc. It requires boring the cases and before going thru all the expense and hassle of doing this I'd like some input either pro or con!?

Overheating? Exsessive ring or piston skirt wear?

The guy I bought the bike from neglected to inform me that the jug had already been bored to 101mm and it shows some taper. It's either go bigger or find a stock jug and start over. I see Wiesco offers a 102.4 but I'm afraid the stock jug just won't have enough metal left to cool properly or resist hotspots and/or warping?!

What do Ya'all think? Any help?


Go with the wiseco kit,as long as you dont let the motor get too hot you shouldnt have to worry about warping the cylinder.Try not to run a high compression ratio because that will increase operating temps as well.

The 720 kit runs too hot, and is not worth the machine work!

I would run the JE piston in no higher compression than 10.5:1, you should be alright with the 102.4 bore. Give Kamell or Chris a call at xrs only they have lots of experience with these motors, and they sell all kinds of good engine parts for the L. Welcome to TT and good luck let us know what you do! Check out www.xrsonly.com :cheers:

You may want to also check with XR's Only and see if they could weld on cylinder fin extensions. I know that this was done on the Baja XR's back in the day before the 650R to help keep the cylinders cool on the full race XR628's.

I've run over 10k with a resleeved cylinder at 102.4 mm bore. Do it! A mild cam and 10.25 or 10.5 to 1 compression makes it into what it should be, ~50hp.:cheers:

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