xs 650 engine upgrades opinions needed

montessa172

montessa172

Been Around the Block
1975, bored first over stock everything else, running a 2 into 1 with 17" reverse cone, BS 38 cv carbs. Engine has 2000 miles on it and I tore it down to fix a leaking base gasket, I'm going to do a clean up on the ports while I have it apart and ( here's where I need the help ). I have a line on a xs2 cam. I understand all the theory on indexing, I have never done it. How much of a pita is it to press off the sprocket to put on my current one with the proper tooth count? What else should I watch for. My goal isn't to make this a rocket ship but if I can take a little extra time on the reass'y I'm sure the small gains I get from the precision will be worth it.
 
Sadly I can't help with this, but will likely have to index my cam when putting it back together as well - rephased to 277 degrees with a Web Camshafts 59a grind on it. My understanding is you need a 20 ton press or so to do it, and I guess repeated access to the press to get it right.

Not sure what you're paying for the early cam, but a Web Camshafts grind is $137 on your old cam.
 
xs 2 cam is coming out of a spare engine :). The size of the press required is what I was concerned about, I have anytime access to a 2 ton and a 5 ton, I was hoping that the 5 would do the job? I have read a 20 to do the crank pins, but I can't find any info on what size is required to get the cam and sprocket separated.
 
I'd suggest, if you haven't already, look over Hugh's website as he has a ton of info specific to the XS
http://hughshandbuilt.blogspot.com

I bet he'd be happy to answer any questions you have as well... he's a really cool dude and has been very helpful to many in the XS community.
 
Read Hugh's blog in it's entirety today, lots of good stuff there, thanks I'll shoot him an email and see if he can help with the size of press required for degreeing the cam. Started on my head work today, just cleaning up the cast marks and making the ports more better!
188d3f00-fdd3-2eb8.jpg


After

188d3f00-fdf7-3d2f.jpg


About 1/2 way started, you can see the factory machining right above the seat…

More to follow tomorrow!
 
The area just above the seat has to be smaller than at the seat to get the gas to flow around the valve. If it's opened up much the gas basically hits the valve instead of flowing around and that hurts flow. Big holes don't always flow more than small ones.
 
There is some interesting reading relating to the work Yamaha recommended for their OU/OW72 racing XS650 heads here;
http://thexscafedotcom.wordpress.com/2011/09/13/xs650-ouow72-heads/

Worth a read before too much material is removed from those ports

Actually there is loads of useful info on this blog if time is spent working through the various posts.
 
Thanks for weighing in your thoughts guys, i appreciate it. You've all verified everything that the internet has provided thus far, ports already too large etc. I'll continue with a light touch and minimize what is removed to smooth out the speed bumps that are there... Cornish thanks for the link thats one 650 site that I haven't perused for information yet! I'm going to continue tonight with eliminating the casting flash and polishing the exhaust ports, i'll post up some proper pictures with my good camera when I get finished up..
 
OW72 is a different head with different port positions, unless you have one the information isn't worth much (even though it IS interesting)
You can do work on bowl side of intakes, ports are set up for 10k motor, problem is, crank fails around 9.5k (factory never managed to fix problem even with OW72 head)
Before I was CB360 'expert' I was XS650 'expert' ;D
There was a1000cc 100bhp motor built (I think Swiss, MOKO?)
High RPM kills crank, keep it below 8,000 and it will be fine.
Some of the KR factory motors made 101bhp but were very unreliable.
Factory also used 144mm rods on some motors (same as CR 500 rods)
Stock 447 motor uses 130mm rods
 
crazypj said:
OW72 is a different head with different port positions, unless you have one the information isn't worth much (even though it IS interesting)
Before I was CB360 'expert' I was XS650 'expert' ;D
Click to expand...

Hi, I could have made my post a little clearer and pointed out that the heads are different, however first thing in the morning posting, not actually posting what I was thinking and all that (it was early in the morning UK time :) ) The web site I was suggesting Montessa has a look at has a load of information relating to XS650's, not just the OW72 and it is run by somebody who is acknowledged both here in the UK and over there in the States as "knowing his onions" when it comes to the XS650.

Please accept my most humble and sincere forelock tugging, bowing and scraping apologies for straying into an area you ARE clearly far more knowledable and "expert" in than me .

I stand suitably chastised and belittled LOL :)
 
Hey 'Cornish, it's all good, at least your not 'English' (I'm Welsh, no sheep jokes yer grockle ;D )
5hr time difference is a bitch, my brother 'forgets' and calls in the middle of he night ::)

Is that site part of the German XS club?
 
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