building a climber. best ways to make power?

[kwilliams]

Just looking for some tips on head work, carbs, an what not. Looking to get as much as I can outta the motor. It will only be running for short periods of time.
I got a pair of 38mm kehin flat slide pj series carbs....

 

[retiredgentleman]

You'll want to use 36 teeth, or larger, on the rear.

 

[Tomterrific]

Check out 650central.com for serious xs tech. MMM is into racing XS.

 

[fredintoon]

Hi kw and welcome,
stick a blower on it?

 

[weaselbeak]

650central is the man.

 

[Jack]

Just looking for some tips on head work, carbs, an what not. Looking to get as much as I can outta the motor. It will only be running for short periods of time.
I got a pair of 38mm kehin flat slide pj series carbs....

get the compression up to 11.1 , 750CC overbore, megacycle cam 250-30 with R&D valve springs with moly retainers from a Canadian guy off ebay , 2mm oversized intake valve, the exhaust port will need to be addressed in reducing port resistance, it's the #1 factor in limiting performance. There's a guy on ebay that sells high quality valves,Schumann motor works(SMW) I believe. Thick valve margins also help in reducing flow resistance. Get the head right for starters,it's the key factor. The engine cases are the weak link limiting Hp outage to around 75 to 78 HP. Being this engine will used for short blast,install plain cast rings,stay away from chrome top rings,you want the rings to seat and seal immediately after the initial start up.

 

[TwoManyXS1Bs]

... There's a guy on ebay that sells high quality valves,Schumann motor works(SMW) I believe...

smw70ss seems to be out of his oversize 8mm valves at the moment, but here's one of his eBay listings:

Item: YAMAHA XS650 CYLINDER HEAD REBUILD SERVICE VALVE JOB

URL: http://pages.ebay.com/motors/link/?nav=item.view&id=231221463149&alt=web

Alt URL: http://www.ebay.com/itm/YAMAHA-XS650-CYLINDER-HEAD-REBUILD-SERVICE-VALVE-JOB-/231221463149

My 2 cents into this thread would be to carefully tune the exhaust to avoid the notorious 4000 rpm torque dip...

 

[hooser]

Got everything you need in stock,JE pistons, 250-30, springs, 1mm over valve will do just fine. Make 70hp with them. email me at gary@hoosracing.com .

 

[650performance]

Check out the information available at 650performance.com. There's also a link to obtain some comparative info about XS650/750 race exhausts you may find valuable.