503 Mods

[ozzydog]

Who has done mods to their 503 for performance besides Clutching?? What are they and what kind of increases did you see??

 

[ozzydog]

Info I am looking for.

I am curious what those with 503 are doing as far as Carb work, Exhaust work, porting, polishing, milling heads, pistons, etc.
Basically any and everything.

 

[cjgodden]

I don't know about hawks but I do know that Aaen has done some porting and head work to the 503 and 550's twoski's with good success. May want to call them.

 

[onewoodsrider]

503 mods

Harley, i installed anti ratchet drivers on my 121" track to be able to run it a little looser then recomended. I dont think it made that big of difference though. I also ceramic coated the header and pipe when i re-jeted and that seemed to help out as far as it flowing better and keeping the temp down. Im running 180/170 mains with 50 pilots with the airscrew out 1-1/2 turns and it will bring the front end up if i exit a corner fast. Looking forward to the rollor secondary to see how it hooks up. The stock clutch im using i have two pucks out of each location and have been running 2500'-4000' feet ( when we had snow ) I would like to know if anyone has installed a holtz attack compensator on a 503 and what thier base jetting was and where they put the sensor.

Later all
Todd

 

[ozzydog]

503 mods

Todd,
I am running the same main jets as you. My pilots are 47.5's. Not much difference there. I have not done anything to the exhaust. Who did your work?? Well have to talk later. The roller secondary, you will love it.

 

[snowhawk jockey]

The Polaris primary seemed to make the single biggest difference in acceleration and especially high speed cruising at lower engine RPMs. The Roller secondary made the backshifting mo'betta. For carbs, I put the UFO's on the bottom of the slides and I have no idea where my jets/needles/pilot specs and screw ended up set, plugs and piston wash determined the spec. I still want to put some "powernow and powernow plus" style splitter vanes in the throat and bell of the carbs to pull more torque with the throttle at less than half open.

http://scaryfastracing.net/pn-info.html
http://scaryfastracing.net/pnp-info-press-dbmag.html

This year I am going to wrap my whole pipe and fork legs in foil/glass wrap to try and get the heat off the fork tubes. I imagine a lot of front end fade is because of overheated fork oil. I'll use one of those little dirtbike motor temp strips to monitor fork leg temp.

Port and Polish?? Big Bore? The fella that fabbed twin pipes and pulled 80-90hp out of his. I want to use that trick!

Maybe just the 550 swap... Roo, how much more did the 550 weigh vs the 503?

 

[roo]

550 weight

The Polaris primary seemed to make the single biggest difference in acceleration and especially high speed cruising at lower engine RPMs. The Roller secondary made the backshifting mo'betta. For carbs, I put the UFO's on the bottom of the slides and I have no idea where my jets/needles/pilot specs and screw ended up set, plugs and piston wash determined the spec. I still want to put some "powernow and powernow plus" style splitter vanes in the throat and bell of the carbs to pull more torque with the throttle at less than half open.

http://scaryfastracing.net/pn-info.html
http://scaryfastracing.net/pnp-info-press-dbmag.html

This year I am going to wrap my whole pipe and fork legs in foil/glass wrap to try and get the heat off the fork tubes. I imagine a lot of front end fade is because of overheated fork oil. I'll use one of those little dirtbike motor temp strips to monitor fork leg temp.

Port and Polish?? Big Bore? The fella that fabbed twin pipes and pulled 80-90hp out of his. I want to use that trick!

Maybe just the 550 swap... Roo, how much more did the 550 weigh vs the 503?

reed blocks and 25cc larger pistons=heavier. plastic motor ducting= lighter
other than this 550 is almost identical to 503, even used mag cover/pullcord and fan/housing off 503. pretty close to same weight.

 

[roo]

built 550

The Polaris primary seemed to make the single biggest difference in acceleration and especially high speed cruising at lower engine RPMs. The Roller secondary made the backshifting mo'betta. For carbs, I put the UFO's on the bottom of the slides and I have no idea where my jets/needles/pilot specs and screw ended up set, plugs and piston wash determined the spec. I still want to put some "powernow and powernow plus" style splitter vanes in the throat and bell of the carbs to pull more torque with the throttle at less than half open.

http://scaryfastracing.net/pn-info.html
http://scaryfastracing.net/pnp-info-press-dbmag.html

This year I am going to wrap my whole pipe and fork legs in foil/glass wrap to try and get the heat off the fork tubes. I imagine a lot of front end fade is because of overheated fork oil. I'll use one of those little dirtbike motor temp strips to monitor fork leg temp.

Port and Polish?? Big Bore? The fella that fabbed twin pipes and pulled 80-90hp out of his. I want to use that trick!

Maybe just the 550 swap... Roo, how much more did the 550 weigh vs the 503?

if you go to dootalk and look up posts by lrd you will find he built the crap out of 550, bigbore 620, lotsa porting. talked to him couple times. does not recomend going his route. really hard time keeping running cool.