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cr500 tuning

26K views 14 replies 11 participants last post by  carlsoti 
#1 ·
is it true the best year for power was 1985 if so i want exhaust port sizes to compare with a 1998 thanks for any help
 
#3 ·
peak power is not the same as useable power. the 80s bikes do have more power but The 90s bikes are supposed to have smoother power delivery which makes for more useable power. From 91 or 92 on they are basically the exact same up through their end in 2001. which is best for your application is for you to decide
 
#9 ·
some of that powerband technology has more to do with "port timing", which on a two stroke is where the port window heighth is in relation to the deck or top of cases..like cam lift heighths or cam timing to a thumper...certain heighths will give over rev and a screaming top end and some will give immediatte roll on torque or a big rush that signs off early.....ive known guys to shim the bottom of the barrel and then shave the crap out of the head to get a screaming top end but it runs like crap off an idle.....i think through the years honda changed these intake and exhaust port heighths (within the cylinder), compressions, intake tract lengths (different reed cages and boot lengths on the older motors), headpipe lengths, and even the stroke and bore if you are going all out....i think 86 is the most horsepower year but hardly useable or rideable in most situations, just my 10 cents! you'd be amazed what you can feel as far as differences by just modifying the compression, jetting, and headpipe lengths. CR500 riders is very good for info. as far as i know you own a 98 CR500 :D
 
#10 ·
apa said:
Scallops??? What is that?
Scallops are very light exhaust reliefs in the exhaust porting. Which i saw someone say they are for easier starting. That is correct. Most of the reason the 85-86 CR500 motors had more power was due to the thinner barrels and higher compression heads. The later models like from 89-01 had a thicker barrel due to stress cracks the 85-86 barrels always had. In 89-01 honda lowered the compression a lot. If you ever look at a 86 head and a 90 head the step on the inside of the combustion area is double the thickness on the later model CR500. Shave the head on the later models, and watch the horsepower grow. There is a few companies now that have a starting relief valve that can be drilled into the exhaust side of the barrel making starting a high compression - high horsepower CR500 motor feel like a CR125. The valve is open before starting and will stay open tell the motor fires. This is the best thing you could ever do for tons of easy starting. Just my 2 cents on works good for me.:thumbup:
 
#13 ·
The "scallops" were like "eyebrows" on the exhaust port. Going to the 2nd oversize will eliminate the "scallops". The CR500 porting , as powerful as it is stock, is actually pretty tame compared to what it is capable of. Another trick to easier starting was to drill 2 holes in from the exhaust port to the bore. At low rpm, this would act as a compression release, where at higher rpm, their affect was nil. 80 rwhp is easily achievable with this motor with just porting, case mods and pipe/carb. Just have to ride it like a 125...easier said than done. Tdub
 
#15 ·
I can say that a tweaked 86 500 motor is huge on power, low on "rideability". I used to have a '85 bike w/ a '86 motor. I didn't bring it w/ me to AZ and my cousin's buddy burned it up not running pre-mix. I miss that damn beast.
 
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