[B]High compression or not??[/B]


14 replies to this topic
  • finthat

Posted December 14, 2008 - 10:43 AM

#1

I am going to be building my engine soon('03 yz450f). Just wondering if it is worth it to use the Wiseco high compression pistons or not. Do they shorten the life of anything in the engine bottom end ect? I imagine jetting and octane levels may become more critical with more compression. I would also think it would run hotter? I am still learning the in's and out's of the high performance 4 strokers. Advice needed.

PS. I am just a "weekend warrior" type. I like racing my buddies on thier quads and bikes on the local mx track. We also do some trail type riding ect. I am not a high performance rider, I still need to go to work on monday's.:thumbsup:
Thanks

  • wobblyknobby

Posted December 14, 2008 - 10:54 AM

#2

Don't do it! I have a 426 with the 13.5 wiseco and its a little too much compression. It wants to ping going up hills in 4th and 5th causing me to have to downshift. Also it makes the motor chug a little at lower rpms. Run the 12.5 piston, I regret the 13.5. Im looking for a deal on the 12.5 and when I get it, its going in.

  • Justin89

Posted December 14, 2008 - 11:22 AM

#3

I have a 13:5:1 in my 08 Kawi and love it. I run 1/4 U4.2 gas just for peace of mind and might even go to a 50/50 mix. I race though A lot and ride nothing but track. I think a HC piston would be the best route if you were ever going to do motor work like stroker, big bore, etc. BUT the 03 was a monster engine was want it?

  • ThumperKid250F

Posted December 14, 2008 - 11:48 AM

#4

i put a high compression piston in all my bikes and i love it. you get more power everywhere..


ive used wiseco on all my bike and i had good luck with them.. my 450 dident have so much luck tho.. the wrist pin snaped and took out my motor so im now useing CP pistons...

when i compaired CP and wiseco you can see that the CP is built better just from looking at it. more oil holes and more ribs for strenght.. and one big thing i loved about the CP is the wrist pin was way thicker than the wiseco..

just my .02

  • offrodeo

Posted December 14, 2008 - 02:25 PM

#5

For sure do it, I have a 2003 yzf450 with a 13.5:1 cp piston. It livened it bit. IT helped all around

  • Justin89

Posted December 14, 2008 - 02:26 PM

#6

Yes I have a CP piston too by the way...CP and JE are great pistons:thumbsup:

  • finthat

Posted December 14, 2008 - 06:31 PM

#7

Don't do it! I have a 426 with the 13.5 wiseco and its a little too much compression. It wants to ping going up hills in 4th and 5th causing me to have to downshift. Also it makes the motor chug a little at lower rpms. Run the 12.5 piston, I regret the 13.5. Im looking for a deal on the 12.5 and when I get it, its going in.


With the high comp piston I guess octane becomes very important. Premium or octane booster?? I know the old '84 cr500 I ran pinged a little on a good day, but if you forgot the octane boost it sounded like a jack hammer down there until I fixed the octane issues.

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  • gtxkid

Posted December 14, 2008 - 08:44 PM

#8

My CP piston is my second best mod.
I installed the new 13/75/1 CP and love it.:thumbsup:

  • Justin89

Posted December 14, 2008 - 09:01 PM

#9

With the high comp piston I guess octane becomes very important. Premium or octane booster?? I know the old '84 cr500 I ran pinged a little on a good day, but if you forgot the octane boost it sounded like a jack hammer down there until I fixed the octane issues.


Were you using an Octain booster like from an auto parts store or something? Those are okay but if they say they will raise your octaine 3points, that means you are going from 91(premium) to 91.3 not 94

  • finthat

Posted December 15, 2008 - 04:32 PM

#10

Were you using an Octain booster like from an auto parts store or something? Those are okay but if they say they will raise your octaine 3points, that means you are going from 91(premium) to 91.3 not 94


Thanks for the info I didn' t know that. Either way that old bike had ping issues and every last octane helped to tame it. They were known as the ping king. Thanks again for the info. :thumbsup:

  • Justin89

Posted December 15, 2008 - 06:07 PM

#11

Thanks for the info I didn' t know that. Either way that old bike had ping issues and every last octane helped to tame it. They were known as the ping king. Thanks again for the info. :thumbsup:


Oh no probelm. I'm having/hadf the same exact issue with my Kawasaki cause Im running the 13:5:1 piston too. With that piston, I think you would be able to get away with running good premium gas but if you're racing or riding hard, might want to do some mixing of race gas/normal gas.:smirk:

  • ClaussR Racing

Posted December 15, 2008 - 06:14 PM

#12

Own A 03 Crf450. Have A Je High Compression Piston Installed. Bike Is Used Exclusivly For Woods Riding In Northeast. Love The Upgrade.

  • finthat

Posted December 15, 2008 - 09:23 PM

#13

Oh no probelm. I'm having/hadf the same exact issue with my Kawasaki cause Im running the 13:5:1 piston too. With that piston, I think you would be able to get away with running good premium gas but if you're racing or riding hard, might want to do some mixing of race gas/normal gas.:thumbsup:


The old cr500 being a big two stroker, fuel air and ping were important....if ignored too long you were buying a new piston and with the old cast sleeves things get ugly quick when they melt down $$. The other option was getting the head dome machined or running some kind of two spark plug contraption with a coil out of an old Yamaha two cylinder snowmobile and more bucks in the machine shop closing up and making new spark plug holes ect..To much to worry about for an old bike.

  • wobblyknobby

Posted December 15, 2008 - 11:40 PM

#14

the thing is, 12.5:1 is high. Its really as far as works well all the time on pump premium. The extra squeeze is sensitive to operating temp and as soon as the bike get hot, it starts to detonate. Detonating is like hitting your piston with a hammer and will blown ur junk up pretty quik. Im suddenly hungry for strawberry milk. The problem is compounded by the fact that extra sqeeze raises operating temps. So u pretty much need to stick with 12.5 for pump gas. Octane boosters are bad news. They leave behind a residue builds up and glows red and causes more detonation then they prevent. They also cause air filter fires.

But do whayever you want, if you find urself wishing you had moe power sometimes, like u have the throttle wide open thinking "why wont it go", then maybe u need to run the 13.5.

If you want to be able to putt around, climb a series of slow hills, pull in the clutch and wait for your riding buddies to catch up without overheating, and run readily available fuel for a 4% less torque, then run what the factory decided was right on.

  • Kasjok

Posted December 16, 2008 - 12:53 AM

#15

I was thinking of getting 13.5, too, but eventually decided to go the middle route and picked a 13:0 CP piston. Haven`t installed it yet, though.





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