selecting a piston for 08 yz 450


9 replies to this topic
  • yamarooter

Posted December 23, 2008 - 12:29 PM

#1

I was wondering which piston would be the best for me. 08 yz 450 mrd exhaust, otherwise stock, except tuning and i ride mosty motocross tracks and like to freeride.(no trails) I was looking at wiseco, je, cp ,. riding around 5,000 ft, dont need more power but could use it, does high compression make better low end? does h.c. piston last as long, looking for something durable, also is there any drawbacks to using a high compression piston. first thumper rebuild since 2 stroke, needed this because carbon deposits caused valves to not seat and could not start the bike. any info on any of this is greatly apreciated, thanks.

  • BC3

Posted December 23, 2008 - 04:26 PM

#2

I was wondering which piston would be the best for me. 08 yz 450 mrd exhaust, otherwise stock, except tuning and i ride mosty motocross tracks and like to freeride.(no trails) I was looking at wiseco, je, cp ,. riding around 5,000 ft, dont need more power but could use it, does high compression make better low end? does h.c. piston last as long, looking for something durable, also is there any drawbacks to using a high compression piston. first thumper rebuild since 2 stroke, needed this because carbon deposits caused valves to not seat and could not start the bike. any info on any of this is greatly apreciated, thanks.



Go to your auto parts store and ask for SEAFOAM read the instructions and you will be happy.....Takes all the carbon off the valves and seats....I use it and will stand by this product.....

  • Justin89

Posted December 23, 2008 - 04:46 PM

#3

:p I have a HC piston in my kawi and I really like it. It is a CP 13:5:1 piston. HC pistons in general make great power gains all throughout the rpm range. My piston has 20 hard race hours on it so far and have zero problems so far. Some draw back are you might have to run race gas if you have some pinging going or if you are a hard racer riding high in the rpm range. Most likely, you'll be fine with a high quality premium gas. (if you dont have pinging going on, you dont need a higher octain) However, I run a mix of 1 gl (VP U4.2)/4 gl premium chevron gas just because I run my bike pretty hard. You might have to do some re-jetting for the race gas if you use it. It sounds kind of like a lot of work but its well worth it.:busted: OEM is the absolute best for reliablity but pistons like JE and CP are very respectable pistons:thumbsup: that many people have had great success with. IMO a HC piston would be the best way to go (suppossed to a big bore or stroker kit, etc) Good luck and keep us posted!:moon: :mad:

  • yamarooter

Posted December 23, 2008 - 05:15 PM

#4

thanks, would a 12:5 piston lessen my chances of having to use race fuel? Is the service life shorter on a HC piston vs a same brand oem spec piston? I ride about 15 hours per week and on the throttle petty hard. Has anyone used 44k to help with carbon buildup, or any other fuel additive? Thanks alot!

  • gtxkid

Posted December 23, 2008 - 05:55 PM

#5

I put the new CP 13-75-1 piston in my bike and was great for low end boost.
CP +++++++++
I also ran it in 2 classes all year:thumbsup:

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  • Justin89

Posted December 23, 2008 - 07:38 PM

#6

thanks, would a 12:5 piston lessen my chances of having to use race fuel? Is the service life shorter on a HC piston vs a same brand oem spec piston? I ride about 15 hours per week and on the throttle petty hard. Has anyone used 44k to help with carbon buildup, or any other fuel additive? Thanks alot!


Yes the "smaller" compression ration would lessen your chances in theory. I mean, there are tons of threads on here of guys using the 13:5:1 in their bike without using race gas. But like you said, you ride a lot and sound like you mean business out there so the race gas is up to you I guess. (if you have no no pinging) Like I said though, I use the VP U4.2,,,this isn't the 110 octain "smells good" :moon: stuff that you smell at the track. This smells almost like normal gas its just oxygenated and I only use 1 gallon a "can" of gas. I havent used any fuel additives at all in my bike so I cant really comment on that other than that the ocatin boosters at automotive stores are kind of deceiving. When they say that they will raise your octain by 3 points, that means you are going from 91 octain (premium in CA)to 91.3 insted of 94. I tried this route instead of buying race gas but found that info on here before hand. OEM pistons are best for service life and reliablity. ON my 2006 yz450f, I went 216 hrs (all race) on the stock piston and it still ran like a freight train:thumbsup: :busted:

  • grayracer513

Posted December 23, 2008 - 08:26 PM

#7

Keep one thing in mind: Your octane requirements at 5000 feet are somewhat lower than at sea level to start with due to the lower air density. A lot of people use 13.5:1 compression with pump premium and have no trouble. If 91-92 octane fuel (U.S. AKI method, (R+M)/2) is available in your area, you should be OK with it.

  • yamarooter

Posted December 23, 2008 - 08:55 PM

#8

I probably had over a couple hundred hours on my stock piston. I was wondering about the fuel additive for the carbon buildup on my valves and piston (not octane). I thought i was close for my jetting, could this be the cause of the carbon or mabe bad fuel. using 91 oygenated but can get non oxygenated from one spot i think. I dont know much about fuel but would this higher octane mixture mentioned by justin help keep things cleaner. is this buildup normal? not complaining but was far worse than any of my 2 stroke. I ride Denver, Cainville, Grand Junction... I think the lowest place ive ridden is about 4,000 ft, Off subject,but can i clean all this with carb cleaner, what if valve guide seals are still in, keep or replace? they look ok???

  • motodreams

Posted December 23, 2008 - 08:57 PM

#9

08 YZ450 also. 40 hours of ride time since I put a 13.5 compression weisco piston in with a hot cams stage one. Also has a Dr.d pipe. By far the best running bike I have ever had... I run 100 octane race gas. Wider power band, more torque. Cold or hot, 1 or 2 kicks to start. This might sound unreal but often starts with only half a kick. I am at sea level and up to 1000 feet. I Ride the old guy expert class and have a tendency to ring it out. I did re jet it... I will see if I can round up what I used and post it for you. BOY I LOVE THIS BIKE!!!

  • gtxkid

Posted February 18, 2012 - 08:58 PM

#10

It is still going well.
Moved to FL
Going to re jet for down here.
Excited to see how much power it will make.
Thinking about putting some new rings in it.





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