08 YZ450F HC Piston

G'day fellow Thumpertalkers,

I'm thinking about putting a HC piston in my 08 YZ450F and I'm looking for feedback from those who have any experience with this. Looking for info along the lines of what pistons work best and any problems you ran into along the way. Your comments will be appreciated.

Cheers,

Rhys

i have a 2006 with the cp full race piston. its 13.75 comp with only 2 rings instead of the 3 and it comes with a skirt coating i love it but the race gas sucks sometimes but only when i try to ride like 80miles in ocotillo then i wear a back pack with water bottles of gas. i cant give you a good review since i did the piston hot cams and a port at the same time.

What are you trying to achieve with the Hi-Comp piston? Anything for off-road, and long distance riding it wouldn't be the best in my opinion. If you ride a lot of MX, the YZF could definitely benefit from a little low end boost. I ride both with my 2007, I could use a little boost down low to keep the abuse off of my clutch in the tight stuff, but when I ride in the woods for two hours I don't want the extra stress on the rest of the motor. At 113.5 hours I am just now doing a minor top end on mine.

There isn't really any extra stress on the engine from the extra compression, except during those times when additional power is being produced and used. Higher compression also absolutely boosts fuel economy. The difference between 12.5 and 13.5:1 might not be great, but it will exist.

The two downsides are in those cases where higher than pump grade octane is needed (generally only at lower altitudes) and where the piston is configure with a single compression ring. Two ring pistons are race-only (or should be) items, and the rings wear to the point of needing replacement significantly sooner than those on a three ring piston.

I have a JE 13.5 in my 06 YZ450F and I love it. I have the skirt and dome coated. The only pinging I get is sea level dune/high load situations. A little 100 octane (maybe 1 gallon in a 5 gallon jug) fixes that right up.

Here is a link:

http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=TR_791130

JE's machining is a work of art!

except during those times when additional power is being produced and used.

.

Which is exactly my point.

Especially if the motor is getting up there in the hours, like mine for instance.

Cool, thanks for the advice guys. I will pretty much only be doing MX racing, mostly outdoors type stuff with some stadium thrown in. All my riding is done mostly at sea level and the highest I would go would be about 1000m (about 3000ft)

I put a CP HC piston in my 08 and frankly did not notice much difference. Perhaps with the other differences between the 06 and 08, it is not as noticeable. I thought the motor picked up a slight vibration, which make sense given the difference in weight of the piston.

I have a JE 13.5 in my 06 YZ450F and I love it. I have the skirt and dome coated. The only pinging I get is sea level dune/high load situations. A little 100 octane (maybe 1 gallon in a 5 gallon jug) fixes that right up.

Here is a link:

http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=TR_791130

JE's machining is a work of art!

What did you have the skirt and dome coated with? Did you order it like that or did someone else do it?

I was always told that boosting compression leads to accelerated engine wear, as a matter of fact Motorcross Action mag. talks about it in this month's "Wrench Tech" that is about big bore engines. I would really like to know because I just bought a basket case 06 and the person I bought it from already had picked up a JE 13.5 piston and hot cams. I'd rather dump that piston to run a standard 12.5 and use the original cams.

What did you have the skirt and dome coated with?

Ceramics, heat reflection on the dome and anti-friction on the skirt.

Did you order it like that or did someone else do it?

Its a JE, they dont have an option for coatings. I had a local performace shop do it for me. Cost $25

I was always told that boosting compression leads to accelerated engine wear

Any modification that increase power output is going to increase wear. If you get a Hp increase from a better air filter, technically there is goign to be "increase in wear" even if the amount is not measurable...

I'd rather dump that piston to run a standard 12.5 and use the original cams.

Do what ever you feel is right, in the end, if the motor fails, it is YOU walking back to the truck, not the guys that gave you advice... :smirk:

Any modification that increase power output is going to increase wear. If you get a Hp increase from a better air filter, technically there is goign to be "increase in wear" even if the amount is not measurable...

Compression ratio increases are not like modifications such as more aggressive cam grinds that put constant additional physical load on engine components.
There isn't really any extra stress on the engine from the extra compression, except during those times when additional power is being produced and used.

I put in a CP HC piston on my 06, and noticed a pretty significant increase in power. I sent my carb to Zip-Ty at the same time and had their $100 mod done, but I think that is only noticeable in the increased throttle response, not the increase power output. I really like my CP piston.

I put in a CP HC piston on my 06, and noticed a pretty significant increase in power. I sent my carb to Zip-Ty at the same time and had their $100 mod done, but I think that is only noticeable in the increased throttle response, not the increase power output. I really like my CP piston.

What would be the life expectancy difference between an engine with a HC piston and one with a standard compression piston? Is it just a couple of hours difference out of the hundreds of hours on any given motor?

The compression itself will hardly change anything related to the longevity of the engine as long as it doesn't result in damage from detonation. Running a single compression ring, on the other hand, will cause the rings to wear to the point of needing replacement somewhat faster, though.

replacing top end of 2008 yz450f and have no manual that shows cam mark alignment. Does anyone have snap shot of a photo they can post with alignment marks in correct location at tdc? have 2009 manual but marks are at 180 degree difference in location.

The '09 timing marks are in exactly the same place as the '08, so the '08 manual will work perfectly for that purpose, but you can also download an '09 book from:

http://www.yamahaownershandbook.com.au/?r=0

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now