13:5:1 or 13:0:1 piston

[450rboy]

the 13 ratio piston is it a good piston to get.has anyone had problems with it. does 4 wheeler over heat and what size of octane do you run throug it

just need a little help on which one to get. if those arn't doing the job i will go for the 12

[ghott]

The bigger the better. Go with 14:1. Baldwin makes a 14:1 piston for the 94mm stock bore 04/05 R's.

Anything over 12.5:1 you will need to run high octane race fuel to keep it from detonating.

Anything under 12.5:1 can run on 93 octane pump gas.

For each point in compression ratio, expect a 3% gain.

Example: Going from 10.5:1 to 11.5:1 is a 3% gain. Going from 10.5:1 to 13.5:1 is a 9% gain.

Good Luck.

[speedfreaksguy]

I doubt you will notice a difference between 13 and 13.5 or 14. I 've been running Wiseco's 13.5 since they offered it for the 2004 with no problems. I run 110 and sometimes mix it 50/50 with 94 (when I forget to get race fuel) I have had no reliability issues whatsoever, still on the stock cylinder (and crank and main bearings) after 3 top ends. You can find the Wiseco pistons for less $ than the Baldwin.
Just my 2cents.

[ghott]

IMHO, if you are going to go with a big piston, why not go with the biggest stock bore piston available? That way you won't be wondering what kind of power you left on the table by not spending a little extra. Spend the extra $100 on a Baldwin 14.1:1. I went with a 13.1:1 Wiseco, and am now already looking forward to my next rebuild with a Baldwin 14.1:1.

You'll already going to be using high octane fuel, why not go big? :).

[450rboy]

well the stock piston in the 05 to the 13.5. will i have a lot more power.

and what will happen if i get the 14.1 will i be having problems with it

which would everyone rather perfer 13 or 14.

and which is more reliable

[ghott]

Going from a stock piston to a 13.5:1 will yield roughly a 9% gain, or between 3-3.5hp. That is...if you have a full exhaust letting that big explosion exhale.

Going from a stock piston to a 14.1:1 will yield closer to a 3.5hp gain under the same conditions. Reliability with a 13.5:1 vs. a 14.1:1 is going to be almost the exact same...it will be mostly "brand name" dependent, and the strengths/weaknesses with the company chosen.

[tltcracing]

this may sound dumb but does the 13 or 14.5:1 piston make the quad any harder to start as far as kicking it over. just thinking about it.

[ghott]

Originally posted by tltcracing
this may sound dumb but does the 13 or 14.5:1 piston make the quad any harder to start as far as kicking it over. just thinking about it.

As far as hard starting, I noticed no difference. My quad, with 13.1:1, still starts just as easily as it did with a 10.5:1 piston.

As far as harder to kick over, I did notice a difference. 13.1:1 compared to 10.5:1 was a good bit harder on the leg, not too big a deal however. But with anything...you get used to it pretty quick.

[morfy]

Check into je pistons... My friend has had one in his bike for two yrs.. And has had no issues... Look at my signiture for the guy to talk to about motors!! i-h racing can build you a very good motor that is reliable to boot!!! Which is good for peeps like me OVER the hill:D

[2muchquad]

I wouldnt be running 14 to 1 piston unless i got my parts for free.Even with race gas its gonna put a huge load on the crank/ rod.Lets say almost several tons of force on the rod at rpm!Also keep in the the new 450s arent built like your daddys xr.Valves especially lose more and more seat pressure ever time you start it up,this is a fact.Even with frequent oil changes and upkeep they can give up the ghost without warning.While they can be more reliable if left closer to stock we all know that no fun.Again unless you get your parts for free stay out of diesel territory with the compression:D

[Architects]

Originally posted by 2muchquad
I wouldnt be running 14 to 1 piston unless i got my parts for free.Even with race gas its gonna put a huge load on the crank/ rod.Lets say almost several tons of force on the rod at rpm!Also keep in the the new 450s arent built like your daddys xr.Valves especially lose more and more seat pressure ever time you start it up,this is a fact.Even with frequent oil changes and upkeep they can give up the ghost without warning.While they can be more reliable if left closer to stock we all know that no fun.Again unless you get your parts for free stay out of diesel territory with the compression:D

Do you even know what your talking about? There are tons of people running high compression with no problems.

As far as compression ratio. Go big. Your already in race gas territory might as well go as high as possible

[2muchquad]

you even know what your talking about? There are tons of people running high compression with no problems.


yeah and there are poeple that have had more than their share of problems.Chances are that while you are online reading about engines and what works im busy doing them seeing for myself...wiseguy:blah:

[ghott]

In my opinion, both of you guys are "sorta" right.

The stock bottom end will only take a beating from a high comp piston for so long. Although I do know of a guy running a 477cc 14:1 piston in his 450R with a 23hp shot of NOS all on the stock bottom end. He has been doing so for months now with No problems.

So yeah, you can run a 13.x or 14.x piston for a while...maybe a pretty long time....but the addition of this piston takes the reliablilty of your Quad down significantly.

4-Strokes love compression...the more you have, the better power they make. But this is also harder on the rest of the engine. Its a chance I'm willing to take tho :).

[chad502ex]

maybe i'll add a couple of quarters to the pot....

everyone has made a good point or two thus far....

lets continue to keep this civil.


Since we are sharing experiences, this is mine:

Ghott is correct- a 3% gain from one point of compression is typical... so, going from 12:1 to 13:1 could yeild about 1.5hp just in compression...

2muchquad has interesting advice... I think he is trying to convey that if your an average trail rider then you may not need to go high compression to be 'competitive' with the trees...

Architech comments stem from many ppl running up to 14:1 compression with zero problems on rods, but if any, more on the crankshaft to piston pack assembly imbalance (harmonics caused from unbalanced crankshafts with new piston)... Of coarse, IMO, this will not be sufficient enough to advise everyone out there not to install a 'shelf' piston. the high compression shelf pistons may unbalance an assembly, but the amplitude of the harmonics from the lighter assembly will not immediately cause components to fail as suggested, but more a long term concern... IMO.


Now back to high compression pistons-

For me there is one concern with high compression pistons, there are none!

Compression is the most reliable power, other than porting, you can buy if the piston recipicating weight is within a tolerable range around the stock piston assembly; otherwise, the crankshaft must be removed and rebalanced to the new piston pack. For example, the 'shelf' pistons on the market available in 14:1 compression, although nice designs, are just that, shelf pistons meaning that more than 99% of the build can take these pistons off-the shelf and install without any concerns... But compression, is simply not what is governing a few isolated failures,.... its the imbalance with the recipicating weight to the crankshaft that generates failures over long periods of 'pounding'.

Now, many of my customers want high compression and all ask what octane fuel do i run... static compression has nothing to do with this, its only dynamic compression that governs octane requirements... For example, my new piston, designed to be over 15:1 static when used with a selected camshaft running can reduce the 'static' compression to near 12.5:1....

my points are, that static compression does not cause failures, its the dynamic compression ratio due to camshaft timing (detonation concerns with octane) and the piston assembly/crankshaft imbalance that cause failures when not considered...

My advice: if you have the money to spend on race fuel, then a high compression piston performance part, or camshaft, or porting is all equivalent hp:$ ratio vested.....

[ghott]

Great points Mr. Chadwick :).

[chad502ex]

Originally posted by morfy
Check into je pistons... My friend has had one in his bike for two yrs.. And has had no issues... Look at my signiture for the guy to talk to about motors!! i-h racing can build you a very good motor that is reliable to boot!!! Which is good for peeps like me OVER the hill:D

yes, JE is my preference, which is why i've selected them to make my new design...



Hard starting when using high compression pistons is an easy one to eliminate--- its called setting the decompression release... :D

[Architects]

I was mainly referring to him saying valves losing seat pressure. How would HC cause you to lose seat pressure. Thats all in the springs which has nothing to do with compression. I could see a radical cam like the 208 causing this but compression? If im wrong someone care to chime in.

[Sjorge450R]

since were on the top. I am currently running 100 octane Low led AV gas in my 300ex and it has seem to make the motor run signifgently cooler. Also, I run a 11:1 in that. Now its will be a while before I tear into the motor in the R, but when it comes time to I was wondering what octance gas taht I need to use on the 13.5 or 14:1 pistons. Will the gas that i currently run be good enough?

[stocktires]

Please put down the AV gas and step away! NOW!

[2muchquad]

I wasnt refering to seat pressure when talking about the high compression,just some of the things that will be addressed eventually with these new 4 strokes.They are not xr's;)

[Sjorge450R]

Originally posted by stocktires
Please put down the AV gas and step away! NOW!

why? Colby and just about every other mechanic told me that it's better than using some VP and Klotz gases.