High Compression Pistons

[dtmichau]

Hey guys! Happy new year!

I got the Stage II Hot cam, full LRD Pipe, KN, jets....


How much more will I get out of the beast with a high compression piston? Would it be noticable? Worth the trouble? Also, which compression would best suit my current mods? 13:1? JE of Wiseco?

[czrider263]

wiseco atleast that what i run for more than 70hrs NO PROBLEMS. great hp to

[Pappy]

check out the dyno section here on the site. several combos available to see what parts is making what power.

im leaning towards the baldwin 14-1 like wppracing has been testing. its pulling 50+ hp with some fairly basic engine work.

[wppracing]

Go with the Baldwin 14.1:D

I have had the sparks 13.8(really 13.5) , VCP HH 13.75 and now the Baldwin 14.1

[MAD450r]

I have hrc can and would like to keep it in there. Im thinking 12:1 is what I can go up to is that right?

Also who makes those pistons. I have yet to see anyone use a ross on an R. So im guessing they dont make one. I love the reliability I have had with the ross I put in my 416 2 seasons ago. all I do is change oil regularly and have 0 problems with it.



If I did go with the baldwin 14:1, what fuel would I have to run in it.

[4LEAFCLOVER]

I tell you someone must was reading my mind because this is the forum I need to find out the answer to that same question. I've heard that 12:1 is the biggest you can go and still run pump gas. I've been looking really hard at that HH 12:25 piston but I don't know if you can run pump gas with it. If anyone knows please let me know. I'm waiting on my Rossier Exhaust now and I'm trying to find out info on the best compression piston to run with that exhaust and still be able to use pump gas. Any help is greatly appreciated.

[jlm996s]

You can use 91 with the HH 12:25. It will work just fine with the Rossier. OKTRX450R is getting 50 hp with a 12:25 HH, Ron Woods pipe, port and polished head, and I think HRC cam. I've got one, but haven't put it in yet.

[4LEAFCLOVER]

Well I just ordered my JE 13:1 piston kit off of Ebay. Decided if I was going to tear it down I might as well go ahead and put the big boy in there. I know i'm going to have to run race gas but what the hell. I didn't want to put a 11:5:1 in there and be regreting it in the future. I 'm now waiting on my Rossier Short Can and my piston. They both should be here within the next week. Then my Black Beast goes in the shop around the 15th of this month. I wanted to make sure I'm ready for the trip home to Georgia this summer because my cousin is having his head port/polished on his KX125 along with a new Carb and Pro Circuit Pipe to run race gas. He's wanting to race me so bad and I've got to be ready for him. The only thing I'm going to do next is get a aftermarket Ignition like Vortex or Dynatex to get somemore RPM's out of my motor. I think that should about do it for the motor mods. Next comes the powder coating and chrome and polish looks. Thanks for all the help from you guys on these forums.

[rap169]

jlm996s, where did u get your hh 12.25:1 and how much was it? does it include gaskets?

[jlm996s]

I bought mine used, but here is a new one for sale with gaskets. (http://www.trx450r.org/forum/index.php?showtopic=14167&st=15)

[tucson450r]

I am running a JE 13:1 with HRC cam and Rossier pipe and Rossier port and polish. I am very satisfied with my performance and have had 0 problems so far!! Joe at Rossier is a good person to talk to about your compression and cam specs for which gas to run on.

[370kingR]

Originally posted by rap169
jlm996s, where did u get your hh 12.25:1 and how much was it? does it include gaskets?

lukester720 on 450r.org has a few of them left. Look him up and ask him on there. Have fun :cool:

[nowukno]

I have a JE 13:1 and i love it. Goes very well with my hotcams stage 2. The piston was exactly the power i was looking for , plus some.

[chad502ex]

Originally posted by tucson450r
I am running a JE 13:1 with HRC cam and Rossier pipe and Rossier port and polish. I am very satisfied with my performance and have had 0 problems so far!! Joe at Rossier is a good person to talk to about your compression and cam specs for which gas to run on.

everything is good to hear.

what rwhp are you making, do you know?

[OKTRX450R]

If you are going hi comp and running race gas why not go with the BMS 14.1? If you really want to run the "big boy"...

[dober250R]

the baldwin makes me nervous with only 2 rings on it for a 4-stroker..................

[nowukno]

Originally posted by chad502ex
everything is good to hear.

what rwhp are you making, do you know?



I have no idea. Sorry :(

[tucson450r]

Originally posted by chad502ex
everything is good to hear.

what rwhp are you making, do you know?

I am not sure, i have not dynoed it yet. I hope to get to the dyno soon to get an idea.

[MR.BIG]

Correct me if I am wrong but I thought you could run 12.5 with the hrc cam on pump gas.

[chad502ex]

Originally posted by MR.BIG
Correct me if I am wrong but I thought you could run 12.5 with the hrc cam on pump gas.

you are correct.

[MR.BIG]

Originally posted by chad502ex
you are correct.

Is that is high as you can go without going to race gas.

[chad502ex]

Originally posted by MR.BIG
Is that is high as you can go without going to race gas.

actually, the static compression ratio isn't as important for running pump gas or race gas- it's the dynamic compression ratio that determines when race fuel or higher octane is required.

static compression ratio is when the piston is still.

dynamic compression ratio is when the piston is moving.

engines make no power when still, so static CR isn't as important as dynamic CR is.

Dynamic CR is when the intake valves finally close on the compression stroke. Larger overlap cams lower the static CR; therefore, the more of a top end cam you install the lower the dynamic CR.

It is possible to have a 14:1 static CR, and still get by with running rump fuel if ya had to get back from the trails to the truck. I dont' recommend running pump on 14:1, but if you had a top end high overlap cam you could run towards idle and not cause to failure or large detonation force on the crank bearings,..

[4LEAFCLOVER]

Originally posted by OKTRX450R
If you are going hi comp and running race gas why not go with the BMS 14.1? If you really want to run the "big boy"...
Well because I think the 13:1 will do me just find for the little amount of riding or racing I do. And plus the JE is in my price range. I think it will give me enough power for now besides I don't think a 14:1 is going to make that big of difference. If I want any more power I'll just get a big bore kit for it in the future.

[chad502ex]

Originally posted by 4LEAFCLOVER
Well because I think the 13:1 will do me just find for the little amount of riding or racing I do. And plus the JE is in my price range. I think it will give me enough power for now besides I don't think a 14:1 is going to make that big of difference. If I want any more power I'll just get a big bore kit for it in the future.

typically the gains are linear- with every increase in CR point there is a ~3% gain in HP.

In other words, from 13:1 to 14:1 will yeild ~ 3% more hp than before...

[OKTRX450R]

Also dont think just going big bore will yield an automatic power increase...there are many stock bore R's out there making more HP then the 480 and 520 kits...

What is the price difference between the JE and the BMS?

[wppracing]

About 75.00 difference

165.00 JE
239.00 BMS

[OKTRX450R]

Originally posted by wppracing
About 75.00 difference

165.00 JE
239.00 BMS

What does 5 gal. of race gas cost?

[wppracing]

CAM 2 leaded 110
$4.50 per gallon