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Do Hi Comp. Pistons lower the engine reliability?
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Posted by: Spokes574---------------------

I am thinking of putting a High comp piston in my Y05 CRF450R.
I was told that:
-jetting is not affected
-1-1.5HP gain
-93 Octain needed - so not full race gas
-if i port the engine I can expect another 3hp
-Increase in breaking compression a tad bit
-Loss in over rev a tab bit

Questions:
Is the above accurate?
Does Hi Comp piston lower the reliability?
Does it increase temp of engine?
Does it increase failure?
Is it better to just port and use a std piston?
Is an extra ~5hp too much and make the bike non smooth?

Thanks,
Spokes574

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by Spokes574

Questions:
Is the above accurate?

The horsepower claims are way too optimistic.

Quote:

Does Hi Comp piston lower the reliability?

Not on this engine

Quote:

Does it increase temp of engine?

Somewhat, but only woods riders slugging slowly along will notice.

Quote:

Does it increase failure?

Not in my experience.

Quote:

Is it better to just port and use a std piston?

No. A high compression piston and cam are the best bang for the buck. The cylinder head is VERY GOOD in stock form. It can be made better but there isn't some huge chunk of horsepower hiding in there.

Posted by: Spokes574---------------------

Thanks Rich for the great informative feedback.

Which high compression piston do you recommend? 13:1?
So it sounds like I should bi-pass paying for porting and just get a hi comp piston and valves/springs/seat done?

In your experiance the porting is not going to gain me much since the head is good as is? I definitely do not want to change the current power band since it is nice and smooth w/o a hit - could porting affect this?

Thanks,
Spokes574

Posted by: chumbucket---------------------

On the same topic, does a high comp piston along with some cams lower reliability on a 03 yz250f motor?

Posted by: Spokes574---------------------

Rich,
Thanks for the input on piston and cam.
I am having MDK redo my engine next week because they are local to me and I can drop the entire bike off, they can do the labor and dyno.
They are putting in a 13.5:1 CP piston and porting the head. I am looking for more bottom end in my CRF450R Y05. I have a Yoshi Pipe that gave a about 1/3 more mid and top without any noticable loss in bottom - but it does rev slower in the mid which is a pain coming out of tight corners- but on the track I ride(club moto) there are a lot of tight 90 degree turns so I just need more bottom or faster reving engine so I can just ride in 3rd gear most of the time is my prefference because it vibrates less and is more smoother than second.

The MDK cam is way too expensive for me at $390 and another $200 for springs that are needed for their cam.
I am already speading a lot for the piston/porting and labor.
Why is the Hot Cam much more affordable than everyone elses CAM by almost 50% less?

My question is the Hot Cam Stage 1 (low mid ) any good? Does the low/mid hot cam need new springs? if not, why not?
Will the low/mid cam affect my top end in any negative way? And if so by how much?

How much of a difference will I expect if I add this cam vs getting the Porting and Hi Comp piston alone?

My ridding style is most of the time 3rd gear and stretch it out. I am hoping that since I have the Yoshi pipe which gave the bike 1/3 more overrev that adding the low/mid cam will still leave me with as much or a tad bit more overev than stock and with a motor that has much more torque and bottom end than my stock honda.

Here are some other alternatives I am thinking about to save money over possibly not doing the cam and just doing the Hi Comp and porting with possibly the following:
- add 1 more tooth to my rear spocket 13/48--> 13/49 $54
- add a Rev Max - Rev Box suppose to improve ignition for bottom and mid performance and rase the rev limit for $129

Please give me some guidance since I do have to drop off the bike this Wed and need to tell them what I want them to do.
I know there are a lot of questions above but answering them will probably be very informative for a lot of other folks as well. I am learning more and more over the years from this site especially from your comments.

Thanks
Spokes574
Pleasanton CA

Posted by: Hevster1---------------------

If you install a hi comp piston ad cams and ride it like you stole it all the time it will lessen reliability but then again so will riding a stock one like that. I am curious, are you guys all top pro's or what? Do you really need the extra power?

Posted by: Spokes574---------------------

Not a pro but still want a bike that is competitive.
Do not like getting passed in the corners all the time.
I have slow corner speed. Do not like to take chances with my knees
so rather slow down and take off - need a lot of bottom end grunt and prefer to stay in 3rd most of the time because its smoother and vibrates less and we have a lot of jumps immediately out of corners so do not want to loop either.

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by Spokes574

Rich,
Thanks for the input on piston and cam.
I am having MDK redo my engine next week because they are local to me and I can drop the entire bike off, they can do the labor and dyno.
They are putting in a 13.5:1 CP piston and porting the head. I am looking for more bottom end in my CRF450R Y05. I have a Yoshi Pipe that gave a about 1/3 more mid and top without any noticable loss in bottom - but it does rev slower in the mid which is a pain coming out of tight corners- but on the track I ride(club moto) there are a lot of tight 90 degree turns so I just need more bottom or faster reving engine so I can just ride in 3rd gear most of the time is my prefference because it vibrates less and is more smoother than second.

Sell the Yosh pipe to one of your friends and pickup a Thunder Alley megaphone slip on to go with the stock head pipe. It will make the type of power you are looking for. Click this link for a TA pipe review ==>http://www.dirtrider.net/forums3/sh...t=Thunder+Alley

Quote:

Originally Posted by Spokes574

The MDK cam is way too expensive for me at $390 and another $200 for springs that are needed for their cam.
I am already speading a lot for the piston/porting and labor.
Why is the Hot Cam much more affordable than everyone elses CAM by almost 50% less?

The guys who run Hot Cams also own Hot Cranks, Hot Rods and Pivot Works. They design cams in the US as billet blanks to be made on high end CNC cam grinders and get them built offshore. As a result of the huge volume they do and how streamlined their process is they enjoy economies of scale that small companies building a handful of cams will never see.

Quote:

Originally Posted by Spokes574

My question is the Hot Cam Stage 1 (low mid ) any good?

I was looking for the same type of power you were and it's the cam I went with in my CRF450. Eric and I have installed a lot of them over the last few years and we have a lot of happy customers as a result.

Quote:

Originally Posted by Spokes574

Does the low/mid hot cam need new springs? if not, why not?

You can run OEM Honda springs with the Stage 1 Hot Cam. If your bike is ready for a top end then you need new valve springs at a minimum regardless of the cam. You probably need intake valves and a valve job as well.

Quote:

Originally Posted by Spokes574

Will the low/mid cam affect my top end in any negative way? And if so by how much?

I didn't notice anything lacking on top with the Stage 1 and the Thunder Alley combo even riding it in on the street with the SuperMoto setup. I'm sure you'll see some difference on an accurate dyno , but I haven't found it translating to anything real world.

Quote:

Originally Posted by Spokes574

How much of a difference will I expect if I add this cam vs getting the Porting and Hi Comp piston alone?

The high compression piston and the cam are the way to get what you are looking for. Porting is a wildcard because there are so many people doing it that have no idea what they are doing. Most never seen a flow bench let alone tested on one.

Quote:

Originally Posted by Spokes574

Here are some other alternatives I am thinking about to save money over possibly not doing the cam and just doing the Hi Comp and porting with possibly the following:
- add 1 more tooth to my rear spocket 13/48--> 13/49 $54
- add a Rev Max - Rev Box suppose to improve ignition for bottom and mid performance and rase the rev limit for $129

If you are serious about this stuff you should have a box full of sprockets and different tires for different tracks. Save your money and forget about that BS rev box. Spend the money on proper fuel that actually works above 6000 rpm.

Posted by: Spokes574---------------------

I will do the piston/porting and add the hotcam stage1
thanks for helping make a decision!
Its great to get input from someone who knows
and builds engines with experiance.

I will post the results of the mods to my bike after I test it on several tracks in the next month.

Spokes574
Pleasanton CA

Posted by: MikeS---------------------

Got to agree with Rich here 150%.. As always well said.

Posted by: Formula---------------------

With a head in hand and time during the winter does smoothing the steps where the valve guides meet the valve and where they are pressed into the head offer anything? No enlarging of ports just turn 2 steps into a smooth ramp? Call it taking out the braking bumps.

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Do Hi Comp. Pistons lower the engine reliability?

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