Big Bore or High Comp.


14 replies to this topic
  • wacker boy

Posted November 03, 2006 - 04:14 PM

#1

I am looking to get somemore low end power with out losing a lot of topend. I already have the hotcams set up in and running a 14-46 sprocket ratio. what i am asking is what is some of the differeces between the to.

  • baha

Posted November 03, 2006 - 04:36 PM

#2

I am looking to get somemore low end power with out losing a lot of topend. I already have the hotcams set up in and running a 14-46 sprocket ratio. what i am asking is what is some of the differeces between the to.

14/46 is a 3.23
14/50 (stock)3.57
13/46 3.53
13/50 3.84

Go back to stock?

I always change out counters for what I am doing on any given day and it is part of my chain adjustment.

I loosen the back up and slide the rear tire forward I can change a counter in a minute and adjust the chain all in the time you adjust your chain.

I have a 13.14.15 and know they make a 12. Desert 14, Woods 13, SM 15

I also have a 51,50,42 rears- not as easy to change. RMC Final drive steel makes this affordable as well. All of these will fit both my bikes.

  • Alley Cat

Posted November 03, 2006 - 08:08 PM

#3

I am looking to get somemore low end power with out losing a lot of topend. I already have the hotcams set up in and running a 14-46 sprocket ratio. what i am asking is what is some of the differeces between the to.

The high comp piston will boost power everywhere.
The bigbore kit will boost torque, boost bottom to mid as well as some top, but generally fall off very quickly.

I went High comp piston route simply due to cost. I also got some hotcams because I was looking for heaps more top end. They haven't arrived yet, I am looking forward to installing them.

If I had more money (always the story...) I would have loved to get a big bore kit. I say since you already got hotcams, go the big bore kit! :mad:

  • MountainMax

Posted November 04, 2006 - 07:06 AM

#4

is the hotcams intake cam very different then our stock ones? i changed my exhaust cam with a yz one for more power but the intake is the same on the YZ. I was also told that high compression will help out more on the bottom end then top end, and i too would change that back sprocket back to a 50 unless youre doing alot of high speed continous driving, that will give you more power also.

  • Alley Cat

Posted November 04, 2006 - 09:40 PM

#5

is the hotcams intake cam very different then our stock ones?

Yes I believe it has more lift and duration most likely more.

Here is the hotcam intake cam specs, I can't find the stock specs.
Intake
Intake lift (mm): 8.86
Intake lobe center (degrees): 110
Intake duration (degrees at 1mm): 269
Intake valve lash (mm): .15

Here is gains over YZ cam set up:
http://www.hotcamsin...58693831348.jpg

Is it worth it. I don't know yet! :mad:

  • Alley Cat

Posted November 04, 2006 - 10:45 PM

#6

I am looking to get somemore low end power with out losing a lot of topend. I already have the hotcams set up in and running a 14-46 sprocket ratio. what i am asking is what is some of the differeces between the to.

What exhaust are you using?

A different header (longer) might do you nicely, such as a FMF powerbomb or megabomb. They will (if you get sx version) move power lower in the rev range.

I guess out there in the desert, you wouldn't want to go to a 50 rear sprocket.....

  • SID013

Posted November 05, 2006 - 04:05 PM

#7

I am looking to get somemore low end power with out losing a lot of topend. I already have the hotcams set up in and running a 14-46 sprocket ratio. what i am asking is what is some of the differeces between the to.


Hiya, When I want to play around with sprocket ratios I have a look at the [COLOR="Blue"]gearing calculator[/COLOR] spreadsheet on this website. I have found it great. :mad: http://www.4strokes.com/tech

Hope it helps.

Cheers from Oz.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • griffithds

Posted November 06, 2006 - 06:08 PM

#8

Hiya, When I want to play around with sprocket ratios I have a look at the [COLOR="Blue"]gearing calculator[/COLOR] spreadsheet on this website. I have found it great. :mad: http://www.4strokes.com/tech

Hope it helps.

Cheers from Oz.




Great site! Thanks for the post.:mad: :mad: :worthy:

  • R_Little

Posted November 06, 2006 - 06:24 PM

#9

The 444 kit on my wr400 is crazy fast!

  • Birdy426

Posted November 06, 2006 - 07:10 PM

#10

Big bore makes lots more power, but the rev is a little slower. It still revs out, but it gets there a tad slower. I abso-freakin'-lutely love the power of my scooter with a 13.5:1 444 cc kit and Hot Cams intake and exhaust cams. The power isn't as "smooth" as a stock WR...it's got the bottom end of a WR, the mid-range hit of a YZ426, and revs out like no other. The only down side is the 13.5:1 piston requires race gas...

  • Alley Cat

Posted November 06, 2006 - 08:38 PM

#11

The only down side is the 13.5:1 piston requires race gas...

That is a big point right there. I know JE pistons make a 13:1 for oversize bores, that might not require race gas. I went with a 12.8:1 (stock 12.3) for my bike for this exact reason.

  • wacker boy

Posted November 07, 2006 - 03:55 PM

#12

Well guys thanks for your in put. I think i will go with the athena 478 big bore kit and a port job due to the fact i dont want to run race gas.Who would you guys recommand to do a good port job?

  • Birdy426

Posted November 07, 2006 - 09:41 PM

#13

Eric Gorr's Forward Motion did mine. Great work. Engine Dynamics has a good rep as well.

  • Fullbore4

Posted November 18, 2006 - 10:48 PM

#14

Yes I believe it has more lift and duration most likely more.

Here is the hotcam intake cam specs, I can't find the stock specs.
Intake
Intake lift (mm): 8.86
Intake lobe center (degrees): 110
Intake duration (degrees at 1mm): 269
Intake valve lash (mm): .15

Here is gains over YZ cam set up:
http://www.hotcamsin...58693831348.jpg

Is it worth it. I don't know yet! :cheers:



According to my Service Manual the stock intake cam has 8.65 mm lift.

  • MountainMax

Posted November 19, 2006 - 11:42 AM

#15

Hehe, looks like about 2 HP over stock YZ, not as much as i thought, although it does hold it to a higher rpm....




 
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