Question about what cam for 03 in need of more top end

[tmcoutts9505]

I have an 2003 crf450r with stock piston and cam. I have a powerbomb header and Q silencer and my carb has been jetted for it. I run 13/51 gearing because I climb a lot of hills but when I'm on an open trails I have no top end. I was going to use either a hotcam stage 2 or stage 3 camshaft but I don't know what the difference between the too.

What are the differeces between the two camshafts?

Also, on the hotcams website it says they require mild porting.

What are the pros and cons of running one of these cams with and without porting?

[Shawn_Mc]

Youd be better off with a 13.5:1 piston and an 02 cam. But most of the culprit of your loss of top end is that muffler...

[frdbtr]

I have an 2003 crf450r with stock piston and cam. I have a powerbomb header and Q silencer and my carb has been jetted for it. I run 13/51 gearing because I climb a lot of hills but when I'm on an open trails I have no top end. I was going to use either a hotcam stage 2 or stage 3 camshaft but I don't know what the difference between the too.

What are the differeces between the two camshafts?

Also, on the hotcams website it says they require mild porting.

What are the pros and cons of running one of these cams with and without porting?

I was told by a local engine builder here that the stock 05 cam will out perform a hotcams stage 2 cam through the entired RPM range and to go witha stage 3. I haven't heard this from anyone else though. He said to go stage 3 if you do anything. The stage 2 and 3 cams from hotcams are supposed to add mid range and top end.

[oakhillbiker]

Have you ever had a smaller sprocket on the back I run a 13/45 I can climb any hill out here. I cracked my rim so I just swaped the rim with my other bike and it has a 54T and that sucks. So where do you ride out here?

[MELK-MAN]

".. the right gearing is worth thousands of dollars in horsepower"

Max Mcallister, Traxxion Dynamics.

[450XJimDirt]

Stock gearing on that should be a 13/50 , so you are killing top end from gearing down , the ONLY way you will gain it back is to go back to stock gearing or higher

A cam will not give you back what gearing takes away , not equally anyway !

[MELK-MAN]

Stock gearing on that should be a 13/50 , so you are killing top end from gearing down , the ONLY way you will gain it back is to go back to stock gearing or higher

A cam will not give you back what gearing takes away , not equally anyway !

Even going back to a 13/50 from 13/51 won't get him what he's looking for. I run 13/49 on my 04crf450 for woods and trails, and i USED to run 14/48 before i did lots of single track. THAT is the area of gearing you would need or even 45-46r if you wan't a "desert screamer" or something that will really HAUL on open trails. Problem is when you get into single track I was having to slip the clutch alot even in 1st gear.

His top speed is limited by rmp limiter, and the $$ he has in the bank to rebuild motors that get run on a rev limiter non stop ..

?

[tmcoutts9505]

Youd be better off with a 13.5:1 piston and an 02 cam. But most of the culprit of your loss of top end is that muffler...

I got a deal on the powerbomb and I got the Q muffler for free from a dealership that was going out of business. Previously I had a Yoshimura muffler and that allowed my bike to rev a little but a substantial increase of top end power. I also had the stock exhaust that had about the same amount of power on top as the Q.

[tmcoutts9505]

I was told by a local engine builder here that the stock 05 cam will out perform a hotcams stage 2 cam through the entired RPM range and to go witha stage 3. I haven't heard this from anyone else though. He said to go stage 3 if you do anything. The stage 2 and 3 cams from hotcams are supposed to add mid range and top end.

The only reason that I was going to go with hotcams is that I've found them for about $180. I saw on crfsonly that the 05 cam is the most popular cam for crf450r's.

However in one of the Dirt Bike or Dirt Rider magazines there was a comparaison between the 03, 05, and 07 I believe (I might have the exact years wrong) and the they said the 07 cam made the broadest amount of power.

Edited June 8, 2010 by tmcoutts9505

[tmcoutts9505]

Have you ever had a smaller sprocket on the back I run a 13/45 I can climb any hill out here. I cracked my rim so I just swaped the rim with my other bike and it has a 54T and that sucks. So where do you ride out here?

When I bought the bike it had 13/53 and that was great for singletrack and gnarly climbs. I put the stock gearing which is 13/49 for tracks and it took forever to accelerate.

P.S. I can climb hills with any gearing. I just like the 51 for climbing tight one line hills.

[tmcoutts9505]

Stock gearing on that should be a 13/50 , so you are killing top end from gearing down , the ONLY way you will gain it back is to go back to stock gearing or higher

A cam will not give you back what gearing takes away , not equally anyway !

Gearing just spreads out where the power is. Engine, Carb, and Exhaust modifications increase the amount of power that can be moved around.

I wouldn't be spending money on my engine if I could gain power from gearing.

[tmcoutts9505]

Any info about porting?

[XC-Kx250]

Gearing just spreads out where the power is. Engine, Carb, and Exhaust modifications increase the amount of power that can be moved around.

I wouldn't be spending money on my engine if I could gain power from gearing.

Have you ever seen dyno results when nothing is changed but the gearing?? Gearing has everything to do with how much power is put to the rear wheel. It doesn't matter if you have 100 hp between your legs if you can't put it to the ground in the most efficeint way.?

Made a boo boo here:banghead:. Hp numbers will not change with gearing, but how fast you get to the peak hp is directly affected by gearing?. I was looking at the wrong dyno sheets that I have. But the statement about how efficeint the power is put to the ground still stands.

[tmcoutts9505]

Have you ever seen dyno results when nothing is changed but the gearing?? Gearing has everything to do with how much power is put to the rear wheel. It doesn't matter if you have 100 hp between your legs if you can't put it to the ground in the most efficeint way.?

Made a boo boo here:banghead:. Hp numbers will not change with gearing, but how fast you get to the peak hp is directly affected by gearing?. I was looking at the wrong dyno sheets that I have. But the statement about how efficeint the power is put to the ground still stands.

Agreed. You are saying what I was trying to say.

[MELK-MAN]

we may have gotten off track a bit however, if i understood the original post.. He's looking for more top speed. You could have 100hp and if it is limited to 9,000rpm and the 13/51 gearing he ain't gonna go any faster top end. He will get to top speed a tad faster (if he can hook up..lol) but the final drive ratio will limit the top speed. More top speed? More gear. 14 up front, 45 out back and that bike will ROLL, but will have more time between gears and not be as friendly in tight stuff.

[tmcoutts9505]

we may have gotten off track a bit however, if i understood the original post.. He's looking for more top speed. You could have 100hp and if it is limited to 9,000rpm and the 13/51 gearing he ain't gonna go any faster top end. He will get to top speed a tad faster (if he can hook up..lol) but the final drive ratio will limit the top speed. More top speed? More gear. 14 up front, 45 out back and that bike will ROLL, but will have more time between gears and not be as friendly in tight stuff.

My cousin has an 2008 CRF450R (more overall power than an 03). He has an aftermarket cam, high compression piston, fmf powerbomb with stock muffler, and 13/51 gearing. I rode his bike the other day and his bike has major power (w/ a top end that almost rips your arms off.)

Summary: More power, same final drive.

Once again I agree with the gearing theory but Im seeking more power on the top end hence the new top end with cam. After I have the top end rebuilt, if I'm still not satisfied I will change the gearing.

My question isn't about obtaing more top-end via gearing. My question is which camshaft to use and whether or not to port the head and what are the benefits and risks of doing so?

[MELK-MAN]

My cousin has an 2008 CRF450R (more overall power than an 03). He has an aftermarket cam, high compression piston, fmf powerbomb with stock muffler, and 13/51 gearing. I rode his bike the other day and his bike has major power (w/ a top end that almost rips your arms off.)

Summary: More power, same final drive.

Once again I agree with the gearing theory but Im seeking more power on the top end hence the new top end with cam. After I have the top end rebuilt, if I'm still not satisfied I will change the gearing.

My question isn't about obtaing more top-end via gearing. My question is which camshaft to use and whether or not to port the head and what are the benefits and risks of doing so?

Final drive gear does not affect hp, the readings on the dyno would be the same. Speed IS affected by final drive gearing.

Others in the know would need to direct you on cams and porting.. There are plenty of places that can do it, but usually only a FEW shops that KNOW what they are doing. Do lots of research. Your cousins bike sounds awesome. Just keep in mind that more lots more hp.. less reliability.

[Shawn_Mc]

My question is which camshaft to use and whether or not to port the head and what are the benefits and risks of doing so?

You can make more power by just porting the head. But with Porting the head and a better cam you can make much more power. RHC has some fuel injected bikes now making 70 freakin HP....

There really arent any risks to the top end, its the crank that you need to think about and how fresh it is.

Its all got to work together. It really depends on what you want to do with it and how much money you want to spend.

A lower dollar combo that works well is the 13.5:1 Piston with the 02 cam. The stage 1 cam is a shorter duration cam and the combo makes huge bottom end power without really loosing on the top. But the 02 cam will get you bigger top end power ( more from 9500-11000) without such a huge bottom end punch. But still plenty down low.

Do a search on cam and porting. Boil up a pot of coffee and start reading....

[tmcoutts9505]

You can make more power by just porting the head. But with Porting the head and a better cam you can make much more power. RHC has some fuel injected bikes now making 70 freakin HP....

There really arent any risks to the top end, its the crank that you need to think about and how fresh it is.

Its all got to work together. It really depends on what you want to do with it and how much money you want to spend.

A lower dollar combo that works well is the 13.5:1 Piston with the 02 cam. The stage 1 cam is a shorter duration cam and the combo makes huge bottom end power without really loosing on the top. But the 02 cam will get you bigger top end power ( more from 9500-11000) without such a huge bottom end punch. But still plenty down low.

Do a search on cam and porting. Boil up a pot of coffee and start reading....

I have no intentions of building a race motor. All I want is more power on top without losing the current bottom. I'm using a stock compression wiseco piston becasue I got it for $100. As for the crank, I'm sure its in good shape because I know the previous owners and they never rode it. Maybe 10 hours when I bought it a year ago. I will have the builder inspect it and let me know if I need to replace anything.