Big CRF mods but bad results

[Slippery]

I Have a CRF 450R 06.

I bought a Athena big bore kit, Hotrods stroker kit and a stage 2 Hot cam for my engine. I also fitted an FMF 4.1 factory titanium exhaust system. The engine capacity is now 510cc.

The parts have been installed and the bike was tuned on the dyno. But I have not gained more than 2 hp from stock. And this is from a dyno that is known to run high figures. The main jet went from a stock 168 to a 175. The 42 pilot was not changed. The result was 49 hp at the wheel.

After asking lots of questions it seems timing may be the issue. This would come from 2 things. The hot cam (not likely but possible) and the barrel that came with the big bore kit. If the barrel is slightly taller or shorter than stock it will alter the cam timing. This was not checked before installation.

After taking the bike out for the day I realized it was more powerful when it was stock. It was very disappointing after the effort that had I had put in.

Upon advice I have received so far, the only thing that can help me know for sure that I am on the right track is an adjustable cam gear. But I can not find one anywhere.

So if anyone knows who sell adjustable cam gears for CRF's, or you think there are other possible reasons to my problem, please help me. I have only ridden my bike once in the last 5 months :bang:

 

[Pete Payne]

Web Camshaft sells an adjustale gear I think .
Did you do a before and after dyno run ?

 

[Slippery]

Unfortunately I didn't get that chance. I stripped down the engine to clean it out after drowning the bike in 8 feet of water. It just seemed like a good opportunity to do the upgrade.
The stock hp estimate comes from tuners experience and Eddie Sisneros from thumpertorque.

Thanks mate.. I will look up web cams.

 

[Slippery]

Web Camshaft sells an adjustale gear I think.

Mate your a champion. I found it. Thanks heaps :cool:

 

[whenfoxforks-ruled]

I thought I recall Eric was going to buy some of Athena's cylinders and fix them for resale. If you still have issues give him a call and ask how much to fix it. His 450 head mods, you would not need an overbore! http://www.eric-gorr.com/

 

[Pete Payne]

Yeah , I installed an athena 490 kit on a customers 450 , It was an 05 . Did the before and after. It only gave it like 1 hp . I will see if I can dig up the dyno .

I seem to have way better results with a high comp piston and a web camshaft .

 

[Ol'89r]

Did you do a before and after dyno run ?

Bingo. :cool:

Pete hit it on the head. You can't determine the degree of improvement on a dyno unless you do a pre-run and then a post-run after making the improvements, ON THE SAME DYNO. Also, if it was a rear wheel dyno, did you use a knobby tire for the test? Knobbys tend to slip on a dyno and don't give a true reading. Put an old worn out street tire on for the next test and you may see a difference.

A big bore and stroker will usually improve the torque in an engine but it can kill the top end rpm and HP. If you had been able to take a reading on the dyno before taking the engine apart you may have noticed a big difference in the torque reading but not so big of a difference in HP. An engine built for torque has to be geared and ridden different than an engine built for HP. Try gearing the bike taller and short shifting in the lower gears to keep the bike in the torque range. This is where the meat of your power will be.

It is also critical to degree your cam in and check all of the clearances between the piston and valves when setting up an engine like that. A few degrees the wrong way can result in bent valves. Webcam does have the adjustable cam wheels and I believe Megacycle cams does also.

Just my $ .02

 

[whenfoxforks-ruled]

Surprised whoever set up the head did not tell you that you need one,or put one on.

 

[Rich Rohrich]

So if anyone knows who sell adjustable cam gears for CRF's, or you think there are other possible reasons to my problem, please help me. I have only ridden my bike once in the last 5 months :bang:

You can fiddle with the cam timing till you are old and gray. Unless you found a way to move around 20% more air through the existing cylinder head, all you are going to do is move the torque peak around, and shift around the area under the torque curve.

You can make incredibly fun power with big displacement and restricted airflow. The engines have a lower rev ceiling and tend to last a lot longer. It's a good combination for most riders. As Ol89r pointed out, it just takes a slightly different approach to riding it.

If your goal is just to see a big number come up on the dyno you need more AIR to move in and out of the engine. There is no getting around that. Cylinder head flow is the key to making power at high rpm with big displacement.

One last thing, the spec for the Stage 3 Hot Cam is much closer to what you need. The lobe centers and lift profile are a much better fit for for a big displacement engine.

 

[1989kx250]

i cant say for sure whether this is your problem or not but i was told not to use a stroker kit with my athena kit but i forget why...... might be no help but just throwing it in there.

 

[spark250]

are the estimated numbers you have rear wheel numbers?

Also it really doesn't make a difference there are so many factors that need to be documented and controlled in dyno runs.

Unfortunately your current numbers really mean nothing!

 

[adam728]

Just chiming in with what the others said about the dyno not meaning much. Numbers vary so much from one to another that it can only be used for a comparison, ie - run your bike before and after on the same dyno and compare the numbers.

On another forum a user did a dyno run with a YZ250 bored to a 285. People were greatly disapointed in his 46 hp peak, saying that stock bikes make that much. But his before run was only 42 hp if I remember correctly. So, the 46 hp number didn't mean anything overall, but it was great as a comparison to stock to show that he gained 4 ponies.