06-08 intake cam differences


10 replies to this topic
  • tribalbc

Posted August 20, 2009 - 10:05 AM

#1

I have an 07 WR450 that I race in Hare scrambles. The bike has a 08 YZ header and can with PMB SA and silent insert to meet 96db's as well as all free mods.
I'm looking for more torque off the bottom to mid. Or maybe just a stronger pull everywhere. I'm not looking for a hit, I like my smooth power for the tight gnarly stuff. Just more of that deep old school 4 stroke grunt.
I've been told the hot ticket is the 06 YZ intake cam with a high compression piston. Since I will be swapping the piston out this winter anyways I thought I'd give this a try.
I'm not interested in swapping out the exhaust cam for the YZ for estart issues and Hot Cams because I'm not really into spending the $'s.

So if I'm correct the intake cams on the YZ's were different through these years. Which intake cam do you think would best suit my needs ?
Or do I just go with the Hot Cams intake for an extra $20 or so ?

  • grayracer513

Posted August 20, 2009 - 11:13 AM

#2

The '07 WR has less lift and a milder, less aggressive grind on both cams than the YZF does, and both of them should be replaced in order to accomplish what you want.

With the YZ450, the cam grind itself has changed very little through the years. The timing and lobe center offset has been changed 3 times from the original '03-'05 version, each time becoming more aggressive, and more biased toward top end power. The '03-'05 cam set will probably produce the most low end of the 4 versions available, but I think the '06 set will give the best power overall, with very good low middle range, and a clean pull past the peak. The '06 WR used the same intake as the '06 YZF, with a more advanced exhaust.

The '07 and '08-'09 YZF's each used progressively more aggressive timing, and each produces about one HP more peak power than the previous model, with a moderate penalty in the lower mid range. I don't have what I consider dependable numbers on the new cams vs. the '07, but with a good pipe, the '08 feels stronger through the middle than the '07 does, and is stronger at peak, so I have the feeling that cam set is "split timed" (different lobe center offsets on each cam).

The '06 YZ450 cams are PN's 5TA-12170-10-00 (intake) & 5TA-12180-10-00 (exhaust).

IMO, if you want a big power improvement over your stock WR, and low-mid power is important, the '06 cam set is your best choice.

  • tribalbc

Posted August 20, 2009 - 11:23 AM

#3

Thanks for your help :thumbsup:

My problem with using both cams is the loss of e-starting with the decompression pin difference on the exhaust cam. Most people that have done the switch of both cams have lost their e-starting capabilities.
I'll try just the intake for now and see how it goes.

So you don't think it's worth bothering with the Hot Cams intake ? It isn't more aggresive ?

  • grayracer513

Posted August 20, 2009 - 11:38 AM

#4

The stage one is roughly the same as the stock YZ450 cam. I don't know that much about the stage two's.

Using only an intake cam upgrade won't yield the power increase that it should because getting more AF into the engine doesn't help much if you can't get it out for the next intake cycle. Remember that the difference between the WR and YZ for several years was the exhaust cam only.

I don't see why the e-start shouldn't work. The pins are different, yes, but that's to compensate for the different timing. Which specific YZ exhaust cams have been reported to cause this?

  • 123BigcoopDawg576

Posted August 20, 2009 - 11:48 AM

#5

Which specific YZ exhaust cams have been reported to cause this?


On the 07+ WR it seems to be any 06+ YZ exhaust cam is causing issues.

See here:

http://www.thumperta...ight=yz exh cam

http://www.thumperta...5&highlight=cam

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted August 20, 2009 - 12:19 PM

#6

OK, from reading that, the YZ cam will allow the engine to actually crank more easily than the WR cams do. I very much doubt it's an issue of inadequate compression, because if that were the case, it wouldn't kick start well, either. In fact, it would be more likely to e-start than kick start. More probably, it is a matter of the valve timing being too aggressive for the engine to want to run at that low a speed, although my own YZF has started several times with ridiculously little input from the kick starter.

If you wanted to experiment, you could carefully trim a smidge off the decomp pin to raise the cranking compression. Be careful, though, undoing that would be at least difficult.

I will tell you that at least the YZF does not like anything in the exhaust while starting, so the comment regarding the stock muffler may have some merit.

It may just be a matter of rejetting for the cams, too, or simply tweaking the starting routine a bit by cracking the throttle very slightly, using the hot start, priming differently, etc.

  • 123BigcoopDawg576

Posted August 20, 2009 - 12:29 PM

#7

If you wanted to experiment, you could carefully trim a smidge off the decomp pin to raise the cranking compression. Be careful, though, undoing that would be at least difficult.

I will tell you that at least the YZF does not like anything in the exhaust while starting, so the comment regarding the stock muffler may have some merit.

It may just be a matter of rejetting for the cams, too, or simply tweaking the starting routine a bit by cracking the throttle very slightly, using the hot start, priming differently, etc.


How about I buy the 06 YZ cam and you can help me get it to work...you are in San Diego so meeting up shouldnt be a problem :thumbsup:

  • tribalbc

Posted August 20, 2009 - 08:36 PM

#8

This is from the Hot Cam website


Can I use the 4022-1E Hot Cam for the YZF450 in my WR450 or YFZ450?
No, the 4022-1E and the 4044-1E cams have the identical cam profile. The only difference is the decompression pin height. The pin height is shorter for the engines with electric start. The electric starter will not turn the engine (with stock compression) over fast enough to build enough compression to start.

So I guess you were right Greyracer that you would have to trim down the pin a bit. But how much is the question ?

Do you think the HC piston would help at all with the e-starting by building more compression :thumbsup:

  • grayracer513

Posted August 20, 2009 - 08:59 PM

#9

Maybe. An HC piston would raise the cranking compression.

As to trimming the pin, it would be interesting if Hot Cams would tell you how much different their two pins are. If you grind it yourself, try to shorten it enough to have it seat the exhaust valve 5 degrees sooner and then try it before grinding further. Also, retain the ball shape, keep the finish smooth.

  • tribalbc

Posted August 21, 2009 - 06:37 AM

#10

Thanks again :thumbsup:

  • grayracer513

Posted August 21, 2009 - 09:44 AM

#11

The idea that the pin needs to be shorter to give the engine more cranking compression for an electric starter to work seems counter-intuitive, but that may be the case. The idea that you can turn the engine over more forcefully than the starter motor seems backward at first blush, but I suppose it could be true.





Related Content

 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.