Fact or Myth


30 replies to this topic
  • 2grimjim

Posted January 01, 2012 - 08:47 AM

#21

That's the reason people start referring to as widening or narrowing the lobe centers. It gives a picture of what you're doing, whichever cam you do it to.

How much confusion do you suppose the reversed port head on the Gen3 YZ450 is going to cause people when they see the lobe position at TDC?


That's funny! I can only imagine!:bonk:

  • 2grimjim

Posted January 01, 2012 - 09:00 AM

#22

I found a totally box-stock '09 YZ to do a little dissecting on. Can get my hands on it next week. Curosity is killing me! Would like to pop the head off too and see how much the port volume changed but I don't think that's gonna happen. Makes me wonder if they went back to a similar port as the 5TA-00 casting used on the '03-'04 YZ's and '04-'05 YFZ's.

  • grayracer513

Posted January 01, 2012 - 09:18 AM

#23

Don't know. I do know that one of the top tuner/builders in the country, Ron Hamp, never got the YZ450 to produce significantly more than 60 HP at the stock displacement until the '08 head was available. His port work on his National flat track engines (podium grade, BTW) has never been stock, of course, and he's gotten considerable gains from piston shape. But with the latest head, he was finally able to reach unexaggerated rear wheel outputs in the 64 HP area.

  • 2grimjim

Posted January 01, 2012 - 09:40 AM

#24

Don't know. I do know that one of the top tuner/builders in the country, Ron Hamp, never got the YZ450 to produce significantly more than 60 HP at the stock displacement until the '08 head was available. His port work on his National flat track engines (podium grade, BTW) has never been stock, of course, and he's gotten considerable gains from piston shape. But with the latest head, he was finally able to reach unexaggerated rear wheel outputs in the 64 HP area.


I know that 5TA-00 casting has better airflow potential than the 5XD-00 that replaced it '05. The 2S2-00 ('06-'07 YZ) head has port volumes almost identical to the 5XD casting.

I have seen some flattrack YZ builds (from Ron Wood) that were making 70 HP with the early YZ head. I assume they were the 5TA-00 casting. But these YZ's had some major port rework, repossitioned carb spigots and I don't think they were stock bore/stroke configuration either (60.3x97?).

I was always under assumption that the only significant change to the 2S2-10 casting was to accomidate the larger exhaust header....now I know different.

  • grayracer513

Posted January 01, 2012 - 10:12 AM

#25

I've seen claims of 70 HP gasoline powered 450cc YZ450's before, and inasmuch as I have also seen Ron Hamp's 62-63 HP bikes pull away from them, I have to agree with his position that such claims are somewhat exaggerated. In any case, inertia dynos are more a comparative tool than an accurate measuring device.

The three valve intake port is extraordinarily difficult make good sense of in an engine running at the upper extreme limit. It's advantage is in providing high flows at low lift and in making high strung engines more civil at lower rpm while still allowing good top end. But the layout has significant handicaps at very high speeds. One of the factors that usually gets overlooked is the "terminal flow" of the intake; what goes on in the combustion chamber as the air charge enters, what with two ports blowing around the sides and one right down the middle. That's where Ron's work with combustion chamber and piston crown shapes has paid off for him.

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  • 2grimjim

Posted January 01, 2012 - 11:26 AM

#26

The three valve intake port is extraordinarily difficult make good sense of in an engine running at the upper extreme limit. It's advantage is in providing high flows at low lift and in making high strung engines more civil at lower rpm while still allowing good top end. But the layout has significant handicaps at very high speeds. One of the factors that usually gets overlooked is the "terminal flow" of the intake; what goes on in the combustion chamber as teh air charge enters, what with two ports blowing around the sides and one right down the middle. That's where Ron's work with combustion chamber and piston crown shapes has paid off for him.


The castings as they come from Yamaha do have a lot of shrouding around the intake ports (the area closest to the seats in the cumbustion chamber) and adding a HC piston with a dome only compounds the problem with its convoluted shape. This was addressed somewhat on the 2S2 casting with its more open combustion chamber but not 'till after they adopted a smaller intake similar to the 5XD casting the year prior(?) in their quest to make the power more civilized. Going to a larger bore and shorter stroke can help a bit by moving the cylinder wall farther from the valve, but that opens up another can of worms.

  • 2grimjim

Posted January 20, 2012 - 05:37 PM

#27

Ok, here's the scoop on YZ450 cam profiles. ALL '03-'09 YZ450's have the SAME lift and duration (as far as I can tell with a degree wheel and dial indicator) and appear to be a symmetric profile.

I checked the lift, duration, lobe center, and decomp pin stats for the following cams;
5TA-00 intake ('03-'05 YZ and WR)
5TA-10 intake ('06 YZ/WR, '06-'09 YFZ)
5TA-10 exhaust ('06 YZ)
2S2-00 intake and exhaust ('08-'09 YZ)
5TJ-10 exhaust ('03-'05 WR)
5TG-00 exhaust ('04-'05 YFZ)
4023-1IN Hot Cams
402-1E Hot Cams

I will be checking a set of '07 YZ cams, GYT cams, and a set of '07 WR cams in the near future.

All of the OEM cams listed above had a lift of 8.61mm intake and 8.43mm exhaust and all had a duration of 244 degrees intake/exhaust @.050" lift. The only difference that I found was with the 'lobe centerline'.

The '06 YZ cams had an LCA of 106.5 degrees intake and 104 degrees exhaust (for a lobe seperation angle of 105.25 degrees)

The '08-'09 YZ cams had an LCA of 102.5 degrees intake and 99.5 degrees exhaust (for a lobe seperation angle of 101 degrees)

The '03-'05 YZ intake had an LCA of 109 degrees.

The WR and YFZ exhaust had an LCA of 126.5 and 127.5 degres, respectively and an LSA of 117.75 and 118.25 respectively.

For a good explanation of what these numbers mean, go to Web Camshafts site http://www.webcamshafts.com/ and click on the menu in the left side titled "Degreeing in Your Cam".

Edited by 2grimjim, January 20, 2012 - 05:39 PM.


  • Mbirt

Posted February 08, 2012 - 02:15 PM

#28

Any update on this? I'm curious how the '07 WR (5TJ) cams check out. I've got my eyes on an '08 YZ intake cam on ebay right now and I'm curious if it's worth the $50. Below is a dyno run with the exhaust cam retarded a tooth.
Posted ImageOpening the intake valves earlier should take more advantage of the work we've done in exhaust tuning and increase dynamic compression ratio after the valve closes (sooner). It's definitely not out of breath at the (stock) limiter, so an improved power peak could come from closing the intake valves sooner.

  • YZPaGuy

Posted February 09, 2012 - 03:49 PM

#29

OK, just so you four guys know, this website runs in an english version! All this spanish is not comprehendable by the rest of us! LOL

I wish I knew this much about an engine, better yet I wish I was a good enough rider to be able to tell the difference!

  • Mbirt

Posted April 14, 2012 - 07:51 AM

#30

This just in: the 07-11 WR (5TJ) profile measures only 7.6 mm lift on the intake cam.

Gray, It would be nice to have a more concise "5-valve Yamaha Cam Data" sticky to make cam information from 2grimjim, you, and others easier to find.

  • Geoffit

Posted April 14, 2012 - 06:04 PM

#31

These cam numbers are pretty much what I have found , any of the 450 engines retiming the stock cams will do the trick. That being said changing the timing of the Yamaha cams is not a job for the inexperienced . Just buying a cam and dropping it in is the way to go for most. Yamaha has been mellowing the 450s every year since 03. Mainly through cam timing , porting and ignition timing, one of the best set ups for a faster harder hitting bike is the 06 + bike with 03 cams and ignition box . Great for flat track and super moto a beast for trails. The great thing about these bikes is their parts interchange. From 03-09 most of the easy to change parts will swap out letting you Tailor them to suit your needs.





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