Does this look stock?


50 replies to this topic
  • grayracer513

Posted January 29, 2010 - 09:43 PM

#41

I tend to doubt that, but it's easy enough to find out by removing the carb and seeing what the installed air box and filter will flow at 25". I think you'll be surprised.

If you build the engine far enough, eventually it will start to matter, but you have to go quite a ways for that.

  • usp4u

Posted January 30, 2010 - 05:35 AM

#42

this is a good thread

  • usp4u

Posted January 30, 2010 - 05:44 AM

#43

If you build the engine far enough, eventually it will start to matter, but you have to go quite a ways for that.


Indeed. Food for thought on the airbox comments: The 450 quads airboxes are larger than on the bike, but not THAT much larger in terms of volume. A couple engine builders (A.T.P./RAGE/DASA/BALDWIN) that specialize in quads have legit 62-64hp motors running completely stock airbox set-ups.

  • motojase316

Posted January 30, 2010 - 08:19 PM

#44

I tend to doubt that, but it's easy enough to find out by removing the carb and seeing what the installed air box and filter will flow at 25". I think you'll be surprised.

If you build the engine far enough, eventually it will start to matter, but you have to go quite a ways for that.


To be honest, i rode the bike with HC piston and port mods and stock air box then ran it on dyno and after with modded aribox and i could not tell any difference.

Just thought I would throw it out there anyways.

  • harrperf

Posted January 30, 2010 - 08:28 PM

#45

The use of 25" rather that 28" is a realistic adjustment to make for the big difference in the bore stroke ratio of the two engines. In the Chevy, the stroke is 87% of the bore, whereas in the YZ450, it's only 67%. The YZ is 27.68 cid, and the small block is 43.75 per cylinder. Although the operating speed of the engines are enormously different, the piston speed, and because of that, the strength of the vacuum on the intake stroke is much higher at any give engine speed with the longer stroke. By using 25", it gives a more representative look at the dynamic realities involved. And anyway, as long as the same vacuum was used in any two measurements, they're comparable.


Gray....I will be brutally honest and say I feel your talking out of your ass on this one!!!!

Peak vacuum in EITHER engine is WELL over 28 inches of water!!!

If I could (and eventually I will after a millon vacuum motors) I would flow 100 inches...

The latest trend in the auto head market is 55 inches.

Odds are they guy isn't quite getting a full 28 inches of vacuum at peak lift on the bench and rather than correct up, is just correcting the rest to 25....or it's just a typo... Heck a lot of flow numbers published are not tested at a true 28 inches of water. 300 cfm at 28 inches of water is quite a bit of power needed in the vacuum motors...and not a lot of mx geared benches get it (most all car benches do)

In either account, 221 is capable of producing very, very good power! and this bike should be tons of run.

The 5 valve design head IMHO can flow more than a 4 valve head. It's one reason it was invented. Now that doesn't mean the YAMAHA head will flow more than developed honda head, due t castings and spacings etc...but the REAL reason 4 valve heads have "reigned surpreme" is combustion chamber shape and development.

The 5 valve head is easily competitive in flow...

It is also much better in a design standpoint for valve life, as evident by the past yamaha reliability on BOTH bikes...each valve is lighter, and has less surface area to attract heat and thus require to cool. All plusses. But sadly the piston design and combustion chamber shape are not ideal as compared to a 4 valve motor.

Not to call you out gray, but that's my take on the whole deal.

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  • TheHarp

Posted January 30, 2010 - 08:39 PM

#46

A local MX dyno tuner in my area says the 06 to 09 airbox will hold back the flow increases achieved through the porting improvements. Back on my 2008 Yamaha yz450f we ran a Cycra powerflow rear fender and had holes through the side of the airbox for the increased demand. might be worth a look.


The Graves Factory supermoto team (when it existed) opened up their air boxes:

Posted Image

  • grayracer513

Posted January 31, 2010 - 04:29 PM

#47

The 5 valve design head IMHO can flow more than a 4 valve head.

Feel free to explain how.

  • Cobra150R

Posted February 08, 2010 - 12:41 PM

#48

If you know anything about Superflow flowbenches you know that the standard for the SF600 (600 CFM) and higher series benches is 25" testing pressure. The 1020 has the ability to operate at above 50" (lots and lots of motors). This is generally done with higher flowing big port automotive heads.

Some of the bike head builders tend to use the 110 or the 120 series benches because of the cost. These benches do not flow the amount of air (CFM) that a current 450 head will. Therefore air correction must be done from 10" or 15" measured pressure to 25" to be comparable. Not to say they are not reasonably accurate but I tend to like the idea of flowing the head within the true range.

Flowing at too high a test pressure for the head's flow capability causes rapid heating of the air and unless you have a computer to do the air temp correction you will lose consistency and burn a lot more energy through the bench motors.

As was stated in another post, the most important part of testing and proving results is that the work be performed on the same piece of equipment and same settings. Although I have tested bike heads on my SF600 with Flowcom and a friends SF1020 for comparison and the numbers are within a couple of percent.

There are claims of big flow numbers out there and having done a lot of work on Yamaha heads I can tell you that to get well above 220 Intake CFM you have to start removing material from the main port section and that affects port velocity. I generally try to produce a head that will meet the airflow demands of the engine in a given operating range, type of use (torque vs high RPM) and the customers budget.

Just adding info, Interesting thread.

Harp I would be willing to test the airbox if you are curious. :ride:

  • TheHarp

Posted February 08, 2010 - 03:41 PM

#49

Harp I would be willing to test the airbox if you are curious. :ride:


Thanks, but I don't want to take it off again right now. It's time to break this bad boy in. :lol:

  • husqy360

Posted February 08, 2010 - 04:03 PM

#50

The Graves Factory supermoto team (when it existed) opened up their air boxes:

Posted Image



it does look better, but i wouldnt use it off road :ride:.

  • mediumfast

Posted February 08, 2010 - 08:30 PM

#51

Looks like he did it while blind folded and/or drunk. That looks terrible.





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