Does this look stock?


50 replies to this topic
  • TheHarp

Posted January 15, 2010 - 07:37 AM

#21

this is going to get expensive with a new head and all of this otherstuff.....you need to decide if it is worth the cost. How much did you spend on this bike if you don't mind me asking? I hate it when sellers sell crap like this....


It doesn't appear to need a new head. He's going to fix up the porting the best he can...otherwise it's in good shape.

I bought the bike in December '08 for $4500. On simple inspection, the bike looked brand new. Once I got it home and started tearing it down I noticed that it had been prettied up for sale...new bodywork and painted engine side-covers. I was disappointed, but learned a lesson.

The good news is that it ran very well all season...ran it hard at the supermoto and roadracing tracks. So, basically, what we have now is a bike that has been run hard for two seasons and needs to be freshened up. The only real issue is with the crappy porting job.

  • NJDirtdog1

Posted January 15, 2010 - 02:46 PM

#22

Yeah that looks awfully scary, i would go find out from whoever did it what the hell they were thinking.

  • TheHarp

Posted January 15, 2010 - 04:13 PM

#23

Engine tear down complete...not bad for my first time. The real challenge will be putting it back together, I'm sure.

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  • TheHarp

Posted January 28, 2010 - 03:49 PM

#24

Ask him what the stock head flows on his bench.


A new/fresh stock head will flow around 190 CFM. Mine was definitely not fresh and not stock and flowed 188. After some work on the flow bench, Franc (Lyons Technical Machining) was able to get it to 221 CFM.

He also found that the exhaust port had been modified (more mindless grinding). He welded up the floor to get the flow back up from 143 to 161CFM.

I can't recommend Franc enough. He did a great job and took the time to show/teach me a bunch of stuff. Give him a call 503-430-5638. He's in Aloha Oregon.

Intake:
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Exhaust:
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  • grayracer513

Posted January 28, 2010 - 03:54 PM

#25

And this turned out to be a pretty good example of how easy it is to loose power by "porting" a head if you don't now what you're doing.

  • delmas

Posted January 28, 2010 - 05:00 PM

#26

If Ron Hamp has seen this, he is probably still vomiting at this moment. Or laughing. Or shaking his head in disbelief.

The bad part is that the 3 valve intake port is very easy to modify incorrectly and actually reduce the power output significantly. A really good head shop could correct it, even if it means material needs to be added back, but the first thing out of your mouth when you take it in should be, "I did not do this..."


I just threw up my self .that is nasty

  • harrperf

Posted January 28, 2010 - 05:16 PM

#27

IMHO the guy who first ported it just "touched" it up...and didn't really change anything on the intake.

As was said above, 188 is very very close to 190...and every head flows a little different.

Pictures dont always look pretty, so I dont want to say it looks horrible!

Your bike should run very, very well now!

  • TheHarp

Posted January 28, 2010 - 06:29 PM

#28

IMHO the guy who first ported it just "touched" it up...and didn't really change anything on the intake.

As was said above, 188 is very very close to 190...and every head flows a little different.

Pictures dont always look pretty, so I dont want to say it looks horrible!

Your bike should run very, very well now!


Yep...not a lot of damage was done...hard to say if the original porting job did any good at all, but likely not much. For the previous owner's sake, I hope he didn't pay much for that work.

I'm looking forward to getting it back together and back on the track. :ride:

  • usp4u

Posted January 29, 2010 - 04:46 AM

#29

It would appear that those flow tests were done at 25" of water. I wonder why that is ? Most Superflow bench test are done at 28" of water. I'm sure there's a reason that I don't know. Anyhow, 221cfm is outstanding. I never would've guessed you could that much flow on a dirtbike head. I would suspect port volume is one of the keys to these engines making the power they do.

To put that 221 number in perspective: I have a $2000 set of Indy heads with about $1500 worth of CNC porting on a small block Mopar that flow 335cfm at 28" of water on a SuperFlow. So, 221 on a dirtbike head to me sounds AWESOME.

  • TheHarp

Posted January 29, 2010 - 07:10 AM

#30

Not sure on the 25 vs. 28" of water question. You could always give Franc a call to find out.

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  • usp4u

Posted January 29, 2010 - 08:37 AM

#31

ehh, I'm sure there's a darn good reason. it's not important though. I must need to read up things a little more b/c i'm still suprised that these heads can flow 220cfm. Pretty cool. But, I was taught a long time ago, port volume is where power is made the easiest.

  • grayracer513

Posted January 29, 2010 - 11:30 AM

#32

It would appear that those flow tests were done at 25" of water. I wonder why that is ? Most Superflow bench test are done at 28" of water. I'm sure there's a reason that I don't know. Anyhow, 221cfm is outstanding. I never would've guessed you could that much flow on a dirtbike head. I would suspect port volume is one of the keys to these engines making the power they do.

To put that 221 number in perspective: I have a $2000 set of Indy heads with about $1500 worth of CNC porting on a small block Mopar that flow 335cfm at 28" of water on a SuperFlow. So, 221 on a dirtbike head to me sounds AWESOME.

Ron Hamp's YZ450 heads flow even better, and a 4 valve head will ultimately flow even more.

Keep things in perspective when keeping things in perspective, too. The bore size, which ultimately determines the limit of the port sizes, is not much different between a 350 cid (5.7L) Chevy small block and a YZ450 at 95mm vs. 101.6 for the Chevy, so the head has potential in spite of the small size of the engine overall.

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.

  • usp4u

Posted January 29, 2010 - 01:36 PM

#33

Gotcha.

This discussions has also got me wondering: On the '10 with it's "intake forward" configuration, I wonder if there is any oppurtunity for additional tuning by playing with runner length. Although, while I havent seen a '10 in person I would guess the location of the air filter precludes any modification lengthwise.

  • grayracer513

Posted January 29, 2010 - 02:15 PM

#34

Gotcha.

This discussions has also got me wondering: On the '10 with it's "intake forward" configuration, I wonder if there is any oppurtunity for additional tuning by playing with runner length. Although, while I havent seen a '10 in person I would guess the location of the air filter precludes any modification lengthwise.

There is such an opportunity, but there was before, too. If you look at the inside of the air boot of a YZ450, you'll see it includes an intake horn of a specific length. The air filter on the new ones limits this in the same way that the old design did.

Bear in mind that harmonic tuning of the intake tract is possible, and is effective, but works within a pretty narrow range. In a dirt bike, it's usually more important to spread the power over as wide a range as possible. According to some people I've talked to the YZF intake is close to optimal length as it is.

  • TheHarp

Posted January 29, 2010 - 02:38 PM

#35

Ron Hamp's YZ450 heads flow even better, and a 4 valve head will ultimately flow even more. ...


Just to be clear, the flow on mine wasn't maximized -- the primary goal going in was to fix it. The time that I was willing to pay for was limited severely by my budget.

Any idea how much more these heads can flow? Are you aware of any charts from RH's heads?

  • grayracer513

Posted January 29, 2010 - 03:24 PM

#36

You might look at his web site. I don't have any numbers on flow that I'd be able to quote reliably, but I do know that one of his engines was one of the first YZ450's to legitimately produce more than 60 HP without a displacement increase. He's put lots of work into them, and the head has been the limiting factor right along.

  • TheHarp

Posted January 29, 2010 - 04:52 PM

#37

You might look at his web site. I don't have any numbers on flow that I'd be able to quote reliably, but I do know that one of his engines was one of the first YZ450's to legitimately produce more than 60 HP without a displacement increase. He's put lots of work into them, and the head has been the limiting factor right along.


OK...since you said that RH's heads flow better, I assumed you had some idea of what they flow. :ride:

Just giving you a hard time. :lol:

  • rcripper

Posted January 29, 2010 - 05:01 PM

#38

make sure u put a new camchain while your in there, cheap protection! and maybe a new top end, at least a bore hone and ringS~!

  • TheHarp

Posted January 29, 2010 - 05:14 PM

#39

New rod, piston, rings, and cam chain are waiting to be installed.

  • motojase316

Posted January 29, 2010 - 08:21 PM

#40

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.





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