08 YZ450F Supermotard on roadracing tracks...what would you do?


13 replies to this topic
  • TheHarp

Posted February 11, 2009 - 06:15 PM

#1

I picked up a good-condition used '08 450...completely stock. I've done the conversion to supermoto (wheels, brakes, gearing), but I'm wondering if there are any engine tuning adjustments I should have done to allow it to run well and survive longer on big/fast tracks?

Any advice appreciated. Thanks.

  • MuDPoUNdeR

Posted February 11, 2009 - 10:20 PM

#2

depends on what you mean by engine tuning ... how much money are you willing put in the bike? If you want more power from the bike then ...

Basics are a full pipe set up and suspension work. After that Head work, like porting, cams, big bore, etc... , Then you can look at possible carb work. Their are a million different things you can do ... All it costs is money though ... haha

  • Geoffit

Posted February 12, 2009 - 06:43 AM

#3

The Yamaha makes a good roadrace engine, the oil system is the best of all the 4-strokes and the standard valve train holds up well. Get the Graves crankcase breather system and you are good to go. as for more power a pipe and re-timing the stock cams give the best bang for the $$

  • TheHarp

Posted February 12, 2009 - 10:13 AM

#4

Thanks guys...not looking for more power...yet. I don't want it to blow chunks going down the long front straight at PIR.

Any suggestions regarding cam timing?

  • DRX350

Posted February 12, 2009 - 10:16 AM

#5

My best recommendation would be to run engine Ice, and to run fully synthetic oil. Jet it real Fat too.

  • grayracer513

Posted February 12, 2009 - 12:17 PM

#6

Any suggestions regarding cam timing?

The '08 already has a high RPM bias to the valve timing as it is. I don't think I'd fool with it that much. Also, remember that changing the timing on the exhaust cam changes the timing of the auto decompression pin, and too much uncorrected change can have a negative effect on its operation.

My best recommendation would be to run engine Ice, and to run fully synthetic oil. Jet it real Fat too.

Engine Ice is an effective coolant, and I use it myself, but water actually cools engines better than anything else as long as you stay below the boil point. I mention that in this case because many organizers of Super Moto events prohibit the use of anything other than water in the radiators.

Jetting an engine excessively rich will not keep it cool. Four-strokes run best under power at around 13.5:1, are truly stoichiometric at 14.7, and can cruise happily at as lean as 16:1 or leaner for long periods with no problems at all. The myth that rich mixtures promote cooler engines comes mostly from the two-stroke world, where a leaner mixture necessarily means less lubricant as well as less fuel. Engines running at full power at leaner than about 15/15.2:1 are at some risk of promoting detonation, which will indirectly raise the temperature, which aggravates the detonation problem further, and so becomes a kind of self-feeding problem. Nevertheless, 4-strokes are far more tolerant off sub-optimal jetting than 2-strokes.

For a guide to determining what your jetting should be, read this, by Eddie Sisneros:

http://www.thumperta...699#post2881699

  • DRX350

Posted February 12, 2009 - 12:40 PM

#7

Yeah, I figured as much.

I meant an A/F ratio of about 14.0:1. 14.7 is always the golden number, but I've have good luck at a heavier ratio, especially when running race gas. But then again, I race older machines too. I haven't blown up a motor yet though.
(emphasis on yet)

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  • grayracer513

Posted February 12, 2009 - 01:01 PM

#8

14.7 is "golden" in the sense that it's stoichiometric, meaning that there is the chemically exact proportion of both fuel and air for complete combustion. But as you note, you do get better power under full throttle situations at a slightly richer ratio, generally between 13.5 and 14:1. That is partly just because of the inherent inefficiency of the whole internal combustion process.

What my post was trying to convey is that there is a pervasive belief that running an engine rich is some kind of path to safety, and it really is not. It can, in fact, actually be bad for a four-stroke.

  • DRX350

Posted February 12, 2009 - 01:15 PM

#9

Yup, Gotcha!

  • swatdoc

Posted February 13, 2009 - 02:18 AM

#10

here's how i did my catch cans for supermoto. having the oil return to the motor automatically is nice - one less thing to mess with

http://www.thumperta...6654&highlight=

  • TheHarp

Posted February 13, 2009 - 09:35 AM

#11

here's how i did my catch cans for supermoto. having the oil return to the motor automatically is nice - one less thing to mess with

http://www.thumperta...6654&highlight=


Thanks for this! I bought those parts, but haven't installed them yet.

Also...thanks to the other guys too. Good advice, all around.

  • stk0308

Posted February 15, 2009 - 06:41 AM

#12

here's how i did my catch cans for supermoto. having the oil return to the motor automatically is nice - one less thing to mess with

http://www.thumperta...6654&highlight=

I saw that Graves system online and wondered how it works. Thanks! Now to figure out how to get it to work on my 426. :lol:

  • swatdoc

Posted February 20, 2009 - 10:24 PM

#13

No Prob - i see the pic of the setup on the Graves website shows the oil return line going back into the ignition cover with no one-way valve like I put on mine. Must work OK, so it's even easier than my setup. Nice they have a mounting bracket too, even though the one I made wasn't difficult.

  • grayracer513

Posted February 20, 2009 - 10:45 PM

#14

The one way valve is a nice touch, though.





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