Yamaha WR250R Mega Thread

Discussion in 'Thumpers' started by Sock Monkey, Apr 7, 2008.

  1. NeilW

    NeilW 2-up Adventure Touring

    Joined:
    Sep 3, 2007
    Oddometer:
    98
    Location:
    Las Vegas, NV
    Well dang, hadn't thought of it that way. I guess the flip side is - when the fan is not running, the air flow through might be better. The holey shroud theory is probably right up there with those people who swap out a 190° thermostat for a 180° unit thinking it'll run cooler. The thermostat opens sooner but max cooling is not improved.

    Oddly enough, the only time my temp light ever came on was when I was on the freeway - doing about 70mph, slightly down hill so not at full throttle. I think the stock fueling is lean at less than full throttle. On the other hand, I've pulled long inclines WFO and the temp stayed in the good range. I have one of those cheesy radiator cap thermometers to help me worry about engine temp.
    [​IMG]

  2. Krabill

    Krabill Long timer

    Joined:
    Oct 25, 2005
    Oddometer:
    4,901
    Location:
    Tulsa, OK
    Many people, myself included, remove the rear shroud all together. I occasionally ride slow, tight, technical single track in 100 deg weather and have never had an overheating issue.

    [​IMG]
  3. KansasBob

    KansasBob Been here awhile

    Joined:
    Apr 27, 2008
    Oddometer:
    515
    Location:
    Topeka
    Some have found the high speed over heating is cured by cleaning the air filter. :deal

    It seems to me the actual surface area of the air filter on these bikes is much smaller than than what I'm used to.
  4. tmotten

    tmotten Lefthand ride Dutchy

    Joined:
    Jun 28, 2006
    Oddometer:
    2,502
    Location:
    Calgary
    You're one the money. Velocity is a function of orifice and volume. Increase the orifice and the velocity goes down. Not sure if this system uses a pressure regulator, I haven't studied this bike yet. But the pressure achieve in the manual can only be achieved with some back pressure either through an orifice blockage or narrowing or regulator.

    On the bm Dakar the fuel pumps are prone to fail when the tank is allowed to run dry often. The fuel is used for cooling the pump. I guess the materials in the pump overheat and expand in different ratios which would/could result in loss of pressure inside pump. This will move the duty point in and area of the pump curve that will exacerbate the situation until failure. I guess letting it cool back down would correct this, but my guess would be that key materials will fatigue early in its design life cycle.

    I'm no pump specialist, but dabbled with it a bit. Centrifugal pumps though.
  5. OldPete

    OldPete Be aware

    Joined:
    Oct 6, 2007
    Oddometer:
    5,785
    Location:
    SoSoCal
    I have to move so I can have a secure garage. My tools are in storage.
    Once move, it will be soon, an R2 will be bought. If I take the 3 month ride a new pump installed and the old unit carried.

    The KTM and Husky bikes of '08 had this same issue but fewer are sold than Yamaha and are ridden fewer miles.

    Scroll down on page 11 and continue to what he found and how he removed too much material.... http://wr250rforum.forumotion.com/t1045p200-fuel-pump-problem?highlight=fuel+pump
  6. fred flintstone

    fred flintstone Been here awhile

    Joined:
    Apr 12, 2009
    Oddometer:
    539
    Location:
    Above 7600 ft.
    That is a great thread, thank you.
  7. ba_

    ba_ Long timer

    Joined:
    Aug 5, 2009
    Oddometer:
    2,847
    Location:
    Westchester County, New York
    .
  8. Longboardr

    Longboardr Been here awhile

    Joined:
    Aug 11, 2010
    Oddometer:
    143
    Location:
    south central PA
  9. Crawdaddy

    Crawdaddy Navigate 2 Adventure

    Joined:
    Jun 5, 2007
    Oddometer:
    2,280
    Location:
    Ramona, CA.
  10. Ed@Ford

    Ed@Ford Long timer

    Joined:
    Jan 16, 2004
    Oddometer:
    1,696
    Location:
    Dearborn MI
    Look for hardware stores that have the assortments in "little drawers"...about 50% of the time they will have the washer head style metric in grade 8,8 and 10.8.....usually an M8 will be 13mm hex in the usa...but sometimes you can find M12 hex. Stainless and stock bolts are unrated so they are weaker than an 8.8....I put on 10.9 when I can get them..often times the 8.8 grade have M10 hex....but these are REAL hard to find. Look for such stuff at Tractor supply, ACE, Valu hardware sections...FORGET finding them at Lowes or Home Depot....McMaster Carr is less than 50% having them.

    Oh, yeah...in the little drawers of them, I've never found M8s longer than 60mm
  11. ba_

    ba_ Long timer

    Joined:
    Aug 5, 2009
    Oddometer:
    2,847
    Location:
    Westchester County, New York
    Thanks

    I found 10.9 in 50mm and 60mm with a 13mm head at ACE. I will try those first.
  12. Ed@Ford

    Ed@Ford Long timer

    Joined:
    Jan 16, 2004
    Oddometer:
    1,696
    Location:
    Dearborn MI
    yeah, i went with the M13 hex on a similar job on my KLR.....found m12 hex, but not enough
  13. HardWorkingDog

    HardWorkingDog Harvey Mushman

    Joined:
    Aug 20, 2009
    Oddometer:
    1,801
    Location:
    Walnut Crick, Cal.
    Those stainless steel bolts are OK (pricey), but my solution to finding longer good quality flange head metric bolts is my local Honda car dealership's parts department.

    The local Ace Hardware has metric flange bolts but they are generic Chinese crap with poorly made threads and rough finishes--not something I trust to hold critical loads or look at and feel like :puke1...

    Turns out Honda's parts numbering system for bolts is readily decoded, and they use the same parts numbers for both motorcycles and cars. An 8x55 flange bolt is 95701-0805508. High quality Japanese-made, beautifully formed and spec'd. to meet the strength needed here. Call your nearest Honda car parts department, ask for that number, if they don't have it in stock they'll get it usually the next day. I paid about $1.25 per bolt, well worth it.

    95701 = flange head bolt
    08xxxxx = 8 mm dia.
    xx055xx = 55 mm length
    xxxxx08 = thread pitch??? (less certain about this...)
  14. Ed@Ford

    Ed@Ford Long timer

    Joined:
    Jan 16, 2004
    Oddometer:
    1,696
    Location:
    Dearborn MI
    That is a great bit of trivia to decode honda bolt part #
  15. ba_

    ba_ Long timer

    Joined:
    Aug 5, 2009
    Oddometer:
    2,847
    Location:
    Westchester County, New York
    Calling now. Thanks
  16. DefyInertia

    DefyInertia Saratogian

    Joined:
    Dec 1, 2007
    Oddometer:
    153
    Location:
    San Francisco
    Lots of discussion regarding the pump being cooled by the fuel...

    For those of you that have added a heat shield when installing your aftermarket tanks, what material have you used? Perhaps you have reused the shields that came on the OEM tank? I have some of that tape that is used on HVAC systems that might help...
  17. Old_Crow

    Old_Crow Been here awhile

    Joined:
    May 4, 2010
    Oddometer:
    134
    Location:
    West Chester, PA
  18. NJ-Brett

    NJ-Brett Brett

    Joined:
    Sep 8, 2010
    Oddometer:
    6,909
    Location:
    Southern New Jersey
    Modern fuel pumps in cars and bikes have the fuel run through the electric motor part of the pump, and the pump itself. The fuel cools and lubes the parts.
    It seems crazy to run gasoline through a DC electric motor, but for some reason, they do not explode.

    Everything I ever looked at had a fuel pressure regulator outside the pump, in some cars its on the fuel rail and excess fuel returns to the gas tank. The pump runs all the time the motor is turning, and runs for a bit with key on to build up pressure. The pump can supply more fuel and pressure then the motor can use at high rpm's, full throttle, cold engine. Once fuel pressure gets past the regulator set point, it pushes the regulator open and fuel returns to the gas tank. Some cars have/had a vacuum assist on the regulator, open the throttle, vacuum goes away, fuel pressure goes up a bit.

    Bikes have the pump and regulator in the gas tank as an assembly.

    Run low/out of gas and there is no fuel to lube and cool the pump and its motor, which has a large amount of plastic in it, and the hot spot is the brushes. They tend to melt their holders.
  19. Gryphon12

    Gryphon12 Long timer

    Joined:
    Aug 10, 2006
    Oddometer:
    1,352
    Location:
    Carnation, WA USA
    It turns out the liquid gasoline isn't really as flamable as we commonly believe. It requires the right percentage of oxygen to burn. The 20.2% oxygen in our atmosphere will do it, so we commonly experience flamability. Toss a lit match in an open pool of gas, and it burns. Do the same with diesel fuel, and you get a wet match. This is why many marine engines are diesel engines. They don't catch fire as easily when bad things happen out on the water, far away from help.

    However, there are lower and upper limits (LEL - lower explosive limit and UEL - upper explosive limit) of oxygen beyond which gasoline won't burn. Too much or too little, and no combustion. (Of course, too high a % oxygen will "burn" all by itself!) A fuel pump emersed in gasoline provides no oxygen, and so the environment is below the LEL. Hence the liquid gasoline can be pumped as an incompressible fluid, and at the same time can be used to transfer heat generated by friction away from the pump, without the danger of "catching fire" in the gas tank.

    Despite this, many race cars use external fuel pumps (outside of the gas tank) for ease of maintenance and replacement. They pump higher volumes at higher pressures and have a correspondingly higher failure rate. External pumps have been tried on motorcycles, but they are usually more hassel than they are worth, given limited space to place them where they can get enough airflow for adequate cooling. The internal configuration is just more compact and easier to keep cool - as long as you don't run it dry (very often?).
  20. NeilW

    NeilW 2-up Adventure Touring

    Joined:
    Sep 3, 2007
    Oddometer:
    98
    Location:
    Las Vegas, NV
    Stock tank insulation.
    [​IMG][​IMG]

    Safari tank insulation.
    [​IMG]

    I don't think you could reuse the stock insulation. It probably wouldn't fit well even if you could get it off. I used the foil-backed plastic bubble wrap type and metal-backed tape to hold it on. It's still holding up pretty well after a couple of years of use.