XR440 kit

Discussion in '4-Stroke Discussion' started by Trailryder42, Aug 3, 2001.



  1. Trailryder42

    Trailryder42 Rookie DRN Member

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    Hey all,
    I was advised to ask Eric Gore if he has an XR440 kit. Anyone know? I rode Cuzs' 440 this last weekend and it rocks. I guess Thumper Racing has a kit? Thanks for any info.


  2. High Desert XR400

    High Desert XR400 Subscriber

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    Powroll

    Hey Trailryder42,
    Check out Powroll, They have a couple different set-up for the XR400 and seem to be reasonable in price. www.powroll.com/honda_XR400.htm
    Good luck and keep us posted!;)
  3. xrsforever

    xrsforever Rookie DRN Member

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    My son has a 440 kit,and I have an 280 kit from Thumper.We both have been very happy. Largest single improvement you can do to an XR.Don't forget the SUSPENSION.:cool:
  4. Trailryder42

    Trailryder42 Rookie DRN Member

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    Powroll offers the kit in either 10.5:1 or 12:1 compression. Question: does it go: the higher compression ratio you run, the higher octane fuel required? or the other way around? What would be the assets and tradeoffs of one over the other? Thanks.
  5. DualSportr

    DualSportr Rookie DRN Member

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    The higher compression, the higher octane required.

    With 12:1 you'll have to run straight, leaded race fuel - at least 110 octane.

    Another option is the 415cc bore kit. This will create quicker reving power than the 440 kit, and some riders like it better. The 440 kit is best for torque and smooth power. The 415cc for rpm and quick power.

    In a drag race on pavement, the 415cc kit will beat the 440cc kit. But in mud, the 440 kit will be better.

    Hope this helps you out a little!
  6. Trailryder42

    Trailryder42 Rookie DRN Member

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    Thanks guys.
  7. Rodzilla

    Rodzilla Lifetime Sponsor

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    Hey Derek,

    Check the XRs only website they have several different kits to punch out your XR. You may consider doing the valves and such while the jug is apart. I think I remeber Eric Gorr replying a Fellow DRN rider saying that going through him would be cheaper. But I may be talking out of turn on that.

    I'm looking at the 430 kit as opposed to the 440. I hear you don't have to resleave with the 430 (again I'm not positive)

    Looks like I'll be splitting cases this winter to replace my shift shaft so I might have Eric do a 430, port and valve deal on my 400 as well.

    Let me know what happens

    Rod
  8. SFO

    SFO Lifetime Sponsor

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    The 400 is another motor that likes Stainless exhaust valves.
    If you are popping it apart for a big bore, you might consider dropping good valves in it.
    You will notice that your valve lash will require less attention.
  9. Rich Rohrich

    Rich Rohrich BioHazard

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    Keep in mind the MON (or motor) octane rating of the fuel is the significant spec in this case. There are a number of race fuels with high overall octane numbers (> 100) but a large gap between RON and MON octane ratings. High RON rated fuel without comparable MON rating is fairly useless in an air cooled XR.

    PJ - Don't forget to remind these guys that the (MON) octane the engine will require is dependent on the CR and the cam they are running, specifically how late the intake valve closes. The later the intake valve closes the lower the MON octane required (all else being equal). Running a 12:1 CR with the stock XR cam run (at stock lobe center angle) will generate very high cylinder pressures and an enormous amount of heat and in my opinion it's not a good idea regardless of the fuel you are running. It's not a coincidence that Honda matched a relatively low stock compression ratio with the stock early intake close timing. :)

    Trailryder - Unless your rides are short and the engine only sees light loads it's best to be conservative with the CR on these engines and make sure you match the compression ratio and cam timing carefully. Don't forget it's still an air-cooled engine :)
  10. DualSportr

    DualSportr Rookie DRN Member

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    This kit leaves the stock liner VERY thin.

    Not recommended for long piston life.

    Rich, right as always - sometimes I just don't like to get that involved unless asked - I talk too much anyway (or should I say type too much!).

    ;)
  11. Rodzilla

    Rodzilla Lifetime Sponsor

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    See this is why I spend time here. It reveals my ignorance.

    So what you're saying is go ahead with the 440 as it will, in the long term, provide a better lifespan?
  12. mtngoat

    mtngoat Lifetime Sponsor

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    I visited and chatted with the XRs Only crew last month and they were pretty hot on their 430 kit, which doesn't require the sleeve. They've always been pretty forthcoming with pros and cons of different approaches and didn't "con" the 430 solution because of thin walls. It'd be worth investigating that option and asking them IMHO. I know it's not the same since Al Baker passed away, but they still seem to have competent and honest staff.

    I also recommend against very high compression. The XRs already run very high head temps and commonly "embrittle" valve seals causing them to smoke at start-up.
  13. Wolf

    Wolf doooode

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    I am extremely interrested in this thread.
    Since I have not been very successful at selling my xr I may keep it and go to one of the above mentioned options. I wasn't sure I wanted to sell to begin with...
    I am looking for a little more in order to have a chance at staying at least midpack at the starts, and have a little more snap out of corners in order to be able to clear some of these jumps that you don't have much time to set up for. Top end is of no significance to me since I am used to not having any to begin with. If any of this rambling made any sense, wouldn't that mean that by the above posted descriptions of the kits, the 415 would be better suited for me??
  14. Rodzilla

    Rodzilla Lifetime Sponsor

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    "The XRs already run very high head temps and commonly "embrittle" valve seals causing them to smoke at start-up. "

    Yep, experiencing it now.

    Rod
  15. SFO

    SFO Lifetime Sponsor

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    I must confess, I can't figure out how a brittle valve seat would create smoking on start up.
    I have seen high head temps on air cooled motors, turbocharged drag bikes and single cylinder rotaxes.
    What I have seen is valve seats lose concentricity to the guide in high heat situations.
    Also I have seen valve seats fall out. Putting new seats in a rotax head we would use .008-.010" interference, or press.
    One or two mile races on a rotax and check your leak down.
    The new liquid cooled stuff is nice because the heads keep a valve job longer.
  16. mtngoat

    mtngoat Lifetime Sponsor

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    That's seals, not seats. If I remember right, the valve seals are akin to plastic. I'll find out this winter when I pull the heads off my XRs for valve jobs. Might be sooner on one though, it's smoking real bad at start-up.
  17. SFO

    SFO Lifetime Sponsor

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    Like I'm a dummy.
    Seals make a lot more sense.
    Feel so stupid now.
    You could check the guides as well, KMPI makes great ampco 45 guides that transfer heat better than the stock iron ones.
    They are more difficult to size, requiring honing, instead of the oem reamers.
    The results I believe are worth the effort.
    They also make one piece stainless valves for this bike that will outlast the oe ones.
  18. DualSportr

    DualSportr Rookie DRN Member

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    Okay, let me apologize in advance - this will be a long one, but I wanted to answer a few different points brought up here.

    Yes, or do the 415cc kit.

    I'm going to stick my neck out here - but here goes --
    XR's Only has always relied on derivative technology - they don't design most of their products, but purchase them from other sources. Because they're not actually designing the product, they don't really know its limitations as well as the company that initially produced the kit.

    They are very nice people. I like them very much. They are able mechanics, but I don't think I'd put them in the same class as a technician who designs and tests this stuff.

    If you want to, ask them what the sleeve wall thickness is at the bottom of the sleeve after the 430cc kit is installed. If they can't answer this question quickly, then they have no way of knowing whether the sleeve thickness will be a problem or not.

    A stock engine will do the same thing - it's not really the heat that does them in - but the motion of the valve travelling up and down. Higher lift cams will cause this to happen much more quickly, and those will cause head temps to drop.

    I do agree the high comp is not good for most applications. Especially trail riding.

    Yes, the seals are made of a rubbery plastic material, with a metal retaining spring. If the engine only smokes at startup, it's definitely the seals. If you want your seals to last, use brown ones, or green ones.

    If you purchased a gasket kit which includes stem seals, if they're black, throw them away and purchase the seals separately (they'll come brown or green that way). The black ones don't work at all.

    BTW, for those of you who are used to doing valve jobs on automotive stuff, you might not know this;

    On ALL Japanese motorcycle engines, the valves are stellite coated, and can't be ground! Even lapping them in more than a few strokes will cut thru the hard coating and you're back where you started. We've seen brand-new engines with cupped valves because they were over-lapped at the factory.

    Cut the seats & grind the seats only.

    Of course, the solution to this problem is Stainless Steel valves!

    It depends on your weight - if you're under 200 lbs, I'd go for the 415cc kit. If you have the extra cash laying around ($1,500), do a cam, hardfaced rockers, valve springs, an FCR carb and a 3 angle valve grind. This is really a pretty neat setup for motocross (but still not a YZF beater :( ).

    The 440 produces more torque than the 415, but the 415 realizes the power much more quickly.
    Last edited: Aug 6, 2001
  19. High Desert XR400

    High Desert XR400 Subscriber

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    PJ you never cease to amaze me!!! Powroll definitely gets my vote!
    When I have "the extra cash laying around" I know where I'm taking my motor.;)
  20. DualSportr

    DualSportr Rookie DRN Member

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    That's kinda what my husband says - actually, it's more like "it's amazing that you can spend that much time on the computer when the house is a wreck!" :confused:



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