The XR400 Thread

Discussion in 'Thumpers' started by Hayduke, Jan 16, 2008.

  1. dlock5

    dlock5 Been here awhile

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    Do u have a link ?, because when I search that part number it came up as a honda st1100 carb part.
  2. hughrk

    hughrk Been here awhile

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  3. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

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  4. dlock5

    dlock5 Been here awhile

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    I guess I should be able to heat it up and stretch it out to fit the carb, because the 250 carb is like 32 or 33 mm right?
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  5. Stretch67

    Stretch67 Mad Scientist Supporter

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    Old glass coca-cola bottles are handy for that sort of thing.
  6. saltyD

    saltyD Been here awhile

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  7. JMo (& piglet)

    JMo (& piglet) Unicorn breeder

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    That dimension is the throttle body side (ie. to the inlet manifold) - there is every chance the side from the airbox to the carb is the same diameter as the 400 as that side is bigger on the 400 carb too.

    Either way, there is only 2mm difference between the carb sizes [36mm vs 34mm], so if the proportions are the same the boot ought to stretch.

    Jx
  8. Jeff B

    Jeff B Socially Awkward

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    I suppose one could be 3D printed. :hmmmmm
  9. Johnnyboxer

    Johnnyboxer Long timer

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    Only way, just checked at my local Honda dealer and no stock of carb to airbox boots for
    XR400R or XR250R
  10. shinyribs

    shinyribs Thumpers for life

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    You can get high temperature silicone at hobby shops. A two part mix that you pour in to a mold. The catch is you've got to have a mold. You can cast a mold off your old intake boot. If there's any chips, cracks or tears you can fill then with something like clay before casting the mold.

    It's not as hard as it sounds, but it's a process that takes time. For defunct things, it's a lifesaver.

    Lots of old rubber parts could be saved with a careful hand. If you can disassemble things without stressing the material you can boil the rubber in a pot of water with a spoonful of wintergreen oil. I tell one friend all the time, " We could've repaired that if it wasn't destroyed", to which he always replies that " it was bad anyway". :fpalm

    It rejuvenates rubber like you wouldn't believe. I did a set of carb boots for a '76 CB750 once. Three years later they were still pliable. Smelled minty, too :)
  11. dlock5

    dlock5 Been here awhile

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    Babbitts still has the 250 connector ill try that for 50 bucks
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  12. bork

    bork Been here awhile

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    I've been wanting to do this to a bunch of old stuff. How long did you boil it? Did it over swell ? then let it sit and shrink back some? I see the average price is a bout $7.00 an once. You say a spoonfull with a gallon is right? (tablespoon or tea spoon?) 2 tblsn = 1oz. BTW sounds deadly if the oil is taken by mouth, especially the youngins.
  13. shinyribs

    shinyribs Thumpers for life

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    I don't think you can over boil it. I think it ends up being a judgement call based on how thick/dense the items are. For a set of four carb boots I boiled them for 1 hour. Above a simmer but not a hard, rolling boil.

    You need to do it outside, though. The smell is VERY strong and will not leave your house for months. Trust me.

    Also, you need to be careful not to let the parts hit the bottom of the pot where they can get burned. A folded up dish cloth in the bottom of the pot works good for this.

    Wintergreen oil is toxic if ingested. Just be careful to wash your hands and utensils afterwards, but it won't ruin your cookware. It will wash out.

    I didn't see any swelling or shrinking. I had some parts that didn't stay soft for very long. It's my understanding that the oil needs to penetrate the rubber to do it's thing, so I started boiling it for longer and longer periods of time. I think the longer you boil the longer lasting the results will be, but since I never saw and shrinking or swelling, that's why I'm not sure it's possible to over do it.

    After I was getting the hang of it, Chinese boots showed up on eBay for $30 for a set of 4. I couldn't be bothered to boil boots anymore :lol3
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  14. bork

    bork Been here awhile

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    Thanks!!!!!!!
  15. shinyribs

    shinyribs Thumpers for life

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    No problem man. I noticed I missed some things you added. $7/oz sounds insane! Must be the essential oil folks jacking the market. I paid $20 shipped for this 16 oz bottle about 8 years ago. Maybe their prices haven't gone nuts.

    If you can't find a decent price and want to experiment with it, shoot me a pm and I'll send a pill bottle or something your way with some oil in it.

    Some guys had luck finding it at their local Walgreens, also.

    IMG_20210921_214849992.jpg
  16. bork

    bork Been here awhile

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    Hmmm interesting. Maybe its the essential in the oils jacking the price. Thanks again! (re-searching)
  17. dlock5

    dlock5 Been here awhile

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    So I put a performance cam in and it doesn't utilize the Auto decomp. What parts would I need to add the manual decompression system back?, the PO took it off so I don't have any of the parts. Thx
  18. shinyribs

    shinyribs Thumpers for life

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    You will need a handlebar lever ( it's like a smaller clutch lever) and a cable. The cable will hook to a lever on the right side of the engine at the valve cover. I bet that part is still there since it's not easily removed.

    Get ready though, because those levers aren't real easy to find. eBay will be your best bet. I'm pretty sure 250 and 350 decomp levers/perches all interchange, but don't quote me on that. Check part numbers first.

    Word on the street is you can use a CRF 450 clutch lever assembly that has a small additional lever originally intended for a bit start ( a carb function the XR doesn't have), but I didn't have great luck with that. The CRF setup didn't offer enough leverage to operate the decomp. It'll do in a pinch, but for the sole way to do it I thought it was pretty difficult. And I've got a pretty strong grip.

    Btw, what cam did you get?!
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  19. dlock5

    dlock5 Been here awhile

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    Stage 1, and thanks
  20. shinyribs

    shinyribs Thumpers for life

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    Love hear what you think of that cam. I was really surprised how the bike respond to it. Good luck!
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