The ground up yz/wr/xt/tt adventure build

Discussion in 'Thumpers' started by yamahaman, Oct 27, 2010.

  1. yamahaman

    yamahaman wannabe bike builder

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    So After the sewing back to the real work I have fabricated a bash guard with a 2.5L (85 Oz) water container on the side bit rough becaue Its been a few months since I have welded aluminium .
    Not entierly happy with the profile/shape a bit boxy,square and low at the front but it will protect the motor from any damage wile I am testing and jetting.

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    :1drink:1drink:1drink
  2. yamahaman

    yamahaman wannabe bike builder

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    So I have been hunting around for a replacement carb and had heard a few guys had fitted raptor carbs to xt's and some had fitted Kawasaki ex250 carbs (250 Ninja's) I couldnt get my hands on a raptor carb for a reasonable price so I had a look at a ninja carb and it worked a treat on my bike. I have been having a hard time trying to get the jetting right and the bike would not idle at all so I just went to a conventional carb setup (not a big fan of the primary and secondary carbs being seperate)

    These are just fairly standard vacume operated carbs I found some info over on thumertalk that because the ninjas rev to 14000 and ours only rev to 7000 or what ever it is the 105 mains they come with should be close to being correct.

    So how hard was it? Super easy on the custom manifold I had made for the original carbs I just brought a tube expander set home from work and expanded the tube ends to the same diameter as the carb bell mouth and fitted a short piece of turbo hose and some hose clamps. The rest just fitted in no problems. Its actually easier to fit the new carb in the frame space.

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    The only tricky part was the cable set up I had to cut and weld the cable hanger because I wanted to reuse the xt cables. I put two cuts in the plate and basically swapped them over and re welded them back together. This picture shows them being tacked in place before welding. You can see the top piece was originaly in the middle and the middle piece was on top just a quick shuffle and all good works perfectly. quick grind when I was finished and a paint.

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  3. BIG ED XT FAN

    BIG ED XT FAN Long timer

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    Thanks for posting!! :deal Looks super easy to fit. :lol3:lol3
  4. thumpthumpthump

    thumpthumpthump Thumpthumpthump

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    I just posted some questions on the regular xt thread before I read this one. How well do the ninja carbs fit the inlet manifolds? The 84-89 are both the same size, but the 90-95 have different sizes . the right side being larger. I put 86 carbs on my 90 by using two left side inlets. Both 86 carb outlets are the same. How about the ninja carbs? How does the choke cable work out? thumpthump
  5. yamahaman

    yamahaman wannabe bike builder

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    I just used a throttle cable in the choke mechanisim with the plastic bend at the carb end and it is loose at the bars at the moment because I havn't figured that part out yet.

    But it rides really well and I am happy with the power so far and I havn't started to jet it yet.
  6. JagLite

    JagLite Long timer

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    Nicely done! :clap
  7. thumpthumpthump

    thumpthumpthump Thumpthumpthump

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    Sorry but I am still a little confused. The carb to head manifolds are different sizes on the 90-95 xt. The left is smaller than the right. The holes on the head are the same but the rubber is different. The older 84-89 have the same size left and right. And these are the same as the left side of the 90-95 xt. I would imagine that the ninja carbs are the same size left and right. Thus the ninja carb would fit the stock 90-95 xt carb to head manifolds differently. As far as the carb to air filter boots or runners I am using pods anyway, so not an issue. The 90-95 cable bracket is on the left , and the 84-89 carbs are in the middle of the carbs so I just moved the cable over. Other than being on the right side what requires the cut and rewield of the bracket. I know you are getting questioned to death but I am not happy with the stock carbs and just want to get my ducks in a row before I pull the trigger and order some ninja carbs. Thanks, thumpthump.
  8. yamahaman

    yamahaman wannabe bike builder

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    Yeah right it must be so close that I didn't notice a size difference and I did notice I had to loosen one of the band clamps off more than the other but it did push on to the motor fairly easily and the clamp did do up fine.

    I don't think it will be much of a problem though. I have been riding mine and it does not seem to be a problem. Will run the verniers over the original carbs tonight and see what I get.

    :1drink:1drink:1drink
  9. yamahaman

    yamahaman wannabe bike builder

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    I measured the engine side of the carb an the left hand side is 37mm and the right hand side is 38.5mm. I didn't measure the ninja carb but as I said earlier it did push on easy on the right hand side and the left was marginally tight so I think that ninja carbs are around the 37mm on both sides. Hope this helps

    :1drink:1drink:1drink
  10. thumpthumpthump

    thumpthumpthump Thumpthumpthump

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    Great , thanks for clearing that up. Well I guess I'll get some ex250 carbs and figure out the air pod connection and the cables. How is the top end power? Going from the stock air box to K&N pods and upping the main gave my xt a big power rush at high RPM that the stock air box would not allow. Going from A 135 and a 130 main jet to 2 105s seems to be much leaner. They are both the same brand carb and the jet comparison should be apples to apples.
  11. steveloomis

    steveloomis Been here awhile

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    This is an interesting thread about updating your carbs. Please keep us posted as to what jetting you wind up with. I am sure many are watching and can benefit from your work.

    I am impressed with the expertise shown here, machining skills are impressive as well as just good engineering, it is not wrong to build on other's engineering success. Really improves the breed.

    Steve
  12. yamahaman

    yamahaman wannabe bike builder

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    They are not the same brand and I dropped the needle (leaner) on the old carb and got better low to mid range power and my plug and pipe were still sooty black and would not make power wide open.

    :1drink:1drink:1drink
  13. JensEskildsen

    JensEskildsen Long timer

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    I've also fitted ex250 carbs on my 2003 xt600e.

    The pilot jet is around #38 stock, i've drilled mine to 0.45mm, in an attempt to get rid of a small lean surge swhich comes as you get on the gas just after idle. Otherwise 0.40 should have been fine. I just think the taper on the needles are slightly of for my bike.

    I've raised both needles around 0.80mm as I recall, and have fitted #116-ish mainjets (from memory). My bike has oversize headers, aftermarked exhaust, and opened up airbox, and aftermarked airfilter. Perhaps I could go down a couple of numbers on the mains, dont know for sure. Stock seemed slightly lean with snorkel removed from airbox.

    The carbs bolted in quite easely, both fitted nicely in the intake rubbers, and the right airbox-to-carb-hose fitted aswell. The left was too small, so i used a larger hose, squized over the original hose coming from the airbox.

    Both gascables was rerouted, and was bolt on the new carb.

    I made a chokecable from an universal car handbrake-cable.

    Hope it all makes sence.
  14. thumpthumpthump

    thumpthumpthump Thumpthumpthump

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    Great info guys! Very glad this is do-able. What issues do you think I will have running just K&N air pods. CV carbs are not supposed to like unrestricted air flow. I was thinking this was the problem with my current setup due to the CV secondary carb. I got so much more power at full throttle with the air pods I would hate to give it up. What altitude you at Jens?
  15. JensEskildsen

    JensEskildsen Long timer

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    Sealevel :)
  16. Francesco2

    Francesco2 Adventurer

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    Hey Yamahaman! Can we have an update on this yz/tt/xt bike? I'm on the point of buying a yz250 '04 rolling chassis to match my tt600 frame and engine. Can you give a good comparison regarding the handling/riding your hybrid?

    How does is steer/ handle? and whats the final weight of this? I'm curious, and gathering good reasons to start a similar maniac build :evil
  17. yamahaman

    yamahaman wannabe bike builder

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    I am really happy with the build there are a few drawbacks though.
    1. 90's Xt motors don't have any snap to loft a front end of a fully loaded bike so I have had a few scary moments. Especially at speed
    2. The low motor in the xt/tt frame setup with yz long travel suspension causes it to case out all the time and I have had my feet swept off the pegs on numerous occasions.
    3. Dual carb setup is a pain in the arse I have a ninja carb on it that has been heavily modified this made it smoother to ride with a marginal power increase.

    Having said that it's a great bike that has taken me on some awesome trips and be taking me across the Simpson desert later in the year. Having done more enduro riding/racing my emphasis is on the dirt not really on the road work so maybe I didn't choose the correct platform to start with but watch this space I may have a ktm 625 in the pipeline to build. This is a never ending process and what I have learned on this bike will be brought forward to the next bike and the one after that too.

    What year is your tt ? if it's one of the later ones with the alloy swing arm I wouldn't bother fitting the yz arm just the forks. I know the motor will not fit in the yz frame because I tried and without major structural rework you can't fit the battery or carbs in

    Good luck post me any time and I will help out where I can

    Cheers
    :1drink:1drink:1drink
  18. yamahaman

    yamahaman wannabe bike builder

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    Well the bike has had its graduation
    My riding buddy and I smashed a 4328 km round trip in 9 days and crossed the Simpson in two days would have been a day and a half if it hadn't of been for some annoying delays it would have easily been a day and a half. (four flat tires and a cracked rack, neither mine)
    :1drink:1drink:1drink

    keep posted for a full ride report and photos
  19. JagLite

    JagLite Long timer

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    Excellent!
    I look forward to reading the full account. :clap
  20. a1fa

    a1fa Throttle Jockey™

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