The XT350 thread

Discussion in 'Thumpers' started by Burtonridr, Sep 26, 2007.

  1. kaisan

    kaisan n00b

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    Just got a new xt350 for my son for Christmas.I traded a boat for it.The guy said it needed a carb kit.I took his word for it.
    Didnt start when I got it.
    Got the carb kit istalled.Tried to start it(good compression,fat spark,air filter off.I just get a pop or backfire out the exaust once in a while.No change if I drop some gas in the head??
    Please give me some ideas,?timing off,rings??Im lost.
    Thanks Jim
  2. Lenz1

    Lenz1 Been here awhile

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    GD whats the big difficulty in setting the float heights ?

    I just pulled the primary off, removed the bowl, tipped the carbie upside down and carefully fixed it in an approx level position. A vise is fine if you're careful what is being gripped ie only grip non critical casting protusions.

    The manual says to adjust at the central "tang" that touches the end of the needle/seat but a central adjustment approach does not correct easily for floats that are at different heights :

    The carbie should be inverted to lightly close the needle/seat.

    Leave the central tang alone and adjust each float height individually by using two needle nose pliers and bending the float plate at the outer 90° arm of the plate. To do this, use one clamp / pliers to hold the float plate steady at a point central of the 90 then the other pliers to very carefully bend the outer leg of the float plate to adjust the float ht. The correct distance is 26mm +/- 2.5mm from the top of the now inverted float to the metal face that mates with the bowl. Best tool for the measuring is a digital caliper using the central slide protusion.

    Since the secondary doesn't have a float then it's just one side to mess with as far as float level.

    The reason for adjusting the floats individually is to ensure they both end up at the correct height - attempting to take out any dislevellment between the two floats with a central adjustment would require minute twist of the central tang - too hard.

    Fuel level also is easy with a clear plastic hose off the bowl drain port. Carbie on the engine, carbie level front to back. Adjust the central tang for correct fuel level after the float height adjustment.

    Simple is good
  3. kwakbiker

    kwakbiker Been here awhile

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    Whats the condition of the rubbers from the carb to the head, common failing point and causes issues
  4. Grreatdog

    Grreatdog Long timer

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    If you think setting the float height with the bike level, the carbs installed and assembled using a clear plastic hose is simple then you a lot more patience than I do.

    Every time you make a float height adjustment you have to pull the float bowl off, do a litle bending, reassemble the carb, put the tube back on, remeasure, disassemble again, adjust again, reassemble again, test with the tube again, repeat until you get it right by closing in on the right setting by pure guess work.

    To me, anything that requires such a healthy dose of pure dumb luck to get right is not simple. My two KTM's, my Honda, my Kawasakis and my other Yamaha are and were all simple workbench measurements. No tubes, no guesswork and no working with the carbs installed. That is simple. The YDIS way is just plain stupid.

    Don't use raw gas. Besdies being dangerous it is a good way to hydrolock the piston. There is almost no squish space for liquid in there. Do yourself a favor and buy a can of starting fluid. You are going to need it with that YDIS carb. Just whiff is all it takes.

    I have said this several times in this thread. a gummed up YDIS carb is very hard for a home mechanic to clean without an ultrasonic cleaner. After mine was stolen and left in some woods for a year I got it to what I thought was surgical clean and it wouldn't run.

    I took it to a shop and a few hours in the ultrasonic tank cleared it up.
  5. kaisan

    kaisan n00b

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    Yah brand new carb rubbers,Plug is wet with gas,but just doesnt want to fire.Even took the exaust off figured it was pluged.
    What else could I check?
  6. StuartL

    StuartL n00b

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    Are you getting air?
  7. LanaTheGreat

    LanaTheGreat Adventurer

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    I just spent an hour of my life trying to upload a picture of the XT350 toolkit, just to see at the bottom that I cannot post attachments. Any reason for this? Mods?
  8. kaisan

    kaisan n00b

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    Tried with the filter out.
    When I kick it I just get the odd loud bang out the exhaust.
  9. Grreatdog

    Grreatdog Long timer

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    Use a hosting site.
  10. Lenz1

    Lenz1 Been here awhile

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    GD - the float height adjustment is absolutely a workbench measurement procedure.

    The manual advises the primary carbie be removed from the engine and inverted with the bowl removed prior to checking / adjustment of the float height (hard to measure the float heights without the bowl off) The implied outcome from the manual is that setting the float height correctly will produce the required fuel height of 6mm +/- 0.5mm below the metal face of the carbie body.

    My take on this is the fuel height measurement is a prior test to see if there is a problem either with the needle/seat not sealing (slow flooding ?) or the floats are not at the correct height. Just adjust the floats individually on the bench as I described a little earlier, get them spot on and unless you've got a faulty seal at the needle /seat the fuel level will be correct.

    So the question must be asked - what is the reason or trigger for a float height adjustment ? In my case I didn't bother with a fuel height measurement prior to molesting the float height because the carbie was in bits anyway for cleaning after a 5 year shed storage of the bike - in fact the whole fucking bike has been in bits and re-assembled - but more betta ....
  11. Grreatdog

    Grreatdog Long timer

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    Your book is different than my Clymer manual.
  12. SkidMarx

    SkidMarx Long timer

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    Mine to.
  13. Lenz1

    Lenz1 Been here awhile

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    The manual I'm working from is genuine Yamaha for the TT350S. The XT350 has got the same carbies as the TT350 I'm working on even if the jetting is varied slightly. If the Clymer manual gives the correct on-bike fuel height as 6.0mm +/- 0.5mm below the bowl mating surface level then the correct off-bike / bench setting for the float height is 26.0mm +/- 2.5mm above the inverted metal face of the carbie body.

    Leave the central "tang" alone and set each float height individually by bending the float plate arms. Use two pairs of pliers as I described earlier. This individual adjustment corrects any dislevellment / height diferences between the twin floats and ensures the float assembly rotates smoothly around the fixed float assembly shaft/pin

    Perhaps the Clymer manual lost something in the translation
  14. Grreatdog

    Grreatdog Long timer

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    In this country XT and TT are two entirely different bikes. The TT here was a competition offroad bike that was not street legal and very different than our XT. We did not get the TT models that are imported to other countries.

    Our XT uses a half CV monstrosity of a carb that is EPA jetted so lean the bike will barely run. There is no float height setting in the manual. You have to buy or a make a special Yamatool and adjust the fuel level through the float drain with the carb on the bike and assembled.

    It is pure trial and error with each error requiring disassembly and reassembly to test. The slightest error and the bike either leaks fuel or won't run. Trust me, it is a bitch to do.
  15. SkidMarx

    SkidMarx Long timer

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    Did you put the new rubbers on before or after the carb kit? If after, try putting the stock jets back in. The bike should run OK stock, it will just be lean which it definitely isn't right now.

    If you aren't messing with the exhaust, or intake for better flow, the only adjustment really needed to the carb is to the pilot needle so that it will start easy.
    Yes, the carb can be jetted to run better, but you need to get it running and then only make one change at a time. To get it running, stock settings should work

    also,
    It isn't that hard to check the timing so that might be a good place to look next. Carefully remove the stator cover(you may be able to save the gasket since it runs dry). Remove the valve cover. Line up the timing marks per the manual.

    Could have. wouldn't be the first thing messed up in the clymer.
    Once I finally got mine adjusted, I took a measurement and wrote it down so I wouldn't have to go through it all again if I somehow knocked it out of adjustment.
  16. NordieBoy

    NordieBoy Armature speller

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    The XT and TT here are also two entirely different bikes.

    As enduros sometimes crossed public roads, most enduro bikes were road legal.

    Even the IT490 and friends.
  17. Earthscape

    Earthscape Have ya got a helmut?

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    This is a genuinely serious question (not directed at anyone in particular). Are there places where people use "official slang" to call a carburetor a "carbie"? I know different countries spell "carburetor" slightly differently, but I haven't seen anything indicating a large group or area consistently use this term. I ask because I think it will bother me slightly less if I knew it was generally accepted in some areas the way "carb" is often used. Is this common in Australia or Europe?
    Again, not trying to poke a hornets' nest, just would like to know.
  18. LanaTheGreat

    LanaTheGreat Adventurer

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    The original toolkit for the Yamaha XT350. The one at the top is from my 2003 XT350, and the one at the bottom is from my wife's 1994 XT350.

    It has a total of 13 parts, counting the bag as a part.[​IMG]
  19. Lenz1

    Lenz1 Been here awhile

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    My understanding is the XT350 and TT350 share the same engine and carbies with variations in jetting, don't know about the cams but I suspect differences in valve timing also.

    If the Clymer manual has the fuel height at 6.0mm +/- 0.5mm then the float height setting for a bench adjustment is as I've suggested. Please yourself on the bench adjustment procedure I've outlined for the twin floats. Maybe there's something to that old saying about Great Dogs and new tricks
  20. duneracerweston

    duneracerweston n00b

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    Alright, i got a few questions for you XT and TT guys on here. i dont have a XT or a TT but i building a hybrid of sorts, im building a yfm350 (warrior) motor and using a XT head, i know its not a direct fit and will take a crap load of modifying to fit, thats not what my question is. i have two actually and they are as follows.

    1. Can you get oversized valves for these motors? this head i have has bent intake valves and was hoping to oversize them.

    2. can you get i higher then 9.2:1 compression? because thats the highest comp ive found, i was hoping for a 11:1 or maybe even a 12:1 which would put this 374cc hybrid to about 12.9:1 which is about the comp im wanting to run. (plan on running 110 VP race fuel and a single carb)

    any help would be awesome! :thumbup

    BTW my names Weston, nice to meet the inmates.