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Koorbloh's XL350 thread

Discussion in 'Projects' started by koorbloh, Mar 23, 2012.

  1. 74 honda xl350 (let's start with this one, sure)

    so, I've never had carb trouble that couldn't be solved by just running the bike.

    I know that this bike has carb trouble. I know this because I can't move the butterfly with my fingers.

    so, I'd like some info...

    1) I'd love to know the "right" process for cleaning and restoring this carb. all out. from replacement parts, which to buy and which to avoid, to which tools I need to buy. unlimited budget, how do I repair (not replace) this carb.

    2) I'd love to know the "free" process for cleaning and restoring this carb. is it as simple as alternating with pb-blaster, wd-40, and spray carb cleaner, then scrubbing with a tooth brush until all the pieces come apart and go back together nicely?

    yes, I know to google it, check thumpertalk, adv, and the xl forums and all that shit...I'm going to spend some of my time today doing this.

    yes, I know there are other things to check on the bike too.

    yes, I know that option 1 is overkill.

    yes, I know that option 2 is no where near enough.

    yes, Andy, I know you're jelly that I saw the post first :nana

    but, I know there are some dudes that have some good experience on both fronts that I've asked about, so please let me know what y'all know!

    Last edited by a moderator: Jan 26, 2013
  2. 3/4 gallon of Berryman's parts cleaner. Assorted hand tools. A a soft drift and a delicate touch. A yard brush bristle and a keystar rebuild kit of eBay should do it.

    You just got to strip that puppy down, noting exactly how it goes back together.

    I'm not super jelly...........yet. I'm hoping it is a diamond in the rough for you.

    Edit - yes PB blaster and mechanical manipulation "frees" up a lot!

  3. more thing........

    You are in over your head! I will can drop the bike off tonight and I won't charge you salvage.
  4. james1300

    james1300 Track School Dazed


    And Compressed air. NOT the cans of the stuff, but compressed air to blow the passages in the carb, clean.
  5. Don't know if it has the same "constant velocity" carbs that were on my '72 CB350, but if it does, you need to inspect the extremely thin rubber diaphragms for the slightest pinhole leaks. One tiny hole will mess up the slide action immensely. I had one and in a cross-wind I would lose almost half my power.
  6. Berrymans and compressed air is good. Ultrasonic cleaning is the better. That and a carb kit then resetting to factory specs for a good starting point. Warm up then fine tune.
  7. .......and one more thing link

    ^^^this is the voice of reason and experience. If you think it has an once of potential check carefully the cam journals before you buy anything!!! The difficult thing will be working out how much you want to spend on a motor that is towards the end of its life.
  8. yup. I've very recently been that voice of reason for my buddy's old cb400 that he's mistreated for the last 20k miles.

    I haven't spent a dime other than the gas to get these, so I'm ahead already!

    the carb is the easiest to access, so that's the first place I'm looking!

    btw, is there any reference on what, exactly, to check about the cam journals?
  9. Having rebuilt a number of carbs in the past, there is a lot of good advise here, and you are heading in the right direction by using the other bike sites for detailed "how to"s.

    If you are going to get the carb back in shape, then spend the time on it. Spray it on the outside before taking apart to get the grit off it - and not in it. Then soak it inside and out with a bucket of carb cleaner (Berryman's Chem-Dip). Buy a full rebuild kit with jets, float, o-rings and gaskets. Anything rubber left on the carb will swell and turn to mush, so have replacements for them.

    Follow the directions you find in your manual(?) or the internets from those who you trust or know how to assemble/reassemble.

    I've had trouble with bowl and diaphram screws on some old Honda carbs. Not sure about this one (too lazy to look up). I'd have a couple on hand after you strip the heads off.
    mjn likes this.
  10. Taking the cap off is even easier/quicker than stripping the carb down.

    A good place to start is locating the chain tensioner securing bolt and removing (somewhere around the end of the gear shift pedal) Directly under that on the belly pan is a 17mm bolt oil drain bolt (not the main one). Remove that and you can pull down, against it's spring, the vertically mounted tensioner arm with a 5 or 6mm? bolt you can screw in the end of it. With the points and advancer removed, see if there is any play in the cam shaft. In fact the cam chain may well be slack enough to forget the tensioner and just pull the points and advancer out and give it a wiggle. But don't be deceived by chain tension or the oil seal holding the cam in place.

    After that pop the cap off and look. Visual inspection is an under rated tool. It is pretty easy to unbolt the sprocket and remove the cam and look underneath too. (Cable tie a mark on the chain that corresponds to the sprocket for reference).

    It sounds like a lot but it will take less time than freeing up the butterfly valve alone.

    I will see if I can find the specs. If it looks good! a plasti-gauge is the next step.
  11. mjn

    mjn Forum Admin Staff Member

    Listen to Andy. Spot on advice.
  12. I can't take any credit since I have been schooled by those wiser than me. I just happened to have done this very recently.
  13. I appreciate all the advice guys! Keep it coming!

    this weekend, I'm going to take some time and check the cam journals and work on the carb!

    pfffft. mine is significantly newer than yours. :nana
  14. Hahahahaha looks like it was really looked after too! You scored :popcorn:
  15. I can't wait to see how this goes.
  16. james1300

    james1300 Track School Dazed

    When it comes to using compressed air and carb cleaner 'USE' nitrile gloves and eye protection! Come to think of it, Using them anytime your working on your bike isn't a bad idea!
  17. JIS screwdrivers will save a lot of heartache
  18. Basics of Carburetor Operation
    The basic secret of carb function is that inside each carb are thousands of tiny gnomes; each with a small bucket. As you open the throttle, more of these gnomes are allowed out of their house and into the float bowl, where they fill the buckets and climb up the carb's passages to the intake, where they empty their buckets into the air stream.
    But, if you don't ride the bike for a while, bad things can happen. Tiny bats take up residence in the chambers of the carb, and before long the passages are plugged up with guano. This creates a gnome traffic jam, and so not enough bucketfuls of fuel can get to the engine. If it gets bad enough, the gnomes simply give up and go take a nap. The engine won't run at all at this point. Sometimes you'll have a single dedicated gnome still on the job, which is why the bike will occasionally fire as the gnome tosses his lone bucket load down the intake.
    There has been some research into using tiny dwarves in modern carbs. The advantage is that unlike gnomes, dwarves are miners and can often re-open a clogged passage. Unfortunately, dwarves have a natural fear of earthquakes, as any miner should. In recent tests, the engine vibrations caused the dwarves to evacuate the Harley Davidson test vehicle and make a beeline for the nearest BMW dealership. Sadly, BMW's are fuel injected and so the poor dwarves met an unfortunate end in the rollers of a Bosch fuel pump. Other carb problems can also occur. If the level of fuel in the float bowl rises too high, it will wipe out the Section 8 gnome housing in the lower parts of the carb. The more affluent gnomes build their homes in the diaphragm chamber, and so are unaffected. This is why the bike is said to be "running rich". If the fuel bowl level drops, then the gnomes have to walk farther to get a bucketful of fuel. This means less fuel gets to the engine. Because the gnomes get quite a workout from this additional distance, this condition is known as "running lean". The use of the device known only as the 'choke' has finally been banned by PETG (People for the Ethical Treatment of Gnomes) and replaced by a new carb circuit that simply allows more gnomes to carry fuel at once when the engine needs to start or warm up. In the interests of decorum, I prefer not to explain how the 'choke' operated. You would rather not know anyway. So, that's how a carburetor works. You may wish to join us here next week for electricity 101, or "How your bike creates cold fusion inside the stator, and why the government doesn't want you to know about it."
    Last edited: Mar 23, 2012
  19. Awesome!

    ....Must spread the love
  20. Parts fiche looks like a standard round slide carb. There should be no butterflies or rubber diaphragms to deal with.
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