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Carb Main Nozzle Question

Discussion in 'The Garage' started by Doug Smith, Mar 8, 2019.

  1. Doug Smith

    Doug Smith XS400 Member

    Question....getting some confusing advice from others.
    When rebuilding '81 XS400 carbs I could not get the main nozzles out of the carbs....stuck solid.
    Reassembled carbs and got bike running today after a 15 year rest. Bike idles perfectly, accelerates fine but has a "mid range" fuel issue. Since I never removed / cleaned the main nozzles I'm fairly certain that some of the "pin hole" ports are blocked. They need to come out and be cleared.

    Problem is I've been given conflicting information of which direction to remove them. Do they extract upward towards the slide chamber?.....or do they extract downward towards the float chamber?

    The Main Nozzle is circled in photo: carb kit.jpg

    Do the main nozzles extract upwards?...….or downwards?

    I've been warned about the little locator pin which sits towards the bottom.....seems to me the pin requires the nozzle to be pushed upwards for removal.....?
    20190225_204050_resized - Copy.jpg
  2. Doug, welcome to the madhouse :) you're in the right place.

    Poke around and you'll find some good resources in tech section. To answer your question, Will is a legend for having made videos on the disassembly, a godsend!


    Congrats on breathing new life into her! Get some pics up when you have a chance!
    Last edited: Mar 9, 2019
  3. xschris

    xschris a lifestyle not a trend Top Contributor

    Up towards the diaphragms. After removing the main jet and washer I screw a bolt in where the main jet was and tap them out.
  4. Doug Smith

    Doug Smith XS400 Member

    Thanks for the reply.....finally a straight answer....plan on taking them back apart today. I'll probably use a butane torch to lightly heat to help loosen the varnish.
    I've rebuilt hundreds of various carbs in my years but never this particular type.
    These carbs were "varnished solid" in every nook & cranny so were quite the feat to clean. The float pins / needle valves were solid even after 4 - 5 days in caustic carb cleaner. Had to resort to a butane torch to "melt" the varnish to free the swivel pins...as soon as they cooled they were stuck solid again. Had to heat / reheat numerous times to CAREFULLY work the swivel pins out. Then had to straighten them (they got "tweaked" during removal) and sand them off with a Dremel Tool....also had to "ream" the float swivel holes with a drill bit (by hand) to remove the varnish. When finally done they worked just fine.

    BBS360 and buztabuzt like this.
  5. xschris

    xschris a lifestyle not a trend Top Contributor

    I would avoid heat like that on these carbs. There are rubber seals and o-rings that can be damaged. Unless you remove everything including the shaft seals and pilot mix screw. Even then I would be cautious. Simple carb spray or penetrating oil will work fine. Just don't let it touch any rubber bits.
  6. Doug Smith

    Doug Smith XS400 Member

    Thanks for the replies! I removed carbs yesterday AM....now knowing which direction to remove the nozzles. They came out fairly easily with just a light "love tap". No heat was needed. Someone had warned me about losing the little nozzle "guide pins", but mine seemed to be securely set in the carb bodies. Sure enough a couple of the nozzle "pin hole orifices" were blocked with varnish. After cleaning up the nozzles, the bike was back together in a few minutes and the "mid range" problem was solved. Runs perfectly now with no issues through the throttle ranges.

    The previous night the bike sat for the first time with fuel in the tank. I had previously disassembled the petcock and all appeared to be OK. Upon attempting to start after carb repair I encountered a "fuel lock"....sure enough some fuel had ran into the cylinders over the night. I pulled the plugs and used kick starter to force fuel from cylinders....not much fuel came out. Obviously the vacuum assist petcock is faulty. For an interim fix, I plumbed in a spare metal, in-line petcock I had amongst my spare parts. I had closely observed the oil level after oil / filter change and it doesn't appear any notable amount fuel entered the crankcase.
    Since the bike sat for so many years, I'll change the oil again after a few miles anyway. I'll likely leave the additional petcock plumbed in as I have never trusted any of the vacuum type petcocks. I've had issues with numerous ones in the past, in fact every bike I've owned that used them, had "leak by" issues.
    The one on this bike has full fuel flow regardless of what position it is set to. I'll need to acquire a rebuild kit....I see some inexpensive, "cheap-o" aftermarket petcocks on eBay, but don't think I'll go that route. I imagine the quality of the Chinese manufactured ones is as cheap as their price.
    Last edited: Mar 10, 2019
  7. Doug Smith

    Doug Smith XS400 Member

    Yes....applying heat was a "last ditch" effort to remove the float pin swivels. The carbs had soaked for over 5 days in a highly caustic carb cleaner and they were still stuck solid. I used spray carb cleaners, P-B Blaster, Silicone spray, 3 other types of penetrating oils I had on hand...none had any effect. Years back I had acquired a Honda Super Sport 400-4 with dirty carbs. Those carbs had the same problem, floats / needles stuck rock solid. The "towers" showed deterioration and corrosion from eons of sitting. No amount of penetrating oil / carb cleaner / any substance I tried would budge them. Eventually I broke off one of the corroded carb float "towers" which hold the swivel pin attempting to remove it. I was not going to take that chance on this bike. I tried a little bit of heat and immediately the heat accomplished what nothing else would, allowing some float movement. Even with light heating / reheating it took a couple of hours to remove both swivel pins...they were simply "welded" into the floats.
    I've rebuilt 100's of carbs over my years and never used heat before, but in this case it did the trick and didn't harm anything, [FAIL....EDIT.....ENDED UP MELTING THE SOLDER IN ONE FLOAT BULB!] just needed to use common sense and not get carried away. .
    Last edited: Mar 28, 2019
  8. xschris

    xschris a lifestyle not a trend Top Contributor

    Using the edge of a knife where the flat part of the pin meets the tower and a few taps from a small tack hammer will break them free. Then and or use a set of wire cutters with a fine edge can grab the end to move it out. Done this dozens of times and never had a post break or a pin stay stuck.
  9. Doug Smith

    Doug Smith XS400 Member

    Oooooh…..that looks like the one to use! No vacuum assembly. On my list!

    Got all the fuel system "quirks" worked out......new needles / seats.....had to replace one float assembly. My last ditch "torch" scenario must have melted a bit of solder in one float bulb seam....she got a bit heavy when full of gas...lol.
    Took the bike out a couple days ago for a 10 mile neighborhood run. Worked like a champ!
    "Mikes XS" was the best.....great price and parts received fast!
    Last edited: Mar 27, 2019
  10. SpikeG

    SpikeG XS400 Member

    That petcock has me wondering... I put a non vacuum OEM Yamaha petcock on my Suzuki which looks to be exactly the same bolt spacing but it has integrated filters on the main/reserve pickups. I believe it was intended for a raptor? It was actually cheaper than the 2fastmoto one too. I'm gonna see if it'll fit when my tank is back from paint.


    Edit: after a little digging, the spacing is off... oh well!
    Doug Smith likes this.

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