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Carby bowl "gunk"

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by sl100, Mar 18, 2013.

  1. Gday all, any thoughts on what this gunk is? Its the bowl off one of the Mikuni carbs on a 1996 GSX250F, the other bowl was similar but not as bad. Bike had been sitting for at least 12 months before i got it.
    Ive cleaned out quite a few carbies over the years but never seen anything quite like this before (n) . It all dissolved/dislodged from the bowl with carby cleaner but was also blocking all the jets, breathers, etc in both carbs. Needles/slides were glued solid with it and wouldn't move. Cleaned out now and looks OK :nailbiting: but I'm still intrigued by what this is the remains of?

    20130318_121724. 20130318_121746.
  2. It is most likely fuel gum & iron oxide (rust) silt. When fuel is left sit for a long time & allowed to evaporate away, it leaves behind these gum like deposits. It is unusual for carbie cleaner to be able to dissolve them completely. Usually you need special carb cleaning solutions & lots of scrubbing.

    Also you will need to pay close attention to the hole at the centre top of second picture. This is usually linked to the hole at the bottom of the fuel bowl, and is where the choke usually draws its fuel from. It has a tiny hole at the bottom which acts like a jet, so do not clean it with a drill bit or the bike will run excessively rich when choke is on. If it is blocked, then bike will be a real bugger the start. Needs to be soaked in solution & gently reamed with a fine wire, or take it to someone who has a ultrasonic cleaning bath.
  3. Usual gum but looks like it may have been left dry too.
  4. +1 oxidation.....
  5. I overhauled a Webber carbie off a Fiat 124 and the carbs on a couple of bikes with something like THIS STUFF. 0996.
    It might not have been the same brand but it's the same idea. Soak the METAL parts over night and all the grime, grease and a lot of oxidation just wash off. Works wonders for cleaning jets as well but you need compressed air to finish the job. Not recommended to soak diaphragms and the like.
  6. Cheers guys, I guess if the bowls have never been off then it could be 15 years worth of the usual gunk. I'll put a filter in between the tank and fuel pump to catch the crap from now on.
    The choke tube/hole/jet/thingy was blocked solid on both carbs. I use wire brush bristles for cleaning out the jets etc. Their firm, but generally they bend before gouging jets or alloy bodies, that's the theory anyway :woot: Those and CRC carby cleaner tend to do the job.
    I'll get it back together this weekend and see if it wants to go now :sneaky:
  7. Just to wrap this up, bike is running really well now. Tinkerer was spot on about the feed to the choke, I had cleared them both out but obviously didn't get rid of the residue in one and it clogged up again before I got the bike going. Was a bastard to start when cold, took em off again and found/remedied the issue and it starts perfectly now. Its got a bit of an erratic idle but its only done about 10km since getting it going. After a decent run to blow out the cobwebs I'll balance the carbs etc. and hopefully that will settle it down a bit.
    I'd better get it some rego and get my learners before that though :whistle: