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Am I being taken for a ride? {groan}

Discussion in 'Technical and Troubleshooting Torque' started by hornet, Nov 25, 2011.

  1. Fuel consumption on the Hornet has taken a serious nosedive, and my mechanic tells me that the carburettor needles are worn, and the seats. He says they are not replaceable, and the only solution is to replace the carburettors....

    I used to have a '98 Hornet shop manual in .pdf format, but somewhere alone the various computer upgrades it's gone missing, so I can't check there, but I CAN'T believe that a part which will wear out should NOT be replaceable; if someone knows the answer to this riddle I'd be very grateful to hear it, since even a second-hand set of carbies are priced at around $300....

  2. What brand are the carbies?
  3. There's a thread floating around somewhere which has links to workshop manuals. I'm not on the pc at the moment but will be tomorrow. Let me know and I can try dig it up (I thought it was a sticky but couldn't see it on my phone). Otherwise a quick search might bring it up.

    As for the carbies, no idea.
  4. ill have a look at work tomorrow, the float needle should be replaceable. but for some reason on allot of the modern bikes the seat is not.
  5. Update, I just downloaded the manual, thanks for the kind offers to do same :), and it clearly shows an 'exploded' view of a carby with the jet needle and the throttle valve/vacuum piston as separate components....

    spenaroo, if you can verify if it's possible or not, I'd be very grateful..

    I just found a nice gentleman in Italy who has a complete set of 600 carbies for sale on fleabay for 70 Euro, plus 50 Euro frieght, but I wonder about Euro regulations for pollution control, etc.....
  6. Easily fixable, if it's anything like California, they just cover up the idle mix screw which you need to drill out.

    Alternatively, see if you can source a set of FCR flatslide carbs from eBay, expect to pay $5-700 for a bank of four, I expect the FCR39's will work & probably add some HP.

    You just need to find the right spacing :)
  7. Bloody Honda's har har
    You can replace the needle and the seat has to be redone. It's no diff to your tap.
    Mechanics suck.
    It will mean you will be out on the mixture a bit. Instead of 3/4 to 1.1/2 it might be more or less as you have shaved a poofteeth off the base of the seat. I doubt it would affect much at all really.
    Find a good spanner
  8. [​IMG]
    as you can see its all re-buildable
  9. The only things that should affect your fuel economy will be the needle (item 3) and the needle holder (item 24) I can't see any reason why the main jet would wear enough, if at all, to reduce your economy, and if the float valve were leaking, she'd be piddling fuel out the overflow. Quite fixable. Big singles will wear these items out quite regularly by the way, and sometimes even the slide (the bit below item 20) will need to be replaced, but I'd find that hard to believe in your case.
    • Like Like x 1
  10. Most motorcycle carburetor circuits are governed by throttle position and not by engine speed.There are five main metering systems inside most motorcycle carburetors. These metering circuits overlap each other and they are:
    * pilot circuit
    * throttle valve
    * needle jet and jet needle
    * main jet
    * choke circuit

    Carburetor troubleshooting is simple once the basic principles are known. The first step is to find where the engine is running poorly. It must be remembered that carburetor jetting is determined by the throttle position, not engine speed. If the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem.

    Needle & seat do wear over time. needle wears and the seat elongates. This affects how much fuel gets past. Because the needle is tapered the amount of fuel getting past is variable. As a generalisation the needle will wear more in 1 section ( usually your 'cruising' throttle position ).

    While a parts book may show needle and seat as spare parts, seats are usually pressed in to the body...making replacement somewhat more difficult.

    Talking CV carbs.. also check the diaphrams for wear and cracks..

    Hope that helps..

    Attached Files:

  11. good info there, thanks.

    I picked the bike up from mechanic A on Friday afternoon

    I genuinely feel that despite him being a nice guy and having done lots of good stuff for me in the past, that in this case he is out of his depth entirely, especially as the problem STARTED when he 'fixed' the airbox and a carby hose!

    Anyway, I have rung mechanic B and he's getting back to me to let me know when he can pick the bike up and fix it; so we wait and see.

    Either way 230kms before running onto reserve vs 148 kms before running onto reserve can't be ignored (or paid for, long term).
  12. Update (of sorts)....

    Mechanic B picked up the bike on Tuesday night.

    I rang him on Friday afternoon, and HE doesn't know what's wrong although he believed the problem to be in the carburettors somewhere.

    So ..... I rang wrecker in Sydney who has a '98 Hornet engine, and bought the carburettors from him, they are being freighted to mechanic B today, so hopefully that will fix the problem. These carbies have only 36,000 kms on them (the bike has 164,000kms) so fingers crossed...

    That said, with this abysmal weather.... :roll: :LOL:

  13. ummmm. there's your problem.

    when fuel economy (or anything) takes a sudden dive, look at what has suddenly changed. If the valve has worn you would have been seeing a slow decrease in fuel enconomy not a step change like this.
  14. exactly the point I made to mechanic B!!!

    Anyway, let's see what replacing the carbies does......
  15. Just as a point of interest, can you 'unfix' the airbox and hose? just to see what happens before fitting the new carbs.. Then let Mechanic A know in a nice way the result of the experiment.
  16. 148km before reserve - your getting into Firestorm territory there! My reserve came on yesterday at 150km and my speedo reads about 20% high.
  17. update, mechanic B has received, stripped and cleaned, fitted and then removed because there was a leak, re-fitted and tested, the 'new' carbies and says it's going fine. Of course he can't test fuel consumption but I get it back tonight and will have to hope for a break in this glorious summer weather so I can see if I have my old reserve point back.

    As always, thanks to all for your concern and advice, what's not to like about Netrider???

    As a sort of sub-set of this, Mrs Hornet has approved the saving of $100 a week from our modest income to permit the purchase of a replacement for the Hornet near the end of 2012.
  18. groan

    Rode home from mechanic B in the pouring rain, (after parting with amounts of cash), all was well

    Rode to a work breakfast this morning, ok

    Rode from the breakfast (after filling up preparatory to heading up the Highlands), 5kms, and the bike stopped, just like it does when it's running onto reserve.

    Started (grudgingly) under choke, even though the engine was up to temp.

    Rode it home and parked it in the garage in disgust.

    Rang mechanic B, needless to say he's closing over the Christmas / New year break and can't look at it for a couple of weeks...