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Thread: Need Amal help 65' Hornet

  1. #1
    Join Date
    Mar 2019
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    Default Need Amal help 65' Hornet

    Hey all! Can someone guide me to whatever I'm missin? Just took the worn out Monoblocks off my Hornet and put two, new, 930 Premiers on. Started off with #106 needle jets and #190 main jets. Tried all three grooves on the needle and no help. Was told to put in #105 needles, put in #180's. No help. Here is what it is doing. Idles great, take off and go through the gears as follows: smooth to midrange, then comes the burbling, missing, and once you get through that, (if the head wind is not to bad, because you won't get through the midrange) hold on tight to the bars because this thing hauls ass in the top r.p.m. of each gear. Plugs, are black so I'm pretty sure we are rich. Should I start giving it more air via air screw. Any advice will be well accepted. P.s. Never have claimed to be good with carbs. Thanks! Kevin

  2. #2
    Join Date
    Jul 2002
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    Quote Originally Posted by beeza View Post
    Hey all! Can someone guide me to whatever I'm missin? Just took the worn out Monoblocks off my Hornet and put two, new, 930 Premiers on. Started off with #106 needle jets and #190 main jets. Tried all three grooves on the needle and no help. Was told to put in #105 needles, put in #180's. No help. Here is what it is doing. Idles great, take off and go through the gears as follows: smooth to midrange, then comes the burbling, missing, and once you get through that, (if the head wind is not to bad, because you won't get through the midrange) hold on tight to the bars because this thing hauls ass in the top r.p.m. of each gear. Plugs, are black so I'm pretty sure we are rich. Should I start giving it more air via air screw. Any advice will be well accepted. P.s. Never have claimed to be good with carbs. Thanks! Kevin
    The air screw only affects the idle mixture. About one and a half turns out from screwed all the way in should be about where the idle mixture sounds good.
    190 is the stock main jet but if you have air cleaners 180 would likely be in the ballpark. The throttle slide should be a 2 and 1/2 cutaway and if the bike runs OK up to 1/4 throttle it would be about right. Between 1/4 and 3/4 throttle the needle position as it comes in and out of the needle jet controls the mid-range and it should be fitted in the middle of the 3 notches. sounds like you might have it in set in the top notch so it is too low in the needle jet and therefore not enough gas.
    AFJ

  3. #3
    Join Date
    Mar 2019
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    16

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    Thanks AFJ for the reply! I currently have the needle in the middle notch. Have tried it in all 3 positions and to no avail. Should be receiving a #200 main today and go back to a #106 needle jet. I'm totally lost on this ordeal. Just keep pecking away at this issue until resolved. Will let ya know how things workout, and again, big thanks. Kevin

  4. #4
    Join Date
    Nov 2018
    Location
    Reno NV
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    200

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    Beeza,
    What size Monoblock's did you take off the bike. I think your model should have had the 1 1/8" 389 Monoblock, which is about 28 mm.
    The 930's you put on are 30 mm, so you have bigger carbies than standard if this is correct.
    Are you running two carbs?
    It seems to me like you need a smaller needle jet, 105, and a larger cutaway,3, to lean it out in the mid range condition you are finding.
    On the 930's, how many turns out are you running the pilot air screw. It should be in the 1 1/2 turn out range if the idle jets are about right.
    Are you running air cleaners?
    What type of exhaust are you running, open, mufflers, megaphone etc.
    If you take the air cleaners off and take it for a run, does it perform better?
    Cheers,
    Mick

  5. #5

    Default

    Plugs, are black so I'm pretty sure we are rich
    What plugs?
    Try clean plugs, they will retain color from any rich circuit.
    106 is correct for almost every 900 series.
    burbling, missing: do you mean 8-stroking with black smoke, or misfiring and popping back through the carburetor? Those are opposites.

  6. #6
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    Mar 2019
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    Thanks guys for all the info and questions!...Mick, the monoblocks are 389's. I have the 105's on the needle jet. Pilot screw seems to be idling smoothly at 1 1/2 turns out. And am using the Amal round air cleaners. It is an East coast high piper with baffles removed,(the straight pipe version). Removed the air cleaners and at highway speed, slowly edged two fingers over the carb inlet and immediately, started to bog down from lack of air instead of pick up in rpm. So that tells me I have plenty of fuel. A friend had a pair of 150 main jets which I tried. The mid range 8-stroking was not as rough, but just was not getting the fuel in the higher rpm's. It never stumbled at higher revs, but the acceleration was not that great like it was with the 180 mains. Also, I have Champion RN4C plugs in it. Just ordered a pair of 170 jets and will try that next week, also, will be moving clip on the needle up and down. To all who have given me advice on this, THANK YOU, THANK YOU for your taking the time to help out. After spending the money on these new carbs, I really don't want to buy a pair of Mikunis…….Yuch, a Jap carb on a Brit bike. (it would probably blow up). I'll buy the first round! Kevin

  7. #7
    Join Date
    Jul 2002
    Posts
    451

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    Quote Originally Posted by beeza View Post
    Thanks guys for all the info and questions!...Mick, the monoblocks are 389's. I have the 105's on the needle jet. Pilot screw seems to be idling smoothly at 1 1/2 turns out. And am using the Amal round air cleaners. It is an East coast high piper with baffles removed,(the straight pipe version). Removed the air cleaners and at highway speed, slowly edged two fingers over the carb inlet and immediately, started to bog down from lack of air instead of pick up in rpm. So that tells me I have plenty of fuel. A friend had a pair of 150 main jets which I tried. The mid range 8-stroking was not as rough, but just was not getting the fuel in the higher rpm's. It never stumbled at higher revs, but the acceleration was not that great like it was with the 180 mains. Also, I have Champion RN4C plugs in it. Just ordered a pair of 170 jets and will try that next week, also, will be moving clip on the needle up and down. To all who have given me advice on this, THANK YOU, THANK YOU for your taking the time to help out. After spending the money on these new carbs, I really don't want to buy a pair of Mikunis…….Yuch, a Jap carb on a Brit bike. (it would probably blow up). I'll buy the first round! Kevin

    As a Hornet it should have ET (energy transfer) ignition as stock as they had no lights fitted and had the mid-level straight pipes without silencers. Champion RN4C would (by the R) be a resistor type plug. I would suggest using N4C or even N3C (for high speed use) since Energy Transfer (which I have on my '67 Triumph T100C Trophy and use N4C plugs gapped 18 thou) needs a non resistor system (no resistor plug wire or resistor plug caps either) to perform properly.

    As a '65 Hornet it would have had a 10.5/1 compression. Original jetting on the '65-'66 with the Monobloc 389/689 carbs was 1 & 5/32 choke, 270 main jet, 25 pilot,#3 slide, needle in position 4, and a .106 needle jet.
    The 1968 set-up with Concentrics is 2 - 930 30mm 190 main jet, 20 pilot 2 1/2 slide needle in position 2 and a .106 needle jet
    I assume that the gasoline intended for these jettings would have been a leaded premium fuel. It might be well to look at the gasoline you are using these days, not only from the octane rating but the composition as, if it has more toluene/benzene in it, or some even small percentage of ethanol, a larger main jet might work better.

    I believe that the "Mikuni carb" was originally an Amal design which they (Amal) decided not to proceed with making - so they sold it to Mukuni.

    AFJ

  8. #8
    Join Date
    Mar 2019
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    AFJ, thanks for the valuable info! I guess that is what these forums are for. The Hornet does have ET ignition and I have been wondering about getting into the plugs on this problem, and will give the wires and caps a check. Will take your advice and see if that makes any changes, (very cheap fix). I do have a pair of 200 mains and 220. The gasoline I use is Phillips 91 octane non ethanol-alcohol, that I add Redline lead additive. Will research the contents of the fuel. I am going to also go to our airport and get a few gallons of 100LL avgas. Your Mikuni story is very interesting. I have been involved with motorcycles all my life, but just within the last 4 years have been getting into the British stuff. Did not know about Amal being involved with the Mikuni carb. Again, I want to thank you for advice! Will keep you and others posted on this issue. I know if I had the knowledge and experience like so many of you, this would be an easy fix. Kevin

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