Hey All, I replaced the old amals on my mk-3 with new amals of the same type. I,am having problems with poor throttle response from the closed position to about 1/8 open. It is very noticeable when stopping at red lights and having to start out. I have to keep the revs high to keep from stalling. the bike idles fine and runs very well at cruise and at full throttle. I have adjusted the air jet to where the bike runs the best about 3/4 turn which is a very rich setting. If the choke is closed half way or a little better the bike runs fine at low speed and at take-off so I,am guessing it is a carb problem. The timming is at 28 degrees as per shop manual. The new carbs have the 230 main jets and the 106 needle jet. They have the 3 1/2 throttle valve.I have adjusted the needle to various settings with no difference made. I wanted to check the float level but the new carbs have the plastic floats that have no adjustment that I can see. Could it be not enough fuel in the bowls and if so what is the best way to check the floats and is there anyway to adjust the plastic floats. I have read various topics on the spray tube. Could that be the problem. The ones in the carbs are of the notched type. thanks Jack
problem with new amals
- Thread starter hershey
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My mk3 needed 260 main jets to run smoothly
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Mains will not be the problem here for the OP. They do not come into play until 3/4 to full throttle.michael levato said:
Tom,
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Hi hersheyhershey said:
I think the float level is where you want to look first as a start. Do a search on Amal float level on this site. Check the “Technical Information & How To Post Photos” and look for info on Amals. That’s up top on the page for Norton Commando Classics. Your idle screws should be about one and a half turns out for starts. Get the bike to operating temperature. Stop the engine and take the air filter element out of the way. With bike not running put two 1/8 drills or something of similar diameter and place them under the slides of the carbs. Let them hang balanced and get on your throttle and slowly raise the slides. The two drills should droop simultaneously. If not adjust the top cup up or down which encapsulates the individual throttle cables. (The front lines) at the top of the carb. Once that is done check the WOT where the slides disappear above the opening and make sure they disappear together and come back into the window together. Use your fingers to feel their transition. http://hitchcocks.sincordia.co.uk/mk1-c ... to-tune-up
Once this is set try riding the bike. If good then find a slight hill where you can open the bike up and do a WOT plug chop to figure out the mains. Read the links. You should be fine. I will also agree with concourse. Check for leaks but don’t over tighten the amals. Report back.
Cheers,
Thomas
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Sure could be float level is too low so lean over whole range and needs rich pilot setting to run slow. To adjust the float requires moving the needle seat which is not very tight interference fit to bump u/d cold though some would put in hot water first, then use a nail or drill to drift it by trail error till float in normal zone or by fine tuning to approach best idle ~1.5 air screws out. Bumping seat deeper lower, raises float level and you won't need much, which leads to the trial error hand eye motion calibration. When float level allows pilot to cause stumble either too far in or out you got it good enough to have normal everything behavior if not peak optimal power. Double check air leaks all the time. Always have known good plugs and spare new ones as bad running does then to foul the weaker plugs. Do have a look in the dark just in case.
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Hershey,
Are your new Amals… “Premier Amal Mk1”? Or the standard replacements amals? This would help... as Hobot is driving at old school tech methods to adjust float height. Not knocking what he stated but if it’s the new Amals then game changes slightly.
Premiers will have the stay up floats where you can just bend the float tab to get equal and correct float levels.
Regards,
Thomas
CNN
Are your new Amals… “Premier Amal Mk1”? Or the standard replacements amals? This would help... as Hobot is driving at old school tech methods to adjust float height. Not knocking what he stated but if it’s the new Amals then game changes slightly.
Premiers will have the stay up floats where you can just bend the float tab to get equal and correct float levels.
Regards,
Thomas
CNN
Did you order specific MK3 carbs with the necessary flats for clearance between each other? If not they may not be seated correctly on the manifolds as none MK3 carbs don't come with flats but you can file them on. My premiers needed float hight setting before use so i would check this also just to rule it out as a possibility if nothing else.
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Okhobot said:
Steve is on the right path here.
Uh my fault for not reading your first post carefully.
Tap, tap, tap away as Hobot suggested.This is a first good step. Get the level right.
Regards,
Thomas
CNN
I,am going to look up float adjustment on the amals on this forum and check level but I got to thinking if the float level is low wouldn,t it affect the performance at full throttle !! Thanks for the info on how to adjust level with plastic floats.hobot said:
[quote="quote]
Spray ether (starting fluid) at likely joints while idling, listen for RPM change. Obvious safety hazards, have an extinguisher nearby, no drama.[/quote]
Use WD-40 instead..... much safer and accomplishes the same thing. Use the the small red extension tube when spraying as it helps to pinpoint the location.
Spray ether (starting fluid) at likely joints while idling, listen for RPM change. Obvious safety hazards, have an extinguisher nearby, no drama.[/quote]
Use WD-40 instead..... much safer and accomplishes the same thing. Use the the small red extension tube when spraying as it helps to pinpoint the location.
Checked the float levels today. They were way off running on the lean side. Adjusted by tapping the seat down into the carb body. Kinda of tricky, a lot of play in the float tang where it slides onto the needle.I adjusted and then tried a liquid test with water and it looks to be okay. I,ll have to wait to take a ride, to damn cold !! Has anybody tried synchronizing the carbs with them unbolted from the head. With the throttle cables and choke cables intact turn the carbs sideways so you can see the slides move and adjust accordingly. Don,t see why it wouldn,t work. I,am going to try and see. Hope the float adjustment does the trick !!CanukNortonNut said:
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