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#859928 10/03/21 6:47 pm
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Have 71 a65l. Bike was running before. Now I try to start it and just get a sputter out of it. Got spark and fuel, just don't want to keep running. Any ideas why? Any help would be greatly appreciated. Had this bike a year now and it's always something.

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How long has it been sitting with the same fuel in it? Much more than 6 months or so can cause problems starting. Also, the carburetor pilot jet clogs up easily from stale fuel or from debris in the fuel.

If it's been sitting a while, drain all the fuel from tank and carb, refill with fresh and see what happens when you try to start it.

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Only sat week or so. Fuel is fresh, carbs are new, about 5-6 months old. Just put new plugs in, same thing, runs for few seconds and quits. Has Pazon ignition, new plug wires. I use non-ethanol gas.

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Do you get a spark at the plugs?

If you do, recheck your timing. If the rotor has slipped (screw bottomed out possibly) then the bike will never start.


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Check your fuel tank is venting.

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I got spark at plugs. I'll check gas cap. Almost had it going a few minutes ago. Last 2 times I rode it, I noticed it would cough after giving it gas over 40 mph.

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Another thing to check is to see if the needle clip has separated itself from the needle. It has happened to me.


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I'll check that too. Will have to wait, calling for rain here off and on all week. If anyone knows of a good brit bike mechanic around York PA, please let me know. Would like to have someone look at it over winter. Had 2 triumphs years ago, never had problems like this. Thanks for all the help everyone.

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is the a battery maintaining sufficient voltage under load ?
( can it run the headlight for at least a few minutes ? )
[Linked Image from cdn.shopify.com]
if the Cylinders will fire on tickled gas , but not run ,
it often blocked idle jets .
this is the smallest jet in the carburetor , so easy to block and is critical to maintaining idle and low speed .

Last edited by quinten; 10/03/21 10:44 pm.
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Starts but wont run .............. if it is starting because you have "tickled the carbs" them it points to something in the pilot part of the carbs , but both?? perhaps the cough was one pilot jet getting clogged, now both are. is your tank clean / do you have a fuel filter?

On the principal that 90% of carb issues are the spark plug, how is your coil? how is your battery? and all its connections? My B441VS quit today because the battery terminals were only letting 9 volts out (eeeek!!!) The Vape ignition called me a few unsavory names, tried gamely to make a few sparks, before telling me to go forth and multiply, and promptly fell asleep.

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Originally Posted by RebelronUSA
Only sat week or so. Fuel is fresh,....
That sounds promising. You could remove the bowl drain plugs and empty the bowls into a container and examine for any water. Then you could turn the fuel taps on and verify fuel flow and possibly flush more water through. If you find water, you will want to empty and dry out your gas tank. Has it rained there or did you wash the bike recently? Sometimes you get water when you fill with fuel too.

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I charged battery yesterday. Bike is outdoors and covered. I know moisture always finds a way to get in covered or inside. Calling for rain here this week but gonna start from tank down when it dries up. I did drain gas into glass bottle few weeks ago, looked good. Gonna replace petcocks and screens, install inline filters and check needles. I really appreciate the help. Thank you guy's so much.

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What sort of ignition have you got ?
Sounds like it is out of time


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How long have you owned the bike? Is it a newish purchase?
Sometimes it’s just about understanding what the bike likes.

Are you using the choke or has it been removed?

Pazon ignitions are pretty reliable.

Sounds like you have spark and fuel and compression as the bike will fire. It won’t run though so that’s fuel supply or timing. If the electrics were failing they would take a while to fail. Not after 30 seconds or so. They tend to fail with heat or load. Not in the garage.


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Ginge, generally agree BUT with electronic ignition it CAN indeed stop sparking after 3s or so. If it only has marginal voltage getting to it in the first place and there is a voltage drop as the current draw increases it will simply stop. Literally happened to me yesterday.

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Runs about 3 seconds when I try to start it. Owned it a year now, usually started first kick after tickling carbs. Never went far on it due to not having anyone to pick me up if it was to break down. Chokes are removed since installing new carbs. I had 12.9 volts on battery after charging. No idea on age of pazon, was in when I bought it. Installed .203" phenolic spacers on due to carbs getting hot, then having hard time starting when hot. Bike seems to run hot when running.

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New doesn’t equal good. There are lots of plugs bad out of the box. battery voltage doesn’t tell the whole story it needs to be load tested.

It only took me a month to become an expert!!!!

I sit at the back of the class but try to pay attention.

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Running for 3 seconds sounds like a carb blockage.
If it starts after tickling then stops, start it up and hold the tickler down, this will raise the fuel level and bypass the idle circuit to some extent.
My money is on a blocked pilot jet or pilot passage


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Guys ........... " Installed .203" phenolic spacers on due to carbs getting hot, then having hard time starting when hot. Bike seems to run hot when running."

Gives a few clues??? Carbs not set up correctly? I would be looking for air leaks between carbs and spacers and heads. Clean the carbs, rich up the idle a tad. Then once running setting them up properly. The AMAL web site gives the tuning steps plus you can check that the jets and needles are the right ones.
Carbs are new so unlikely to be stuffed.

Still worth checking the voltage AT THE PAZON (who cares what the battery says). Plus don't rely on the frame being earth at the coil,... if the PO hasn't already done so, run a separate wire direct to the battery, it matters (don't ask me how I know).

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Gonna check all the above. Hoping it's something simple. Thanks for the info guys.

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Carbs off, both looked clean. Cleaned everything with carb cleaner. Inside mounting nut for right carb was not tight. May have been getting air in? Looked over wiring, replaced a couple ring connections to frame. Gonna install inline filters before installing carbs, and have battery checked.

Thanks for all the help.

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Clip on needle is on 2nd pos. Manual says position 1. Gotta change that too. I've read on here that most use pos 2, will moving to 1 make much difference?

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I would start with the basics which is to have the mixture screws turned out by 1 1/2 turns and the idle/throttle stop equally adjusted so they just lift the slides off the bottom. Adjust the throttle cables so that the slides lift equally and also close at the same time, if you place your finger over the end of the throttle stop adjuster you should be able to 'feel' when the slide hits the adjuster. I think the needles should be in the middle clip position but may be wrong.

Spraying out the carb with cleaner often isn't enough to clear a blocked idle jet, have a read of Bushmans Carn Tuning Secrets available in PDF format Here which has some good advice on cleaning and tuning Amals.

Check the static timing using the plug at the front of the crankcase and if its reasonably accurate move on to other areas such as checking the voltage at the coil and pickup plate.

Also worth checking the fuel supply, sometimes the taps and filters get clogged so test how much fuel is actually coming out of the taps.

Last edited by gunner; 10/06/21 7:04 pm.

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Took everything apart off carbs and them. Thanks for the bushman site. Couldn't ever find it on Google. Lot of good info.

Thanks gunner👍

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If the bike won’t start when hot it could be something as simple as a idle mixture adjustment issue, but if this is the case, you should be able to hold the throttle fully open and start the bike (this is how I start troublesome B50’s). If it does not. It’s highly likely you have an air leak between the carb and the head. You can prove this by spraying some wd40 or some easy start (I prefer wd40 as it is not flammable) around the mounting faces. Wd40 will cause the engine to stumble and easy start will increase the revs. But again this will only work if you can start the bike from cold.


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Cleaned carbs. Nothing found in jets or filter in banjo fuel inlet. Drained all gas using inline filter, didn't see anything in filter. Removed petcocks and found both filters rotted away. Ordered new petcocks w/filters due to not sure if old ones are opening all the way. Seemed to flow good but want to be sure. I want to clean tank out in case there is debris from old filters in it. Would alcohol be OK to rinse it out with?

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Do you have a tool for cleaning the pilot jet yet? Despite everything I'm thinking this is your problem.
Put the chokes back on. You will need them for the cold starts this fall.
Do you have the Stock OIF filters or after market pancake filters?
Are the coils original. Did you check them with an Ohm meter?

Be careful tightening the nuts on those carb flanges. Too much will bend the flange causing air leaks and stuck slides. How much is too much? I turn the nut down till the lock washer is *just* flat and go 1/16th of a turn more and no farther. Same for the float bowl. if you are worried about the nuts or screws backing off then a drop of purple locktite will ease you mind. Make sure the o-ring on the carb flange is new and paper gaskets on both side of the phenolic spacer.

The bike was running before but you did say it was running hot.

1) Carb set up should start with setting the fuel height in the float bowl. See my post somewhere in this thread: https://www.britbike.com/forums/ubbthreads.php/topics/860468/concentric-mk1-setting-float#Post860468

Last edited by Semper Gumby; 10/16/21 9:02 pm.
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Cleaned carbs and jets best I possibly could. Replaced petcocks (old ones were about half plugged up and filters were disintegrated) and Replaced all fuel lines. Still, no start. Haven't got to electrical parts yet, will be next thing to check. Gonna also check timing.
Thanks for all the help and info here. Much appreciated.

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Has OIF air filters. No idea how old coils or ignition system (pazon sure fire) is since it was on bike when I purchased it last year. Looking now to see how to check coils. Then go from there.

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The only way to properly clean the pilot jets is a # 78 drill, anything less , spray, guitar string, wont cut it.

Clipped this from vintage bike mag.
"pilot jet can be cleaned using a #78 drill (.016″ diameter). It will have to be securely mounted in in a brass tube or equivalent. It is a confounded nuisance when the drill gets stuck in the pilot jet and comes out of the brass tube! Twirl it between your fingers in a clockwise rotation and it will draw any “swarf” down stream of the fuel flow and help prevent the drill from becoming stuck.

Yes, a guitar string can remove “swarf” from the pilot jet orifice. It doesn’t insure the jet orifice is returned to its proper size. Also the “swarf” in the jet is pushed up stream of the flow of fuel. This allows the “swarf” to flow back into the jet and potentially partially block the orifice. The guitar string technique works only if you modify the carburetor where the body is drilled and tapped to accept a modified pilot air screw opposite the working air screw. This way you can push the “swarf” down stream of the orifice. See AMAL’s web site to see this modification."

The whole article is here. http://vintagebikemagazine.com/technical-articles/AMAL/


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Since 90 % of carb faults are electrical, have you tried hot wiring the ignition so the key switch is by passed. i have owned my 71 A65 for nearly 40 years, its on its third ignition switch, these are low quality switches located in a terrible place .


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What's the easiest way to bypass ignition switch? As you said it's in a poor location. Bent 2 keys kicking it, may be switch.

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At the back of the switch , pull the brown/blue wire ( feed from battery), pull the white wire ( goes to ignition system), join these together.

If you have an ohm meter, check the resistance between the spades at the back of the switch, it should be zero when " on " , infinity when open, if you see wavering numbers when on, its defo the switch.

Also , open up the fuse holder in the brown/ blue line , give it some love, clean any oxides off the contacts .

Get a #78 drill, they are not expensive, buy more than one. If you have an AMAL Concentric this is an essential tool.
1971 BSA A65 workshop manuals are also still available. try e bay.
https://www.ebay.co.uk/itm/271386641948?hash=item3f2fe7861c:g:ir8AAOSwvMVcjNk0

Last edited by gavin eisler; 10/18/21 11:14 pm.

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Thanks for the info Gavin. Think I'm gonna relocate switch with new one anyway, so I don't break key off. I'll post if it was switch.
Thanks again👍

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