MK1 Amal Carbed 76 T-140v Has High Load Cut Out

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Z

ZILCH

Active Member

During a short test ride when I twist the throttle for more power when in 4[SUP]th[/SUP] gear the engine starts cutting out and returns to normal when I return the throttle to about the ½ position. But on the way back the symptom of cutting out happens more frequently at lower throttle settings. Up until the cut out begins to show up (about ¼ mile into the test run) the bike runs strong at any throttle position.
These are the things I have checked so far:
I have made sure the battery is charged before the run
The tank gas cap vent was restricted and is now clear (use to cut out worse)
I have checked the wiring on the Boyer ignition.
The carbs have been removed cleaned and floats set 2 times.
Both carbs have been snyc’d and full travel checked
New petcocks have been installed
The plugs have been gapped and cleaned
The valve clearances have been set
The ignition wires have been checked for condition and covered with spiral plastic protection
Battery connections and wiring in the battery box area have been checked
My suspicions’ are:
1. The battery may be glitchy
2. The coils may be breaking down
3. The alternator is not putting out enough power
4. The new petcocks have an flow restriction
5. The carb floats are heavy or sinking
How can I check the alternator output accurately?
Do you folks know what else I can check and the way to check it?
Thanks,
Zilch56
 
I don't think it's electrical at all.

My guess would be that after warm-up to normal operating temps, the bog is due to carb mixture. I would carefully adjust the air mix on both carbs keeping close track of how much you turn them....a very small turn makes a big difference. Take it for a spin with a screwdriver in your pocket and after warming up, make tiny adjustments to each side equally and increase the adjustment as the bog becomes less and less until you've eliminated it.
 
I read this information on the Boyer iginition site:

Frequent Problems​
Whereas the typical “points and coil” system can operate quite nicely with a dyingbattery supplying 7 or 8 volts, the Boyer demands a full 12V. This means yourbattery, charging system and all connections must be kept in tip-top condition.1) The first thing you’ll want to do is make sure your battery is healthy. With yourengine turned OFF, leave your headlamp ON for 2 minutes. With the headlamp stillON, place a voltmeter across the battery terminals. It should read something like12.3V. If it reads below 12.0V, then you need a new battery. Period.2) Even if your battery tests “good”, that does not mean that the Boyer is getting allthat voltage. Your motorcycle might have a worn ignition switch, frayed wiring, badkill button or poor system grounding keeping the Boyer from receiving the full system​
Copyright RF Whatley, Suwanee, GA 3 Jan 2006, Revised May 2006​
voltage. Be sure to unplug the Boyer box and take an Ohm-meter reading between therectifier center wire (usually BRN/BLU) and the wire going to the Boyer WHT. Alsotake a measurement between your rectifier ground and the wire going to the BoyerRED. Both readings should show zero resistance.3) When the battery cannot hold a charge or cannot get the proper charge from thealternator, then the Boyer fails to receive the proper voltage. When this happens theengine will “blubber” like the choke has been turned ON or the fuel has suddenlygone bad. Often the bike will stumble enough to quit all together. But then it maymysteriously crank and run great minutes later! To diagnose this malady when ithappens, simply turn OFF the headlamp while the engine is still running. Theheadlamp, being the biggest user of electrical energy, will relinquish enough voltagethat the Boyer will once again have 12V and the engine will instantly start to run​
better again.

I checked the battery voltage after it had been charged and sat overnite. The voltage was 11.9, aftter a test run of 1/2 mile the engine started cutting out even worse. After shutdown the voltage at the battery was 11.2. I installed a new battery after putting the acid and charging it for 12 hours. The bike ran great with no cut out in any gear with varing loads and throttle position.
 
Sorry......I completely forgot that the Boyer DOES require a very healthy battery to run.

I almost said initially that you bike doesn't even need the battery to run (well, it has to be wired into the system unless you install a battery eliminator).

My bad.....had I said that, the Boyer/battery topic would have come up. Just wasn't thinking along that line.

Well, the bottom line is that it wasn't hard to fix!
 
I have a Boyer in both of my old bikes and they work great. If there is any drawback to the system it's the 100% need for a good battery and no weaknesses in the electrical system that gets spark to the plugs.
It seems you have found the problem TUP
 
Seeker please no apologies needed, I asked for help and you folks obliged. That is truely appreciated. A new (to you) bike is always a learn as you go process and that is what forums like this are great for sharing ideas and experience. In addition I learned some good methods you employ for road tuning. I was thrilled to final feel the old girl kicking up her heals unfettered. I can't wait to get it licensed and go on a real ride. I still working on the issues short list.

Thank you folks for your help and experience.
 
Boyer ignitions are THE MOST voltage-sensitive ignitions on the market, PERIOD.

Repeated / continuous exposure to low voltage damages them permanently.

Maybe it's just that there are more of them out there, since they were first in the aftermarket, but I have seen many times the failure rate with Boyers than any other.

I've not seen other brands damaged by low voltage; when they give up, they just give up out of the blue.
 

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