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

[zilch56]

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

During a short test ride when I twist the throttle for more power when in 4th 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

[tango911]

jetting on the carbs stock, is the airbox stock and the exhaust?

check the floats for holes?

is it a 12 or 6v system. Have your battery tested first, then run a volt meter on it while not running, then while running at about 3k rpm to see if the alternator is working. Im not an electrics specialist. Are the plug caps resistored?

just some thoughts

[zilch56]

The exhaust has larger Norton peashooters the jets, airbox, etc. is stock.

It is a 12v system

I am not sure how to check for resistor caps

I will have the battery checked then check the alternator as you suggested.

Thanks Tango

[tango911]

if you set your meter to ohms you can check if there is resistance on the caps, by putting the meter lead on each end of the cap. most older hondas have resistered plug caps.

correct me if im wrong anyone or add some info.

[550fi]

Can you put new wires on the coils or are they made in one unit?You can buy plug wire splice kits and add new wire to the coils if you suspect the wires.

[zilch56]

I did some searching and reading. I found out what resistor caps are not installed on the bike. Boyer advises the use of resistor caps as the Boyer unit is susceptible to RF interference. Going to do the other checks and order some NGK caps. Thanks for the suggestions and help

[550fi]

Cool, maybe its simple.

[zilch56]

I checked the charge of the battery static, it was 11.9 volts after sitting overnite. I started the bike the output was about 14.5 volts. I went on another test ride it started cuting out about an 1/8 down the road and I barely made it back. Checking the barttery voltage again, it was 11.2. I think it is the battery.

Thanks for the help guys

[williamc89]

was it 11.2 runing or off, if off its kind normal, a battery will be 11 to 12 volts when no charge going to it.. 13 or higher if bike runing, no more than 15 volts or you have a over chargeing problem, but u should be at 13.5 runing,, go get a spark tester and ride it and watch the spark and see if it cuts out when u have the problem

[tango911]

well try another battery. strange, sounds like under load it starts cutting out. could be the advance?

[zilch56]

Got the recommended battery C9B-B at Orielly's. It is on the charge. I try it tomorrow. I will try the spark plug tester if the battery dosen't work.

[novafrk]

I've got a dollar on the battery being at least part of the issue... motorcycle batteries don't last as long as car batteries. :-)

[zilch56]

I bet your dollar is going to be good, Tell you what if it solves it or partially solves it I pay you that dollar.

I did some reading about Boyer Systems last night:

Frequent Problems
Whereas the typical “points and coil” system can operate quite nicely with a dying
battery supplying 7 or 8 volts, the Boyer demands a full 12V. This means your
battery, 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 your
engine turned OFF, leave your headlamp ON for 2 minutes. With the headlamp still
ON, place a voltmeter across the battery terminals. It should read something like
12.3V. 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 all
that voltage. Your motorcycle might have a worn ignition switch, frayed wiring, bad
kill 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 the
rectifier center wire (usually BRN/BLU) and the wire going to the Boyer WHT. Also
take a measurement between your rectifier ground and the wire going to the Boyer
RED. Both readings should show zero resistance.
3) When the battery cannot hold a charge or cannot get the proper charge from the
alternator, then the Boyer fails to receive the proper voltage. When this happens the
engine will “blubber” like the choke has been turned ON or the fuel has suddenly
gone bad. Often the bike will stumble enough to quit all together. But then it may
mysteriously crank and run great minutes later! To diagnose this malady when it
happens, simply turn OFF the headlamp while the engine is still running. The
headlamp, being the biggest user of electrical energy, will relinquish enough voltage
that the Boyer will once again have 12V and the engine will instantly start to run
better again.

[novafrk]

Yea boyers get weird under 12 volts.

[zilch56]

Changed the battery and all is good. The bike pulled strong through all gears and loads no cut outs. Now I can start fine tuning it. I double checked the time and advance and as the Brits say it was spot on.

I really appreciate the input folks it helps to work through an issue like this. Looks like I owe a some tacos on Taco Tuesday.