Triumphrat

brooks8970

Hi,

I recently picked up a 77 bonnie and Im having stalling and misfiring issues. Im new to working on motorcycles and old triumphs so any help, no matter how basic, would be greatly appreciated. Im thinking of taking the bike to a mechanic but Im short on cash and not on time, so Id rather do any work myself if I can.

When I picked up the bike, it was running great but it has gone downhill fast. I was having some stalling and misfiring issues initially and so I switched out the black and sooty NGK B8s with new champion N3s and it was running better for awhile. Now, I am having constant stalling problems and the new plugs are already black and sooty. I took the bike for a ride last week in traffic and it was stalling every time I let off the throttle so I had to keep it revved at every stop.

I was out of town for a week and today I picked up a multimeter and checked the battery which measured 9.8V and the bike wouldnt start. I jumped the battery with my friend's car and started it. I was hoping to check the recharge at 3k rpms but I couldnt keep the bike idling long enough to hop off the seat and connect the meter, so I took it out for a ride to recharge the battery. I stopped for gas after a few laps around the block, filled it up and restarted it after it misfired a few times. When I pulled back onto the street, I switched the headlamp on and it lost power immediately, so I turned it back off and continued around the block and tried to turn on the headlamp again with the same problem. So I have a few questions:

Is my battery fried?

Could a bad battery cause the plugs to keep fouling?

Do I need to keep the battery on a tender at all times? Im storing the bike in the lot behind my house with no electric power so Im hoping not...

Also, can anyone explain to me how to test the front brake switch.
The brake lever wont engage the brakelight and Ive fiddled with the screw in the lever which I believe controls the switch.

Thanks!

RetroRod

Fault finding is a process of elimination. You change one thing at a time, and if this does not fix the problem then you change one more thing and so on.

You do not say, but knowing what ignition system you have helps. i'm going to assume you have an electronic system of some sort and it is not operating properly because the battery is not providing enough DC voltage.

You need to know if the cause of this is a faulty battery or faulty charging system. The fact that the ignition failed when the headlight was applied may indicate a low charge rate, as a good alternator should cover all electrical requirements, with the engine running above 1000rpm

A simple test is to firstly charge the battery. It should show 12+v when charged. Try running the engine with this. If all is go, then the batt may well be culprit. If the batt will not hold 12+v toss it and replace. A good battery will hold charge for weeks at a time.

Don't worry about the sooty plugs, the modern petrol will soot up all plugs in city driving. Plugs are not your problem. RR

OzBloke

Brooks,
I think you may have a few problems here.
1. Your charging circuit most likely isn't working properly, thus not keeping the battery up to charge. Check alternator, rectifier, zener (unlikely to be the zener). here's a link to doc that may help http://www.mediafire.com/?qknm0rmmmjr

2. Battery could be fried - charge it on the bench and test it when fully charged (don't charge at greater than about 1.5 amps). If at all suspect, replace with an AGM-type.

3. Sounds like it's running rich. Have you left the choke half-on?, the lever near the left carb must be all the way clockwise - cable must be pulled out tight to fully raise the air valves (choke). Other causes could be blocked air filters, incorrect jetting, wrong carb slides (#3 cutaway)

4. The front brake switch is most likely misaligned in the rhs handlbar switch housing. Take it apart (carefully, and don't spill brake fluid everywhere), clean the contacts, and align properly so the screw hits it dead on.

HTH

__________________
Per Ardua Ad Astra
(Through difficulties to the stars)

brooks8970

I am running a Boyer ignition and a conventional Yuasa 12N9-4B-1 battery.

Can anyone recommend an AGM replacement? Ive searched the forum but am seeing mixed results for minimum ah guidelines...Anything else I should be aware of when switching to an AGM?

Ill charge and check the battery tomorrow to make sure that's the issue. Thanks for the help.

Caulky

I`d say 99%, if not 100% of your trouble is the battery.

"Is my battery fried?"....yes

"Could a bad battery cause the plugs to keep fouling?"...yes
Electronic ignitions need at least 11V to work properly.
Misfiring/weak spark causes incomplete combustion, which results in sooty plugs compounding the problem.

The front brake switch is in the lever assembly, and is a fragile, corrosion prone, naff component.
Which is why I replaced mine with a hydraulic switch in the front-brake plumbing.
Seen here behind the headlamp shell:

brooks8970

I charged up the battery a bit and could see it losing charge on my meter, so I went ahead and ordered a replacement. This seems like the right place to start.

The choke had been removed by the previous owner so I dont believe that to be the issue with the plugs.

I carefully took apart and reassembled the brake switch assembly to get a better look and am a little confused. I removed the switch and it looks like there is a plastic rod in the corner of the plastic plate which engages the switch, however the screw in the lever is not aligned with that point no matter how I align the switch. If the screw isnt aligned properly with the switch, shouldn't the brake light be on all the time? Im going to have to take another look when I get the new battery mounted but if the switch is broken, can anyone recommend a replacement source? Is the hydraulic switch an easy mod?

Thanks for all the help!

jumbocomic

Check you are not earthing out on your ignition switch.

RetroRod

Dave, where did you get that headlight shell? RR

Fearless Fly

Had EXACTLY the same same problem/symptoms as this recently on my '69 Bonnie.
DUD Battery.New one fixed it immediately.Have to add that my ride has an EI fitted.

__________________
Cheers,
Fearless.

Caulky

RetroRod, I really cant remember where the headlight shell came from.
I bought it back in the '80s, and it was stored in my old mans loft.

According to the workshop manual, both stop switches are individually adjustable.
They are set-up initially to be 'on'. (ignore the wiring diagram)
Then their adjuster screws are set to be just 'off', so that as soon as the brake is applied, the lamp illuminates.
Obviously, the hydraulic switch is not adjustable but it`s sensitive to the pressure of the fluid.
And its robust and reliable.
It needed a bit of careful pipe bending to install...not a pretty sight