Bonneville America Forums Forums Technical Forums General Tech 1970 Bonneville Starting Issues Please Help!

Hi guys, i'm new to the vintage bike ways but im quickly learning. I bought a 1970 Bonneville 650 T120 just over a year ago and was having minor starting issues. The odd day after kicking it over and over it wouldn't fire, then surprisingly the next day it would start after about 6 kicks (super inconsistent) which is good for my bike. But towards the end of the year it was getting worse. I did a compression test and had ample amounts, plugs were fine and still wouldnt go. I thought it was a ignition issue but I ran it down a small hill numerous times even in 2nd and still it wouldnt go. Any reason this could be? there are probably many factors I assume but I thought it could be a carburatore issue. I cleaned them at the beginning of the riding year as soon as I bought the bike. Maybe their due for another check up?

Thanks
Tegan

Check the points see if they fire. Then there is wiring and relays. Coils go bad. There is only a few things to test. Start at the spark plugs fire no fire? No first test the wires, no fire see it you are getting fire to the coil. Then the points so on and so forth. More than likely its points or coil.

Look for oil on the points, Those bikes are known to lose the seal on the end of the cam where the advance unit mounts. Also always set the timing fully advanced. Those points should be adjusted regularly. There is an upgraded Lucas timing plate available for those too that does away with the stupid eccentric adjustments. Also I always had best luck running AC R45XLS plugs, those things will burn dirt. If by chance the seal is bad you will need a small slide hammer to remove the advance unit that is made for that task it is on a taper. The later models have an index on the taper and in the cam making replacement much easier than the old smooth ones. The seal can easily be pulled out with a small hook and new one pushed back in but be careful not to roll it. There is a hole at the base of the jugs above the trans, that is where the timing plunger goes. The plunger drops into a hole drilled into the crank, there are 2 and you want the firing position hole not the TDC hole. Time the left side first then the right, again fully advanced. Pull the plugs and get the rear wheel off the ground ,put it in high gear, rotate the engine by the rear wheel watching the valves when the intake opens start feeling the timing plunger for the index. That bike should start every time on one kick if timed and everything is adjusted right.

Which carbs? The Amals have brass parts that are known to wear out of spec causing both starting and running issues.

The O-ring on the idle screw is another one to check as well as the screens on the bottom of the bowls. (Amal)

Tegan, as a '71 650 Triumph Tiger myself who has had to go through my own personal apprenticeship of owning, maintaining & riding and old Triumph Meriden twin, here are a few things I would be looking at first.
Ignition: Are you confident the points and timing are correct?
Voltage: Have you measured it? These old twins demand a full 12 volts to get them started. Out of curiosity, have you tested horn or lights work just to ensure you positive earth battery polarity is correct?
If you have correct voltage, are you getting spark when you hold one of your HT leads to earth when kicking it over?
Fuel: How old do you think the fuel might be in your tank? If it is over 3 months old, toss it into your lawn mower & start with fresh stuff. Have you opened up the bottom drain on your Amal carb bowl drains to ensure that the fuel isn't contaminated?
Flooding the carbs: Probably the most important single issue when starting these old bikes. If everything mentioned above checks out OK, do you tickle the plungers on each of your Amals sufficiently to have fuel run down the side of your carb? Most new owners of these old twins are petrified of flooding their Triumph when the first get them. If your Amal float settings are correct, it is virtually impossible to flood them. If you think you have ticked the carb sufficiently, try giving the engine a couple of kicks with the ignition still off then tickle the buggers a bit more then turn on your ignition & see if it fires up when you kick it over. Everyones old Meriden Triumph starting procedure may be a little different but one thing my Tiger does not like is for me to twist the throttle prior to it starting. I have to flood it by tickling the plunger, and as I kick it over and hear the engine beginning to come to life, I then catch it with the throttle and give it a good rev into life. Twist it too early and it just wont start.
Good luck and I hope you get it started. Ain't nothin more frustrating than a kick starting bike that doesn't want to start.