1970 Bonneville 650 T120 Starting Issues Please Help!

teganbarr

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Hi guys, 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?

Apologies in advance, im new to the vintage motorcycles, i'm learning quickly.

Thank you
Tegan
 

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I'm leaning towards saying it is still an igntion/electrical problem....

Perhaps timing or points?

Have you ever done the timing and checked the points gap? I'm even thinking weak coil(s). Did you observe if it made a strong spark at the plugs?

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teganbarr

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Shoot, was hoping it wouldn't be electrical, this could be a nightmare. I did check the spark and it was pretty solid when I kicked it over if thats what you mean.
 

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Yes....I meant if you remove a plug but keep the plug -wire attached, then kick it with the plug touching the engine so it grounds. If there's a nice spark on both sides, then coils are OK.

I'm going through steps to eliminate things first. And then moving to the next step.

You mention cleaning carbs....did you dismantle them? Did the bike ever start on 1-3 kicks and run well? Did the problem begin after anything was done to it?



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teganbarr

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Figure that's what you meant! sorry about that, no for sure coils are good yes. Never on first kick unless it was warm from riding previously, usually around 3-5 on best days, but whenever its running it rides great from what I can tell. As for the issue arising not necessarily, I cant say after I tuned the carbs it got worse. It just always had a bit of an issue starting. I did replace the kicker spring after it broke but when I put everything back together it started pretty good. Ever since my battery slowly started to die it worsened. but like I said even pushing it down a hill it wouldnt fire after multiple times. Bit of a head scratcher, thanks so much for the help.
 

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Barely with us here....we know nothing about your bike. But Triumph's are generally forgiving and should start with a couple kicks when things are in order.

Unless the bike has a pointless ignition like a Boyer unit installed, the battery shouldn't matter much. So it's weird that there battery condition seemed to coincide with the starting problems. Have you ever looked inside the points cover?
 

teganbarr

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Nope it doesn't - I guess thats just when it got worse i suppose, but non relative information like you said, my bad. Interesting about the triumphs, I just assumed all old british bikes were a pain to start. As for looking inside the points cover, I have not.
 

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Then it may have an electronic ignition instead of points. Most likely a Boyer which needs a very strong battery to start it.

We need to ascertain that for sure first.

Above meant to say bare with us....it takes a bit of back and forth to diagnose a problem from afar. We'll get ya going....don't worry. It just might take some time and checking things out in an orderly progressive fashion

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teganbarr

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Yeah no worries! I really appreciate everything so far. It doesn't have an electric ignition. So maybe I should look into the points... possibly after I dismantle the carbs, I have a new kit and am planning on putting in a new float since they leak once and awhile after I tickle it.
 

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To me this is starting to sound like an electrical issue of some sort. Maybe a bad connection on the battery or a short at some point or other. Have you checked to make sure the battery is 100% and is grounded correctly. Also try having it jumper leads connected to a car when kicking it over.
 

teganbarr

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Because its a kick start is the battery of primary importance? other than turning my key for headlights etc. Since im bypassing the battery by pushing down the hill a dozen times, and still wont start. Do you think I have to look further than the battery such as the points gap. I did hook up my battery as well having it jumped to a car and tried kicking and still nothing.

Thanks for the help
 

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If it were mine I would start with the basics – Fuel, spark and air are required.
Check the fuel, if its been sitting for a while, drain it and replace it with fresh fuel – both in the carbies and the petrol tank.
Spark – as its points ignition , give the points a quick clean up with some fine wet and dry sandpaper (say 800) , and remember to clean off any residue by passing a business card between the points afew times. Then check the points gap is correct. Now try taking out a plug and kick over to see if you are getting a strong spark across the electrodes, not from the plug to the bike. Maybe also try fitting new spark plugs. (on the fuel we have here, if I leave my Kawasaki 900 with fuel in the bowls for more than 2 weeks, the fuel will have evaporated off to the point where the green sludge left will foul the plugs- seen by the spark travelling down the side of the ceramic on the centre electrode.)
Air – is the filter blocked it will not be getting enough air, maybe try removing the air filter.
Then turn the fuel on, ignition on and try starting with and without the choke.
 

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If it has points, it should start on a nearly dead battery. The battery needs to be connected ...that's it.

If it has an electronic ignition, you need a strong battery.

The points could be in poor condition??

But it is sparking OK.

If it starts quickly when warm, but not cold....perhaps the choke isn't working?



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teganbarr

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Ya I started with the basics before consulting the thread thats for sure.. but havent checked the points, tickler definitely works - I can see the fuel dribble down the side of my carb most times. Just have a hell of a time starting it cold now. It doesnt have electric start, so kickstarting on a good day is around 3-5 but that is few and far between. Plugs look great and have spark. Looks like I have to check points overall by the sounds of it. Thanks alot guys, hopefully I can figure this dilemma out soon enough.
 

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Welcome to the forum!

...and welcome to the world of classic bike maintenance.

You should certainly have a shop manual. I'm not personally nit-pickey about WHICH shop manual.

Time to take a deep breath and turn to the first page in the maintenance and servicing section, then go right through to the last page. You can skip parts about chain adjustment and lubricating the throttle cable.

The book is laid out in order so that each progressive section is dependent on the previous section to be correct before proceeding.

Remember, 90% of carburation problems are electrical, and 90% of electrical problems are carburation!

DO AS I SAY, NOT AS I DO!

I might personally pull the carbs and soak the bare bodies in Berryman's Chem Dip for 1/2 hour, then carefully clean & adjust the points, and give it another try, but then you'd be shortchanging yourself from having a thorough servicing that will last you all riding season...
 

teganbarr

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Thanks a lot fella's I do have a manual and was reading a few chapters last night haha, I should force myself to a front to back. I know it will only help in the future.
 

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The best clue I pick up is that it starts fine when warm as if the choke isn't working correctly.

You DO pull the choke lever when trying to start it cold right?

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teganbarr

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I do ya, I tickle the carb enough and it kinda dribble's down the bowl a little bit on the outside of the carb. When I bought the bike the previous owner said it isn't a bad thing if it trickles down a bit on these old bikes? - I guess its just a solid indication hah. The odd time it sticks open then I have to do a old fonzie hit to stop it but its nothing major I don't think. It is odd though but YES once I do get it started and go for a little ride and what not, I can come back after an hour or even more and it fires up like a beauty. Its just if I can't ride it for a couple days then I hop on one morning wanting to go somewhere and It won't want to start. Then i'll try another time and it will. Just super inconsistent its so frustrating. I just have to simply give up some days it feels like and pass on a ride. The days that I can't ride when I'm kicking it just feels dry and empty hardly any kick back, the force is there - I still have to give it a solid boot, but I know when its going to fire the kick before, cause when it does generally my kicker bolts with compression or force.. what have you, back at me knowing she is ready to rip. If that makes sense!
 
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