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Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

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Old 10-20-2013, 11:50 PM   #1 (permalink)
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1971 t120r won't start, help!

Hi everyone,
this is my first post but I have been browsing threads on this forum since almost one year. So here goes my story : a year ago, I bought a 1971 triumph bonneville t120r. Since then I didn't ride it alot (I just had my liscnece less than 2 mouths ago). When I bought it, it was hard to start, but after a few kicks it would fire and no problem occured during short rides.

To resolve the hard starting problem, I set the ignition timing with a strobe to exactly 38 degres before TDC. The bike started at first or second kick! (Pazon ignition on the bike)

A few mouths after, the bike was hard to start again. What I have done since then :

-Remove rust from tank with white vinegar
-Clean amal 930 carbs
-Charge battery
-Fill with fresh gas

The motorcycle started after few kicks. I tried to ajust the fuel mixture (getting highest possible idle speed, then enrich it a little to avoid hesitation on throtle). After a few rides, I filled it with fresh gas and while returning home, I had to keep RPM really high so it wouldn't die! Once cold, it wouldn't even fire. I checked the timing, it was ok. I installed homemade teflon spacers between manifolds and carbs after I had glass them. I cleaned the carbs once more. I set spark plugs gaps (beautiful blue sparks) and valves clearance. It still doesn't start! I just don't know what else to do ... Any help will be appreciated!
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Old 10-21-2013, 01:31 AM   #2 (permalink)
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You might have a clogged pilot circuit in your carbs which is common in Amal Concentrics if the bike sits for a long time between use. It will cause the symptoms of hard starting that you describe.

You said that you cleaned the carbs, but did not go into detail about how you did that. At any rate you can clean the pilot circuit with the carbs on the bike.

Over time the gas passages slowly clog up with scale and varnish from dried gasoline and eventually clog right up. The only remedy is to physically unclog the jet with a wire probe.

The pilot jet is drilled 16 thou dia. (0.016"), a very tiny orifice. If you can find a wire that size you can probe the jet from the air side, after the mixture adjuster screw is removed (use a flashlight to locate the orifice). Or go to your local hardware store and get a #78 drill, mount it on an end of small brass or plastic tube, The drill will re-size the orifice, so be careful and make sure all swarf is blown out by compressed air.

Also you might want to post your issue on the Classic and Vintage forum for more responses at this link:

http://www.triumphrat.net/classic-vintage-and-veteran/

Good luck!

Chris
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Old 10-21-2013, 01:34 AM   #3 (permalink)
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Old 10-21-2013, 04:34 AM   #4 (permalink)
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Check your battery voltage.You might well have a spark but the ignition could be on full advance or something if the voltage is low.
Best way to start a non-starting bike is the easy start spray ether.Engine starter spray or whatever they call it out there.Once running,jets may rinse themselves out.Try these two things first.
A welcome to the fountain of knowledge here !
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Old 10-21-2013, 06:30 AM   #5 (permalink)
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Quote:
Originally Posted by rambo View Post
...Engine starter spray or whatever they call it out there...
In England, "Easy Start" - factual but boring. In Oz they like to use more interesting language and over there, I'm reliably told, its sold under the brand name "Start Ya Bastard"!
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Old 10-21-2013, 08:58 AM   #6 (permalink)
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I have a BSA addicted to easy start.Always need a squirt after a long lay up.It does not want to pull petrol through its 32mm carbs and my leg is too weak to kick it hard.T120 is a good starter
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Old 10-21-2013, 09:17 AM   #7 (permalink)
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I'll go with rambo. You may have a charging problem, you charge your battery, bike starts, ride for a while then it starts playing up.

Are your lights nice and bright at 3000? You need 13.5 - 14.5v lights on or off.

Difficult to tell the time-line from your posting but batteries do self-discharge if you don't ride your bike regularly. If you leave your bike for months then it needs a maintainer on the battery. I use an Optimate.
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Old 10-21-2013, 10:13 AM   #8 (permalink)
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They sell a little folding set of carb reamers on eBay for About $15 U.S. they are less aggressive than drill bits but will get the job done. I thing to note : the reamer must go in as far as the center of the carb, about 1 1/2" , to clean the whole passage. If it only goes in part way it's clogged. Spray it with carb cleaner after to remove debris. Wear safety glasses, it will splash back and blind you.
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Old 10-21-2013, 04:09 PM   #9 (permalink)
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Wow, thank you for all these responses.
To answer to SeeMore, I completely removed the carbs, and sprayed carb cleaner into the pilot circuit. I could see the carb cleaner coming out of the air screw hole and out of a little hole placed right after the mainjet. I also cleaned every pieces of the carbs. The battery voltage was 12.4 V (is that enough?) when I last tried to kickstart it, but it is getting lower with more and more tries at kicking it.

I like the start spray ether Idea, I will try to find some before winter!

Thanks again for the fast replies, it is hard, here in montreal, to find someone available and experienced with these old bikes.
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Old 10-21-2013, 04:50 PM   #10 (permalink)
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O.K, my silly, but have to ask queston: you are "tickling" the carbs before you try to start it, aren't you?
The "village idiot" has seen stranger things in his time: Jim
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