1971 t120r won't start, help! - Triumph Forum: Triumph Rat Motorcycle Forums
Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

LinkBack Thread Tools Display Modes
post #1 of 20 (permalink) Old 10-20-2013, 11:50 PM Thread Starter
Main Motorcycle: 1971 bonneville t120r
New Member
Join Date: Oct 2013
Location: Canada
Posts: 4
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!
Schrodinger is offline  
Sponsored Links
post #2 of 20 (permalink) Old 10-21-2013, 01:31 AM
Main Motorcycle: 2007 Bonneville T100
Senior Member
SeeMore's Avatar
Join Date: Jul 2010
Location: Southern California
Posts: 206
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:


Good luck!


2007 Triumph T100
1974 Norton Commando
1989 Honda GB500, 1984 Moto Guzzi V65SP
1984 Honda Ascot Cafe Racer
2003 Suzuki V-Strom
SeeMore is offline  
post #3 of 20 (permalink) Old 10-21-2013, 01:34 AM
Site Supporter
SOTP Vintage Series
Main Motorcycle: 2006 Thruxton
Lifetime Premium
jonkster's Avatar
Join Date: Jan 2009
Location: Sydney, Australia
Posts: 6,874
Other Motorcycle: 1971 T120
Extra Motorcycle: Ossa 6 day replica
moved from Twins to Classic/Vintage/Veteran

Aunty Mabel
jonkster is offline  
post #4 of 20 (permalink) Old 10-21-2013, 04:34 AM
Team Owner
Main Motorcycle: 1971 t120r
Senior Member
rambo's Avatar
Join Date: Mar 2005
Location: exmouth devon uk
Posts: 5,701
Other Motorcycle: Triumph Rocket 111
Extra Motorcycle: Triumph Thunderbird LT
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 !
rambo is offline  
post #5 of 20 (permalink) Old 10-21-2013, 06:30 AM
Team Owner
Main Motorcycle: Triumph TR7
Senior Member
Join Date: Feb 2012
Location: Norwich, England
Posts: 4,174
Other Motorcycle: T140
Extra Motorcycle: Most of another T140
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"!
JohnA is offline  
post #6 of 20 (permalink) Old 10-21-2013, 08:58 AM
Team Owner
Main Motorcycle: 1971 t120r
Senior Member
rambo's Avatar
Join Date: Mar 2005
Location: exmouth devon uk
Posts: 5,701
Other Motorcycle: Triumph Rocket 111
Extra Motorcycle: Triumph Thunderbird LT
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
rambo is offline  
post #7 of 20 (permalink) Old 10-21-2013, 09:17 AM
Formula Extreme
Main Motorcycle: VFR
Senior Member
Join Date: Apr 2009
Location: Ancaster, UK
Posts: 914
Other Motorcycle: T100S
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.


'69 T100S being rebuilt - very s-l-o-w-l-y - some say stopped!
DerryUK is offline  
post #8 of 20 (permalink) Old 10-21-2013, 10:13 AM
Team Owner
Main Motorcycle: 1977 Triumph Bonneville
Senior Member
Join Date: Sep 2011
Location: Grass Lake , Michigan,USA
Posts: 4,663
Other Motorcycle: 1996 Ducati 900ss/cr
Extra Motorcycle: 2007 Ducati S4RS
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.
duc96cr is offline  
post #9 of 20 (permalink) Old 10-21-2013, 04:09 PM Thread Starter
Main Motorcycle: 1971 bonneville t120r
New Member
Join Date: Oct 2013
Location: Canada
Posts: 4
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.
Schrodinger is offline  
post #10 of 20 (permalink) Old 10-21-2013, 04:50 PM
Pole Position
Main Motorcycle: 2012 Bonneville T100
Senior Member
Join Date: Aug 2003
Location: Massachusetts, USA
Posts: 3,784
Other Motorcycle: 1970 TR6R: SOLD....
Extra Motorcycle: 1999 Yamaha Virago 1100
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

Jim Ballard

The older I get, the faster I was....until lately!! (Speed IS the fountain of youth)!
jimballard is offline  
Sponsored Links

Quick Reply
All posts must adhere to Forum Rules

Register Now

In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Thread Thread Starter Forum Replies Last Post
Just been given a 1971 T120R Gino The Welcome Center 1 12-17-2012 09:35 AM
1971 T120R Footrests leylandauto Classic, Vintage & Veteran 3 11-08-2012 08:31 AM
Bonnie 1971 t120r slatept Classic, Vintage & Veteran 9 01-31-2011 06:54 AM
1971 T120R problems rocker_jw Classic, Vintage & Veteran 1 05-03-2010 12:36 PM
Ny 1971 T120r sangalfie Classic, Vintage & Veteran 6 04-30-2010 10:05 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

For the best viewing experience please update your browser to Google Chrome