Ignition pick-up coil / Crank position sensor (nerdy AND boring) - Triumph Forum: Triumph Rat Motorcycle Forums
» Main Menu

Discussion Forums
 » Twins
 » Tiger
 » General
 » RAT

 » Blogs

Motorcycle.com Links

 » Photo

Motorcycle Forums
» Insurance
» Sponsors
» Our Partners
»ATV Reviews
»Motorcycle Games

Twins Technical Talk Technical Talk for Hinckley Triumph Twins: Bonneville, T100, Speedmaster, America, Thruxton, and Scrambler.

LinkBack Thread Tools Display Modes
Old 11-20-2010, 07:32 AM   #1 (permalink)
Lifetime Premium
Site Supporter
Main Motorcycle: 2009 Bonneville SE
Forchetto's Avatar
Join Date: Jun 2009
Location: Asturias, Spain
Posts: 15,216
Other Motorcycle: Yamaha XV1100
Extra Motorcycle: Qingqi QM200GY-BA
Ignition pick-up coil / Crank position sensor (nerdy AND boring)

A cursory trawl through the forums shows this component to be responsible for no end of problems on Bonnies. I can't understand why this should be so. Similar devices have been used on all manner of bikes for donkey's years and they mostly last the life of the engine. It's a relatively simple, passive device with no moving parts. The working principle was worked out by Michael Faraday as long ago as 1821. Another mystery of British electrics...


This simple component is just an assembly consisting of a metal bracket holding a plastic housing that encloses the two active elements in it: A coil of very fine enamelled wire wound around a magnetised iron core. It is in effect a tiny generator stator.

I have got hold of a spare one and close examination shows a well-built, robust and well epoxy-sealed assembly that should be reliable. I can't see the windings inside though, so this is where the troubles could stem from, cheap enamelled wire or faulty soldering or strain-relief of the many turns of very fine wire necessary to obtain the sort of resistance and inductance values required in such a small component.

On carbed models Triumph call it an "Ignition pick-up sensor" and on EFI models it's called a "Crank Position Sensor". Other manufacturers use names such as "Pulse coil" or "Pulse generator".

It's actually the same component on both: Part number T1290131 and costs 49.61 ($79).

On both models it's positioned inside the triangular cover on the right of the engine and fitted very close to the alternator rotor.

On carbed models the rotor has some metallic strips bonded to it called reluctors that pass very close to the magnetic core as the rotor turns. Everytime they do this a tiny electrical pulse is generated and sent to the igniter. This signal is processed by the program or map loaded into the igniter to work out the moment of ignition and the degree of advance and retard to be applied, depending on engine revs. The advance and retard function is entirely electronic, unlike the old centrifugal weights system. No moving parts, just time-delay circuitry that applies more or less delay to the received signal.

On EFI models it also sits close to the rotor but this is fitted with a toothed wheel. Everytime a tooth passes the sensor it also sends a signal to the Electronic Control Module (ECM) and it's used not only to work out the ignition timing but the moment of fuel injection as well. Between the signals sent by this sensor and the MAP sensor (manifold absolute pressure) the ECM knows exactly in what position the crank, and herefore the pistons, are at any given moment.


If the pick-up sensor is on the bench like the one in the photo the resistance can be measured using the multimeters probes. If however it's still fitted to the engine the connector can be difficult to access, being stuck between the right hand seat rail and the top of the airbox. Brilliant bit of engineering this...

Unplugging is often impossible without further dismantling. You can see the two wires that go into the connector though, so you could just use the following method:

Using a couple of pins prick the insulation of red and black wires under seat tube above the airbox. Drive the pins deep enough to pierce the insulation and contact the conductors inside the cable. Connect the multimeters probes to the pins and set the meter to the appropiate Ohms range.

The quoted resistance to be expected is 560 ohms +/-10% at 20C .This means you should see somewhere between 504 and 616 Ohms. If you measure it with the engine hot the resistance would be higher, as much as 640 Ohms or so.

You could even measure the voltage output with this method. Just ensure the two pins and meter probes are not short-circuited, set the meter to a low DC volts scale and start the engine. You should see at least 0.6 volts although at idle this would be pulsating and the digital readings difficult to pin down.

This nice drawing I've found shows how the pick up generates two pulses: one positive and another negative, the first one as the reluctor first meets the pick-up coil and the second as it leaves it:

A simple tester can be made using a couple of green LEDs that will detect any pulses above around 2.2 volts, both the positive and the negative pulses will show up as the LEDs light up alternatively as the engine is cranked:

The gap for the pick-up coil is quoted in service manuals as 1.0 mm +/-0.20 mm but was changed during production due to warranty issues. The following was sent out as a statement by the Factory in a technical release to dealers:

Affected Models: Bonneville/T100, America, Speedmaster, Thruxton and Scrambler.

Should a bike (see above) demonstrate faulty ignition coil type symptoms (most commonly an engine misfire), please initially check and adjust the ignition pick-up (IPU) air gap (we recommend an air gap of 0.8mm).

Since changing the IPU air gap in production to 0.8mm, we have had no ignition coil warranty claims.

As far as I know this only applied to carbed models with chronic ignition faults, often blamed on the ignition coil.

The 2008 service manual of which I have a copy, only covers bikes up to 2008, including EFI models, and the gap is still quoted there as 1.0 mm so maybe that technical note came out later than 2008.

The pick-up coil to rotor gap is set by positioning the alternator rotor with a reluctor strip facing the magnetised core and measuring the gap with a suitable feeler gauge. If found to be incorrect the fixing screws are loosened slightly, not too much, but enough to enable the component to move a bit, ensuring the feeler gauge is a firm sliding fit between the two points and re-tightening the screws to 10 Nm (7.3 Lbs/Ft). Re-check the gap after tightening.

Last edited by Forchetto; 11-21-2010 at 04:35 AM.
Forchetto is online now   Reply With Quote Quick reply to this message
Sponsored Links
Old 11-20-2010, 08:02 AM   #2 (permalink)
Senior Member
Main Motorcycle: Bonneville -01 (sold)
kenneth_k's Avatar
Join Date: May 2009
Location: Skotterud, Norway
Posts: 1,433
Other Motorcycle: Scrambler -06 (hardtail)
Extra Motorcycle: looking for a new #1
ctrl+s... enter!

have to check that on Davids bike.. he has allready changed the coil ones!
I never seen so many sissy men on a bike forum. "Good judgment comes from experience. Unfortunately, the experience usually comes from bad judgment."
kenneth_k is offline   Reply With Quote Quick reply to this message
Old 11-20-2010, 08:07 AM   #3 (permalink)
Senior Member
World SuperBike
Main Motorcycle: 04 cafed Bonnie
ozbon's Avatar
Join Date: Aug 2005
Location: Toowoomba Queensland Australia (soggy bottom)
Posts: 2,499
Other Motorcycle: Two '68 Benelli 350's,
Extra Motorcycle: '60 Morini Tresette 175
For someone like me who has no concept of electrical wizardry that was a good read, thanks Forchetto.

"Yeah, look.....Baz just vanished, like a.....fart in a fan factory, ya`know?! ".
ozbon is offline   Reply With Quote Quick reply to this message
Old 11-20-2010, 04:25 PM   #4 (permalink)
Grand Prix 250
Main Motorcycle: Thruxton
Join Date: Nov 2010
Location: East Coast, USA
Posts: 67
Always wondered how that worked. However, after a frustrating bout with intermittent spark, I dismantled, checked resistence and gap, found satisfactory, but the problem persisted. A dealer ultimately fit a new one and problem gone. Yup, those buggers cause some headaches!
carmi52 is offline   Reply With Quote Quick reply to this message
Old 11-20-2010, 05:04 PM   #5 (permalink)
Site Supporter
Main Motorcycle: 2013 Tiger 800XC
propforward's Avatar
Join Date: Mar 2008
Location: MN, USA
Posts: 28,343
Other Motorcycle: 2007 Bonneville, ST1300
Extra Motorcycle: G12DL, ZX1100, KLX400
Linking this in the electrickery part of the info sticky.

This thread is a lot better than the crush washer one.
Foreigner zen navigating America by motorcycle for 18 years.
propforward is offline   Reply With Quote Quick reply to this message
Old 11-21-2010, 07:29 AM   #6 (permalink)
Senior Member
Main Motorcycle: My 09 Bonneville Black
Join Date: Apr 2009
Location: Canada
Posts: 1,296
Other Motorcycle: Want the new CB1100
Just happened across this post. Great write up, explanation and contribution Forchetto. The Bonneville library of technical fixes etc. in the stickies is really filling out much of it thanks to your well presented write ups. Thank you bro.
LuckyBonnie is offline   Reply With Quote Quick reply to this message
Old 11-21-2010, 08:34 AM   #7 (permalink)
Senior Member
Supersport 600
Main Motorcycle: 08 Bonneville T-100
chadwick's Avatar
Join Date: Jan 2010
Location: Iowa
Posts: 157
Extra Motorcycle: 1982 CBX
I agree, another winner from Forchetto. Nice job!
chadwick is offline   Reply With Quote Quick reply to this message
Old 11-21-2010, 05:29 PM   #8 (permalink)
Lifetime Premium
Site Supporter
Main Motorcycle: 2007 Bonnie T100
bonza's Avatar
Join Date: Sep 2007
Location: Melbourne, Australia
Posts: 1,385
Other Motorcycle: Jeep Wrangler
Thumbs up

well done Forchetto, brilliant write up

have saved it for future reference. thankyou
2007 Tuxedo T100.
Dom Tourers, TTP breathe, baffle gone, 40/140/1 shim 3 turns, TTP stage 1, Hagon Nitros, Dart screen, Pingel fuel valve, Monza gas cap, Burton seat, Avon Roadriders
I like a man who grins when he fights -
Winston Churchill
bonza is offline   Reply With Quote Quick reply to this message
Old 11-21-2010, 09:21 PM   #9 (permalink)
Senior Member
Formula Extreme
Main Motorcycle: GS 1200
Texascat's Avatar
Join Date: Mar 2006
Location: Bentonville, AR
Posts: 531
Other Motorcycle: Speed Triple 2008
Extra Motorcycle: Scrambler 2011
Thanks a bunch... the power of this forum is incredible... leraning a ton from guys like you Forchetto...
2014 BMW GS 1200W
2011 Triumph Scrambler
Texascat is offline   Reply With Quote Quick reply to this message
Old 11-23-2010, 06:21 PM   #10 (permalink)
Senior Member
Main Motorcycle: 03 T100
mikeinva's Avatar
Join Date: Mar 2007
Location: richmond va
Posts: 8,088
Have you got a pic of the efi alt rotor?
Why do I feel young on my bike
mikeinva is offline   Reply With Quote Quick reply to this message
Sponsored Links

Quick Reply

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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
Display Modes

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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Ignition Sensor (Coil Pick-up) Repair Legend JJ Hinckley Classic Triples 2 07-22-2010 09:38 AM
New pick-up coil, ignition coil, & ignitor. No Dice... Flyhalf_Keith Twins Technical Talk 22 04-18-2010 03:19 PM
Ignition pick-up sensor j98sprint Maintenance & Workshop Talk 4 02-21-2006 01:42 AM
crank position sensor Seeker Trophy 7 12-05-2004 07:20 PM

Powered by vBadvanced CMPS v3.2.2

All times are GMT -4. The time now is 03:35 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Motorcycle News, Videos and Reviews
Honda Grom Forum Harley Davidson Forum Honda 600RR Forum Kawasaki Forum Yamaha R6 Forum Yamaha FZ-09 Forum
1199 Panigale Forum Roadglide Forum Honda CBR1000 Forum Vulcan Forum Yamaha R1 Forum Yamaha R3 Forum
Ducati Monster Forum Harley Forums Honda CBR250R Forum ZX10R Forum Star Raider Forum Yamaha Viking Forum
Suzuki GSXR Forum V-Rod Forums Honda Shadow Forum Kawasaki Motorcycle Forum Star Warrior Forum KTM Duke 390 Forum
SV650 Forum BMW S1000RR Forum Honda Fury Forum Kawasaki Versys Forum Drag Racing Forum Ducati 899 Panigale Forum
Suzuki V-Strom BMW K1600 Triumph Forum Victory Forums Sportbikes BMW NineT Forum
Volusia Forum BMW F800 Forum Triumph 675 Forum MV Agusta Forum HD Street Forum Suzuki GW250 Forum
Yamaha Motorcycles Victory Gunner Forum Victory Charger Forum Honda Vultus Forum HD LiveWire Forum Ninja H2 Forum
Ducati Scrambler Forum Kawasaki Ninja 250SL Forum

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.