Service Bulletin - Triumph 1966 and Early 1967 650cc and 500cc Twin Models Ignition Cam Replacement

Sep 27, 2026

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Service Bulletin dated April 7, 1967 addresses ignition problems on 1966 TR6/R and T100/R and early 1967 TR6/R models fitted with Lucas 12-volt coil ignition. Symptoms include loss of power, serious overheating, and engine seizure under load at around 3700 RPM, caused by a “maverick spark” during the inlet cycle. The bulletin instructs dealers to unplug three alternator leads to confirm the fault, then replace the ignition cam 54441729 with the new 54419124 “1606 cam,” plus ordering guidance and cautions excluding A.C. ignition models.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages24

Reading Time1 h 0 min

AccessFree to download

Service Bulletin

Ignition trouble (Lucas coils) and symptom diagnosis

Cause: “maverick spark” during inlet cycle

Cure: replace ignition cam (54441729 to 54419124)

Ordering, returns, and cautions

Service Bulletin

Headlight bulb failures and gearbox problem (1966)

BULLETIN April 7,1967 67/3 TO ALL EASTERN TRIUMPH DEALERS SUBJECT:1966 and Early 1967-650cc and 500cc Triumph twin models with 12 voltbattery ignition system, Service Problem ---Ignition trouble with models that have Lucas coils,1966-TR6/R and T100/R models.Alse 1967-TR6/R(1967-T100/R models have Sibacoils). SYMPTOM:Loss of power and serious over-heating that could lead to a piston seizure.Owner complains that engine is "bogging-down"as though brakes are dragging orengine selzing,at engine speed of approx.3700 RPM. CAUSE:A "maverick spark"can occur during the inlet cycle,This "extra"spark willcause premature burning of the inlet charge(mlxture)to produce overheating andloss of power.The spark is caused by a voltage surge when the points close,Itusually happens with Lucas 12 volt coils.It is not likely to happenwlth the Sibacoilsfitted to 1966-167 T120/R and 1967-T100/R models, To check for this condition,try to eliminate the symptom by unplugging the threealternator leads at the junetion bloek.If thls eliminates the symptom you can bereasonably certain that the over-heating or piston seizure Is caused by this "extra"unwanted spark. CURE:Replace the original ignition cam 54441729 by the new type 54419124.This newcam has a much longer dwell when the points are closed and is known as the"160⁶cam".The longer dwell allows the points to close muchearlier and at atime when combustion eannot occut. We can supply the 1600 cam(54419124)from stock,The older style(54441729)should only be used for 6 volt battery ignitlon models up to and inel.1965.If youfit the new 160°cam to a6volt model it would cause extra drain on the battery. Note for Ordering:We suggest thatyou order a few of the new 160°contact breakereams immediately.If you will return to us the original equipment cams(shortdwell)we will zeplace them free-of-charge with the new type,At the sametime if you will return to us any early sleeve and action plates,we will also sup-ply free-04-charge replacements of the lateat type pazt454415751.This sleeveand action plate can be identified by the black finish and it has the smallest slot(for the locating pin)which reduces distortion of the taper that can cause a"wobble"of the contact breaker eam. CAUTION:None of the information in this Service Bulletin applies to A.C.ignitionmodels such as the T100/C,TR6/C or the T120/TT Special. 1967-TI20/R and TR6/R models after Engine No.DU51771 and T100/R models afterEng.No.H51616 have the new 160igmition cam fited at the factory.THE TRIUMPH CORPORATION -Service Mgr. SERVICEBULLETIN October 3,1966 1966=B=RAMCEB TMIN MODES BULLETIN No,19 # SUBJBCT:Hoad Li的t Bulbs and Gearbox Problem Me have just receivad a large shipment of 12 volt head 11ght balbs,part 6 thathave been on order writh our suppliers for nany veeks and ve are now shipping againtdealers back-ordors.If you need bulbs and do not have any on back-ordor we suEgestthat you place an order now. ## HEAD LIGHT BLLB FAILUEBS Refer to Yellou Index Balletin 66/5 of August 5th on this aubject.Som dalersreport that our head 11ght rubber mounting kit CDL63(Liat Prlce 32.0OA)has helpedto reduce the murber of bulb failures.Unfortunately,we do not have enough reportaas yet to know whether the rubber mcunted head light is a defini te cure.This canonly be proved by more toating. Mith every box of head light bulbs we are sending you aainst your back-orders,werdll supply one head light mounting kit.Lease let us knDW as soon as poss1ble ifthis kit v1l effectively reduce the nunber of bulb failures. GEARBOX PROELE:1966-650cc "Bn Range Hdels "Juping out of high gearl SYMPTON:Gearbox shifts in the normal fashion with no problem oxept twnen crulaingin high gear,the gear wdll muddenly dis-angage. CAUSE:Inproper nachining of the "Y"notch in the edge of the camplate can causethe camplate to rotate a fou dogrees to produce this aymptom. CURE:F1t a replacement canplate. As of Septerber.30th we have inspocted our c

FAQs

What symptoms indicate the ignition trouble described for the 1966 TR6/R and T100/R models?

Loss of power and serious overheating that could lead to piston seizure, often described as “bogging-down” or as though brakes are dragging, with engine speed around 3700 RPM.

How can dealers check whether the overheating is caused by the unwanted “extra spark”?

Eliminate the symptom by unplugging the three alternator leads at the junction block; if this removes the symptom, the overheating or seizure is reasonably certain to be caused by the extra unwanted spark.

What is the required cure and cam replacement part number?

Replace ignition cam 54441729 with the new type 54419124, known as the “1606 cam,” which provides a much longer dwell and allows points to close earlier.

Sep 27, 2026

Upload by Kurz