Sorry corrected myself.
So it might be an air leak in one cylinder. Maybe carb/manifold gasket. Perhaps head gasket.
1971 T100C Refresh
- Thread starter Sundance
- Start date
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So it might be an air leak in one cylinder. Maybe carb/manifold gasket. Perhaps head gasket.
Seem like it wouldn't be an air leak. Both cylinders will fire regularly and separately, so the head gasket I think would be fine. The carb manifold gasket is new and just replaced when I rebuilt the carb as a way to try to fix this.
Also, try new spark plugs, correctly gapped? That'll eliminate one more thing if nothing else.
Might be dirt in tank?
It's possible the head gasket is slightly leaking? I had a small head-gasket leak, only started playing up when hot, ran better at high revs, if stopped and let cool, was okay again until running for a couple of miles. Testing cylinder pressure might show this.
Other thing could be a loose electrical connection somewhere, or shorting. Starts playing up when riding, more bumps and vibrations. Changing gear would alter vibration frequency. Way to test this is hot wire bike and go for ride, only ignition circuit active. Are the connections to coil good?
Ok. If not an air leak, not electrical, head gasket is fine, carb is fine, might be fuel supply to carb? Perhaps doesn't flow well through petcock? Not enough for two cylinders to optimally be going together? Is there a vent in fuel cap? Have you tried unscrewing cap when problem starts, in case there's a vacuum?
Might be dirt in tank?
It's possible the head gasket is slightly leaking? I had a small head-gasket leak, only started playing up when hot, ran better at high revs, if stopped and let cool, was okay again until running for a couple of miles. Testing cylinder pressure might show this.
Other thing could be a loose electrical connection somewhere, or shorting. Starts playing up when riding, more bumps and vibrations. Changing gear would alter vibration frequency. Way to test this is hot wire bike and go for ride, only ignition circuit active. Are the connections to coil good?
Did the cylinders react differently at all when components were switched? Perhaps the issue is with the carburetor.
If not already, +1.
Should not be resistor plugs - Champion RN4, NGK BR7ES, etc.
Should not have HT resistance, period; not plugs, not caps, not leads; however, the photos with the o.p.'s first post appear to show original plug covers, in which case the plug terminals are crimped on the leads - the covers are just that.
@Sundance:-
. Detach each plug cover/cap from its plug and look inside the cover; while holding the plug cap, wiggle the HT lead; if the plug terminal moves in the cover, the HT lead and plug cover is correct D2207 (60-2207) listed in the parts book, probably original to the bike.
. Plug covers or caps, probably wise to check the resistance - detach each HT lead from its coil, measure the resistance between each HT lead's coil terminal and its cover's/cap's plug terminal; should be close to zero Ohms.
. If the reading is not close to zero Ohms, if it is a cap and not a cover, unscrew cap from lead, test the resistance of each component individually. If both components then test close to zero Ohms, follow @solomon's advice but only temporarily until you can replace separate leads and plug caps with correct D2207.
.. If either lead or cap does not test close to zero Ohms, discard both, replace with a D2207. As I say, these (should) have both coil and plug terminals crimped to the lead (avoid any that do not), eliminates both the possibility of a separate plug cap "going high resistance" and also the separate lead-to-plug connection that persistently loosens causing HT problems.
Should not be but things you should check:-
. Two separate coils, one mounted each side of the frame tubes above the engine, the Boyer Transistor Box Black wire is connected to only one coil's -ve terminal, only this coil's +ve terminal is connected to the other coil's -ve terminal and only that second coil's +ve terminal is connected into the bike's Red harness wiring. This is known as "connection in series".
. LT resistance between 1.5 Ohms and 2.2 Ohms.
Because the coils' LT are "connected in series" between the Boyer Transistor Box Black wire and a harness Red wire to battery +ve, any problem with one coil LT will affect both; LT affected will affect the HT.
When checking coils' LT resistance, also check each coil between:-
. HT terminal and each LT terminal in turn, should be ~5,000 Ohms but old PVL's could be up to 7,000 Ohms;
. coil's casing and each of the three terminals in turn, should all be very high Ohms = no continuity.
What exactly did you do during the rebuild?
Either the bike is working correctly or it is not. If it is not working correctly, why discount suggestions before checking them?
Engine idling, if you can hear a chuffing sound from the head gasket, it is leaking. No chuffing sound, the other possibility for a leak is between the cylinders; this will need a leak down test to detect, the simpler compression test will give the same pressure from each cylinder.
When the engine is idling, spray a flammable liquid around all three manifold joints in turn. If the idle changes/speeds up after a spray, the flammable spray is being sucked into the inlet through that manifold joint and is improving the mixture.
Did you fit both the E11459 gasket and the E2968 Insulating block between the carb and the manifold?
Thanks for this. I probably should consider a head gasket leak as you say also. There is a vent in the fuel cap and I've tried running with and without the cap with no difference between them. I can check again but I think the tank is clean, also I did rebuild the petcocks and when re-installing them let them flow and cut them off to see that they were working properly. Loose electrical connections - still seems the might be the case so when I get the time I'll need to carefully follow the wiring. Unfortunately, as is probably the case most of the time, this will be a bit tedious. Thanks again.
Rudie, again thanks for all this. Lot's to check out. I've got the 60-2207 leads on order as my current leads seem like they are a bit loose. On the plugs my bike has the NGK B-7EC plugs that "were" working fine. These were the type suggested in my book and from what I see are non-resistor plugs. On the plugs you mention NGK BR7ES and Champion RN4, just making sure you are saying these ARE resistor plugs so should be avoided.If not already, +1.
Should not be resistor plugs - Champion RN4, NGK BR7ES, etc.
Should not have HT resistance, period; not plugs, not caps, not leads; however, the photos with the o.p.'s first post appear to show original plug covers, in which case the plug terminals are crimped on the leads - the covers are just that.
@Sundance:-
. Detach each plug cover/cap from its plug and look inside the cover; while holding the plug cap, wiggle the HT lead; if the plug terminal moves in the cover, the HT lead and plug cover is correct D2207 (60-2207) listed in the parts book, probably original to the bike.
. Plug covers or caps, probably wise to check the resistance - detach each HT lead from its coil, measure the resistance between each HT lead's coil terminal and its cover's/cap's plug terminal; should be close to zero Ohms.
. If the reading is not close to zero Ohms, if it is a cap and not a cover, unscrew cap from lead, test the resistance of each component individually. If both components then test close to zero Ohms, follow @solomon's advice but only temporarily until you can replace separate leads and plug caps with correct D2207.
.. If either lead or cap does not test close to zero Ohms, discard both, replace with a D2207. As I say, these (should) have both coil and plug terminals crimped to the lead (avoid any that do not), eliminates both the possibility of a separate plug cap "going high resistance" and also the separate lead-to-plug connection that persistently loosens causing HT problems.
Should not be but things you should check:-
. Two separate coils, one mounted each side of the frame tubes above the engine, the Boyer Transistor Box Black wire is connected to only one coil's -ve terminal, only this coil's +ve terminal is connected to the other coil's -ve terminal and only that second coil's +ve terminal is connected into the bike's Red harness wiring. This is known as "connection in series".
. LT resistance between 1.5 Ohms and 2.2 Ohms.
Because the coils' LT are "connected in series" between the Boyer Transistor Box Black wire and a harness Red wire to battery +ve, any problem with one coil LT will affect both; LT affected will affect the HT.
When checking coils' LT resistance, also check each coil between:-
. HT terminal and each LT terminal in turn, should be ~5,000 Ohms but old PVL's could be up to 7,000 Ohms;
. coil's casing and each of the three terminals in turn, should all be very high Ohms = no continuity.
What exactly did you do during the rebuild?
Either the bike is working correctly or it is not. If it is not working correctly, why discount suggestions before checking them?
Engine idling, if you can hear a chuffing sound from the head gasket, it is leaking. No chuffing sound, the other possibility for a leak is between the cylinders; this will need a leak down test to detect, the simpler compression test will give the same pressure from each cylinder.
When the engine is idling, spray a flammable liquid around all three manifold joints in turn. If the idle changes/speeds up after a spray, the flammable spray is being sucked into the inlet through that manifold joint and is improving the mixture.
Did you fit both the E11459 gasket and the E2968 Insulating block between the carb and the manifold?
On the carb rebuild, I took it all apart, including removing the needle block and clearing all, including the smallest air holes. Most of the on-line videos remarking on amals don't include removing the needle block but a friend said this is part of the rebuild - and I replaced all the washers and gaskets. I used the O ring on the carb to manifold and have the spacer block on the manifold too.
I tried the bike again after the carb re-build and had an interesting result. It started right up, albeit with the rough running, like is seemed to not be firing on every stroke, but then it also "spontaneously" started to un properly for about 15-20 seconds, then back again to rough running. I shut it down and tried again with the same result, that is it would occasionally start running for 10-20 seconds as if all was well in the world.
So I know I have a lot to check, but wonder if this might be a telltale of an electrical problem, loose connection, faulty coil, etc.
Sounds like you’re getting close.
While the lack of a "R" in the code indicates they lack a resistor,
I cannot find any reference to B7EC in the current NGK data; the only reference Google returns is a post in another forum that says they are "no longer made", that forum post is dated 2003 ... Otoh, if the centre electrode is thin wire and the plugs' code is "B7EG", indicates the centre electrode is nickel.
Triumph fitted Champion N4 when they assembled the bike, the NGK equivalent is and always has been B7ES. Versions with thin wire centre electrodes - B7EG, B7EV, B7EVX, B7EIX - are less likely to foul when the engine's cold, but are more expensive.
Even if the existing plugs are B7EG, if they are not recent replacements, I would at least try a new pair of B7ES (just because they will be the cheapest).
The "R" indicates they have a 5,000 Ohm resistor.
It has been known for decades the Amal needle jet wears relatively rapidly. It would seem to be foolish to spend much time overhauling an Amal and not replace at least the needle jet, better all jets.
You might reasonably suspect a loose and/or corroded connection, being affected by the vibration from the running engine.
Also suspect any terminals that do not appear loose but have been soldered; vibration can crack soldered joints, if under insulation ...
I would replace soldered connections with crimped as a matter of course, if only to avoid the possibility of future problems with them.Rudie,While the lack of a "R" in the code indicates they lack a resistor,
Otoh, if the centre electrode is thin wire and the plugs' code is "B7EG", indicates the centre electrode is nickel.
Triumph fitted Champion N4 when they assembled the bike, the NGK equivalent is and always has been B7ES. Versions with thin wire centre electrodes - B7EG, B7EV, B7EVX, B7EIX - are less likely to foul when the engine's cold, but are more expensive.
Even if the existing plugs are B7EG, if they are not recent replacements, I would at least try a new pair of B7ES (just because they will be the cheapest).
The "R" indicates they have a 5,000 Ohm resistor.
It has been known for decades the Amal needle jet wears relatively rapidly. It would seem to be foolish to spend much time overhauling an Amal and not replace at least the needle jet, better all jets.
You might reasonably suspect a loose and/or corroded connection, being affected by the vibration from the running engine.
Also suspect any terminals that do not appear loose but have been soldered; vibration can crack soldered joints, if under insulation ...
On the spark plugs, so there was no "official" notation in my original owner's handbook, my mistake. It was a notation written in the book by most probably the original owner. Since this is the plug that was in the bike, then may be the original plugs from 1971.
OK, just now getting back to diagnose and fix this T100. So I went ahead and got new coils and plug and leads and installed them. Now, when trying to start, my ignition switch seems to be on the fritz! I'm not getting that red light coming on when turning the key on. Any thoughts on how to troubleshoot this? Thanks.
suzook12
Well-Known Member
Are you running points or electronic? What does the red light symbolise? How many Volts is plenty? Have you wired your coils in parallel or series? Are coils 6V or 12V.
If points, do you have power at the points? If EI, do you have power there?
Errrm... in your photo:-
NGK are/were originally a Japanese company; BSA/Triumph would never have bought anything from a Japanese company, particularly post-WW2.
As has been posted already on TriumphRat for you:-
. The ignition switch is between the battery and the coils (that are actually supplied by the electronic ignition); if there is plenty of power at the battery and the coils, how can the ignition switch be faulty?
. What is "plenty" of power?
It would help @Sundance if you read the thread, and also possibly his corresponding thread in the TriumphRat forum:-
. The bike has Boyer e.i.
. Red idiot light on any 69 onwards Triumph or BSA is the oil pressure warning light. On Triumph twins, it is switched by the switch screwed into the front edge of the timing cover; original Smiths switch would turn off the light between 5 and 7 psi, replacement 74 onwards Smiths switch would turn off the light between 3 and 5 psi, pattern switches turn off the light at unknown pressures but probably about the same as the Smiths.
. The Boyer was already fitted to the bike when the o.p. got it, so we hope he connected his new coils the same (in series). Otherwise the Boyer is toast (literally).
. Because coils are connected in series to any e.i. for these bikes, we hope he did not buy new 12V; however, even if he bought 6V, we also need to know the make of the new coils, because some 6V have too high primary resistance to be connected in series to any e.i.
Any e.i., coils are supplied by the e.i. O.p. has posted, "plenty of power at the battery and the coils" so we both await clarification of "plenty" ...
These (crankcase) oil pressure switches can fail. So try another switch, or see if there is power at this switch to save buying another. Use a multimeter. Or a 12v light bulb.
If it's failed, bike would still start and run. Could be a connection in headlamp of course.
If it's not failed, there is voltage, you might want to remove, clean, and test pressure-relief valve. Could be idiot light blown, worth checking.
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Thanks for all the help. I know I should have studied my old posts and the very good information from so many. Sorry for not being more careful.
On the power from the battery to the coils - well I did not check this properly so no. The battery is at 12.6 volts. I've kept it on a tender.
So step one for today. I did wire directly from the battery -ve terminal to the transistor box white wire. I got a spark in each plug, and got it to start. At first it sounded ok, but then it went back to the way it was running previously, seeming to misfire on one cylinder, run rough and smoke a bit - the problem I've been trying to fix all along.
The ignition switch was not a problem before, but obviously it is now too.
So I guess this narrows it down - ha - to a problem with the BB wiring/electronics or something not electrical?
On the power from the battery to the coils - well I did not check this properly so no. The battery is at 12.6 volts. I've kept it on a tender.
So step one for today. I did wire directly from the battery -ve terminal to the transistor box white wire. I got a spark in each plug, and got it to start. At first it sounded ok, but then it went back to the way it was running previously, seeming to misfire on one cylinder, run rough and smoke a bit - the problem I've been trying to fix all along.
The ignition switch was not a problem before, but obviously it is now too.
So I guess this narrows it down - ha - to a problem with the BB wiring/electronics or something not electrical?
Switching the HT leads to other cylinder would answer that. If persists on one side it's not the e.i.
As you've got only one carb, can't seeing it being carb/fuel/air.
Doesn't leave much. Valves? Smoking/poor running might mean oil getting past valves in one cylinder.
Are you confident it's just one cylinder? Is one plug fouled?
