OK well recently I took my favourite 2001 Bonnie 'Britt' out for a spin and it was the first with the lights on since I bought her. She lost all engine power after about a mile and I stuttered and coasted to a stop. Tried to start her again with no joy until I pulled the choke out and she ran but, after a short distance, she died again. Turned off the lights and this seemed to help a bit but she was still choking up, stuttering and losing power. I limped home in short bursts with intervals inbetween where I sat for a few minutes in the hopes that, if it was, indeed the battery/charging system that had gone duff it would build up a little charge and I kept the lights on low or off as it wasn't fully dark yet. Couldn't find my multi meter ( A Fluke meter no less but I haven't needed it in years so no idea where it has gone) so had to wait for a cheap Draper one to arrive off of Fleabay. Anyway the meter arrived and I checked the battery and charging system and all was fine. Something made me have a look around the Carbs and intake manifolds and, when I squeezed it I discovered that the rubber 'blanking cap' on the intake of the right hand cylinder had a split in it. I put a temporary neat fitting rubber cap I had lying about on it for the moment but I haven't taken her out for a spin yet. Anyone got any experience of this kind of problem and, if so, were the symptoms the same?
Not uncommon on the America bikes....it pays to check once in a while to make sure they're all seated correctly and tight. Alan
A split vacuum cap will weaken the mixture but only on one cylinder..... more likely to cause a splutter than a stop. Your symptoms are maybe a failing coil - ignition or crank position sensor - that dies as it heats and revives as it cools. You need to see if it behaves with the vacuum port blocked or whether the problem is electrical.
The coils were replaced by the previous owner for Lucas ones but I do have a spare new TEC unit that I can substitute in if the problem persists. The stator checks out electrically with no shorts and outputting the right voltages although I guess it could be affected by heat also. I will need to get her out on the road and see if she behaves now the air leak has been fixed.
Not heard of Lucas coils on Hinckley bikes. The original Gill ignition coil is normally replaced with a PVL 356-1-00 while the OEM item is the only crank position option (gap .8mm)
It's a known fault on the range that the coils and ignition components can play up over time, I fitted this set up on mine for peace of mind not cheep but better parts than original https://www.triumphtwinpower.com/bo...crambler-speedmaster-ignition-refresh-kit.php
The receipt is for a 'Genuine Lucas Dual outlet Digital 12v Ignition Coil Triumph T100 800/865 L356100' from Brit Bikes Ltd. and that was installed in May 2019. I wonder if that was an attempt to fix the very problem I am experiencing with her.
Look at the part no - it’s a Lucas badged PVL....in the States they are sold as Nology. So start to suspect https://www.triumphtwinpower.com/bonneville-america-thruxton-scrambler-speedmaster-pickup-coil.php
Hi Marty, sounds like a stupid question but what was the weather like when you were out? Were the roads wet? I had a similar problem on a 2005 Bonneville I had several years ago. The vent tube from the tank ends behind and just below the engine and normally ends up cut square. If the roads are wet I found that damp and crud were blocking the end of the pipe, caused by a venturi effect, it only happened when wet. The cure is to cut the end of the drain pipe at 45 deg, angled backwards so that wet cannot stay there - that solved it on my bike
Well I can now confirm that replacing the cap on the intake didn't cure the problem. I can also state unequivocally that pushing a 205kg bike for about a mile on roughly level ground before then pushing it up a gravelly rutted incline marginally shallower than your average domestic staircase and about twice as long is no fun and should probably be considered as an event for Strongman contests!!!! I went out on the bike to see if the problem was cured as running her for a fair amount of time on the centre stand she sounded sweet and wasn't exhibiting any problems even when she got really hot. I figured that even if I got some distance from home, if the problem was affected by heat and the engine cut out all I had to do was wait for her to cool down and then try for home. Well.... I got about a mile from home and she was roaring and sounding beautiful when, stutter, stutter and then the engine just cut out altogether! OK thinks I, I'll wait 'til she cools and make for home. At that point a pal turns up heading into the village so a 15 minute blether killed the time while Britt cooled off. Pal heads off home and I try to start her, putt, putt, putt and then nothing! Tried numerous times and she wasn't firing at all so it was time to push. It's at this point I realise that, although I live a little more than a stone's throw from the shore my home actually sits maybe forty or so feet above sea level and the road into the village has a number of up's and down's on it's way and takes the long way round to reach my home so I decide to take the forestry road that leads much more directly to my house. Only problem being that, while most of that route is on the level and even marginally downhill in places although very pot-holed and made of gravel, there is one point at the end, where it leads to my little cul-de-sac where it rises very steeply. I had to do it in stages of a few feet at a time, grab the brake, put the side stand down, catch my breath and repeat. By Christ I think I was close to death by the time I got her to the top especially as I was wearing a freakin' Irvin flying jacket! I had to throw the jacket off and literally collapse on the ground for a couple of minutes before attempting the final few yards to home but I made it in the end. @Samsgrandad My problem occurred in the dry, well it was ever so slightly spitting with rain but that counts as 'dry' in Scotland and the bike is kept in a beautifully dry shed so I don't think it's a moisture problem in my case, unfortunately. @mpllineman Was it the Ignition Pickup Coil that was the cause for you?
Well the good news is that it appears to be good and broke, so the problems are easier to find. Ignition is probably the place to start. Got Spark?
Too late to test tonight (it was nearly nine and pitch dark when I finished pushing her home) and I was in no state to get the sockets etc. out at that time. I will get down to testing tomorrow. I am actually wondering if, and this may be daft, the previous owner replaced the coils but used the same leads and, perhaps the leads are duff but I don't hold out much hope that it could be that simple. The bike was lovingly maintained by it's previous owners and has covered less that eight thousand miles to date so I am a little peeved that something has packed up. My other 2001 machine has covered 18 thousand and had much less care and attention but, apart from a carb problem brought about by modifications that I have now sorted (fitted bigger pilot jets) is still on it's original coils etc. Maybe they like being treated mean? Once I've checked the coils and tested the ignition pickup coil to see if it's faulty I guess the next step would be to try swapping in the igniter from my other bike to see if that's the problem. There is nothing as embarrassing as pushing your lovely shiny machine along the side of the road Does anyone know if TEC MP10 coils fit the 790 Bonnies? I was given a brand new set of these in a bundle of spares and was told they fit Bonnie's but I can't find any fitment list online to say if they will fit although I did find someone talking about them on EFi Bonnie's on the Triumphrat forum (I'm not a member there).
There are a lot of TEC MP10 variations and part numbers. I bought a Nology coil recently and the spec is 0.6 ohms, twin tower.
OK well this is really frustrating..... I have checked the ignition sensor and it's showing 580 Ohms. I then checked for a spark and both cylinders are showing a nice spark and the plugs are just the right colour to indicate that the mixture is fine. Tried starting her and she fired up after a few turns and seems to be running fine even though I let her get plenty hot. One thing I discovered that I guess I should have checked sooner is that she still has her snorkel in place on the airbox although she does have a uni-flow air filter fitted. I literally brushed my hand over the mouth of the snorkel and she died almost instantly. I can't think how this would only be an intermittent problem showing up when on the move though and why it didn't appear from the first time I rode her unless the air being drawn in from the damaged vacuum blanking cover was making up for the strangled air box? I hate intermittent faults!
Nope it doesn't seem too oily at all but the engine definitely seemed to be extremely sensitive to any additional impedance of the airflow. I passed my hand briefly across the snorkel several times and it choked the engine on the spot where, ordinarily I would expect to have to fully block the intake to cause an engine to die that quickly. I am reluctant to try going for a run given my near death experience of last night pushing her home and for once I have to curse my rural location as I don't have a small 'block' to go around with travelling in any direction being downhill with any return push being, of course, up hill. Hmmmmm a connundrum!
If you cast your mind back to the engine stall was it: A splutter such as going from main to reserve Or An instant shut down? The difference is between fuel and electrical (maybe!)...... some electrical problems are an intermittent fade out and the 580 ohm reading is not conclusive that something isn’t opening up under heat and electrical load. Sometimes you have to substitute to eliminate. Equally, I’d be tempted to just pull the rubber snorkel out completely and see what gives. It is merely a press fit in the oval cover.
I would still look at fuel starvation, if you can pluck up the courage take it for a run and if it sputters to a halt undo the filler cap, if you hear a rush of air into the tank then you have a blockage in the vent pipe. This is quite a simple and cheap fix, and it was not an uncommon problem on the early Bonnevilles. As I mentioned in my earlier reply the fuel vent hose hangs down behind the engine and is in direct line of all the road crud. Over the years it can get blocked. If you can't pluck up the courage to take the bike for a run at the moment then have a look at the end of the vent pipe or put an air line on the top of the vent pipe inside the filler neck and make sure it is clear. I had this problem several years ago and your symptoms sound remarkably similar. Best of luck!
