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post #1 of 16 (permalink) Old 04-07-2019, 02:47 PM Thread Starter
Minitwins
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Left cylinder intermittent firing

Hi, firstly I have a confession. I have neglected my 2004 t100 over the winter and didn't drain the carb float bowls and didn't start it regularly as the battery was fried.

This weekend the new battery arrived. It was a liitle tricky to start. Initially firing just on the right cylinder. Gradually the left cylinder has fired but its running rough and popping and backfiring. I have taken it out a few times after adding some redex to the fuel tank and draining the float bowls a few times.

It's improved but still sounds a bit rough at low revs. When you twist the throttle it hesitates and then after a second or so of rough it snaps into life and takes off. At low throttle its rough open it up and fine. However the left exhaust is cooler than right so there's still a problem.

I have a good spark. Pick up coil and coils were changed last year.

I'm wondering if it's the pilot jet especially as it was on the side stand over the winter.

There's a tiny little Bit of petrol being spat or puffed out from the left cylinder carb inlet intermittently and not frequently when it misses, goes when warm.

Sorry for long post but wanted to give as much detail as possible. Any thoughts of wisdom would be greatly appreciated. In return I will make a promise to the triumph God never to neglect my pride and joy again. If only lifes complexities didn't get in the way.

Best wishes Nick
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post #2 of 16 (permalink) Old 04-07-2019, 03:06 PM
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Your suspicions concerning the pilot jets is most likely correct. The pilot and main jets need to be removed and cleaned as well as spraying some carb cleaner through the carb passages. After reassembly run some injector/carb cleaner through a couple of tanks of fuel.
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post #3 of 16 (permalink) Old 04-08-2019, 01:47 AM Thread Starter
Minitwins
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Hi that's rweb, helpful to have your thoughts. Should also have said I have swapped ht leads over and have ordered new spark plugs.

Am assuming coil is OK since other cylinder fires ok?

Thanks Nick
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post #4 of 16 (permalink) Old 04-11-2019, 01:39 AM
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Cool What about the float needle and seat are they clean?

You say the left seems to run cooler than the right and fuel sputters out of the left carb intake when it starts running rough. Running hotter indicates a lean condition (less or not enough fuel), while cooler would indicate a rich condition (more or too much fuel). To me it sounds like you should check the needle and seat on the left carbs float. It could have some varnish buildup keeping it from sealing. It could also be a bad float that is sinking and allowing too much fuel into the bowl. This would cause too much fuel to be sucked into the carb at idle hence a rich condition, running cooler and spitting out some of the fuel on misfires/partial misfires at or near idle. Another indication of this scenario would be that the left side spark plug would be darker or black compared to the right.

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post #5 of 16 (permalink) Old 04-11-2019, 08:33 PM
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Did you drain your old fuel out of the tank and replace it with fresh fuel, sounds like stale fuel to me, mine did the same thing after sitting for 6 months but I regularly started it up but after 6 months it did the same thing as yours then it wouldn't start at all, drained my fuel tank, put fresh fuel in and it fired straight up running perfect, modern fuels go off pretty quick, not like the old leaded fuels of days gone by.

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post #6 of 16 (permalink) Old 04-11-2019, 10:32 PM
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If you suspect fouled pilot jets, it's as often quicker, easier, and cheaper to just buy and install new ones. Main jets, needles, nozzles, etc can all be cleaned with a little bit of effort, but the tiny bore of a pilot, and the massive change in fuel flow caused by the smallest fleck of gunge or rime of laquer, makes cleaning them more trouble than its worth.


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post #7 of 16 (permalink) Old 04-12-2019, 01:44 AM Thread Starter
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Hi thanks for all your well thought out advice and time taken in replies. I have put clean fuel in and some redex. Runs better but only on right cylinder and kft cylinder when over 3 to 4000 rpm. Idle rough and definitely not firing at low revs.

I'm going to take carbs off, change pilot jets and clean main jets out. I'm going to change screws to allen bolts. Just need to find time to get it done now. Will update you on progress
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post #8 of 16 (permalink) Old 04-12-2019, 08:02 AM
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Be very careful when thinking about swapping the carb bowl screws for Allen bolts. The soft brass Phillips heads act as 'torque fuses', and will strip out long before the threads are torn out of the $$$!!! carb bodies. Hardened steel bolts with positive-drive heads can, with the right - wrong! - tool rip the threads out before you realise it.

If your carb bowl screws are chewed up, it means they've done their job. Drill them out if you have to, clean the gunk out of the body threads, and replace them with fresh parts.
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post #9 of 16 (permalink) Old 04-12-2019, 02:42 PM
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If, after all the carb cleaning, etc., the problem doesn't go away, swap the plug wires from side to side. If the problem persists, a new coil will be in order. I don't know how many have had the coil on one side start to fail first at low rpm and later altogether (including yours truly). Chased what I thought were carb problems from disassembly, soaking, rebuild to finally find out one side of the coil was failing. One can test the coil, but it can show that it's good but break down under a load. The carb chase is intellectually stimulating, though, revealing much wisdom through experience. Good luck.
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post #10 of 16 (permalink) Old 04-12-2019, 03:11 PM
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You have two areas to look at here... 1. fuelling 2. Ignition
For the first, I would have the carbs off and clean them out paying particular attention to the jets, remove them and make sure they are clean. ( a can of carb and intake cleaner is your friend here ).
Secondly, I know you changed the coils last year but that sounds to me like a coil breaking down under load, replace with a known good one. You can check a coil out using a multimeter (static test) but it does not prove how that coil is behaving under load.?

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