Bonneville America Forums Forums Technical Forums General Tech 07 America misfiring...

Got my Triumph America out of storage this afternoon, Happy days?

Well, almost!

Going down the road & it started to die so i flicked it over to "reserve" & all was good again. Went to garage & stuck £20 worth of fresh fuel in & flicked the fuel tap back to the "on" position. The next 15-20 miles of the journey home was good, but then, as i was red-lining it through the gears from the traffic lights, it developed a massive flat spot & had no power?
I pulled over, switched it off & started it up again, misfiring like mad & sounded like it was only firing on one cylinder. Pulled away & it struggled to hit 60 mph. On the straights the power would cut in intermittently for a split second then go again, on right hand corners & roundabouts the misfire disappeared but came back again on exit of corner/roundabout?

Im thinking either... spark plug, HT lead or coil pack? What do you guys reckon? Managed to nurse it home with no power, popping & banging like a sh!t house door in a storm!

Sounds fuel related to me.

Duncan,

That could be caused by anything. Check the obvious electrical items like you mentioned. Cracked spark plug, loose coil and or leads. Check both coils/wires/plugs for spark by pulling them, grounding the plugs to the engine then looking at the plugs when then engine is turning over.

Also check the intake rubbers closely to see if any are cracked especially under the clamps. While you are at it check the vacuum caps also. A bad vacuum leak could cause backfiring like you mentioned.

How long was the bike in storage? Did you add fuel stabilizer when parked? If it was a long time, you could have some gelled fuel in a carb messing things up.

Grasping at straws here.

try riding with the gas cap loose to eliminate a venting issue.

And maybe give it a healthy drink of Sea-Foam, if your vent hose isn't plugged. Wait, do they market Sea-Foam in the U.K?

you can buy seafoam in uk but is expencive

How long was the bike sitting?

If it were mine, this is what I would do:

1. Drain the float bowls into a clear container & check for water or contaminants - if any found, also drain the tank and refill with fresh gas

2. Check the hidden filter, remove it, & install an inline filter between the fuel valve & carbs

3. Confirm spark at each plug

4. If any question about spark plug condition, replace both.

FWIW, in the USA, at my local Lowes, a can of Seafoam is approx. $8.00 USD (5 quid?)...good stuff.

It had been sitting for 5 weeks without a charger connected. It started first time & ran perfectly good. It wasnt until i was giving it some beans down the dual carriageway that it started to play up.

No spark at left hand cylinder, traced back to being a faulty coil. I changed the left hand coil, fitted new HT leads, NGK caps & spark plugs. All working ok now.

Yea it happens. Glad ya got it solved.