Bonneville America Forums Forums Technical Forums General Tech Engine starting to miss

Recently my bike has started to miss quite a bit. If it starts missing it won't smooth out even after it warms up. If I stop the motor and restart it goes away and doesn't come back until the next time I start the bike. Any ideas what could be causing this? The bike is stock except that I've remvoed the secondary air injection and the CARB plumbing.

Thanks,
Hugh

Chy wrote, “Is it a stumble type feel or more like a "fish Bite"? If it's a stumble or fade at speeds, it's likely fuel related.. if it's more of a jerky sensation, it's likely ignition. If it is secondary ignition (coil, wires, or plugs) it would likely do it under load (low RPM, hard pull) … [if you think it is the fuel system]…you might try loosening the gas cap (weird little check valve problem). Also, have you tried pulling out the choke a bit when it's doing it? If it goes away or gets better, it's fuel related. “

If you think it to be on the ignition side, start with the spark plugs. Advanced Discount Auto Parts, about a buck sixty apiece. Put em in and rule out those first. As all you have left on that side are the coils and the ignitor. (an ignition pickup coil too).

It's definitely not a "fade at speed". It's definitely jerky when I'm trying to accelerate but it also does it while idling. I'll try your suggestions. Oh' I've also added an automatic turn signal canceller / running lights so it looks like I've messed with both the carb and electrical side of things.

Thanks,
Hugh

A fast check would be your spark wires. Check for good tight fit at coil and spark plug sides...

Caca in the fuel will be jerky too. Bits of paint and such. Buy some brand new spark plugs. Gap them then install them. Run your bike. No better? Oh well that was cheap, but as it didn’t work you need to do a couple other things.

Have you opened the tank cap while the bike is running? Better now? Yes—unkink the breather hose. No? -- Did you try pulling out the choke a tad? Did it run better? Yes? OK, Check your fuel side. Drain each of your carb bowls into a clean jar. Look at the fuel you drained out. Dirty gas come out?

The fuel side should start with the draining the bowls, then go to the tank and at least partially drain it too. Disconnect the fuel line and place a hose on the petcock port and the other end of a hose into a clean jar. Open the petcock and observe both the fuel flow rate and the fuel itself. Good flow rate? Clean Fuel? You can skip dropping the petcock, maybe! Now onto the carbs. If you got dirty gas when you drained the bowls, you need to inspect and clean the hidden fuel filter. Drop the bowls, the pilot jets the main jets. Inspect them. You might even need to blow them out. BE careful of the main jet tube's collar. Real careful dropping the air mixture screws tiny o-rings and washers and springs…If you find some garbage in any of the jets, blow the jets out put everything back and take a ride.

If you think your problem is electrical, find a friend and borrow his coils. Borrow his ignitor too. Swap these parts out to see if you can isolate the problem.

You issue sounds fuel related. I have had a fuel starvation problem and a dirty gas problem before. Most issues with our rides have to do with the fuel side.

These are just some steps. If your carbs are real dirty you’ll need to clean em proper.

Gotta go Ocean Key Resort is calling…

Check your battery cables too, especially the ground, at both ends. A momentary interuption in the battery connection will cause the ignition computer to reset and the engine will miss. The vibration caused by the miss will rattle the loose connection, interupt the current, reset the computer, etc. etc. so it keeps on missing untill you shut it down and restart it.

Thanks for all the tips.

I checked the battery and spark plug cables and everything seems snug.

I drained the carbs and got a bunch of black junk in my glass but I'm not sure if that was from the hose that I used or not. I then connected the the vacuum ports on the carbs and reran the breather hose that connects the carbs. It ran real well for about 500 miles and then started missing again.

I then drained the carbs again and everything came out clear but the bike ran better afterwards so it's probably a fuel problem. I guess the next step is to check the fuel.

Other than the engine missing, the oil leak, and the rusting frame I really love my Triumph (seriously).