Bonneville America Forums Forums Technical Forums General Tech coughing on acceleration

2005 America, 74,000 miles, Procom ignition, otherwise completely stock
Symptoms: Coughing and spitting on acceleration under load only, starts and idles fine,
Already checked: Plugs, plug-wires, carburetors cleaned surgically, Procom re-programmed to "0", all parameters.
Fuel system verified clean, out of ideas.....

Coughing back through the carbs is generally caused by running lean. Check that the rubber bungs on the inlet manifolds haven't perished.

All squirrel condoms are new....no leaks found...thanks though...

Rubbers between inlet manifolds & carb plus between carb & airbox?

Removed float bowls, removed jet on each carb, found the left carb jet clogged, AGAIN. Cleaned both carbs best I could without removing them, re-assembled float bowls, runs like a new bike now. Installed Auto-Zone fuel filter between tank and carbs...

More Gasoline quality issues?

Probably...I always use supreme unleaded (92 octane), which is the highest octane I can find around here. Maybe ethanol induced?

My TA does the same thing only on acceleration, used 87 now use 89, it did get a little better after I changed. Now staring to cough again. Was thinking of carb cleaner again. How often does one use carb cleaner?

87 ignites easier than 89, I rarely have an issue with my carbs and almost never use carb cleaner. I only use it when disassembling them for a problem.This goes for my antiques too. I think if an engine is set up correctly (so few seem able to do so) it will run trouble free for a very long time with only basic maitenence , oil change etc.. You can spray cab clean around any intake rubbers and listen for the idle to change, if it does you have a vacuum leak. There is no reason to use anything higher than 89 octane unless you have put higher compression pistons in (or raised your compression in any other way) Those ratings are not quality ratings. The terms regular, plus, and premium are misleading. That rating is the fuels resistance to pre-ignition so the lower number actually burns easier. You should run the lowest octane you can without pinging.Pinging is the fuel igniting before it is supposed to. You may need to clean your carb if there is dirt in the fuel you used.

Loaded the bike for a camping trip about 90 miles from home, the bike ran flawlessly going up, and a 40 mile ride Saturday morning, but started coughing again on the way home. Got gas, rode another 40 miles going home, coughing and spitting again appeared. 12 miles from home, had to shut down the engine due to failure to accelerate, and minor "knocking" coming from engine. Loaded onto the trailer, removed carb bowls yet again, jets and bowls appear clean and unobstructed, but blew out all and reinstalled, short test ride started out good, but once engine was good and hot, would not maintain power up hills without severe coughing and backfiring from one cylinder. Suspect valve clearance issue, and will remove valve cover next weekend to check clearances. Thanks for the input guys!

Check float valve and orifice, the alcohols fuels can leave deposits that cause the valve to stick.

Is this why I put some Seaform in every tank refill?

Nope, floats working as advertised, Startron ethanol equalizer used as well. Valve cover coming off whenever I get time....Problem appears more abundantly with engine hot.

Gonna need alot of help on this one guys...all valve clearances within limits now (had to replace a couple of shims on the right outside intake and exhaust). After disassembling and cleaning carbs surgically, I started the bike and she ran wonderful. Put on the helmet and the bike ran perfect the first 7 miles. I turn onto the 4 lane which has a couple of good hills and open her up to 75 mph, then bang spit quit. Engine totally quit, and appeared to run on the left cylinder only, but still wouldn't stay running. Trailered it home, pulled both plugs, both firing a bright healthy blue. Ohmed out coils, both read .7 ohms. Gas tank had been drained and thoroughly cleaned before the test ride, and still appears to be putting out clean gas. I'm stumped at this point....

Do you have the mixture adusted correctly and have you balanced the carbs?

I had a Procom go south, just as the OEM did.
If you can find another CDI to test it with I would give that a go.

Procom says that if it goes south, you will lose a cylinder, which I did, but now both plugs firing normal, and probably have been. Mixture, from what I understand, only affects idle, right? Carbs balanced Saturday, and are dead on. Right cylinder appears to be very hot according to spark plug and appearance of the header pipe coming out of the cylinder. Both mixture screws turned out 2 1/4 turns, but doesn't seem to have an effect at any position. When "blipping" the throttle from idle, one cylinder (probably the right) is spitting.....Open to any suggestions you guys may have, thanks in advance!!!

Intermittent problems are just the worst to diagnose. Have you checked the rubber manifolds on the intake for dry rot? Sounds to me like you have an intermittent vacuum leak on the right side. Or a corroded coil spade connector. Maybe both.

I suggested to use cab clean to look for a leak a while back, running hot is a sign of a vacuum leak too.
CDI goiong south you can lose one cide then have it come back then lose it again, so good spark when you check doesn't mean it is at fault.

My TA 06, 84,000 miles, coughs on acceleration from a stop, tried carb cleaner, no improvement, also happens when engine hot. Bringing bike to Red Line power sports in Winsted today. Mechanic, said may be coil. Hope it is something simple.

Thats a good idea, using the carb cleaner at idle. I must have overlooked that earlier. I did OHM out both coils, and both read .7 ohms. I took the right bowl off the carb last night and re-inspected it, no debris found, bowl was clean. Started the bike up, and it idles okay, but still spits when throttle is blipped.

Gonna bite the bullet and go ahead a pay $269 for a new PROCOM CDI...wish there was a way to verify the problem, but I'm pretty convinced at this point...

I would recommend the Triumph Twin Power Firestarter stage 1, vs the Procom.

I've had both and I'm very pleased with the TTP Firestarter.
Plug and go, no mapping to deal with.

Got really discouraged, just telling myself the bike has just lived its life, but a good old 30 minute drive to work got me thinking HARD. First, I have to determine if it's a fuel issue, OR an ignition issue. Now when it coughs or spits on acceleration, you can put your hand on the bottom of both carb bowls, and distinctively feel the right carburetor banging. I'll swap coil input wires and see if the banging goes to the left carb, and if it does, I'll know it's ignition, and if not, it's the carb. If it is ignition, I'll shoot the crank pick-up for continuity and AC peak voltage while spinning the engine. To me, this part is either good or bad, but will shoot anyway. If that's good, and I determine it's not a carb issue, I will order the TTP Firestarter stage 1. I talked to PROCOM today, they say it's either broke (dead cylinder) or not. right now, like I said, both plugs are firing laying on the cylinder.....She's way too sweet a bike to give up on!

So you've inspected the manifold and the carb diaphragm and all the rubber is good?

Yes, carb diaphragms are good, boots between cylinder head and carbs good, not sure what you mean by "manifolds". Hopefully I'll get time to work on it this weekend.

That's what I meant, I think....Crank pick-up reads continuity statically, and produces 5.5 VAC while spinning engine. Ordered CDI.

$214 CDI showed up, installed and started per instructions, no help. Spitting and sputtering, then dies. Placed a strobe timing light on left and right plug wires, increase throttle to about 2000, and strobe simply stops on both plugs, just like someone switching the ignition off.
Removed kill switch, disassembled, inspected, re-installed. Disconnected kick stand switch, no effect. Disconnected crank sensor with engine running, engine continued to run (how I have no idea), Removed fuse box and inspected all connections, all solid.. Shook entire wiring harness with engine running, no effect (still idles fine until plugs stop firing). Shot resistance readings through ignition switch, rock solid.
Battery charging 13.5 to 14.3, and at this point, Im clueless without a wiring diagram. Any help or suggestions welcome.....Definitely an electrical problem..MY FAVORITE

My bad. That was the alternator I disconnected. Didn't realize there were 2 wires coming out of that right cover. Disconnected other wire, engine quit. I try to OHM out the sensor, and the meter shows "open", and produces nothing with engine spinning (AC or DC). What the hell, it's only another $80, will order THAT tomorrow....

Installed new pick-up coil, replaced cover gasket, started right up. (No special measurements (no book). Took 2 trips around the neighborhood, so far so good. Wouldn't be convinced until the bike successfully completed my "proving circuit" of 12 miles of challenging conditions, that it has failed 4 times, all at the same spot!
The bike had passed the test so far, but as I approached the exact spot that killed it before, she quit again......I was able to get off the road, and switch to reserve on the tank, and she fired and got me to a gas pump. Filled her up (3.8 gallons) and started the proving circuit from the beginning. This time, she ran like new the entire route. Un-believable!

If you did not set the pick up coil gap correctly you will be in for more future issues.

If I remember correctly the original spec was changed to 0.8mm around 2007 to prevent igniter failure. I remember setting mine to that after my original igniter failed and I never had any problems afterwards. The replacement igniter came well used from Pinwall...

Your memory is way better than mine:
http://www.bonnevilleamerica.com/forums/...rt=all&vc=1

Next time anyone needs to check the pickup coil, take a look at how Mike did it in 2012. In the vault. "What I've Found"

Once I received the new pick-up coil, I put my digital meter on it to see if it would show any resistance. It, as well as the old one, did not. I switched the meter over to 200k (I think), and it did show resistance of like .005 or something. Placed same on old pick-up, and it too read the same reading. Attempted to heat old pick-up, no change, still read same resistance as the new one. Was convinced this too wouldn't fix my bike.
Went ahead and installed the new one after measuring original gap, replaced gasket, and she fired right up, and ran as stated above.
Parked bike until new Triumph shop manual arrives Wednesday to make sure pick-up coil is installed correctly.