| Author | Message | ||
     Buellmeister57 |
My 1999 Cyclone has developed a pretty bad miss under load, full throttle. It pops thru the exhaust almost like a machine gun. It starts, idles and runs perfectly until I open it up in the lower gears. I've removed and cleaned the gas tank and screen, replaced the plugs & wires, removed and cleaned the carb. The bike bike has 30,000 miles on it, a Borla slip-on, Yost power tube and Screamin' Eagle air cleaner. It doesn't always miss, sometimes it will redline, running like it always has. Any help will be greatly appreciated. | ||
| Whodom |
Sounds like an ignition problem to me. Could be a bad coil. | ||
| Tripp |
maybe the ignition module? did you upgrade your front header mount when you got the borla? maybe it's the voltage regulator ground. | ||
| Henrik |
Sounds like you've tried to eliminate the "usual suspects." Maybe some more information would help. How long has it been happening? Did you change anything shortly before it started happening? when you say "open it up in the lower gears," what exactly happens? Which gears? At what RPM does it miss? Does it clear up after a certain RPM is reached? Can you "pull through" it, and if so how does it feel up top? Can you replicate these symptoms if you do a similar roll-on in higher gears? When it doesn't miss, are you doing anything different? - could you have an exhaust leak? - intake leak? - ignition cutting out in a certain RPM range? Not terribly helpful at this point, I realize ... but maybe it'll spark some ideas with you or other board members? Henrik | ||
| Buellmeister57 |
Thanks for the replys. The miss seems to occur about 3000-4000 rpm, it will sometimes pull thru and redline. The bike still feels as strong as ever. Haven't changed anything on the bike for several years, just routine maintainance. In normal riding it does fine, although it feels/sounds like it will "skip a beat" once in awhile. After it does this, I know the next time I open it up it will cut out pretty badly. I checked the ohms on the coil and it was within spec. My first thought was a fuel problem, water in the gas. The bike sat uncovered in a 2 day downpour, the miss started about 3 days later. | ||
| Tripp |
if it's an intake leak like henrik suggested that'd be something that if you "pull through it" it might blow your motor! i would rule that one out next! | ||
| Buellmeister57 |
How's the best way to check for an intake leak? Spray WD-40 around the manifold while the bike is running? | ||
| Natexlh1000 |
Yeah, I'd vote for an ignition problem too. My ironhead did that until I replaced the coil. | ||
| Whodom |
The WD-40 trick is pretty good for checking a vacuum leak, but I don't think that's your problem. Engine vacuum is approximately 0 at WOT so a vacuum leak would be very unlikely to cause a miss under the conditions you describe. WOT, especially at low RPM, requires the highest spark voltage to fire the mixture and therefore puts the biggest "stress" on your ignition system. If it's worse when the bike is hot that would be another clue that it's ignition-related. | ||
| Mikej |
Start with the easy stuff, have you eliminated the sidestand safety switch as a possible culprit? | ||
| Buellmeister57 |
Yes, it seems worse when the engine is hot. I'm going to double check the sidestand switch in the morning. Gotta go to work......... | ||
| Henrik |
Whodom; I'm not sure I understand how the pressure in the intake tract can be 0 at WOT? Besides, the motor no doubt "sucks in air" at all RPM and throttle positions, which means, if there is an intake leak, it too will suck air at any RPM and throttle opening as well. No? That aside, I agree that it doesn't sound like an intake leak, and that the coil could be the likely culprit. Henrik | ||
| Whodom |
Henrik, the logic is that vacuum is highest when the throttle is closed, when idling and especially when coasting down at speed (if you've ever had a car with a vacuum/boost gauge you can see this). When the throttle is wide open, there is very little restriction between the air intake and the intake valves, so vacuum is very low. You could still have an intake leak in either case, but the leak flow rate will be relatively much higher with the throttle closed than at wide open throttle and therefore will make the bike run too lean at idle causing problems there. | ||
| Natexlh1000 |
If it was a vacuum leak, it would have a sucky idle. | ||
| Oldog |
this sounds like an inttermitting electrical problem. Following the premise easy stuff first, visual inspection of wiring and connectors. would be my next step. He's replaced the plugs & wires, and checked the coil, but the coil may break down under load this usualy gets worse rapidly as the spark errodes the insulation in the assembly. Checking the grounds on the various parts and even the battery & system grounds may be a good idea. are there any other symptoms? bypass the stand switch if you are in doubt or test it. When mine went it was obivous that it was bad. Spending 30 min studying the diagram in the FSM may provide you with some insites as well | ||
| Mikej |
Check your gas tank vent line as well as this is the season that some regions have bugs crawling up into dark places making their winter homes. I've blown more than a few mud wasps and worms and such out of vent lines over the years. | ||
| Blake |
I have nothing to add. If I had to pick the culprit though, I would be leaning towards the kickstand safety switch explanation. Been there, done that. ARGH! | ||
| Blake |
Just one more thing... Don't y'all know that BadWeB doesn't allow any posting of Buell problems? Sheesh. I guess we'll let this one slide by for now.  | ||
| Henrik |
Whodom; got it - thanks Henrik | ||
| Blake |
Move to KV - Troubleshooting topic. 172689 |
