So I've been chasing this problem for about two years now. It's one of those sporadic issues that the bike does it, you take it to the shop, they have it for a day and it never shows up. Then I take it home and two days later it happens again.
The main symptom is the bike running sluggish for a period of time. now for the details.
Picture yourself having a drink from a bottle, the contents of which, I'll leave up to you. Bottoms up, that glug glug when you drink, let air in, drink more, let air, etc.
- With the throttle open that is what the bike feels like: rev, pause, rev, pause. It migt be subtle enough not to hear it much but you'll feel the bike rocking a bit forward and back as it pauses for the slightest moment. If it's bad enough it might sound like I'm running on one cylinder even.
- When this happens, if I clutch all in or leave it on neutral and rev it up maintaining for a few seconds I'll get a couple backfire pops
- If I engine brake I might get a few backfire pops
- If I'm slowing down and let the throttle hang around between just before accelerating and letting the throttle go, it might get a few pops as well
- Sometimes this will clear it up and I can keep going with no issues, sometimes I'll need to pull the choke out to alleviate until it gets over it.
- If it is in the middle of this ... asthma atack, for lack of bettter description, and I need to come to a stop, sometimes it will just die on me unless I pull the choke out to keep it alive.
Recently I took the Carb out and had it all cleaned up. Since then it feels like it picked up a new symptom. Lets say im doing 50mph
- it's having the fit
- Throttle down
- Throttle up, nothing happens
- throttle reaches about where it was to maintain my speed and it kicks back
While it'll do the other symptoms, after having the carbs cleaned, it feels like the symptoms are more organized with the addition of the new symptom.
At this point the shop has mentioned that it might be a fuel pump issue. That, with a full tank, bypass the pump and go to the carb. It should let me ride around for about the first gallon or two aided by the weight of the gas before needing the pump. If the problem doesn't happen then I might have the issue there. The only problem is that the symptoms can show up every day this week on my way to work, and just the one day next week. I might go a full tank with the issues not showing up and next fill up, it might show up after a few days of riding. My paranoid self at this point has started to, probably falsely, notice that if there is a crosswind, chances are higher for the problem to occur.
I've cleaned carbs, changed vacuum lines, put a fuel filter between tank and pump. I' had to even swap out the engine (completely different issue), and the problem survived en engine swap. Needles to say, this is a frustrating problem and I'd rather not keep swapping $100 parts to go deeper down the rabbit hole of an elusive problem.