The bike is a 2002 750ie, pod filters, cored exhaust....
I've read through a bunch of the other "backfiring" posts, which were helpful, but plentiful. So, where to start?
The bike has always had nice pop or two on decelaration or while downshifting. The problem seemed to expand to a pop while accelerating in the 3500RPM area with no other symptons. Now, well... it runs like crap. It hesitates and lurches when throttle is applied, pops like crazy throughout the RPM range, though mostly still in that 3500-4500 area. To me the pop sounds like air being forced back up the throttle body, if I down shift it will bog down considerably and it sort of gurgles (many pops strung together). When it lurches it feels like I'm dropping a cylinder perhaps...
I had a new set of plugs so I swapped those in, it got a tad better but not by much. I've also gone over the exhaust system to check for any leaks and that seemed fine.
Bad coil? Easy way to check?
Water in the fuel system?
Stator?
Anything else? What does everybody think?
Thanks so much!
Sounds like it is running too lean. I had the same issue on the same bike. I have a Power commander with a custom map, arrows, and open airbox. I cut the arrows down 6 inches after the dyno tune. It started to backfire about the same rpm as you describe. I added a little more fuel at that rpm range and it works fine now. I will get another dyno tune soon just to double check but for now the backfiring is gone.
So you probably need a PC3 and get it Dyno`d.
Hmmm... Thanks for the input. While I agree that a re-map is definitely in order... It seems weird that it went from running reasonably well to absolute crap with no equipment changes, like if I had just changed to pods lets say. When you ran into this issue was it just bad or did it progress to bad? Thanks!
If you just changed to pods and it just started, the pods are letting in too much air and you need extra fuel to compensate. That's why probably running lean.
Check to make sure the fuel lines under the tank aren't kinked.
Pop the gas cap open, and turn the key on.
Any fuel flying around in there when the pump is running?
Thanks again for the help...
Definitely not the pods or mod related. The bike has been in the same mechanical configuration for 2+ years-ish. I do believe based on the "normal" downshift pop that for 2+ years-ish I've been running it just a touch on the lean side...
That said thanks for the tip on the fuel lines... I definitely wouldn't have though of that and once the kids are down I'll give that a check and post back. Thanks!
Errrr... No Dice. The fuel lines are not kinked and fuel pump is swishing gas around. I'm at a loss... Guess I'll order up some coils and try that next. Is there a definitive way to test a coil before I start the buy part and swap process? Thanks!
fuel filter, fuel pressure, sensor inputs are all worth checking. coils are down the list of stuff i'd check.
I had a similar problem. the exhaust gasket at the head had completely blown off. replaced it and suddenly all was well again. I'm voting for exhaust problem. 90% of the time i've noticed this is the primary culprit.
I had the same issue but I got a Techlusion EFI controller (Like PC but cheaper) and I did it...ohh its runs smooth now. Only time I pop is if I shift from 4th to 2nd real quick (slowing down)...
btw what Pod filters do you have?
Quote from: MTKLI on October 19, 2011, 06:11:39 PM
Errrr... No Dice. The fuel lines are not kinked and fuel pump is swishing gas around. I'm at a loss... Guess I'll order up some coils and try that next. Is there a definitive way to test a coil before I start the buy part and swap process? Thanks!
When you say swishing, can you see fuel spraying in the tank?
The return is way down the bottom by the pump, and unless the tank is nearly empty there shouldn't be much to see.
Old post, but I had a similar issue with my 2002 M750Sie and wanted to share my experience and what it ended up being. Bike was running great to my destination (quick 10 mile ride) and for the weeks before, but on the way home it suddenly died at a stop light at idle. I started her back up and she was backfiring like crazy, idle was terrible, and just sounded rough. I made it to the next light where she promptly died again, and really couldnt get it going consistently. I pulled off and got my husband to bring the trailer to pick me up. The switch from "fine" to "I dont think I can make it home" was pretty instantaneous with no warning.
My gas light wasnt on and I could see gas in the tank. We are wrenchers and we maybe went a little overboard and checked the big stuff first. We checked valves and timing, and everything was good. My husband found in another post that the culprit could be a corroded throttle position sensor, but mine was fine. Pulled the plugs and they were a little fouled, but not horrible. Turns out it was the fuel filter - it was barely flowing at all. That fuel filter had only ~4000 miles on it, but we saw some REALLY crappy fuel on the trip out to South Dakota and back we did last year. Very gummed up. We put her all back together and she's running perfectly again. ;)
Quote from: MTKLI on October 19, 2011, 06:11:39 PM
Guess I'll order up some coils and try that next.
I've had the same problem for a while now on my 2007 M695. Ended up spending $1,000 with the bike in the shop for many months having the valve guides replaced / valves adjusted. It was to no avail. Noob question:
What are the coils you're talking about?Check for vacuum leak. (I used starting fluid and sprayed it around the throttle bodies looking for RPM rise. Mine didn't have any but it could be the culprit. -the reason i mention how to check here is because I had to do about 1,000 searches and ask multiple times before I ended up just looking on youtube to find out how to really check for vac leak.) [thumbsup]