BiKenG Posted September 28, 2014 Share Posted September 28, 2014 Having just cured my way too high idle speed problem (http://www.vfrdiscussion.com/forum/index.php/topic/79282-idle-way-too-high), I now notice that there is bad hesitation above about half throttle. I'm pretty sure this existed before I fixed the idle speed problem, so I don't think they are directly connected. At low throttle opening, it seems fine, but as I open it more it starts to hesitate, then picks up and hesitates again, just as if there's a bad misfire. The way it stutters does not seem to me to be due to the throttle butterflies' fluctuating. It's more like, as I said, a misfire which is ignition related. From reading other threads about similar sounding problems, I don't believe this is the same thing. It's not a stumbling just off idle, or engine occasionally simply stalling. The bike runs fine at low throttle, but the problem can be easily induced by opening it to about half way when it'll falter and not accelerate much more. As soon as the throttle is closed again to less than that threshold position, it clears up. I've not yet checked out the ignition system components and obviously there is now another process of troubleshooting, but has anyone else experienced this? Link to comment Share on other sites More sharing options...
suzukijo Posted September 28, 2014 Share Posted September 28, 2014 I would invest in new spark plugs. NOT that I know that's the problem, but if it is, its an easy fix. Link to comment Share on other sites More sharing options...
Taycio Posted September 28, 2014 Share Posted September 28, 2014 Check the plugs right off. With all your starting and stopping the bike with looking for the idle issue I bet they fouled out. The bikes run pretty rich when cold until its up to temp. I have had to put numerous sets of plugs in Sportbikes that guys fire up just to show their friends 10 seconds of running and then shut it back off (multiple times). It also could be a failing coil among other things... Link to comment Share on other sites More sharing options...
BiKenG Posted September 29, 2014 Author Share Posted September 29, 2014 Yes, plugs will be the first thing to look at. Of course all the air box has to come off again to get at the front ones. Oh well Mind you, at the price of plugs nowadays, they're not a cheap fix. Link to comment Share on other sites More sharing options...
Bizbat Posted September 30, 2014 Share Posted September 30, 2014 In my late teens I bought an old beat up '76 6-cylinder mustang in Spokane, WA for what i thought was the killer deal ($100!!).. It had been sitting exposed to the weather for several years, looked like crap, but the seller was convinced it would fire and drive away, so we gave it a shot... I lived in Kennewick, about 2 hrs away. My buddy and I spent too much time trying to get it started, and finally it fired, so with much excitement I threw my tools inside, put her in gear, verified the brakes worked good enough, and headed her to the interstate (buddy following behind). Damn thing wouldn't go faster than 35 mph! It got to 35 fairly quick, but anything faster and it would sputter and seemed to misfire. We were nearly out of town, exhausted, so we made the decision to just "go for it" and drove to Ritzville with great frustration.. My buddy followed with his hazards on for the 60 miles to Ritzville...All the while running through my head what I was going to do to further troubleshoot the problem when we reached this mid point. Vacuum advance not working? Points out of gap? Crappy plug wires? Plugs fouled? Sure seemed like an ignition problem.. But strangely it would rev just fine when disengaged from the drive train.... I pulled into the service station very frustrated and my buddy runs up to me.. "Jimbo, I bet that the fuel filter is plugged up!". Made sense! More speed requires more energy requires more fuel!! We certainly had enough time to come up with this as a plausible explanation! No filter for sale at service station (stupid thing was built into the carb!).. I yanked it out, drove a screw driver through it (yes, I was this frustrated by now), connected the line, added more fuel, and headed to the interstate. Wow!! That old beat up mustang did 110mph before it got too wobbly! I share with you a life lesson that I will never forget: More speed requires more energy requires more fuel. If any vehicle can rev up when not under load, yet the vehicle is limited in speed regardless of the gear it is running, then the immediate suspect is the engine is starved for fuel. Link to comment Share on other sites More sharing options...
BiKenG Posted September 30, 2014 Author Share Posted September 30, 2014 Yes, could be fuel, but this feels so much like ignition loss. I need to confirm it, but I'm sure that the problem will occur even while not under load. I will have it on the stand today and try and see when it occurs and whether the butterflies are being moved by the ECU. That should give me a better idea of what's going on. I'll also try and measure fuel flow to check the pump is operating OK, although sounds like it is. My money's still on ignition though. Link to comment Share on other sites More sharing options...
BiKenG Posted September 30, 2014 Author Share Posted September 30, 2014 Thank you all for your forbearance, this will be my last post on this topic as my VFR1200 is now cured and running perfectly and what a lovely bike it is to ride. You can't beat a good V4 :-) I took it all apart again today, cleaned everything I could and put it all back together again making sure all the connections were good and sound. Took it for a ride and it's perfect. Not just a bit of an improvement, the problem is simply not there and it's running like a train. So all's well that ends well. Thank you all again for putting up with my ramblings. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.