Loss of Throttle Responsiveness

So, I had a few moments to do the quick check to see about the pipes and sure enough, #3 took a long time to heat up. It probably only heated up because of radiant heat from the other exhaust. My next plan is to check the plugs as dizzy suggested. I'll let you know how it goes. Thanks all.

Adam

 

So today I was able to get out and check a few things. I pulled off the plugs on #1 and #3 to check them out (pic enclosed). #1 is on the left and #3 is on the right. This pic was before I cleaned them off and checked the gap. #3 gap was off for some reason. I was also able to pull the air filter off, start the bike and look at the carb slides. #3 was the only one that DID move when given throttle. All other didn't move at all. #3 was the only one that "wiggled" as I gave it throttle. Also, I checked the vent tube for the gas tank, and it is completely clear, no problems there.

If there are any other suggestions, let me know.

 

Inspect the slide diaphams for damage and that they are sealing. You should have similair resistance in all of the if you push them open rapidly with your finger.

 

So I opened up the airbox and pushed rapidly on all of the slides. I haven't torn anything apart yet. I found #2 and #3 slide in and out with some resistance and ease their way back. While #1 and #4 move with little to no resistance and kinda slam back. So, my question is which is correct. I am assuming that #2 and #3 are correct because they have resistance and ease their way back signifying that they are sealing. Again, from my previous post, #3 was the only one that moved, rather wiggled, when I had the bike running with the airbox off and giving it throttle. All the others did not move at all.

 

So I took #1 slide apart, put it back together, fired her up and now #1 and #3 move (wiggle) as you give it throttle. I haven't done anything with #2 or #4 yet, and they don't move. Looks like I'm removing the carbs, again, to get to those.

 

Sorry, thought that I posted it before. I took out the spark plug on #3, kept it in the wire, grounded it, pushed the starter and checked for spark, nothing. I haven't had a chance to check #1 or even swap the two to see if the problem moves. I'll keep you posted.

 

Got it. I bought a new set of plugs today and plan on installing them soon. I am currently using the OEM NGK's, but I bought the Iridium set for the replacements.

 

Hey guys I'm having the exact same problem with my 84 VF1000F....my bike idles fine until I roll the throttle and it will either burp & die or just dies. I tried manipulating the choke but starting it isn't "my" problem. All week my gas tank was poppin pin holes in it. I pulled the tank, flushed & epoxied it, then changed the fuel filter which was totally clogged (I cut it open & it was like mud inside). Now with that changed, it still has the same problem. I think mine tho has the vent in the gas cap, which by the way is really tough to close / lock.

I'm going to try the same thing. I know the pump is working fine + a new filter...so I have the tank off now, I'll pull the plugs check/gap and then check the sliders and check the tank vent.

We all should be riding right now

 

what tinker said... also if your tank is that rusted chances are your vent tube aint venting..... I would also check the wee little filter screens in the carbs....

 

Ok, so I pulled the plugs cleaned(rustish red/brown hue) & re-gapped them. Pulled the carb set out, removed the seat & jet and there isn't any filters in there but they weren't dirty anyway. So, next I'm going to drain the tank & look at the vent tube like you suggest. Whatever is happening, it has to be something that would effect all four cylinders at the same time, to kill the motor at full throttle....in theory lol

 

So today I finally got off my ass and changed out the spark plugs. I put in the iridium plugs this time, heard good things. I put everything back together, started her up and noticed an immediate difference. I took her for a 30 mile or so spin to check things out and there was definitely a difference in that there was much more power. However, it still feels like it's lacking some. Before I put the air filter back on, I started her up and checked the slides again. #1 and #3 "wiggle" when given throttle, and #2 and #4 don't move at all. Correct me if I'm wrong, but they should all wiggle a little when I give her throttle, right? This may be where the slight lack of power is coming from. So, I've fixed the spark issue (thank you tinkerinWstuff for the suggestion), but this may have been a duel issue problem. I just may need to delve into the carbs again, only the upper half this time. Or, the other possibility is that maybe when I took apart #1 slide to get it to move, it messed up the sync. I didn't re-sync after that. Could that be a possibility? Let me know any suggestions, everyone has been a great help so far. Keep 'em coming.

Adam

 

Well, between yesterday and today, I took the carbs off, took off the slides for #2 and #4, inspected and put them back together. I made a tool out of the inside of a syringe and a pair of forceps so that way I could hold the slide open so that way they fit back in the groove easier (pic enclosed). It really helped out alot. After I put everything back together, I did a sync with my homemade tool. I got them within about 1" of each other (using 10W40 motor oil in the tubes). So I just took her for a little test run around the block and the power is definitely back. I'm going to take her on a little 30 mile run here today, got an errand to run, and I'll see how she performs. Thanks again to everyone for their help. All the suggestions made it easier for me to pinpoint what was wrong. Now maybe I can participate in that photo game that I keep seeing. Ride safe.

Adam

 

So what's the update here? Is the bike doing better? My '86 500 is doing this and I just had the carbs cleaned. Wanted to see what you figured out.

 

Bike is doing alot better. Figured out that my problem was 2 fold. First, I wasn't getting spark on #3 cylinder. So I replaced all the spark plugs. When I did the beginning of the season checks, I only checked the plugs and put them back in. So, now I've got 4 new ones. Second, after I rebuilt the carbs, all of the slides were not moving when I gave it throttle. Only #1 and #3 were moving. So I had to take the carbs back off and mess around with #2 and #4 slides to get them to work. Put everything back together, sync'd the carbs, and viola, better bike. I do seem to be running a little rich, so I may mess with the idle screws, maybe not, we'll see. But all in all, things are running alot smoother.