1984 VF500F power/surging at highway speeds

I tend to agree about the fuel pump.

I pulled the fuel line off, and made sure that there is ample flow out of it. Turning the key on does not cause the fuel pump to run, it only would run after I hit the starter and the bike started. Since on the magna, the reserve tank is actually lower than the bottom of the bowls, there is no way to have gravity fed fuel. If the pump stops, the bike stops.

I just was reading this page:
http://users.rcn.com/kochc/moto/carb/carb.html
and it spoke of the pilot needle assembly about halfway down, which is hidden behind an aluminum plug. I followed his instructions, and pulled all of them. Shot carb cleaner into each of them. Then, blew them out with air and lubed them with WD40 before reinstalling the needles.

Now, I don't know if this has done anything to my surging issue, but it sure is more responsive at idle right now. I was having to feather the throttle a little when taking off, but it's way more solid right now. I ran down the street and back, and it ran fine, but I won't really know if the other issue is fixed until I have time to run the highway for a while.

I'll post back after my drive to work tomorrow.

 

Please do, I'm interested to hear if that solved it.

 

Still surging. <sigh>
Full choke still smoothes it out.
It doesn't happen below 5000 rpm.

I believe I should just find a person to rebuild my carbs, and stop trying to troubleshoot anything else. Once that is eliminated, if the problem is still there, I could at least rule out any carb related issues.

 

If the choke makes it better, it's fuel related. If it only "acts up" above 5000RPM, sounds like something in the main jet circuit.

 

check your petcock screen. possible debris blocking a lot of it and your not getting the fuel to the pump or motor? seeing nothing has changed with all the work you have done so far. fuel hose from tank to pump good? possible collapsing?

 

Hoping by now the problems above are resolved.
Here is for new people making a search on surging.

Bought an 86 Interceptor that was stored.
Bike would surge (slow down and speed back up) between 4500 adn 5500 rpm or 100 and 120 KMH.
Took carbs off the bike but not apart as to not have to recalibrate.
Took everything off teh carbs (jets except the one that is pressed in, floats, diaphragms and sliders).
Using a spray can of carb cleaner (did not want to soak teh 4 carbs with hoses, o rings, etc still assembled) sprayed each hole making sure cleaner would come out another hole somewhere (it has to, you don t need to understand how it works).
Found out on 2 of 4 carbs, when spraying in the pressed in jet, the cleaner was coming out a hole that is underneaht teh diaphragm (when assembled of course).
At that point I was sure this was my problem, those two carbs slides did not open at highway speed (normally will start to open at 25% throttle).
That pass has a 90 degree so can not clear with a wire or anything.
Went out and blew them with the garden hose at full pressure (yes I got wet).
After 3 iteration of this, i could see bubbles starting to form when spraying cleaner. it finally gave in and started coming out like it should.
An hour later I was back on the road, bike running like a new one.
if your slides are not sliding up and down smoothly in the carbs but tend to stick, rub them with a piece of paper, acting like if you were sanding them with sandpaper but just use plain paper. This will remove the sticky black crud off of them and will smooth things out.

 

my 86 vfr is also doing this.. I think the slide is pssibly sticking.. and i possibly recall it running like a monster at some point. Just finished setting valves - so will pull carbs off soon and do a THOROUGH clean, check floats etc.. it did stand for a year!

Mine would surge at almost any rpm - esp part throttle and almost make a like a soft gurgle sound until i throttle it more it would start driving. Really feels like one or 2 cyls are getting either none or VERY low fuel in a circuit. When I decelerate/coast it would pop quite loudly as well indicating a lean / blocked circuit somewhere..

Ill pop some fishing line thru the tiny holes and see if the spray comes out a hole somewhere else (i also use this method), had many burning eyes from it lol..

Hope that clears it up(!)

 

^^ Fishing line is useless for cleaning carbs. Steel wire only !

 

pulled carbs yesterday and found 3 of my 4 jets were literally blocked. In 15 yrs of tearing egines down ive had ONE blocked jet.. that was 15 yrs ago - yesterday I found 3, plus my friends 2 stroke yamaha had one as well.

Sorted my issues out, bike runs like a champ!

 

Nothing new about blocked jets, very common with crap fuel these days, leave them sit with fuel in and bingo

 

Can't imagine the revenue spent on bad fuels causing problems. Luckily I can fix my own stuff but imagine how many poor sods can't.. The weird stuff caked on brass parts is quite alarming.. Makes me consider actually running a fuel cleaner every 4th tank or something.

 

just a side note to all this, flow bench testing on carbs show that the pilot jet supplies as much as 10% at wot, so if the pilot cct is blocked it will cause a lean condition. i have seen many snowmobiles melt a piston due to this. info can be looked up by searching carb ufo or go here
http://www.xs650.org.au/UFO Installation Guide.pdf
and i do know the dif with flat slides, they are efficent and will have the same results

 

here is a better write up
http://3cyl.com/mraxl/manuals/ufo/UFOreview.pdf