1983 vf750f idling problems

hey guys, new to the site, avid interceptor rider. ive been having some issues with the bikes idling and response on the tach... im wondering if anyones dealt with this problem or similar to it
i just rebuilt the carbs because the bike was acting up, it starts, but have to keep the throttle cracked open to keep the bike running. ive changed sparks, fuel filters, carb kits, still having issues. [video=facebook;10153998729295790]https://www.facebook.com/photo.php?v=10153998729295790&set=vb.727430789&type=2&theater[/video]

 

When you 'rebuilt' the carbs, what did you do? Anything along these lines:

http://vfrworld.com/forums/mechanics-garage/22449-cleaning-carbs.html

 

i used Toe Cutters guide basically. also had an experienced bike tinkerer with me who has done it hundreds of times. i tried posting a video of ignition... will try again[video=youtube_share;4PbWhUYIgeQ]http://youtu.be/4PbWhUYIgeQ[/video]

 

It all started last july. the bike fell over at a stand still, i was hot and tired! the bike ran for a few more days with no problems. then i was cruisin down the highway and my tach started acting up, so i ended my ride prematurely, and headed home. the bike was sluggish and unresponsive. i can start the bike and get it running but the tach wont respond. i replaced the spark plugs, replaced the inline fuel filter, swapped my ignition coils with some extra ones i had kickin around, still, no changes. i tore the bike down to the carbs ordered some nice carb kits and proceeded to rebuild the carbs. tore them all down separately and cleaned carbs, new seats etc... put it all back together and fired er up, still same problems. im having issues with this. any wisdom from the vast years of experience here would be greatly appreciated... also. the might as well effect set in on me during the winter and i painted the bike to a black/white stock paint scheme. with a little of my own twist. will post some pictures of that but the underlying issue still needs to be addressed. please help, im so lost

how she was


how she is

 

Still no progress on this issue, maybe floats are out of alignment? Clymers calls for a special tool to measure 7 mils ? Anyone concur ? Tips tricks ? Ideas? Runnin outta days off here!

 

Even if you think you cleaned carbs proppaly, some things could have been missed. Small passages under the idle mix screw or tiny holes under the closed throttle plates. You used wires to probe all holes ?? You had 80psi compressed air ?? Chances of a good job are worse without these.

Yes, floats need careful checking anytime needles and seats are replaced, and you must read the FSM on this !~! No special tools needles, just something like this:





Check your plugs' colors after a couple minutes idling and see if one isn't noticeably lighter or darker than others. A proppaly combusting plug has a distinctive appearance, kinda like:



Next, experiment with turning each idle mix screw in and out 1 turn, and note whatever differences.

Of course, if compression is too low or cam lobes are eroded it matters not how clean the carbs are cuz no bike idles well with that stu7ff.

 

I just adjusted the knob on the bottom of carbs, I'm assuming that's idle adjustment, got the bike to idle, somewhat erratically for 5 minutes... Am I on the right track now?

 

After about 2 or minutes from startup, bike should idle smoothly and evenly without using any throttle or choke inputs, even at a speed below recommended idle speed, like down to 800 rpms. If not synch carbs with sticks or gauges first thing.

 

So, I've adjusted the pilot screws as per clymers manual, got the bike idling right around 1000, I felt confident enough to test er out, took her around the block and half way my tack started dropping and running erratically...perhaps my ignition coil is wearing?

 

If you were able to tweak with the carbs some and get it to run better temporarily, then it is likely a fuel issue and not electrical, but i could be wrong. But you will need to isolate it.

Use the clear tube method to measure fuel level, see Squirrel's post down below for details...

 

You have no tac. That indicates the 1/3 ignition box is bad and or flaky the way the bike runs. You need a box. The 1/3 was the box that went on mine.

 

Well, me too,on my gen2 the box quit firing on #3 one day, might have been Tuesday.

 

Hell will freeze over b4 i disagree with KB, but it's been a really bad winter ! Specifically, i would expect most bikes to begin serious overheating by about 15 minutes even if the fan is running. Not enuff air cooling while sittin still, imo.

Checking fuel levels is more accurate, easier and quicker by using a clear tube from the float bowl to measure against the front carb sides (holding the bike exactly vertical), where proppa liquid level is exactly even with the bowl top seam + or - 1mm.



If not, the float setting is inaccurate or needles are leaking.

 

I believe Ive isolated my issue to the spark box at the back of the bike, I'm fairly certain I have the correct box cause I tap one box and see my taps on the tach. What is this box called ? As I will need to order the part and just for general knowledge sense. Thanks guys, been a big help here, I feel quite accomplished having gone over this bike so thoroughly in the last few weeks.

 

That is the igniter box that controls the ignition spark and sends signal to the tach.

Good catch to find it.

Obviously i was off on the fuel issue, but i said as much going in. And Squirrel had much better advice on how to measure the fuel level, so i'm going to delete all that mess.

 

All the information helped, I'd been reading my clymers manual like crazy I think I even slept with it once. Lol

 

Ebay is the only place to find those boxes. I have one but think it's for 2/4. You need 1/3 for the tac circuit.

 

That's the white clip spark box then. Ill have to order the part soon as I can.