I am getting horible gas milage...

Its my 84 VF700f interceptor and I want to start from the beginning on what I should check out.
I think that it is carb related. I have been getting popping out the rear pipes like its lean but that is only that front side. I have been getting about 20-25 MPG and it is pissing me off. What would you do?

 

Check plugs and make sure the carbs are clean. New air filter, new plug wires if there is a weak spark at the plugs..these are just some general tune up ideas that come to mind.

 

I should start there at the beginning. Plugs wires... But where do I get new wires? I did see some at the junkyard that were brand new. But they only were for the back ones. It was on a converted racebike.

 

Look for any place that sells NGK Race cables..(thats what they are called but they are actually cut to length plug wires). Also look for anyone that sells parts from Motovan or Parts Canada (though in the states i doubt the latter applies). Because both catalogues have universal cut to length wires in them.

 

As already mentioned check your ignition components first. Pull your plugs and check the condition. Replace them if they don't look good. You should also be able to spot problems by looking at the plugs like rich or lean conditions. Also check for fat blue spark on each plug wire. If you have weak spark make sure to verify with known good plug.

Common for these old bikes is the carburetor float valves to wear out and not seal well anymore. When that happens you will get a rich running condition which should be apparent by looking at the plugs (wet and black). If your ignition checks out good I would rebuild the carbs next.

 

I concur.

Your carbs are the most likey to be the problem. I don't know if you have after-market jetting and pipe installed, but it could be numerous problems with your carbs. List all your symptoms- i.e. poor idel, poor performance, black smoke out of the exhaust during acceleration,and ect. This will make easier to diagnoise the main problem. You could have some gummed up jets or worn out seals.

 

I have had them out several times. I checked the float valves. Cleaned the jets too. I had a dead cylinder for a while but that was a plugged jet. I got popping from the front left cylinder after I brought it back to life but now it only pops when I am using the gears to slow down. There seems to be a sync problem because when I lay into it the power comes later. Like a turbo kicking in. I don't get black smoke but I will check the plugs and see what they look like. The last time I checked they seemed nice a white/brown ashy.

 

Deceleration pop is usually a lean indication on the low speed jets.

 

Its barely turned so it doesn't pop. Should I turn it out another half turn or something? I suppose that I should sync the carbs again I have had them apart a few times since the last time I synced it. I should pull the plugs but I went other way today when I was working on it. I cut off the fender and changed the turn signals.

Once I took off the tail light.

Another one...

And yet another one...

And after a quick zip with a saws-all.

And here it is after the drilling and changing of the turn signals.

He's the side...

Here is another one. Notice the soot around the tailpipes. I did notice some white smoke when I lay into it. But its not black and there isn't alot of it.

Here is a side picture. OTOH... Looks at the dick head code enforcement van in the background. They came out on Sunday to try and bust my balls. I told him that it was legal to repair cars as long as its done before 9pm. And I told him that even if it wasn't I would still do it because I own this house and I will do what I want here. I think they don't understand that and take offense to people standing up to them. He asked if I have a dog here. (I haven't had a dog in a year since they made me get rid of it) And I told him no. He asked if there is any women here? (Not are you married? Is your wife here? And what does that have to do with pretty policing?) But I told him nicely to get his own women and walked away. Sorry for the rant but they piss me off something fierce.



Last one. Sorry for blowing up your computer if you have dialup.

 

Anymore idea from the group?

 

Well, I love the pipes on that rig, if you change them, I have paypal.

 

Heh welcome to the cut down fender club lol

 

I think that it is a great mod that didn't cost me anything really.

 

Test the Coils

one coil controls the front bank of cylinders and the other controls the rear bank

one sparkbox controls the front bank of cylinders and the other controls the rear bank

The tach gets its signal from one of the coils. Check the wiring diagram, but I believe it's the yellow wire.

You can use this to test the coils. If the tach acts up then the associated coil/sparkbox is the issue. Swap the sparkboxes, if the tach acts up, it's the coil. If not, it's the sparkbox.