Need help RE: 83 fuel pump

[QBS]

What are the symptoms of fuel pump failor in 83's?  How does one test for fuel pump failor in 83's?

Was working on the bike today attempting to diagnos an apparent fuel starvation condition when the bike is at the reserve fuel level.  When tank is full bike runs well.  But, when the fuel level gets down to close to reserve, it starts to act like it's running out of fuel.  Switching to reserve makes no difference.  The bike won't quit running, but barely manages to keep going.  It really struggles.

Today I had the tank off and rigged up an auxhillary fuel supply and observed the fuel return volume from out of the fuel pump to tank fuel line.  There was a small but steady dribble.  Certainly no high volume or high pressure.  Later in my investigations there was no return volume at all.

My current thinking is that the pump, or its vacume source, has failed and that when the fuel level in the tank drops below the gravity feed level, fuel starvation is the result.  I visually inspected the pump vacume line and could find no obvious vacume leak.  Of course, this is not a definitive test for vacume.  Later, when I get some correct sized vacume line, I'll replace the OEM line.

All observations are appreciated.

Bernie:  It's comforting to know that you are still looking out for us.  God bless you.

Cheers.

[jasonm.]

Try it on prime. See if that makes a difference. Prime by-passes the vacuum aspect of the petcock and draws from the reserve valve. The reserve screen could be clogged.

[Lucky]

You can disasemble the fuel pump and usually the gaskets are ok. if not you can make new ones.  if you find a cracked plastic diaphram or rubber valves bad, I believe I have some 82's you can have cheap, or try the 82 kit from Keyster on Ebay.

[Walt_M.]

Sounds like a fuel pump problem. The return line flow on mine is pretty healthy, certainly more than a 'dribble'. I would try the Keyster rebuild kit, which reminds me that I have to get one too, while they are still available.

[jamesr ransom]

check the fuel tank screen filter

[jasonm.]

Always do the simple thing first. remove the petcock and check the screens. If my pump ever went I would just get an electric one that delivers 1-3 psi. They are everywhere.

[Ken_Williams]

I recently experienced the symptoms of insufficient fuel pump output on my 83 model.  Even with the fuel level well above the carbs, fuel flow was insufficient.  I also noted fuel would not flow through the pump with the engine off.  

My solution was to purchase one of the Keyster fuel pump rebuild kits.  The kit contained every soft part in the pump except for the rubber rods that retain the check valves.  So during the rebuild, you have to be careful not to damage the rods.  The only part that was bad in my pump was the diaphragm between the vacuum and the fuel.  It was stretched so that it had one concave and one convex side.  The new one is flat.  When I took the pump apart, the convex side was pressed against the check valves, keeping fuel from flowing through the pump.  I assume that when the engine was running, the convex side moved to the vacuum side of the pump.  In this position it almost filled the chamber.  This resulted in the diaphragm moving only a small bit and pumping only a small bit of fuel with each vacuum cycle.  

Anyway, my rebuilt pump works great.  

There is actually a diaphragm on each end of the pump.  If one had a pump with a stretched pumping diaphragm such as mine and one wanted to be frugal, my guess is that interchanging the two would also fix the problem.  

[Lucky]

So QBS, What did you end up finding?

[nvdranger]

I know the kits are mislabled but do the 83 kits work for an 82?  I assume not but would be nice for future reference.

Ken

[Walt_M.]

I don't think so, they are so physically different. Lucky or Rick G. would know for sure. Have you considered an electric pump? I have and might go that way even though there kits available for '83s.

[Lucky]

The only kit mislable is for the 83 carbs, it's labeled as an 82.  the 83 fuel pump kit will work in the 82, it just won't include the triangle shaped diaphram or spring for the fuel pressure regulator.

[nvdranger]

thanks for the info, now I'll know if I ever have a problem with mine.

Ken

[Humber]

Electreic pump would be great but one doesn't know if pressure in our bowls will manage to switch it off when it is really needed. This is what pressure regulator does or fuel return line.

I considered this and I found that there are many kinds of those pumps. I was looking for ones that are ?powered simply by two wires + and -. Pressure regulator is built in probably but I am not sure if our bowls produce enough pressure to stop it from pumping.

Another interesting use for an electric fuel pump would be to treat is as a fuel return motor.

U certainly saw the pictures of my tank, at the highest point of it I mouned a fitting which will serve for fuel return line. The fitting is above the fuel level so I believe the fuel pump on the carb will manage to pump it there.

If not, I will use an electric pump to force fuel to go up to the tank.

I considered using a car windscreen washer motor too, think it would work great for this purpose...

[jasonm.]

Humber, on Ebay there are electric fuel pumps from crashed Yamaha Sport bikes, like R6, FZR600, etc. These are bikes with carbs. The regulators are built in.I have the same pump on my '87 Venture. 65k on it...still pumping. Or an auto store has pumps that put out about 3psi.