Guest Nocalnative89 Posted September 7, 2012 Share Posted September 7, 2012 So here is the deal: 1986 VFR700 Ive had for about two years. This previous spring I had the carbs professionally rebuilt and it ran like a champ. Over the summer it had started to slowly lose power but so slowly that I didnt really notice. This past month (6 months-ish after rebuild) I started noticing a severe loss of power (Especially in 4-6k RPM range) every time I rode for over an hour at a time. When I did this it also had a very low idle and would sometimes die if I did not keep the throttle open a bit. Thinking I had just gotten a bad tank of gas or something I put some carb cleaner additive and premium fuel in for my next tank. The bike starts normally and rides fine for 10-15 minutes then refuses to idle and has barely enough power to get moving. Power is very rough (spits and jolts when Im trying to accelerate). I let it sit for a few hours and re start it and its still running poorly. If it sits for a few days it will again run 15 minutes without issue before returning to crappy-state. Ive replaced the fuel filter and added gas (to try to dilute the carb cleaner in case that was the issue) but nothing has worked. Im stumped because I cannot figure out why it would run fine at first then die once warmed up? Is that a carb issue? Fuel pump? I would like to be able to save money by not going to a shop and I can do basic repairs but Im new to working on Bikes (And Carbs) Thanks for your help Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 7, 2012 Member Contributer Share Posted September 7, 2012 this bike is NOTORIOUS of having a bad fuel pump. do your self a favor.. turn off the gas. remove side left side panel disconnect the fuel pump and add a duel male connector or a fuel filter . go test ride.. Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 7, 2012 Member Contributer Share Posted September 7, 2012 there is a chance this could be vapor lock... but.. from my experience.. the pump develops a leak.. and the gas flows to the electrial side. shorting out the pump.. which stops.. allowing the gas to dry.. which allows the pump to start up again.. and/ or catch fire. been there and done that ! roasted nuts are not what i ordered!! part of the problem ..the pump is mounted horizontal .not vertical. in any case.. by pass the pump.. if the your problems go away.. you now can either leave it off. or get a new one.. just change the mount to vertical on the new one. to test for vapor lock...leave the gas cap open and go for a ride. put a shoe string around the cap to stop it from flapping around. but dont beak the lock cover by tying to tight. Link to comment Share on other sites More sharing options...
Guest Posted September 7, 2012 Share Posted September 7, 2012 Thanks Guys. Ill bypass, test, and report back. Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 7, 2012 Member Contributer Share Posted September 7, 2012 make sure the gas line is not kinked.. make it nice and smooth a lightbulb shaped loop Link to comment Share on other sites More sharing options...
Guest Posted September 7, 2012 Share Posted September 7, 2012 Sorry for the huge picture but I bypassed the pump like so: And tried to start it and nothing. How do you prime the carbs to get it started when you are only using gravity feed? Fuel flows out of the tank, through the lines and filters just fine but it seems its not getting to the carbs. If Im doing it right then Im afraid the problem wasnt the pump? Link to comment Share on other sites More sharing options...
Member Contributer gll429 Posted September 8, 2012 Member Contributer Share Posted September 8, 2012 you may need to lift the tank as there may be an air bubble trapped in the line... try draining a flost bowl and let some gas pour out.. this will allow any air to get out the line. Link to comment Share on other sites More sharing options...
Member Contributer unbalanced Posted September 8, 2012 Member Contributer Share Posted September 8, 2012 Make sure you have a full tank, right now your gas line will need to pull the fuel 'up hill' and without enough pressure it will not flow. Also move your line UP... Link to comment Share on other sites More sharing options...
Guest Posted September 9, 2012 Share Posted September 9, 2012 Shortened the line to where its basically a direct feed through a filter and into the carbs and started it up no problem. Let it warm up and went on a ride and smooth as can be. Responsiveness/Acceleration is a bit down (Im assuming thats normal w/o a pump?) but still pulled strong at every RPM I tested it at and didnt sputter at any point. I appreciate the help guys. Link to comment Share on other sites More sharing options...
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