Guest Jerry2dt Posted March 8, 2014 Share Posted March 8, 2014 Good day, members, Hi, I'm Jerry and new to this forum. I live in the USA, in Oregon. I have my VFR which I bought new in '96. I got into homebuilt aircraft a dozen years ago and consequently didn't put many miles on her, mostly back and forth to the airport and just on dry days during the summer. Lately she refused to start and I discovered the gas had gone bad as well. I drained the tank and carb float chambers. I tested the fuel pump by jumping the pump relay and pump works fine. I have question for any good wrenches here... 1. First of all, why does a carbed bike need a fuel pump in the first place? Carbed airplanes with high wings have no pump, just rely on gravity to do its thing, Why is a bike any different? My old Triumph 650 had no pump either. 2.When does the pump run, part time/ full time? On testing the pump is noticeably noisy and if you put your hand on it can feel the vibration. But while engaging the starter no noise/vibration so seems not to be running then. I figured I'd best get some advice on this before I attempt the startup. I've scanned this forum quite a bit since joining and search did not come up with much re these questions. I did note how passionate everyone seems about the various VFRs and Interceptors. I think that's a good thing. I am 77 and a cancer survivor. There is a good chance the FAA will refuse my medicle license soon, so if/when they do I'll be enjoying my VFR once again. Best to all and Thanks! Jerry Link to comment Share on other sites More sharing options...
Member Contributer rangemaster Posted March 8, 2014 Member Contributer Share Posted March 8, 2014 Sir, Some folks have run the carbed VFRs without a pump-depends on your riding habits. A long blast at high rpm will eventually starve the carbs. The pump works about once every 2 seconds to keep positive pressure to the carbs. Check the points on the pump to make sure they aren't fuzed together or badly pitted. Good luck on your license renewal. Link to comment Share on other sites More sharing options...
Guest Posted March 8, 2014 Share Posted March 8, 2014 I think I get it then... Would that necessarily mean the pump should run when you hit the start switch? Or does startup just depend on gravity? Thanks for the help. Jerry Link to comment Share on other sites More sharing options...
GadiantonRob Posted March 8, 2014 Share Posted March 8, 2014 I was just out messing with my carbs on my bike, and I had a clear fuel hose connected to a funnel filled with gas. Upon running, I noted that the pump only 'pumps' fuel every couple of seconds or so, and only does it with any kind of rhythm whenever rpm's are up. When idling, it hardly ever pulsed. I believe on start up that if it doesn't need to pulse, it doesn't. It only supplies like 1 psi or so, what I have read. And it's near silent and hardly goes bad. Link to comment Share on other sites More sharing options...
Guest Posted March 9, 2014 Share Posted March 9, 2014 Well, I got it started and found out from another source it's like Squid just said. It turns on/off as needed. It ran just fine at first then started pulsing between 1150 and 4000 R's and not surprising since it's set for awhile. I think I'll start running it every day and see if the pulsing goes away on it's own and hope those complicated carbs don't need to come off. Or, if someone knows the fix for pulsing, please let me know. Thanks guys, Jerry Link to comment Share on other sites More sharing options...
Member Contributer kgsmotorcycles Posted March 9, 2014 Member Contributer Share Posted March 9, 2014 While your at it check the R/R connector block and 3 yellow charging system wires for heat damage all the way up to the engine block.... Ive been running without a pump on road and track for some years now with no issue. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted March 9, 2014 Member Contributer Share Posted March 9, 2014 Search for my post "ride to hell part deux". ;-) Link to comment Share on other sites More sharing options...
Guest Posted March 9, 2014 Share Posted March 9, 2014 Thanks Duchy, I enjoyed your tale of riding to Hell and the busted fuel pump. I think it might be a good to dress those pumps say, every oil change or so. Back when we had distributors with points it was pretty common knowledge that regular dressing of the points extended their life a lot. For those that dislike the USD 200 for a new pump, I have replaced a $500 aircraft pump with $100 Bosch racing pump which had a lot more capacity. Do you happen to have any idea why my VFR would be surging between 1100 to 5000 from idle? Ever had that happen? Being new to this site, I am befuddled with the search option. Thanks, Jerry Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted March 9, 2014 Member Contributer Share Posted March 9, 2014 Hi Jerry, Nope never had the engine surge since I bought her new in 97. Link to comment Share on other sites More sharing options...
Dmitry Posted March 10, 2014 Share Posted March 10, 2014 Hawks have similar electric pumps and may have ditched them due to pump or relay failure, since Hawk will not run well without it (fuel starvation at high speeds) many opted to replace the electric pump with a vacuum operated Mikuni commonly found on SV650, I think it's $50. I still run electric, have not had an issue in almost 20 years... Link to comment Share on other sites More sharing options...
VFRBert Posted March 10, 2014 Share Posted March 10, 2014 Sir, i think the surging is caused by clogged slow jets. Modern gas cannot be stored longer then a few months, before it goes bad. You will get gum in the carbs, clogging up the jets. I think, that the slow jets of youre bike are clogged up. Nr 32 in the part fiche: http://www.cmsnl.com/honda-vfr750f-1997-usa_model7620/partslist/E++1603.html#results. Sometimes putting a fuel treatment like Seafoam will help. The other option is removing the carbs from the engine and clean them, preferably ultrasonic, because it is difficult to clean al the small parts, like jets. Link to comment Share on other sites More sharing options...
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