fabio222 Posted August 24, 2013 Share Posted August 24, 2013 Hi all, I hope I am posting this in the right place here but I'm having problems with my 4th gen VFR. ABout a week ago I was pulling away from my part-time job in the university and noticed the bike seemed down on power, it seemed to need a lot of throttle in order to ensure it didn't stall. I thought maybe the engine was just colder than usual but then it did cut out and stall after a couple of minutes of running. It would start up again but it was very difficult to keep the engine running. It would rev up to the higher parts of the rev range eventually but if you let the revs fall below 5000rpm or something like that it would want to stall. In the workshop today I tried to sort it so I pulled off the air filter and sprayed a load of carb cleaner into the intake trumpets, which all looked clean, and then started the engine. It would keep the revs consistent with the choke on but if the choke was turned off and I gave it some throttle, it would die. It also would not hold idle, it would just peter out and die. With that I decided to take the carbs off so I loosened the clamps that keep them on to the inlet manifolds. These were all good and tight and it took some leverage to get the carbs off so there's no leakage there (I don;t think). The fuel lines and breather lines etc are all ok and were not kinked etc. The best description I can give of this problem is that it 'feels' similar to when you spray a load of carb cleaner into the carbs and rev the engine to suck it all through but you don't rev the engine enough and it suffocates and dies out. It feels the same as that. - I am wondering is there air getting in somewhere? If so where? - Is it the fuel pump? I opened the float blows and let fuel flow out of them and it looked fine and the fact there was fuel in there must mean the pump is ok (and if you can get the engine up to higher revs it works fine so would that rule out the pump?) Any help at all would be appreciated as I was really hoping I'd sort it today so I could go for a spin tomorrow! Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted August 25, 2013 Member Contributer Share Posted August 25, 2013 Hmmm... My first thoughts: -Perhaps a bit of debris (even something very small) in a carb float valve causing the engine to flood at lower throttle openings? However if it's been running fine and it hasn't been sitting much your carbs should be ok... -I had similar symptoms this year and it was ignition coils causing the problem (although my issue was related to switching to GSXR coil on plugs that may have been bad). I had to keep the throttle open quite a bit at a stop to keep the bike's "throat clear" and it only worked okay once underway using a decent amount of throttle. The problem would only appear however after the engine reached operating temperature. Is the problem consistent or more prevalent after the bike warms up? Have you pulled plugs and looked at them? There are tests in the service manual for the fuel pump. Sorry I can't help more... Link to comment Share on other sites More sharing options...
fabio222 Posted August 25, 2013 Author Share Posted August 25, 2013 That's a great help thanks for replying. To be honest it does not get a chance to warm up, the problem is there from the get go. I'll try test the fuel pump today as I was initially suspicious of that due to it having 65000 miles the clock but I would have thought the fuel pump would have had more of an effect on it in the higher end of the Rev range. I dunno? Any way of testing coils? Link to comment Share on other sites More sharing options...
fabio222 Posted August 25, 2013 Author Share Posted August 25, 2013 Fed fuel straight to the carbs and still have this issue so it ain't the fuel pump. All four downpipes were hot when I ran it where it was smooth enough from 0-4000rpm and then would begin to feel bogged down. If I get the throttle open here I could hear pops from the exhaust, like backfires. Something jammed in a carb and causing a flood? Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted August 25, 2013 Member Contributer Share Posted August 25, 2013 I think I have run out of expertise in this area... if It was my bike I would probably pull plugs first to see how they are doing, maybe even just buy new ones and see if it helps the issue. If it helps but doesn't get rid of the problem your coils might be the culprit. But there's likely a good chance your carbs are the issue. I just hesitate to tell you to tear into them as sometimes the rubber seals will need replacing and that can be quite expensive. Is it possible you got some bad fuel? Are you sure all your vacuum hoses are in good condition and hooked up correctly? CV carbs need the vacuum to work properly and could give you a hesitation to rev past 4000rpm. I really hope I'm not pointing you in the wrong direction, the fact that it was running fine up until having issues has me a little stumped. Was it sitting for a while (even 1-2 weeks?) before the symptoms started? Not sure if you have ethanol in your fuel over there but it can cause carb issues in short time. Link to comment Share on other sites More sharing options...
Member Contributer wagzhp Posted August 25, 2013 Member Contributer Share Posted August 25, 2013 Sounds like bad gas, or some debris has fouled your carbs. Did you clean the jets and low speed/idle circuit when you had the carbs off? That's where I would start. While plug problems can affect the whole rpm range, usually bad plugs cause problems in the upper rpm range where the mixture is harder to ignite. Sent from taptalk with spell check and political correctness disabled Link to comment Share on other sites More sharing options...
fabio222 Posted August 25, 2013 Author Share Posted August 25, 2013 Thanks everyone for the help with this. Here is an update on what I did... Earlier on I pulled the carbs off and then went and took the bottom of the carb off to expose the float. I ensured to clean all of this with carb cleaner but did not insert anything into the jets, just gave them a spray with the carb cleaner. To be honest to my own eye nothing looked dirty. The float valves were moving fine too. With this I put the carbs back on the bike and while it would idle ok it would not go above 4000rpm for me. At this stage I feel like just bringing it to a garage somehow... Link to comment Share on other sites More sharing options...
Member Contributer CasualSwede Posted August 26, 2013 Member Contributer Share Posted August 26, 2013 Something to note - when you put the carbs back on the bike, did you put the airbox and filter back on too? The reason I ask, is because without the airbox and filter my bike wouldn't rev above ~5000 rpm (I didn't have a tach at the time, so going by ear) when I started it for the first time this year. With the airbox and filter, it pulled cleanly up to 11 grand. So even though it wasn't initially part of the problem (assuming you ride with the airbox and filter), I'd make sure to put it back on when you're troubleshooting, just to eliminate it as a variable. Edit - clarification of effect of airbox. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted August 26, 2013 Member Contributer Share Posted August 26, 2013 It would appear as though your first issue is different than what you are describing now. Will it idle now but not rev past 4000rpm? If that is the case I would echo what FSAE said and double check your vacuum lines. Link to comment Share on other sites More sharing options...
fabio222 Posted August 26, 2013 Author Share Posted August 26, 2013 Thanks everyone again for contributing. I'm gonna try the carbs again by blowing compressed air through the jets. Will let ye know what happens. Link to comment Share on other sites More sharing options...
Member Contributer dalesvfr Posted August 26, 2013 Member Contributer Share Posted August 26, 2013 If you have good spark and the air filter isn't clogged I'd guess the carbs need a rebuild. Dump some Seafoam or Chevron Techron (do you have that over there?) in the tank and let it sit for a day or two first just in case it is only a little varnish hanging things up. Link to comment Share on other sites More sharing options...
Member Contributer hondalover Posted August 26, 2013 Member Contributer Share Posted August 26, 2013 I just had to clean the carbs on my wife's bike. It started running on just two cylinders at idle, and mimicked your first issue. The pilot jets were blocked on #1 & 2 carbs which hinders the idle and slow/low speed circuit for those cylinders. It seems like you got that taken care of. And like others have said with the airbox/airfilter removed you'll have a hard time with it revving. The way CV carbs are designed is they are looking for a "constant velocity" (hence the CV) for the slide to operate which is the mid-range and upper end of the rpms. Link to comment Share on other sites More sharing options...
fabio222 Posted August 26, 2013 Author Share Posted August 26, 2013 Hi all. Well I took the day off from phd work and gave it another go. Blew air through all the jets and upon reassembly it all worked. I then put the tank on and my new delkevic exhaust and it'll stop running if given a sniff of throttle. Close to just giving up now. As an aside thanks for being so helpful to a new forum member such as me. Link to comment Share on other sites More sharing options...
Member Contributer dalesvfr Posted August 26, 2013 Member Contributer Share Posted August 26, 2013 New exhaust? Were you supposed to rejet for it? Does it run with the original can on there? Link to comment Share on other sites More sharing options...
fabio222 Posted August 26, 2013 Author Share Posted August 26, 2013 No its meant to run same as stock that's why I bought this particular exhaust. I think the problem was coming back before the new exhaust was put on anyway and I have run the bike before (for just a few seconds!) with no exhaust just to hear the sound and that worked fine. I think the carbs may need a proper garage clean in a solvent bath or something. I've done all I can at this stage...and its eating up my time for other stuff like work haha! Link to comment Share on other sites More sharing options...
fabio222 Posted August 30, 2013 Author Share Posted August 30, 2013 UPDATE!!!!!!!!!! I'm collecting the bike from the dealership tomorrow (I gave up on Monday). As it was with them I asked them to do the valve clearances too. It turns out that the fuel pump was what was at fault. The flow rate was poor and inconsistent. They tried to replace the contact points in the pump but the problem was still there so they were going to order a new one but they did some fiddling around and have it working now but did warn me that I will be needing a new one. I'm thinking over these two options for fuel pumps: http://cgi.ebay.ie/ws/eBayISAPI.dll?ViewItem&item=281114895027&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en OR http://www.ebay.ie/itm/HONDA-CBR600-900-VFR750-Replacement-Fuel-Pump-/111142109343?pt=UK_Motorcycle_Parts_13&hash=item19e096009f Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted August 30, 2013 Member Contributer Share Posted August 30, 2013 Glad to hear its running again! I'm a little curious why it did the same thing when the carbs were gravity fed? Link to comment Share on other sites More sharing options...
fabio222 Posted August 31, 2013 Author Share Posted August 31, 2013 I think that was because the carbs were dirty cos after I cleaned them out the second time it worked on an auxiliary fuel supply... Now just have to decide on what pump to get... Link to comment Share on other sites More sharing options...
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