ridered Posted December 18, 2015 Share Posted December 18, 2015 Lately I've notice the VFR is running rough, and now started to a slight miss below 5K RPM. Also my fuel consumption is terrible, only 150 out of the last tank. It is usually closer to 180. The flat spot at 4500 RPM seems more pronounced too. Fully stock bike, and pre 02 sensor model. 56,600 on the clock. No warning lights. Just changed the oil, and sparks got changed last night. Didn't ride today, but I'm hoping it was the plugs, because they were over due. I'm going to run a bottle of fuel injection cleaner as well. Checked the air filter and it is fine. If the plugs don't resolve the problem, any suggestion of what to look for next? I ride the bike almost every day, so it is not bad gas. It gets a fresh tank every other week at least. RideRed. Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted December 18, 2015 Member Contributer Share Posted December 18, 2015 What is the engine temperature reading after a few minutes ,these have a habit of a sticking thermostat which will cause the above problems .The temp should be up around 185-195 . Link to comment Share on other sites More sharing options...
ridered Posted December 18, 2015 Author Share Posted December 18, 2015 What is the engine temperature reading after a few minutes ,these have a habit of a sticking thermostat which will cause the above problems .The temp should be up around 185-195 . I'll check. It has gotten much worse now that is actually cold here. Link to comment Share on other sites More sharing options...
Member Contributer MaxSwell Posted December 18, 2015 Member Contributer Share Posted December 18, 2015 What is the engine temperature reading after a few minutes ,these have a habit of a sticking thermostat which will cause the above problems .The temp should be up around 185-195 . I'll check. It has gotten much worse now that is actually cold here. I noticed much smoother engine operation after I'd had my valves adjusted. (actually cold in San Diego?!!!!) Link to comment Share on other sites More sharing options...
squirrelman Posted December 18, 2015 Share Posted December 18, 2015 Something's wrong. Honda eliminated all fueling problems when they switched from balky carbs to perfected, computer-controlled fuel injection, right? A change of plugs would have been my first suggestion, but you've done it already. Good luck. Link to comment Share on other sites More sharing options...
raoufhakam Posted December 19, 2015 Share Posted December 19, 2015 in cold weather i notice my engine runs cooler than summer, and my fuel consumption gets worse, but i notice it only runs a little rough and idle rpm decreases between engine temps 65-75C (150-165f). i was told by a good guy at the local Honda dealer (who owns an ST1300) that this is cause by the fast-idle wax body (thermostat-like) closes earlier than it should when the engine is still cold Link to comment Share on other sites More sharing options...
Member Contributer gmtech94 Posted December 19, 2015 Member Contributer Share Posted December 19, 2015 No wax unit on a 98 only 2000 or 2001 units . Link to comment Share on other sites More sharing options...
raoufhakam Posted December 19, 2015 Share Posted December 19, 2015 No wax unit on a 98 only 2000 or 2001 units . i know that 98-99 had choke lever, 2000-2001 had wax unit (mine is 2000) OP did not the year of his, just mentioning what i've noticed with mine though Link to comment Share on other sites More sharing options...
Member Contributer MBrane Posted December 19, 2015 Member Contributer Share Posted December 19, 2015 I would suspect the thermostat if it was not missing. That leads me to think it's a fuel injector. I had one clog on me once. Oddly enough it happened right after fueling at an independent station in south San Diego county. They're not difficult to clean yourself if you're reasonably handy with mechanics. Lot of info online. Link to comment Share on other sites More sharing options...
Member Contributer Cogswell Posted December 19, 2015 Member Contributer Share Posted December 19, 2015 +1 on the fuel injector. It doesn't take a lot to reduce their flow or prevent them from shutting off completely. There's no substitute for removing them for cleaning. Even if that turns out not to be the issue it's still good maintenance. Link to comment Share on other sites More sharing options...
ridered Posted December 21, 2015 Author Share Posted December 21, 2015 No wax unit on a 98 only 2000 or 2001 units . i know that 98-99 had choke lever, 2000-2001 had wax unit (mine is 2000) OP did not the year of his, just mentioning what i've noticed with mine though 1998. Still haven't ridden since installing the plugs. Tomorrow I should know. Link to comment Share on other sites More sharing options...
raoufhakam Posted December 22, 2015 Share Posted December 22, 2015 any updates? good news i hope! Link to comment Share on other sites More sharing options...
ridered Posted December 22, 2015 Author Share Posted December 22, 2015 It rained today, so I drove to work. I will post updates once I have the information. I also plan to do some maintenance to the bike, so I will inspect everything mentioned: 1. Check all vacuum lines. 2. confirm in the plugs helped. 3. Check the thermostat. 4. Clean the injectors and throttle bodies. Initially with FI cleaner in a bottle. If that doesn't work, I will pull the injectors and clean them. 5. Check the throttle body boots. I hate the bike to be down, because I ride almost every day so I've been neglecting maintenance. I also have some other stuff I'll do when I have all the plastics off. If when I'm done it still runs rough, I'll do a valve check. I'm planning on getting a new bike in January (a VFR1200) so then the 5th gen will be ready to be reconditioned. It also needs forks serviced, and some other work. Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted December 22, 2015 Member Contributer Share Posted December 22, 2015 It rained today, so I drove to work. I will post updates once I have the information. I also plan to do some maintenance to the bike, so I will inspect everything mentioned: 1. Check all vacuum lines. 2. confirm in the plugs helped. 3. Check the thermostat. 4. Clean the injectors and throttle bodies. Initially with FI cleaner in a bottle. If that doesn't work, I will pull the injectors and clean them. 5. Check the throttle body boots. I hate the bike to be down, because I ride almost every day so I've been neglecting maintenance. I also have some other stuff I'll do when I have all the plastics off. If when I'm done it still runs rough, I'll do a valve check. I'm planning on getting a new bike in January (a VFR1200) so then the 5th gen will be ready to be reconditioned. It also needs forks serviced, and some other work. I'd be surprised if a regularly ridden 5th gen injectors needed to be removed and cleaned... they are a relatively large bore single hole injector, not like the later 6th gens with multiple small orifices. Were any of your old plugs that were removed sooty or wet with gas? Link to comment Share on other sites More sharing options...
Member Contributer MaxSwell Posted December 22, 2015 Member Contributer Share Posted December 22, 2015 I'm with Rush 2112. My first fifth gen, a 2001, had 105,000+ miles when she was KIA. Her injectors were never cleaned. She ran like a fine Timex. Took a licking and kept ticking. Link to comment Share on other sites More sharing options...
ridered Posted December 23, 2015 Author Share Posted December 23, 2015 Update: Finally rode the bike today in spite of the rain. Here are my findings: 1. Plugs helped. Runs smoother, and the flat spot is back to a normal minor annoyance. Idled better, and power felt better. 2. Thermostat does seem low. It was around 50 today, and the bike stayed around 175. My guess is the PO installed a lower temp one to combat our usually hot weather. Might change it, might not. Probably better for the bike in the summer. Does anyone know the normal operational temperature? This would explain my poor mileage lately though. Will check the rest of the items in a few weeks when I have time to pull the plastics and go over the bike. This bike is amazingly durable. Link to comment Share on other sites More sharing options...
Member Contributer MBrane Posted December 23, 2015 Member Contributer Share Posted December 23, 2015 It's normal for a 5th gen to run cold when it's cold ambient, and likewise hot when it's hot. It's the nature of the side mounted radiators. Link to comment Share on other sites More sharing options...
Shooter Posted December 23, 2015 Share Posted December 23, 2015 Had same issues with my 2001. Serious flat spot at about 4500rpm, I could only get about 130 miles per tank, temperature would not not rise above 160 - 165. It generally ran, but very rough. It was the thermostat. Once I replaced it (took about 2 1/2 hours), all was right with the world. This would be my guess for you as well. Link to comment Share on other sites More sharing options...
Member Contributer wagzhp Posted December 23, 2015 Member Contributer Share Posted December 23, 2015 It's normal for a 5th gen to run cold when it's cold ambient, and likewise hot when it's hot. It's the nature of the side mounted radiators. Yep, the thermostat opens at 174 Degrees Fahrenheit. My bike runs at 174/175 when the ambient temps are below 50. Link to comment Share on other sites More sharing options...
Auspanglish Posted December 23, 2015 Share Posted December 23, 2015 Try synchronising the starter valves. Can't hurt. Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted December 25, 2015 Member Contributer Share Posted December 25, 2015 My five minute test for a stuck thermostat: Start the bike from cold and keep it revving at 2k or so with the fast idle lever. Touch the radiator every now and then. If the temperature at the radiator rises slowly, the thermostat is stuck open. If the radiator stays cold for a few minutes and then suddenly gets too hot to touch, the thermostat is working as it should. The thermostat will keep the running temperature at or above its opening temp which should be 80C; mine will generally sit between 78 and 82 under all running conditions, but will happily rise much higher when there's no/slow airflow through the radiators. At around 100C the fan should come on. If you have a dirty injector, you may also find your oil level rising. I have found that fuel will gravity flow from the tank to the fuel rail with the engine off (discovered this swapping a fuel pressure regulator) so if an injector is slightly stuck open, in addition to high fuel consumption, the oil level may rise slowly as fuel drips down into the cylinder and past the rings. This may be less obvious to a daily rider than for us weekend warriors! Link to comment Share on other sites More sharing options...
E-Ticket Posted January 23, 2016 Share Posted January 23, 2016 Great thread .... I need to "all of the above" on my 55K mile '98. Cheers! - ET Link to comment Share on other sites More sharing options...
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