Member Contributer rangemaster Posted May 11, 2016 Member Contributer Share Posted May 11, 2016 Working through an issue with my '97 with 35,000 miles on it. The problem: on cold start with or without choke (less than 50 degrees out) it fires up great, but after about 30 to 60 seconds it starts to load up (again with choke off, I don't ever leave it on more than about 10 seconds. and will sometimes gas foul a plug or two (not always the same one. If I rev it up to about 2500 to 3000 it still does it but will clear itself out with some popping. Once it's warmed up it runs perfect-1400 idle to redline, no popping on de-accel, 40+ mpg in town, 50+ plus on the interstate. Will idle all day at a stop light without loading up. I run non-ethenol gas, the Iridium plugs have about 5000 miles on them and the carbs are spotless. The carb rubbers are flexible and seal fine. I have replaced the needle valves to no effect. Carbs are synced and because of the altitude here (5500 ft) the mixture screws are 1 3/4 turns out. Air filter has about 2000 miles on it and looks new. So, air cut-off valve? Something with the diaphragms? Needles? Let me know what else to look at, much appreciated. Dnot know where the strike through came from and can't get rid of it. Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted May 11, 2016 Member Contributer Share Posted May 11, 2016 I chased a "carb" issue for a while and it turned out to be a lack of voltage for sparks, due to corrosion in connectors. There will be some specific diagnostic checks for resistance and voltage that you can do to rule that out. I've also read where an expiring battery made for really poor cold running, probably for a similar reason. But I would suggest you check float levels, as if these are too high you will get rich low-rev running. Also (and I don't know whether VFR's are affected) the emulsion tube (which is where the needle sits/seals against) can wear and produce low end richness. If you pull the diaphragm covers off and remove the slides, the hole in the floor of the carb venturi that the needle sits in should be absolutely circular, if it is oval then that might cause an issue. Link to comment Share on other sites More sharing options...
Member Contributer Kingmdm Posted May 11, 2016 Member Contributer Share Posted May 11, 2016 The voltage stuff is good advice but the floats are not adjustable...on the RC36 anyway. How is that done? Link to comment Share on other sites More sharing options...
750 Posted May 11, 2016 Share Posted May 11, 2016 I think they are adjustable, I'm sure mine were adjusted during the complete rebuild. They're meant to sit at a precise height, this just falls out of spec over time. Link to comment Share on other sites More sharing options...
Member Contributer Kingmdm Posted May 12, 2016 Member Contributer Share Posted May 12, 2016 The carbs are dirty and the jets are clogged. Each carb has about 8 different orifaces and jets that clog. There are 16 pin holes in the slow jet alone and about the same amount in the main jet nozzle. Whether it's the pilot jet, slow jet or the many air/fuel holes, they all clog with time. If you restore the carbs like new ($250 parts and 12 hours labor) you'll won't have a problem again for another 20 years. Link to comment Share on other sites More sharing options...
Member Contributer rangemaster Posted May 12, 2016 Author Member Contributer Share Posted May 12, 2016 Thanks everybody for the input, I'm going to look at most of the stuff mentioned. When I mentioned the carbs are spotless, I've had all the jets out and cleaned and had them under a 10X optical comparator to make sure they weren't worn or plugged. When you can see the machine marks inside the bottom of where the jets go I can only assume they're 'clean'. I use canned air on all the orifaces and they're clear. The bitch in figuring this out is once it gets past the cold initial hiccup, it run perfect all day. It'll idle 15 minutes without loading up. The only thing I haven't done is gauge how round (or out of round) the inside on the emulsion tubes are from needle wear. Terry's electrical cause will also be addressed but I'm running Ox-Guard and any connection I can get apart. Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted May 12, 2016 Member Contributer Share Posted May 12, 2016 I think adjustable floats might be something that EPA/CARB have prevented the US from having, just like adjustable fuel screws. On my ST1100 the floats have a small aluminium tang moulded in, that is the part that contacts the float valve. By bending the tang up or down you can change the float height. Link to comment Share on other sites More sharing options...
750 Posted May 12, 2016 Share Posted May 12, 2016 14 hours ago, Kingmdm said: The carbs are dirty and the jets are clogged. Each carb has about 8 different orifaces and jets that clog. There are 16 pin holes in the slow jet alone and about the same amount in the main jet nozzle. Whether it's the pilot jet, slow jet or the many air/fuel holes, they all clog with time. If you restore the carbs like new ($250 parts and 12 hours labor) you'll won't have a problem again for another 20 years. Fuckin' hell that's expensive. I had mine completely disassembled, all seals replaced with litetek kit, cleaned to perfection, rebuilt and shipped back to me for £190. Unless labour is about one dollar an hour or something?! Link to comment Share on other sites More sharing options...
Alhazred Posted May 12, 2016 Share Posted May 12, 2016 That would be about $280US or $350CA. Are you sure there is even a problem here? My bike won't idle off a cold start until that temp needle is nearing about half way to operating temp. I run the choke full for about 30 seconds and turn it down until it's just at idle until it will rev freely, I have been doing this for about 50,000km now. I can ride it in 4th gear at 2500rpm with no surging and it will pull cleanly from there. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted May 12, 2016 Member Contributer Share Posted May 12, 2016 For the past 17 years/96,000km's my 4th gen needs ~ 2 taps on the starter button (always!) with 20 seconds on choke and idles fine after that. Carbs were 1st taken off at 90k and cleaned (ultrasone), none of the internal parts showed any wear (I was told :-) ) Link to comment Share on other sites More sharing options...
Member Contributer rangemaster Posted May 12, 2016 Author Member Contributer Share Posted May 12, 2016 5 hours ago, Alhazred said: That would be about $280US or $350CA. Are you sure there is even a problem here? My bike won't idle off a cold start until that temp needle is nearing about half way to operating temp. I run the choke full for about 30 seconds and turn it down until it's just at idle until it will rev freely, I have been doing this for about 50,000km now. I can ride it in 4th gear at 2500rpm with no surging and it will pull cleanly from there. Yes Sir, That's exactly how mine started for years, until the turn it down part. Now it idles about perfect for about 10 seconds then starts loading up. If I don't rev it to about 2500 for at least 30 seconds it will gas foul at least one plug. Everybody thanks for the input, I'm making a list. Link to comment Share on other sites More sharing options...
Alhazred Posted May 12, 2016 Share Posted May 12, 2016 You said you never keep the choke on for more than 10 seconds, mine will act the very same way when it's cold. I don't see it as an issue that's what the choke is for,it will sit up at around 2500 for 30-40 sec and then turn it down. Link to comment Share on other sites More sharing options...
Member Contributer rangemaster Posted May 13, 2016 Author Member Contributer Share Posted May 13, 2016 3 hours ago, Alhazred said: You said you never keep the choke on for more than 10 seconds, mine will act the very same way when it's cold. I don't see it as an issue that's what the choke is for,it will sit up at around 2500 for 30-40 sec and then turn it down. Your way was how I used to start it-now I start it with no choke at all and baby the throttle up to 2500 so it won't foul a plug. I'm hoping with the warmer weather I can put off pulling the carbs until the fall, the weather is getting to nice to be in the garage. Defiantly something with the idle circuit (I think) Link to comment Share on other sites More sharing options...
Alhazred Posted May 13, 2016 Share Posted May 13, 2016 Maybe lean out your pilot screws, service manual says 1-5/8 turns for 5000ft and below. Your 1/8 above that at 1-3/4 at 5500ft Link to comment Share on other sites More sharing options...
750 Posted May 13, 2016 Share Posted May 13, 2016 Manual says put choke on for 30 seconds in all conditions other than sub zero. I'm sure Honda know what they're talking about. Link to comment Share on other sites More sharing options...
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