Member Contributer MadFrog Posted May 17, 2017 Member Contributer Share Posted May 17, 2017 I am frustrated with my bike's idling. I have recently cleaned and synced the carbs,c hanged plugs, checked valves and cleaned air filter. After re-assembling everything I have been struggling to set my idle speed. Once the bike is warmed up, when I come to a stop the idle will quickly come down to about 1500-1600 rpm and over the course of 30-60 seconds dip back down to about 1100 rpm. If I set it lower, the bike will often stall. The idle is also a bit "lopy" as it fluctuates between 1k and 1200rpms. What have I screwed up? Maybe I need to re-check the sync? This has always been a bit of an issue on this bike, but it seems worse since I have cleaned everything up (the bike runs better and smoother in all other conditions). I have not touched the air mixture screws nor have I moved the carb needles. Link to comment Share on other sites More sharing options...
gonerydin Posted May 17, 2017 Share Posted May 17, 2017 Could be a vacuum leak. Or not. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted May 17, 2017 Member Contributer Share Posted May 17, 2017 I think that's the standard answer for these symptoms. Check all of the vacuum lines, especially near the nipples, for cracks. It's cheap to replace vacuum lines... Ciao, Link to comment Share on other sites More sharing options...
Member Contributer MadFrog Posted May 17, 2017 Author Member Contributer Share Posted May 17, 2017 From memory, there are two plugs on the rear cylinder ports, and two line on the front cylinder ports for the pairs crap. What other vacuum lines are there?Are the ports that connect the pairs system back to the air box considered part of the vacuum system?This may be a good excuse to de-pair the thing. I just need to find some block off plates for the cylinders and some plugs for the front cylinder vacuum ports. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
coupedupsubie Posted May 17, 2017 Share Posted May 17, 2017 Block off plates http://m.ebay.com/itm/Honda-VFR-750-VFR750-Interceptor-Exhaust-Emissions-Plate-AIS-Smog-Block-Off-Kit-/232139921877?nav=SEARCH Items 6 and 18 are what you need for the ports with the small hoses(Where you attached to sync the carbs). http://www.partzilla.com/parts/search/Honda/Motorcycle/1994/VFR750F+A/REAR+CYLINDER+HEAD/parts.html For the ports on the airbox you just need a couple rubber caps the right size. Link to comment Share on other sites More sharing options...
Member Contributer COS_VFR Posted May 18, 2017 Member Contributer Share Posted May 18, 2017 I had good luck with these: https://tpoparts.com/cat093/index.php?route=product/product&keyword=S-0062&category_id=0&product_id=53 Can't remember if the rubber caps that they included fit the airbox though. Link to comment Share on other sites More sharing options...
atx Posted May 18, 2017 Share Posted May 18, 2017 Yeah and when you replace those vac lines i'd go ahead and resync after. Did you check/adjust your valves? That shouldn't cause your intermittent issues, but IMO when you've got it all apart for the 2nd/3rd time i'm one for starting a fresh job to make it feel like i'm getting something new done as well. It'd be like if i had to put my shoes on 3 times, maybe the 3rd time i'd change socks or something just to make it feel worthwhile hehehe Also while you've got the fairings off check the stator connector. Poor charging can cause the weirdest issues. Link to comment Share on other sites More sharing options...
Member Contributer MadFrog Posted May 18, 2017 Author Member Contributer Share Posted May 18, 2017 Thanks for the links guys. The TPO guys are out of stock of the VFR kit so I ordered on ebay. atx: thanks for the tips. I did check the valves (all in speck) while I was in there. Also replaced the plugs, cleaned air filter. I have a voltmeter mounted on the triple tee to monitor charging voltage to the battery - no issues there. Link to comment Share on other sites More sharing options...
Member Contributer MadFrog Posted June 4, 2017 Author Member Contributer Share Posted June 4, 2017 Update: what a pain it was to get to the rear cylinders! But I got it all done and re synced the carbs. It's better but when coming to a stop the idle is still a bit high by 300-500 rooms and very slowly drops down to its setting. It's manageable and I may try another sync once the burns heal on my forearms...Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
squirrelman Posted June 14, 2017 Share Posted June 14, 2017 since you didn't adjust them, it would most likely help your idle by custom-adjusting each idle mixture screw with a proper D tool. OEM setting is EPA lean. Link to comment Share on other sites More sharing options...
slovcan Posted June 14, 2017 Share Posted June 14, 2017 Classic symptom of a way too lean mixture, although it is usually caused by a vacuum leak. If you are sure beyond any doubt that you don't have a vacuum leak (I know you have looked) then turn your pilot screws out a quarter turn and see if that helps. If it does, go ahead and do the idle drop method of setting them properly. Cheers, Glenn Link to comment Share on other sites More sharing options...
BluRoad Posted July 3, 2017 Share Posted July 3, 2017 On June 13, 2017 at 8:44 PM, squirrelman said: since you didn't adjust them, it would most likely help your idle by custom-adjusting each idle mixture screw with a proper D tool. OEM setting is EPA lean. ...and where does one acquire the D tool? I just picked up a '97 but I'm used the the 2d-gen; nice simple straight-blade screwing device is all that's needed. JOE in IL Link to comment Share on other sites More sharing options...
squirrelman Posted July 3, 2017 Share Posted July 3, 2017 4 hours ago, BluRoad said: ...and where does one acquire the D tool? I just picked up a '97 but I'm used the the 2d-gen; nice simple straight-blade screwing device is all that's needed. JOE in IL Motion-Pro sells a tool for that, but it's damn-near impossible to access the screws on the front right and rear cylinders ! Link to comment Share on other sites More sharing options...
Member Contributer Forbes Posted July 4, 2017 Member Contributer Share Posted July 4, 2017 Not sure about your particular model, but the vf750 and I believe the earlier vfr750's ran 38 idle jets. The slow return to idle is a symptom of this, the solution is to change to 40 idle jets. Bear in mind that front carbs are downdraft and rear are normal, some models are jetted differently between front and rear and I've even read where one carb is jetted differently to the other three to compensate for exhaust scavenging.....it's never simple!As slovcan said, make sure no leaks first, but you also mentioned it was always a symptom just more pronounced now.M2C'sSent from my HTC_PN071 using Tapatalk Link to comment Share on other sites More sharing options...
mcrwt644 Posted July 6, 2017 Share Posted July 6, 2017 as far as the d tool is concerned. If you are willing, pull the carbs, scribe a line into the mixture screws. Use a straight sharp flat screw driver and voila, instant tool! I've done this dozens of times. As far as the slow return to idle...I'd chime in and vote vacuum leak and possibly a vacuum slide hanging up. I'd pull the carbs, and verify all the slides are aligned correctly. I'd also utilize some metal polish and polish the slide bores to allow for easier return of the vacuum slides. Those slides need to return in their bores easily. They need to 'clunk' when the top of the carb is off. They need to return quickly to their original position when assembled. Make sure that the throttle cables are also not bound and that the throttle snaps back to it's original starting position and that it's adjusted correctly. Getting back to a possibly vacuum leak, check all the carb sync lines, caps, and also the PAIR system. Manifolds also could be an issue, and verify the manifolds are on the head correctly and the bands are tight on both the head and the carb. Link to comment Share on other sites More sharing options...
Member Contributer MadFrog Posted July 27, 2017 Author Member Contributer Share Posted July 27, 2017 Thanks all for the tips. I've been riding the bike since I don't have time to work on it. :) I have a D tool somewhere but yeah, adjusting and/or syncing the carbs while on the *running* bike is a painful affair. I guess I should take everything off the bike again and go through it one more time. At least I've gotten pretty good and removing and reinstalling the carbs now. Ha! Polishing the carbs can't hurt, and I should re-check all the jets again. I sprayed them with carb cleaner and blew them out last time - I suppose it wouldn't hurt to run some wire through some of the holes to make sure there's no ethanol gunk left. I didn't take apart the slides and tops of the carbs last time, got lazy and they seemed ok but who knows. About vacuum leak: I've removed the PAIR system and replaced all 4 caps on the sync lines with new OEM Honda caps and clips. I should probably recheck the blockoff plates and double check the bands. Link to comment Share on other sites More sharing options...
mcrwt644 Posted July 27, 2017 Share Posted July 27, 2017 as far as the rear block off plates are concerned; simply remove the rear valve cover and you will have more than adequate room to verify they are tight. When you put the plates on, did you verify that the little piece of 'foil' from the pair system went on the block off plates? there would be a big vacuum leak Link to comment Share on other sites More sharing options...
Member Contributer MadFrog Posted July 28, 2017 Author Member Contributer Share Posted July 28, 2017 17 hours ago, mcrwt644 said: as far as the rear block off plates are concerned; simply remove the rear valve cover and you will have more than adequate room to verify they are tight. When you put the plates on, did you verify that the little piece of 'foil' from the pair system went on the block off plates? there would be a big vacuum leak I don't remember if they have a metal gasket, but I did use some hondabond on all of them. Link to comment Share on other sites More sharing options...
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