MikeZ06Allen Posted June 16, 2011 Share #1 Posted June 16, 2011 Ok a somewhat new development in my saga with the VR. Lately, (yesterday and today) the bike has idled high on initial decel and then slowly drops to around 900 RPM. The choke is off, and the linkage is free, all other throttle linkage is free moving as well. My theory is this could be carb float related as I am having hard start issues when the bike is warmed up and a strong smell of raw gas when the ignition is turned on. Otherwise performance is awesome with very crisp and smooth acceleration, plugs all look good and about 5 oz of Seafoam in every tank of gas. I am puzzled as carbs are not a strong point for me. Give me an ECU, injectors, O2 sensors, a MAF and a laptop and I can get most things purring. So gurus of the carb please enlightened me. I have done a rudimentary float level check, cleaned everything I could with the carbs on the bike and I believe the floats need adjusting but I am curous if this high idle could be related. Thanks Link to comment Share on other sites More sharing options...
GaryZ Posted June 16, 2011 Share #2 Posted June 16, 2011 I am pretty sure that float level would not cause a slow return to idle. I have been told this is an indication of a "lean" condition. You may have a vacuum leak . . . Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #3 Posted June 16, 2011 i have the same problem, checked every possible place you could have a vaccum leak, manifold boots,air box, hoses,diaphrams, checked carb sync. everything was good.mine doesnt do it with the boost sensor unhooked, bought one off ebay last night . hope that fixes it if not i dont know where to look next . good luck Lee Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #4 Posted June 16, 2011 my thought from my car days is, advancing and retarding the timing afects idle,also timing to far advanced make them turn over very hard when hot. mine cranks like a dream when cold ,cranks very slow when hot ,accelrates like a beast , but slow back to idle and i never know where its going to idle 900 to 2500 .this slowly got worse now im just affraid to ride it anywhere. Lee Link to comment Share on other sites More sharing options...
Condor Posted June 16, 2011 Share #5 Posted June 16, 2011 I've had the slow idle return on several bikes. Everytime it was a sync problem in that the idle was being controlled by the right side carbs and not #2. It usually happens when a previous owner adjusts the idle by using the sync screw next to #4. It will actually work... sorta.... but it will screw up the sync. The bikes always responded by backing off the rightside carbs, and the #1 carb and starting from scratch with the #2 carb controlling the idle. Afterwards the throttle is responsive and returns quickly to a smooth idle. Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #6 Posted June 16, 2011 carb sync .hasnt needed adjusted for five years and checked good last week . i dont understand why it slowly got worse .and dosent do it at all with boost sensor unhooked from carb ????. i have rode this bike 45,000 miles withouit adjusting the carbs. i would ride it with the sensor unhooked but afraid it will run to hot. Lee Link to comment Share on other sites More sharing options...
Condor Posted June 16, 2011 Share #7 Posted June 16, 2011 carb sync .hasnt needed adjusted for five years and checked good last week . i dont understand why it slowly got worse .and dosent do it at all with boost sensor unhooked from carb ????. i have rode this bike 45,000 miles withouit adjusting the carbs. i would ride it with the sensor unhooked but afraid it will run to hot. Lee Just relating my experiences, you probably have something going on I'm not familiar with... Link to comment Share on other sites More sharing options...
MiCarl Posted June 16, 2011 Share #8 Posted June 16, 2011 I am pretty sure that float level would not cause a slow return to idle. I have been told this is an indication of a "lean" condition. You may have a vacuum leak . . . Agreed. Usually a vacuum leak. Supposedly can be sync, but I've never seen that personally. i have the same problem, checked every possible place you could have a vaccum leak, manifold boots,air box, hoses,diaphrams, checked carb sync. everything was good.mine doesnt do it with the boost sensor unhooked, bought one off ebay last night . hope that fixes it if not i dont know where to look next . good luck Lee Leaking boost sensor......... Link to comment Share on other sites More sharing options...
MikeZ06Allen Posted June 16, 2011 Author Share #9 Posted June 16, 2011 An air leak sounds about right but I think I can rule out the carb sync as Skydoc_17 just accomplished this with the last round of work we did. Now that I think of it, we removed the charcoal canister from the system too and replaced all of the vacuum port rubber plugs with brand spanking new Yammy parts. Maybe I didn't get one of the plugs on tight enough? Although, an air leak may or may not explain the hard start on warm-up, keep in mind I am saying hard start, not a slow crank. The bike cranks over fine it just doesn't want to fire off for several seconds (I do not crank for more than 10 seconds for fear of burning up the starter). Spark is good and battery has been tested and shows good. All connections have been cleaned and retightened. I wonder if the boost sensor is the culprit? Is this gizmo engaged during cranking or is it only used to adjust timing when the motor is under load....i.e senses a vacuum? Meaning it really isn't a boost sensor per say but rather a rudimentary MAP sensor. Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #10 Posted June 16, 2011 condor, i am glad you are trying to give information i was just trying to let you know where i was at and what i had done. i have a vacuum sensor on the way, i will let you know if that helps. i think mine is sticking on full advance or returning to normal advance really slowly.thanks for your info. Lee Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #11 Posted June 16, 2011 mike , it is just a vacuum sensor i believe it reacts as soon as it senses vacuum. then advaces or retards the timing accordingly. advances timing for higher rpms and retards the timing for slower rpm. so in my opinion if its not working correctly advanced timing at adle will increase idle rpms alot just like twisting the dist. on a car after you set the timing you have to set the idle, on a car that is. i just hope new sensor works i am really tired of this problem.Lee Link to comment Share on other sites More sharing options...
reelay Posted June 16, 2011 Share #12 Posted June 16, 2011 couldnt stand it any longer , cut sensor open there is a white seal that seals vacuum pipe to sensor, mine was broken, diaphram looked good but had a chunk of stuff in it. so in my thoughts i can see the diaphram working then the case pressure changing then the timing changing. once you cut it open prolly un fixable lol . Lee ps. case acting like a vacuum canister maybe causing everything to react slower Link to comment Share on other sites More sharing options...
mbrood Posted June 16, 2011 Share #13 Posted June 16, 2011 (edited) The outside tube on the boost sensor is molded into the case. There originally was a silicone seal on the inside that sealed the actual vacuum sensor to the bottom of the case when it was originally installed... these can degrade over time and destroy the seal and effect the performance. The gummy sealant that they put in above the OPEN circuit board inside also protects microscopic circuits attached to the board and tampering (even carefully) has NEVER been successful by me. I could reseal the sensor itself but then the board refused to respond correctly. Sad, but that's my experience with four of 'em. My rule of thumb for a slow return to idle follows the standard: The mixture is lean if: the bike surges while holding a steady throttle at about 4000 rpm in second gear. there is excessive back-firing on closed-throttle overrun. the throttle is lightly 'blipped' and the idle speed 'hangs up' before dropping to the set idle speed (set the idle to 1000 rpm to start). Correction: turn the pilot screws OUT 1/2 turn or so. If the pilot screws end up turned out very much more than three and one half turns total (stock is about 2 1/2 turns), you should use larger pilot jets. The mixture is rich if: the plugs are excessively soot-ed up or fouled. the throttle is lightly 'blipped' and the idle speed drops below the set idle speed before rising up to the set speed. Correction: turn pilot screws IN 1/2 turn. Please remember, this assumes an "adjustment" is required. If your bike hasn't been worked on and suddenly developes the lean condition, an air leak is the main suspect to be followed down. Have you checked your carb diaphrams for pinholes? Edited June 16, 2011 by mbrood Link to comment Share on other sites More sharing options...
Marcarl Posted June 16, 2011 Share #14 Posted June 16, 2011 I would closely check the vacuum line coming from the left front cylinder. Look for cracks. Link to comment Share on other sites More sharing options...
bkuhr Posted June 16, 2011 Share #15 Posted June 16, 2011 the bike has idled high on initial decel and then slowly drops to around 900 RPM. performance is awesome with very crisp and smooth acceleration, plugs all look good hard start on warm-up, keep in mind I am saying hard start, not a slow crank. . Just thinking out loud-slow return to idle/hard start/smell of gas/good sync sounds like over rich almost flooding to me, need to blow out excess fuel from cylinders before start, too much fuel fed into cylinders during decel. Now what could cause this? Vac leak would cause diaphrams/main jets to open slow-late, wrong problem A plugged vent could cause vacum to be slow to bleed off leaving diaphram and main jet open too much and too long I think I would look at the vent/overflow tubes on the carbs for obstructions such as kinked/pinched hose or bugs in the tubes Along the same idea maybe a piece of debris in the carb under the main needle-might pull the diaphrams/sliders/needles and inspect the needle for wear/scaring from debris, and spray pressurized carb cleaner into needle jet to try to dislodge anything Just my thoughts Link to comment Share on other sites More sharing options...
BradT Posted June 17, 2011 Share #16 Posted June 17, 2011 spray pressurized carb cleaner into needle jet to try to dislodge anything I would go with a dirty carb issue. Pull all the jets and soak them in a cleaner then hit them with air. Brad Link to comment Share on other sites More sharing options...
CaptainJoe Posted June 17, 2011 Share #17 Posted June 17, 2011 Take your tank and upper air box off.... Start and rev your bike while looking at your slides. If one or more is returning slowlY, pull carb diaphrams, inspect and clean. My reves was also hanging. One of my carb slides was hanging up and after cleaning it everything was fine... Link to comment Share on other sites More sharing options...
V7Goose Posted June 17, 2011 Share #18 Posted June 17, 2011 Most probably your pilot jets are gunked up pretty bad, so you are mostly running off your main jets at idle. Also possible you have some partially blocked air passages to the diaphragms - constant velocity carbs work on a pressure differential on both sides of the diaphragm, so if that pressure cannot equalize quickly enough, you will get that symptom. But the bottom line is old bike = dirty carbs. Take them off, take the jets out and soak them, and use spray cleaner with a little straw nozzle to blow cleaner through the passages. But be sure to follow up with compressed air in those passages so you don't leave too much cleaner in there to work on the rubber bits until you get the carbs back on the bike. While you are at it, take the diaphragms out and inspect them closely for pin holes and other damage. Goose Link to comment Share on other sites More sharing options...
MikeZ06Allen Posted June 17, 2011 Author Share #19 Posted June 17, 2011 All great suggestions and I now have my laundry list of things to check this weekend. I am really reluctant to pull the carb rack because...well I know almost nothing about carbs, and, quite simply put, the bike runs great once started and cruising down the road. I use this as my daily commuter and am in a bad mood on days I can't ride. Maybe I need to bribe Skydoc_17 to come back down to VA for a visit. Rocket is patiently waiting with your favorite stick Earl PM me on when you and Jean can visit. I will cover the travel and your time. Link to comment Share on other sites More sharing options...
BradT Posted June 18, 2011 Share #20 Posted June 18, 2011 I am really reluctant to pull the carb rack because...well I know almost nothing about carbs,. Don't really need to know much about them, if you are fairly good with tools. Take it apart just enough to get to the jets and other ports, then put it back the same way it came apart (after cleaning). Just do not touch air mixture screws and you should be okay. Good time to check you floats. Brad Link to comment Share on other sites More sharing options...
reelay Posted June 22, 2011 Share #21 Posted June 22, 2011 freebird, you win the prize, you hit the nail right on the head. put new boost sensor on and it was somewhat better but still returning to idle slowly and popping when cold. looked for vacuum leaks again none. started backing out sync. screws then returning them till it made a difference. i dont know what the carb order or number is but as soon as i backed out the sync. screw on the rear carb on left side problem almost imediatly dissapered. i guess my sync. gauge and system stinks. thank you very much , thanks everyone. i used to be a member here but got away from it and motorcycling for awhile thinking about rejoining was reelay before. just trying to decide whether to keep the old venture. shes still one of the prettiest bike you can get . Lee Link to comment Share on other sites More sharing options...
reelay Posted June 22, 2011 Share #22 Posted June 22, 2011 by the way where is the best place to get a sync. tool (gauge). Lee anyone near heath ohio want to make a few bucks for a quick loan. Lee Link to comment Share on other sites More sharing options...
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