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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Poor idle/Engine quits when throttle closed /cgi-bin/YaBB.pl?num=1452552140 Message started by delaPlanet on 01/11/16 at 14:42:20 |
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Title: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/11/16 at 14:42:20 Hi everyone - I've been reading everything here on the white spacer mod, carb adjustments, backfiring, afterfiring, etc. I can't figure out my particular issue. This has a lot of elements, so bear with me: I just finished a Ryca build...so I have the shorty pipe with a K&N filter. The bike ran great before I took everything apart. I went up a size to 52.5 and 155 pilot and main jet. I did the white spacer mod with washers...currently I'm running a single, thin washer. 1. The bike won't start without the choke. Once it has started, though, I have to turn off the choke within 10 seconds or it starts a loping, missing, slow idle and dies. So - I pull the choke out, start it, then after 10 seconds, put the choke in and it ALMOST dies, but then it picks up to a nice-sounding idle. 2. When I'm riding it, it has great power and sounds great under acceleration in all gears. The second I let off the throttle, it starts crackling and popping and if I close the throttle and pull-in the clutch (coasting to a stop) the idle rpm drops way down for 2-4 seconds, then comes back up to normal (1200-1300)...sometimes the idle drops down so low after closing the throttle/disengaging the clutch that it dies. It drops, and then it recovers...every time I pull-in the clutch/let off the gas. If I don't pull-in the clutch but rather let it engine brake, the pipe starts making a loud "brrrappping" sound as soon as the throttle is totally closed. 3. I have adjusted the idle mixture screw up/down a bunch until I get the smoothest/highest-speed idle I can when the bike is warmed-up. The idle screw it turned-out 2.5 turns. Here's what I don't get - If the idle mixture is TOO LEAN, I would think that the bike would idle better with the choke pulled-on...or at least for awhile...but if the bike is running and I pull on the choke, it IMMEDIATELY dies (even when it's cold). BUT I need the choke to start it for just a few seconds. If the idle was TOO RICH, I would think that I could close the idle mixture screw all the way down and it would run better...but it doesn't - if I close down the idle mixture screw, it idles rough and then dies. It idles best with the mixture screw turned out 2.5 turns. I have sealed the pipe/header with exhaust sealant. I have also checked for vacuum leaks using carb cleaner all around the carb. Any ideas out there from you carburetor experts? The carb has a new gasket, new main and pilot jets, and a new diaphragm/slide assembly (b/c I couldn't get the little screws out of the old one, no matter how hard I tried :). thanks everyone! delaPlanet :-/ :P |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Serowbot on 01/11/16 at 15:29:17 Try a #50/150 pilot/main combo... |
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Title: Re: Poor idle/Engine quits when throttle closed Post by verslagen1 on 01/11/16 at 15:35:04 Quote:
If you didn't clean the carb before, most likely you have a dirty TEV (the little triangle plate on the side) I wouldn't adjust the spring, but cleaning is good. If you just put a pod filter on if can be difficult to tune because of inherent problems. 1. pod filters sometimes has a tall step on the inside that closes off the eyebrow inlet. 2. this carb likes a lead in duct. brrrappp on max engine brake is normal. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Jer on 01/11/16 at 17:06:35 I had the same problem after I built my RYCA. It acted like a TEV problem, but TEV looked perfect when I checked it. My theory was that the pilot jet was too rich and, in combination with the TEV dumping fuel on deceleration, the bike got way too rich and died, especially with quick RPM drops. I turned the mix screw in and the problem was solved! I still think it is too rich, and I'll change the pilot jet sometime. My bike was way too rich at idle speeds. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/11/16 at 18:54:51 Interesting...OK. If I turn in the idle mixture screw, it idles very badly, though. It lopes and misses and dies. I will turn it into the borderline of running and see if the throttle roll-off drop is any better, though. TEV looks perfect on mine - I cleaned everything in the carb before putting it all back together. I tried running with a 47.5 pilot jet and it ran about the same as it does now...maybe worse. What is a "pod filter"? I'm using a K&N "puck" filter that plugs right onto the carb...it's only like 1" away from the carb. Thanks a bunch for the suggestions, guys - delaPlanet |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Jer on 01/11/16 at 19:05:00 I had to adjust my idle speed when I made any adjustments to the idle mixture screw.... |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Savageman on 01/12/16 at 15:56:52 Check to make sure your float needle is shutting off when the float is raised. Also check your float level. Remove the float bowl and With the gas on (reserve if it still has the vacuum petcock) the fuel should dribble out until you raise the float parallel with the carburetor body (where the float bowl mounts) then shut off. Make sure you put a cup under the carb to catch the fuel in. If it's to low will be lean if it's to high it will be to rich. And be careful gas is explosive! It may need a new float needle and seat assembly. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Dave on 01/12/16 at 16:49:14 Why are you only using a single thin washer on the needle? Most times 3 works best......occasionally if there is a surging just off idle, then 2 washers is the best. A single washer may be letting too much fuel flow at low throttle settings....including idle. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/13/16 at 10:08:45 Good question on the washer - I tried 2 washers and it wasn't idling well, so I went down to 1 washer. Maybe I should go all the way back up to 4 to start with...it's sounding more and more like everyone here suspects the idle mixture is too rich. Still, though, I can't help but counter that opinion by noting that when I turn the idle mixture screw IN, it dies. Question for you guys - Is subtracting washers on the slide the same thing as turning the idle mixture screw out? Don't both of them just enrich the idle mixture? |
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Title: Re: Poor idle/Engine quits when throttle closed Post by justin_o_guy2 on 01/13/16 at 10:13:56 Just remember that the more time spent just barely idling, on the sidestand, the less the cam is happy. If you can't get the idle speed up, at least get the bike standing up as vertical as you can safely. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Dave on 01/13/16 at 13:31:02 The number of washers on the needle should not have any effect on the mixture at idle. The Pilot Jet circuit controls the idle mixture - the needle does not allow any fuel to flow until the slide begins to rise.....and that does not occur at idle speeds. The needle (and number of washers) begins to have an effect at about 1/8th throttle.....the kind of acceleration and speed that would occur when you slowly leave an intersection where a Police car is watching you! The fact that the engine will stop when you turn the Idle Mixture screw in is a very good sign....you know the mixture is not too rich. The ideal Pilot Jet size is indicated by the best idle smoothness occurring between 1.5 - 2.0 turns from lightly seated. If you have to go out more then 2 full turns - it is time to try the next larger pilot jet. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/18/16 at 11:34:10 Right - OK...so I'm learning something here. I went up to 3x washers and there was zero change in the idle performance, which is what should be the case. Now - choke-vs-idle mixture screw: The bike should run better with the choke pulled-on when it's cold. It doesn't. It actually idles MUCH better/higher RPM/smoother with I push the choke in (when cold). It won't start without the choke on, but if I push it in immediately after starting, the idle picks up and smooths out. Sounds like it's too rich...but if I turn that idle screw in, it dies. It's about 2.5 turns out for max idle with a 55 pilot jet. So - too rich or too lean? Is there even a bigger pilot jet than a 55 I can get? RPM still drops off a lot when I let off the throttle to idle...sometimes it dies. I opened up the TEV and it all looks fine in there. The diaphragm is in great shape, good spring, no gunk, etc. This is driving me nuts :-X :-/ |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Dave on 01/18/16 at 11:47:03 I don't know for sure what that RYCA style air clean does to affect the mixture - but I suspect it has almost no effect at idle where the air flow is very low. A #55 pilot jet is way more fuel flow than a carb in good condition requires....it sure sounds like there is a carb issue that is causing this problem. Is the rubber adapter and O-ring between the cylinder and carb in good condition? Those can get old and crack and provide an air leak. The problems you describe sure sound like you have an air leak between the carb and the cylinder. My 2007 ran fine and it never wanted any choke to start and run....and even after I used the O2 sensor and gauge to jet the bike - it still never wanted any choke. The 2002 Rescue bike was jetted nearly the same, and it liked the choke to start and for just a few minutes of warm up. I really don't know why the two bikes were so different. (Both carbs had #150 mains, the 2007 had a #50 Pilot and the 2002 used a #52.5 pilot)...and both bikes idled best with the mixture screw between 1.5 - 2 turns. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Dave on 01/18/16 at 12:05:46 I almost forgot....one method to check for an air leak is to start the engine and get it running. Then you can use a small spray bottle and spray a water mist on the intake manifold area and listen for any changes in the engine sound. You can also use a propane torch (unlit). (Don't be fooled by the propane going through the air filter). https://www.youtube.com/watch?v=HnJFjFbpy-k |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/18/16 at 15:49:19 Thanks! I actually did a vacuum leak test with carb cleaner awhile ago - I couldn't detect any leaks. Interesting - I just went down in size on the pilot jet to a 52.5 after looking at the plug and seeing that it was all sooty. Going down to a 52.5 produced no change whatsoever. I didn't even have to mess with the idle screw. It runs the same as it did with the 55. This doesn't make sense. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Steve H on 01/19/16 at 04:17:02 That probably means it's still too big. Or, there might be some other problem. I'm thinking still too big for the application. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Savageman on 01/19/16 at 10:46:37 How does it run without the air filter on? Are valves adjusted to .004" in and ex? Do you have the stock vacuum gas petcock or the raptor replacement? What does the compression read? Does it have a nice strong spark? Check all that stuff then post your findings. :-? |
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Title: Re: Poor idle/Engine quits when throttle closed Post by justin_o_guy2 on 01/19/16 at 13:23:38 2C3335322F2819291921333F74460 wrote:
I'm also wondering what happens when you adjust the idle speed up. As suggested above I would try it without the air filter, and if it attaches with a rubber boot, you have to be careful that it doesn't cover any of the passages in the carburetor inlet. At idle the vacuum is higher than at higher RPM,, but the petcock can do screwy things. How old is the gas? |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/22/16 at 14:27:59 Thanks, guys - Savageman, that's a lot of stuff to check, but it's all a great idea. I'm new at rebuilding/tuning bikes, so that is probably all going to take me a long time to get through. As far as trying it without the air filter, I will do that - good plan. The Ryca kit is weird b/c the carb only JUST fits in the frame with the air filter on it...maybe it's not sealing that well. Also - I have the Raptor petcock installed. I figured I might as well just get rid of the petcock as a variable a few weeks ago. The gas is new. Idle speed - I keep playing with idle speed: It helps to keep the bike running when I pull in the clutch/coast with it...but the RPM still drops really low when I do that after a hard acceleration. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by justin_o_guy2 on 01/22/16 at 18:05:45 Mine died many times when I was riding hard and shut down quick. The idle was too low. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by KennyG on 01/22/16 at 20:27:27 Dela, I would clean the Transient Enrichment Valve if your engine is shutting down when you twist the throttle shut. Kenny G |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/24/16 at 15:57:36 So - she seems to run better with the air filter off... What is that telling me? There is still an RPM drop after I roll off the throttle/pull the clutch in...it almost dies sometimes - maybe I need a new TEV diaphragm. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by KennyG on 01/24/16 at 17:02:48 Dela, You only have to remove 3 screws to take the diaphragm out for inspection. DO NOT use carburetor cleaner to clean the rubber diaphragm. Use warm soapy water and be careful not to tear the diaphragm. When you remove the screws there is a spring behind the cover, watch that it doesn't get away from you. Before you reassemble the carb, drop by ACE Hardware and get 3 M4 x 10 MM Allen Head Screws. Stainless steel screws are preferable but anything will be better than the Mikuni screws. Kenny G |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Savageman on 01/24/16 at 21:16:54 Take some pictures of the inside of that air filter. I suspect it is blocking some air passage ways. Also I see fine dirt in the air cut off valve. Is there dirt in the opening when you take the diaphragm off? Did you blow out all the passages in the carburetor when you cleaned the inside of it? |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/30/16 at 14:45:55 That pic of the TEV is not a pic of MY TEV - the one on my bike looks new. Also, the air filter is a K&N "pancake" style filter - it's brand new and totally clean inside/outside besides the K&N oil. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by delaPlanet on 01/30/16 at 15:56:57 I'm so close to having this bike running well...but this last issue is a real pain to figure out. The bike idle dips really low and sometimes it dies when I close the throttle. It's worse when it's warmed up. Here is a video: https://vimeo.com/153636240 |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Savageman on 01/30/16 at 19:52:41 All it can be is a plugged idle circuit on the carburetor. Take it off and disassemble it and let it soak in some berryman carburetor cleaner overnight then rinse it off with hot water and blow it out with compressed air. That carburetor cleaner in a can is not to good for cleaning small passages inside the carb. Make sure there is no crap in the pilot jet (small hole). Make sure you blow out all the internal passages with air. Also check the float level when reassembling. There is a small screen filter on the float needle seat. Make sure it isn't clogged. Do all that and it should run fine. |
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Title: Re: Poor idle/Engine quits when throttle closed Post by Dave on 01/31/16 at 09:27:04 It is not a plugged up idle circuit - but the idle fuel/air mixture could be just a little bit on the lean side. Try opening the idle fuel mixture screw a 1/4 turn and see if it improves....try an additional 1/4 if it doesn't. If the smooth idle mixture requires you to have the mixture screw out more than 2.5 turns, it is in need of a larger pilot jet. A 50.0 pilot jet normally works fine with the stock air filter...sometimes a 52.5 if you are at lower elevations. Seldom is a #55 ever needed. |
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