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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Low cold idle, High hot idle /cgi-bin/YaBB.pl?num=1561671632 Message started by WunGun on 06/27/19 at 14:40:32 |
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Title: Low cold idle, High hot idle Post by WunGun on 06/27/19 at 14:40:32 I can start the bike usually without choke when its warm outside and it will idle pretty good for about 30 seconds then it slows until it stalls. It seems to get enough fuel as I can chop the throttle without any problems but if I let go it stalls. When the bike is hot the idle seems a little high unless I am coming off of a freeway or any mild cruising speeds to a stop then it stalls if I don't hold the throttle until the idle catches up. What could this be? Plug looks fine and riding quality seems fine its just the idle. The idle itself also sounds fine it just stalls. |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 06/27/19 at 14:44:50 On the warm side ounds like a lean pilot circuit. What jet do you have installed in the pilot circuit? Have you tried to adjust mixture screw? What is the condition of the air filter? Do you have an in-line fuel filter? It could also be a vacuum leak. |
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Title: Re: Low cold idle, High hot idle Post by Serowbot on 06/27/19 at 14:52:42 Is your idle too slow?... |
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Title: Re: Low cold idle, High hot idle Post by justin_o_guy2 on 06/27/19 at 18:33:27 I call that normal. I either raise the idle or hold the gas a big when cold, I.E., not warmed up. If I drive away with the, off choke, engine idling at recommended R.P.M.s , I have to dial it back in fifteen minutes, It's just a biggass lawnmower motor, with a carburetor. |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 06/27/19 at 19:36:30 I say not normal. Yes, you adjust idle for warm conditions not cold, but if the OP did that his bike wouldn’t run without throttle jockeying when cold. I always start with my choke which gives me about 1200-1500 rpm. After the bike has run about 15 seconds I remove the choke and begin my ride. By the time I make it to the end of my driveway (1/4 mile) my engine will idle at 1400 rpm. |
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Title: Re: Low cold idle, High hot idle Post by VortecCPI on 06/28/19 at 04:48:37 Typical air-cooled engine issue. As the engine gets hotter and hotter The A/F ratio gets lower and lower (richer) to a point. If the engine gets very hot and/or the ambient air temperature gets very hot it will run rich. When it's colder my idle mixture screws are further out. When it's hotter my idle mixture screws are further in. The rest is compensated by way of idle speed screws. Even if your jetting is spot on one day it can be off another day. It is always a compromise, especially with air-cooled engines... |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 06/28/19 at 08:39:34 Well then I must be a carb set-up genius. All three of my bikes with carbs, and everyone I've owned before (over 25 bikes) all run exactly the same; near normal rpms with the enricher out, lower rpms with the enricher retracted (cold engine) but will still idle, and idle within 50 rpm (all season long) of where they were originally set. WunGun, if the carb is jetted and adjusted properly, you should rarely - if ever - need to adjust the idle from cold to warm engine. |
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Title: Re: Low cold idle, High hot idle Post by stewmills on 06/28/19 at 09:24:51 Maybe not helpful, but I had issues with my bike stalling after I would come down a long straight run to a stop. I ended up realizing that I had shaved the needle washer too much thus raising the needle too far, which caused a slightly rich condition at ~1/4 throttle when transitioning from running speed to idle. The longer downhill with the bike slowly idling to a stop allowed the vacuum to keep the slide slightly open and fuel to build up in the carb to a point it choked (flooded) the engine out. I would have have a hard time restarting it and when it finally did, I would have to get hard on the throttle to blow out all of the excess fuel in a nice little plume of smoke. I dropped the needle back down a bit so the bike is no longer too rich at that ~1/4 throttle position (or thereabout) and it doesn't stall at idle any longer. Your situation may be different, but that's my experience I can share. |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 06/30/19 at 08:00:13 So I just checked my bike to get exact info. Cold start, enricher out, 78 degrees, 1500 rpm 15 seconds later remove enricher, 1200 rpm A mile or so later, stopped at intersection, 1300 rpm After the ride, idling before shut down, 1400 rpm That’s the way a well adjusted carb is supposed to work. |
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Title: Re: Low cold idle, High hot idle Post by WunGun on 07/04/19 at 11:47:08 Thanks for the reply's. I will check my needle jet. I dont notice excess smoke but it does want to stall after releasing throttle from cruising. Stewmills you may be onto something. I used washers in place of shaving my white spacer so Ill remove one to slightly lean it out. Gary I don't have a tach so I ear tach it against youtube videos and my sporty at 1000 rpm's but that can be slightly difficult since they sound different. Maybe I should get one. It would also seem 1000 rpms is too low compared to yours so my high idle may actually be a more correct speed. I appreciate everyone's input, thank you. |
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Title: Re: Low cold idle, High hot idle Post by batman on 07/04/19 at 16:12:18 Warm the motor ,find a level road ,place the bike in 1st gear , throttle closed clutch released, the bike should do 8 mph (13kph) if the idle speed is 1000 rpm. If not adjust the screw under the choke . |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 07/04/19 at 18:03:49 I believe that some on the forums use an app to check rpm. Does anyone have details on that? |
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Title: Re: Low cold idle, High hot idle Post by verslagen1 on 07/04/19 at 21:57:27 http://suzukisavage.com/cgi-bin/YaBB.pl?num=1303712067 |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 07/05/19 at 04:26:29 516473737865627764160 wrote:
Sorry I didn’t pick up on this yesterday. The needle circuit has nothing to do with idling. I would focus on cleaning the carb, especially the enrichment circuit. You never told us, what jet do you have installed in the pilot circuit and how many durns out is your mixture screw? |
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Title: Re: Low cold idle, High hot idle Post by batman on 07/05/19 at 06:25:37 606A6E646F66626B353337070 wrote:
Sorry I didn’t pick up on this yesterday. The needle circuit has nothing to do with idling. I would focus on cleaning the carb, especially the enrichment circuit. You never told us, what jet do you have installed in the pilot circuit and how many durns out is your mixture screw?[/quote] Removing a washer on the spacer mod does not make it leaner, it makes it richer. |
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Title: Re: Low cold idle, High hot idle Post by VortecCPI on 07/08/19 at 15:10:03 I have never owned nor ridden an air-cooled bike with a carb that did NOT require manual changes to idle speed screw between cold start and warmup. As the engine and intake and carb come up to operating temperature A/F ratio decreases (becomes richer). If your A/F ratio was spot on when first off choke it would be rich after warmup. If your A/F ratio was spot on after warmup it would be lean when first off choke. Very generally speaking carbs are lean when first off choke because we set the idle mixture screw AFTER the engine is fully warmed up. As the engine and intake and carb come up to operating temperature A/F ratio decreases (becomes richer) and idle speed increases. Jetting for an air-cooled engine is ALWAYS a compromise as we have no control over ambient air conditions. For every 9 degrees F we need to adjust A/F ratio buy 1% and this is not possible with such an archaic fuel delivery system. Humidity can also play a big part in this equation as high humidity displaces available oxygen and increases A/F ratio. In the Old Days autos with carbs used CCS (Controlled Combustion System) that kept incoming air at a static temperature in an effort to control this issue. When I first start an air-cooled bike with a carb I give the idle speed screw somewhere between one half and one full turn in. As the engine and intake and carb come up to operating temperature I turn the idle speed screw back out to suit target idle speed. Obviously bikes with EFI do not suffer from this issue. Have you adjusted your isle mixture screw for best/fast idle after warmup? |
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Title: Re: Low cold idle, High hot idle Post by Gary_in_NJ on 07/09/19 at 07:16:06 Our carbs don't have a choke, it's an enrichment circuit that flows additional fuel. With a cold engine (or anything less than normal operating temperature) the A:F will be less than optimum, but that doesn't mean that you should have to chase the idle with the adjustment screw, as the OP is describing. It will however mean less than optimum throttle response and some lean surging at part throttle settings. I'm quite surprised how many riders are willing to put-up with a misadjusted carb. |
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Title: Re: Low cold idle, High hot idle Post by ohiomoto on 07/09/19 at 08:19:50 I'm surprised at how many people are willing to misadjust their carbs!!! LOL I'm also surprised how overanalyzed some of this stuff gets on this forum!! Especially for a ~30 hp (claimed) lowish-performance motorcycle. ::) ::) Your idle should be adjusted once the bike is warmed up. I think the factory calls for ~1100 rpm. (It's not supposed to sound like a douchebaged out HD.) The choke, or enrichment circuit, is there to aid the "low cold idle" until the bike warms up. It doesn't mean your bike will idle perfectly while it warms up. It might actually idle a little low even with the choke out. The best way to fix that is to ride it. I suppose you can do whatever the hell you want, but I set mine and leave it alone. It might "high hot idle" slightly on the hottest of hot days. I don't sit in traffic on my way home from work and I shut my bike off if I get stuck at a railroad crossing, so I don't mess with it. I'd argue that most people have no business even attempting to adjust their idle. Suzuki did a fine job of that at the factory. The guy I got my bike from set the idle at ~500 rpm. Probably thought it sounded cool. ::) Idle war!! |
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Title: Re: Low cold idle, High hot idle Post by stewmills on 07/09/19 at 11:50:47 Here is a very good illustration of how our carbs work: https://www.youtube.com/watch?v=wyspAHrMbb8 |
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Title: Re: Low cold idle, High hot idle Post by VortecCPI on 07/10/19 at 05:48:00 7E74707A71787C752B2D29190 wrote:
Semantics my friend. The Owner's Manual calls it a "choke" and any reader knows what we mean when we write "choke" just as any reader knows what we mean when we write "idle mixture screw" as we know it can be an air screw or a fuel screw. I would also like to think any reader knows what we mean when we write TEV, Air-Cut, Coasting Enricher, etc. They all serve the exact same purpose... How about slow jet versus pilot jet? |
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Title: Re: Low cold idle, High hot idle Post by WunGun on 09/17/19 at 22:50:47 Rise! RISE my post and live on the top of the forum once again! So I leaned out my needle jet and and it seems to work a little better but it will still die and at very low rpms it seems rich and it will hesitate and do an airy belch of black smoke when giving it a quick twist from idle. My pilot jet is 55 and when idling it seems ok. It seems that the belch of smoke is worse the more I lean out the needle but that could be just my perception being wrong. It will also idle really slow at a stop and gradually get faster until its at the correct speed, while slow it seems rich and if the idle is slow the hesitation and belch of black smoke is worse. A neighbor said my air filter could be too small causing problems with the vacuum. I have the Ryca pancake filter on it. In the carburetor slide where the needle rests is there are two open holes, those are aligned so that both holes are open and not obstructed if that matters. |
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Title: Re: Low cold idle, High hot idle Post by stewmills on 09/18/19 at 06:45:59 Remember, black smoke is a sign of being rich. If you get that black smoke twisting the throttle from idle, then I would agree that it is rich at idle which is flooding it out. Now when you introduce the non-stock filter situation that adds another variable. If your filter is too small, that limits the oxygen getting into the engine and hence you have an overly rich situation. And it could also limit the vacuum as you stated. Basically, I have no real answer for you other than you seem to be on the right track. Maybe try removing the ryca filter temporarily and seeing if the additional air flow makes it run better. If so, that tells you something. |
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Title: Re: Low cold idle, High hot idle Post by batman on 09/18/19 at 07:09:04 It sounds like your 55 pilot is too large ,I'd try going back to stock 52.5(reset your mix screw) , and using the "choke " on cold starts. On a 75 degree day you may still have to choke the motor when starting , the motor warmed up is at least 270 degrees ,and the oil temp may not reach that until you've rode a mile or two. The main jet (needle) is part of the idle circuit ,the idle speed adjustment screw on the left side of the carb holds the throttle plate slightly open , and the slide slightly up , so some fuel is flowing from the main jet area . the pilot jet doesn't supply all the fuel at idle. your 55 pilot may be to large and when you close the throttle the fuel mix goes rich and could cause the motor to bog and stall , pumpimg out black smoke and soot from the tail pipe ,and backfiring can be caused by the over rich fuel igniting in the hot exhaust header. What size main jet are you running? |
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