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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Bike sputtering on initial throttle /cgi-bin/YaBB.pl?num=1633065423 Message started by BB57y5e on 09/30/21 at 22:17:03 |
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Title: Bike sputtering on initial throttle Post by BB57y5e on 09/30/21 at 22:17:03 alright guys so I just bought my first motorcycle being the s40, and I love it but I am having a hard time getting the bike to run right. I bought the bike with around 25k miles and it runs and starts great except for the initial throttle from idle, the bike starts to sputter and even has died on me one time at a stoplight. The bike has a voodoo aftermarket slip on exhaust and a raptor petcock however is still factory jetted initially the bike was running really rich the spark plug was straight black, which I thought was odd due to the exhaust I would have though it would run lean which makes me think it may be something else... However I got the carb sonic cleaned and messed with the fuel mixture screw and it seems to have leaned out as there is no more black smoke coming from the exhaust however it still sputters at initial then starts to run good. I havnt pulled the sparkplug out again to confirm the rich running to go away however I wanted to know what else I could check to fix the sputtering if my carb seems to be ok I even checked and the spark plug is getting a strong spark, the bike idles good starts right up just decides to sputter at first. I did notice when spraying carb cleaner at the intake where the carb and engine meet if enough carb cleaner is sprayed on the intake the bike will die so maybe a vacuum leak??? I am trying to fix it myself so any advice on what to check would be greatly appreciated lastly I did try to increase my pilot jet (before knowing it was rich) and the sputter went away however there was a terrible rough idle and a hanging idle.... Tomorrow I will remove my air filter to see if that helps, however I am hoping it is not the valve clearences or cam chain however if I need to check those I will again to restate the bike idles and has great midrange and full throttle (may need a bigger main jet as it a\oulls a little harder when i let off the throttle a little) however when idling and then giving it 1/8 to 1/4 throttle it sputters before catching up also when cold there is no sputter only when warmed up!! any advice would be great!!! :) :) :) :) |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/01/21 at 03:57:35 Welcome. An old dirty spark plug won’t tell you much about the pilot jet. What size pilot jet was in there? What size pilot jet did you install and how many turns out on the mixture screw? What rpm is the idle set? You likely miss read the plug, and took a too lean condition and made it leaner. |
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Title: Re: Bike sputtering on initial throttle Post by justin_o_guy2 on 10/01/21 at 06:14:57 Instead of spraying flammable stuff hunting a leak try soapy water. It will change how it runs and you can see Where it's hitting, unlike shooting something that has invisible vapors. Most squirt bottles can be adjusted to work like a squirt gun instead of a shower. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/01/21 at 11:48:53 well I woke up to it pouring outside so I will have to wait for the rain to stop as I dont have a garage, I am currently in college just trying to get the bike to be reliable for transportation. As for the spark plug I did replace it with a new one when I initially got the bike and thats how I discovered it was rich as it sooted out after just running it for like 10 min. also when giviing it throttle it would sputter and spit out a little black smoke and smell like gas. After getting the carb sonic cleaned I believe it isnt running rich anymore however I havnmt been able to pull the plug out to varify I will update yall when I check and I currently have everything stock in the carb the pilot jet is a 52.5 and the main is a 145 I did before cleaning the carb try one up of the pilot and the sputtering went away however the idle was horrible at all rpms the idle would hang when let off the throttle and just seemed to run a lot better as when I put the 52.5 jet back in the idle was good but the sputtering came back also the needle jet is stock also no white spacer mod I will try the soapy water next too the bike bogged down when I sprayed a lot of carb cleaner near the engine intake and I could get the bike to die, not sure if i was just spraying too much and thats why or if it needs the gasket replaced. If a video would help I can take a video of spraying the cleaner or soapy water on the intake and also the sputtering |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/01/21 at 11:55:00 oh also just checked thew fuel mixture screw it is 3 1/2 turns out the way I adjusted that was turned the biked idle really low before it would die then adjusted the mixture screw to where it would idle the highest. It would die or run rough if too far in and then eventually would run rough if too far out so i tried to find the happy medium then increased the idle to where it ran smooth. I dont have any way to exactly check the idle speed just going by ear and where it sounds smooth as I know these bikes are supposed to idle faster for the oil pump or what not !! Again thanks for the fast replies before I joined the forum I had been looking at about nearly every post haha |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/01/21 at 15:08:18 Here's the thing, plug reading is for WOT runs, not idle. Jet the carb for good throttle response....something you don't have. 3-1/2 turn out on the mixture screw is a clear indication that your pilot jet is too lean. I don't care if the spark plug looks like tar or a shiny diamond - your throttle response tells be that you have a lean bog. Regarding the mixture screw - the sweet spot is 1-1/2 turns out. If you can close it (screw it all the way in) it is an indication that the pilot jet is too large. If you can screw it all the way out and the bike continues at the same idle as it did at 2 turns - it's too lean. I'm telling you, go two sizes up from your current jet and you will loose the lean bog and the mixture screw will be at 1-1/2 turns out. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/02/21 at 18:04:27 I tried to switch the pilot jet out to the next size bigger as I didn’t have 2 sizes up and the bike stutters even worse now and just sounds like it has wayyy too much fuel I did get the fuel screw to 2 1/2 turns out but the bike just sounds super choppy and won’t stay running now once you start to ride and let off the gas it just dies so I don’t think it needs a bigger pilot jet(I could be wrong but it’s also shooting out black smoke on the initial throttle more then it did before) I’m thinking replace the intake rubber gasket and o ring since when I spray carb cleaner there the bike does maybe that will clean up the sputter? After these gaskets/ boots are replaced I’m not so sure what to check after that hopefully this helps any ideas would be greatly appreciated :) |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/02/21 at 18:18:55 Usually a bad carb boot results in a run away idle. Did you ever change the air filter? You mentioned that you have a manual petcock, was the vacuum nipple capped? |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/02/21 at 19:07:19 Stock air filter and even with removing the filter it still bogs a little better but doesn’t cure it. Then the vacuum has like a gas line attached to it but isn’t capped looks like the previous owner just out a gas line or vent line on it |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/02/21 at 19:08:02 Maybe the voodoo exhaust is too much for the bike and needs a different slip on muffler? |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/02/21 at 19:31:09 163B2D3036263B373F540 wrote:
Now we’re getting somewhere. That line has to be capped off. For the time being, stick a golf tee in that line and see if that cures the problem. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/04/21 at 10:30:20 Almost there!! I capped the line and it forced me to screw in the air mixture screw all the way in and it is still is sputtering a little but not where I believe the bike is gonna die. It also idles a lot quieter not sure why maybe it was just way out of whack before It is also still running rich as it still spits out black smoke on the initial throttle however everything else is running great! Went up one on the main and man no back firing and it runs really good just need to fix that initial throttle still l >:( Do you think I need to upgrade the air filter? Or maybe the air intake in the engine side maybe I need to replace the gasket maybe air is escaping and making the mixture rich? Thank you for all the help I think I’m getting close! |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/04/21 at 12:03:48 A crack in the carb boot introduces air - not fuel - into the mixture. So it causes the engine to run lean. This is not your problem. Tell me more about the smoke. Perhaps it's oil. Once again, a black spark plug tells you little about the pilot circuit, but it does tell me that you need to clean or replace the plug. What jets are installed and what is your (approximate) altitude? |
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Title: Re: Bike sputtering on initial throttle Post by justin_o_guy2 on 10/04/21 at 12:38:25 forced me to screw in the air mixture screw all the way in I hope you were gentle with that. It's a wimpy ,pointy thing and not gonna handle torque. If it's not happy with that anywhere but closed,, that isn't right. It's supposed to be open a coupla turns IF it's jetted right and everything else is working right. I'm sure a carb guru will chime in and give you actually beneficial information. I would be happy to help, because then I would be a guru.. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/04/21 at 12:40:01 The smoke is black and only on the 1/8 throttle which is why I figured it was fuel cause I thought white was oil, but I am at 338’ according to google and I am ringing the stock pilot jet which is 52.5 and then my main jet is one up from stock so 147.5 maybe I should just go down a pilot size and call it good? |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/04/21 at 12:44:07 And yes I was very gentle with the screw no torque was applied just until it was seated and it will run with more turns out it just keeps getting richer and richer until it wants to die |
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Title: Re: Bike sputtering on initial throttle Post by justin_o_guy2 on 10/04/21 at 12:53:23 That's good news.. I don't want to go back and read it all, it's easier to just say Can't let it idle on the stand. Oil won't get to the high end of the cam. |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/04/21 at 14:17:39 52.5 is large for seal level. Go down one size, but you may go down further. Carb tuning is a iterative process. Big jumps can hide important information. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/04/21 at 14:28:02 Just bought a 50 pilot jet when it comes in I’ll let y’all know how it responds to it! Thanks for all the help in the mean time should I check valves or cam chain? |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/04/21 at 15:49:20 If the bike is new to you, yes that would make sense. |
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Title: Re: Bike sputtering on initial throttle Post by justin_o_guy2 on 10/04/21 at 16:17:12 How many miles on it? |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/04/21 at 16:25:35 28,000 but the previous owner didn’t take too good of care of it I’m starting to figure out… luckily I have this forum ;D |
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Title: Re: Bike sputtering on initial throttle Post by justin_o_guy2 on 10/07/21 at 14:32:48 I wouldn't start it again without putting eyeballs on the cam chain. |
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Title: Re: Bike sputtering on initial throttle Post by Hiko on 10/08/21 at 14:25:55 Could it be getting extra fuel on low throttle from somewhere else ? Choke /enrichment valve ? needle too high? Just saying |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/08/21 at 15:36:24 Possibly I checked the choke and it’s fully closing and the needle is in stock position has the full white spacer and one metal one per the spec sheet. I will check the cam chain and valves this weekend and the new smaller pilot jet comes in Tuesday! |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/12/21 at 15:16:04 I instlled the smaller pilot jet and got the fuel mixture screw at about alittle over 1 turn out it helped the sputtering quite a but but still not completetly gone. I have a feeling the valves need to be adjusted and hopefully that fixes it. That will be what I try next then if that doesnt work check the cam tensioner. The reason I am thinking the valves is cause it runs good until warmed up, am I thinking in the right direction?? right now I am running 1 size down on pilot and 1 size up on main for jetting from factory |
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Title: Re: Bike sputtering on initial throttle Post by Hiko on 10/13/21 at 13:08:47 Runs good until warmed up? Seems like too rich Have you checked the carb float level? Easy to do with a piece of plastic tube on the drain thingy. High float level can do what you are experiencing Checking valve clearances and tensioner would be good to do as the bike is new to you Drain thingy??? I didnt write that ;D ;D ;D ;D |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/13/21 at 14:12:58 No I have not checked float level as I wasn’t sure how to do it. Do I need to buy a caliper tool for measuring or what do you suggest |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/13/21 at 14:13:44 Also what torque wrench do you all suggest to buy before I start digging in to the motor |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/13/21 at 15:14:40 517C6A7771617C7078130 wrote:
A ruler can be used. If you are building a tool kit, I find a digital caliper essential. |
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Title: Re: Bike sputtering on initial throttle Post by Gary_in_NJ on 10/13/21 at 15:19:29 1835233E38283539315A0 wrote:
I have Craftsman torque wrenches in 1/4 (in-lbs) 3/8 and 1/2. They have served me well for decades. When I calibrate them they are never off by more then a few tenths. Most 3/8 drive torque wrenches don’t go below 10 ft-lbs…and they aren’t very accurate at that low value. That’s why a 1/4 drive up to 240 in-lbs is a good tool as well. You can save some money by purchasing them as a kit. |
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Title: Re: Bike sputtering on initial throttle Post by Hiko on 10/13/21 at 16:14:16 On the bottom of the carb bowl is a black plastic tube for draining purposes If you replace that with a clear plastic one about 6 inches long hold it up alongside the bowl and open the drain screw and petcock with the bike held level the fuel will rise up until the float valve shuts it off. the level should be near the bowl gasket level. I just use a cheap spring torque wrench that goes up to 150 foot pounds Covers all that I have come across The torque settings are elsewhere in this forum for the different bolts and screws |
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Title: Re: Bike sputtering on initial throttle Post by ohiomoto on 10/13/21 at 16:29:51 Since no one mentioned it, a sticky slide can cause a bog, but it will be a lean condition, not rich. But it's possible the rich smoke is due to a different issue. The point is that you don't want to accidently overlook something. You can pull the airbox boot and make sure the slide response when cracking the throttle. It's vacuum operated so it might not be instant but it should be opening. |
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Title: Re: Bike sputtering on initial throttle Post by BB57y5e on 10/20/21 at 11:06:07 Finally got around to checking the cam chain tensioner it was out at 18-19mm so I do need to get the verlsagan mod but I don’t think that’s that issue right now also checked the valves it looked like if I did it right 1 exhaust and 1 intake was too tight so I fixed them and the engine seems to run quieter now but I havnt had the chance to take the bike out and actually run it I did however before adjusting the valves drive the bike to class in stop in go traffic and by the time I got to class my spark plug was about to foul out as it was started misfiring .. If when I drive the bike and the engine sounds good but still sputtering is it time to find maybe a new/used carb on eBay or does it sound like engine problems?? I have to be getting close as I have almost torn the complete bike apart by now besides the internal of the motor… |
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