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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Thoughts on pops, backfires during decel /cgi-bin/YaBB.pl?num=1373491541 Message started by apache snow on 07/10/13 at 14:25:41 |
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Title: Thoughts on pops, backfires during decel Post by apache snow on 07/10/13 at 14:25:41 I have a lot of pops, poofs and farts on decell and between gear changes. Nothing real loud but aggravating. I am running a 52.5 pilot, a 150 main and the needle is raised .030. The fuel screw is turned out 2-3/4 turns from closed. I have a Harley dyna muffler and thats when it got bad. There are no leaks. I had none of this with the stock muffler. Well none that I could hear. I can get it to stop by using a 55 pilot with the fuel screw turned out 3 turns. Not good as that makes the idle circuit too rich all the time but the pops are all but gone. It runs good with the 52.5 or the 55. Both have good performance. I had rather stay with the 52.5. I read about cutting the spring on the TEV but don't see this as a solution. There only needs to be extra fuel on decell at high engine vacuum. With a weak spring fuel will come in sooner and be too rich when you don't need it. :-? There needs to be a way to slightly increase the fuel flow through the TEV only during decel at high engine vacuum . Thats when the idle circuit goes really lean and needs a shot of fuel. What say you learned people as well as shade trees. Is there a way to increase the fuel delivered through the TEV and keep the stock spring so you only get it on decell at the highest engine vacuum. 8-) Or do you have other solutions I havn't heard about. :-? |
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Title: Re: Thoughts on pops, backfires during decel Post by WD on 07/10/13 at 15:30:12 I run a basically open exhaust, 155 main, 55 pilot, about 2.5 turns out past factory on the air screw. No decel or shut down noises unless I force the issue. Which I do, kinda like the noise from time to time. Standard running doesn't seem any worse than a stock piped Dyna with the idle speed correctly set. |
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Title: Re: Thoughts on pops, backfires during decel Post by justin_o_guy2 on 07/10/13 at 15:34:14 you can eliminate the shift change noise by throttle & foot control, dont slap it shut & get on with swappin cogs,, piddle fart around & its liable to growl some. on decel, if mine didnt rumble & growl, id rejet till it did..runnin down thru th gears, lissnin to it rumble? dude! |
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Title: Re: Thoughts on pops, backfires during decel Post by oldNslow on 07/10/13 at 17:59:19 Quote:
Quote:
I wear ear plugs most of the time. :) Saves a lot of dickin' around with the carb. |
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Title: Re: Thoughts on pops, backfires during decel Post by justin_o_guy2 on 07/10/13 at 18:42:40 7A4445495B4746280 wrote:
I wear ear plugs most of the time. :) Saves a lot of dickin' around with the carb.[/quote] 7 answering annoying questions |
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Title: Re: Thoughts on pops, backfires during decel Post by Dave on 07/10/13 at 18:44:42 When I had the O2 sensor on my bike.....I learned a lot. Anytime you close the throttle completely while the engine is slowing down, the engine goes lean as the fuel orifices all get closed - except the idle circuit which cannot provide enough fuel. The O2 sensor showed the TEV valve has little effect. Even jetting richer has very little effect as it is still that tiny little idle orifice that is providing fuel when the throttle is closed. You can reduce a lot of the noise by keeping the throttle just slightly open between shifts, and while slowing down. Don't keep the throttle open too far.....just enough to keep things calm. Roll the throttle off slowly while changing gears when accelerating and clutch and shift at a pace that is just a bit quicker and see how that works for you. If you learn to use the throttle in a way that avoids the throttle being completely closed except when idling at a stop.....you can keep the bike from backfiring or popping most of the time. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/10/13 at 18:51:03 I guess what I was looking for was how the TEV works, how it supplies the extra fuel on decel and how to modify it. I know how to ride to keep the pops to a minimum. But even doing that there are still too many. |
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Title: Re: Thoughts on pops, backfires during decel Post by justin_o_guy2 on 07/10/13 at 18:51:49 you are ever so much more diplomatic than i, good sir.. |
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Title: Re: Thoughts on pops, backfires during decel Post by Dave on 07/11/13 at 04:57:41 677667656E6375686971060 wrote:
My experience with the O2 sensor and stock carb shows that the TEV is not effective in reducing the lean condition that results when the throttle is closed while the engine rpm's are above idle.....as occurs when shifting gears or coasting/decelerating. I don't know if the TEV is overly restricted in an effort to reduce emmissions, and if allowing it to work sooner will be beneficial. To date a few have tried modifying the spings......but I am not aware of anyone trying to change the jetting of the TEV to allow more fuel flow. One fellow claimed to have success by using a spring from an automotive carb accelerator pump to replace the stock TEV spring. You might be blazing a new trail if you want to explore fuel flow rather than how soon the TEV kicks in. I don't know if the problem is the TEV not coming on soon enough.....or not providing enough fuel. Here are links to what has been done so far: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1342323516 http://suzukisavage.com/cgi-bin/YaBB.pl?num=1268545171 http://suzukisavage.com/cgi-bin/YaBB.pl?num=1318209614/0#0 |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/11/13 at 05:59:59 Thanks, I've read all of those threads. I could be wrong but I don't believe the TEV coming on sooner is the answer. I do believe it was never set up rich enough to be effective. You only need the extra shot of fuel on decel under high vacuum. There is just not enough fuel supplied to get rid of the very lean condition at that time. I spent a little time last night searching the web on TEV operation. I didn't find anything useful. I did find something on TEV calibration but there were no details listed.It seems no one has persued this avenue. :-? I have not given up. I will keep searching till I find something. :) |
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Title: Re: Thoughts on pops, backfires during decel Post by justin_o_guy2 on 07/11/13 at 06:02:30 What If the Hokey Pokey Really Is What It's All About? ive wondered that very thing for years |
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Title: Re: Thoughts on pops, backfires during decel Post by Pine on 07/11/13 at 06:52:07 Most of this is above my head.. though I do wonder about it. Like others I can certainly see the trends: I know if I run say 50 mph for several minutes then shut off the throttle.. I get a report. ( actually that's not accurate.. I have to "load up the exhaust" that is ride in such a way as to go fast.. go slow.. go fast.. go slow. then heat up the exhaust, then shut down the throttle) But instead of linking the lean fuel at high vacuum... I more look at it as high exhaust temps, with unburnt fuel, do that with a low air volume and presto a report. What does adding fuel do? I can only assume it cools the charge in the exhaust thus preventing the report. Seems like an expensive coolant. I don't think I am smart enough to come up with a solution, but if I did I just don't think it would be to increase fuel charge so it acts as a coolant. Cool the exhaust Cool the exhaust charge burn, dispose, render un burnable... the fuel laden charge that is burning remove "embers" that ignite the charge disallow the low pressure in the exhaust that draws o2 from the exhaust tip and feeds the report anyway my humble and unlearned thoughts... |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/11/13 at 06:59:06 When the bike goes lean you get imcomplete combustion so some of the fuel gets in the exhaust. If the mixture was richer you would get a more complete burn and less fuel in the exhaust. Thats my understanding anyway. :) |
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Title: Re: Thoughts on pops, backfires during decel Post by justin_o_guy2 on 07/11/13 at 07:21:09 idk what youre looking for, really, if its the volume or just the fact that its grumbling,, rumbling & growling,, i know i just love the sound of an engine in decel with the exhaust growling. not a series of 22, 45 & shotgun type reports, but just a rumbling growling sound. |
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Title: Re: Thoughts on pops, backfires during decel Post by Blinky-FSO on 07/11/13 at 07:24:57 I know you said there were no exhaust leaks but have you checked the exhaust header bolts? They have a tendency to loosen over time. Did you loosen or remove them when you installed the Dyna? Replace the header gasket? Just a thought |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/11/13 at 07:28:38 Yes all bolts are tight. A new gasket was installed at the head. There are no carbon tracts at any junction and have checked all junctions with a flame. I can detect no leaks. :) |
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Title: Re: Thoughts on pops, backfires during decel Post by Dave on 07/11/13 at 07:31:51 5849585A515C4A57564E390 wrote:
Apache....I believe you are correct. The O2 I had installed was an eye opener for me. I had always assumed that when you closed the throttle and the slide or butterfly was closed the high vacuum would pull lots of fuel and make the mixture rich - What I failed to understand was that the high vacuum is on the engine side of the slide or butterfly and the high vacuum does not reach the places where fuel flows (except for the idle circuit). What I found with the O2 sensor is that the exhaust shows a lean fuel condition when the throttle is closed. I believe at these lean conditions there is not an adequate amount of fuel or compression to allow the spark plug to ignite the mixture and the lean fuel/air mixture flows unburned out into the header pipe where it can be ignited either by the hot exhaust of by a flame that comes from the cylinder the next time the fuel/air mixture is ignited by the spark plug. For those times where the fuel/air mixture is just on the border of being ignited by the spark plug.....that is when you get the quick burbling type noises that aren't very loud. The big bangs occur when the mixture is not fired in the cylinder and builds up in the exhaust.....and when it does ignite there is a considerable amount of fuel and air that is ignited. The TEV valve is supposed to allow a larger amount of fuel to flow when you shut off the throttle. This may be a long shot....but I wonder if the use of gasoline with no ethanol would make a difference? The jets in the TEV may be set up for gasoline that is not mixed with ethanol (1986 was the first years of the Savage).....and either increasing the TEV fuel jet or running pure gasoline could help? Using the DYNA muffler instead of the stock exhaust combined with the ethanol may have just tipped the balance a little more and made the mixture too lean during deceleration. ADDENDUM: There is a trend on this site to increase the pilot jet size to cut down the backfiring. I believe that this does help as it allows more fuel to flow through the ilde circuit and provide more fuel to flow when the throttle is closed. The probem I have with this is that it makes the engine too rich during normal operation at low throttle settings. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/11/13 at 07:39:15 I don't know if no ethanol fuel would help but you don't know what you look like till you have had your picture taken so I may try a tank full of pure gas next. Can't hurt. 8-) The only thing I have found so far is there is a small vacuum passage that supplies vacuum to the TEV diaphragm. That pulls the diaphragm out uncovering a passage to the pilot circuit that allows more fuel during decel. Not sure it can be modified. :-? |
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Title: Re: Thoughts on pops, backfires during decel Post by mechanikhan on 07/17/13 at 18:23:48 I got rid of 95% of the backfiring by changing the spring in the TEV to a shorter spring. The length of the stock spring has two negative effects on the valve's operation. Having measured the pocket that the spring resides in, I came to the following conclusions: 1. There was not much room for the diaphram to move or open during the high vacuum present at full throttle, thus limiting the enriching effect the valve is supposed to provide. 2. The stock spring was stronger than necessary and was closing the valve too abruptly during the low vacuum present at deceleration, thus the backfire. Instead of cutting the stock spring, I chose to find a shorter one. I'm satisfied with the first spring I chose, a #90 spring I bought at Ace Hardware. Listed below are the dimensions of both springs: Stock #90 Free length 1.400 in. 0.715 in. Wire Diameter 0.032 in. 0.035 in. Outside Diameter 0.483 in. 0.597 in. My bike is a 2002 model with just under 4000 miles. I installed the #90 spring at around 2800 miles. The bike is stock with one exception: a previous owner drilled out the baffle. The bike is much more pleasant to ride, and I would recommend this modification before I changed anything else. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/17/13 at 18:41:25 Thanks for your post. I had thought about the spring being too long as to not allow the valve to open as much as it needs to. I had wrote down the stock springs dimensions and was going to Ace to look for another one. I guess I need to get my butt over there tomorrow and look for one and experiment some more. Now I have the size for the spring to look for. :) I will say the 55 pilot will make the pops go away but the bike runs smoother and better with a 52.5 pilot. |
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Title: Re: Thoughts on pops, backfires during decel Post by verslagen1 on 07/17/13 at 18:55:01 Anyone thinking of this mod should exercise caution. I think you've done it the right way by swapping out the spring. several had tried to mod the spring only to find out it didn't work for them. WE HIGHLY RECOMMEND THAT YOU DON'T MOD THE STOCK SPRING and 1st try to clean the carb and the TEV valve in particular before trying any mod. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/17/13 at 19:11:10 Thanks for the warning, but I wouldn't screw up my stock spring. ;) |
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Title: Re: Thoughts on pops, backfires during decel Post by Borracho on 07/17/13 at 19:35:12 I like the pops. I miss them when I ride other motorcycles. |
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Title: Re: Thoughts on pops, backfires during decel Post by verslagen1 on 07/17/13 at 19:48:05 435243414A47514C4D55220 wrote:
even when it appears someone is listening to your advice, they are not. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/18/13 at 08:08:50 Well I tried the shorter #90 spring from Ace this morning. It does help the pops a little but no more than a 55 pilot and it seems to make the idle a tad rich, just like the 55 pilot. So now I am back to the stock spring. The idle and cruise are the smoothest with a 52.5 pilot and a stock TEV spring but I do get a few pops. This experiment only cost 40 cents to try. Unless I discover some other magical cure I am living with it for now. :) |
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Title: Re: Thoughts on pops, backfires during decel Post by strang on 07/18/13 at 13:08:22 There's also the other TEV mod - something about adding a spacer? |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/18/13 at 13:14:20 Why would I want to make it leaner on decel than it already is. :-? I believe that mod was for bikes that were dying when coming to a stop from a too rich condition. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/18/13 at 13:45:17 I have read that the TEV doesn't technically add fuel, but instead decrease air flow into the pilot circuit to enrichen the mixture. This was on an Intruder forum. I'm not sure if the Savage TEV works this way. Any one have a clue. :-? I did find this. TRANSIENT ENRICHMENT SYSTEM This transient enrichment system is a device which keeps fuel/air mixture ratio constant in order not to generate unstable combustion when the throttle grip is returned suddenly during high speed driving. For normal operation, joining of the air from upper part of carburetor inlet side to pilot air passage obtains proper fuel/air mixture ratio. But if the throttle valve is suddenly closed, a large negative pressure generated on cylinder side is applied to a diaphragm. The valve @ which interlocks with the diaphragm closes an air passage, thus, the pressure flows out to the pilot air passage. This is system to keep the combustion condition constant by varying the fuel/air mixture ratio by controlling air flow in the pilot circuit. I'm trying to find out what part the pilot air jet playes in this. |
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Title: Re: Thoughts on pops, backfires during decel Post by apache snow on 07/18/13 at 16:20:53 found this.. http://www.vx800.net/man_eng/06_Fuel%20and%20lubrication%20system.pdf http://i621.photobucket.com/albums/tt292/dlstewart01/Scan0004_zpsdc3c889e.jpg |
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