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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Re: Backfires & Afterfire gone completely!!! /cgi-bin/YaBB.pl?num=1335447146 Message started by Cookie1247 on 04/26/12 at 06:32:25 |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Cookie1247 on 04/26/12 at 06:32:25 This mod has never worked out as intended and has been replaced by a TEV-2 thread in the Tech Section which has never worked correctly either. The original thread is locked and referenced to the second, but the second is still open for comment. Neither thread meets the "tested & proven to work" TECH SECTION requirements, so both threads may eventually be moved out of Tech and back to RSD until someone figures out the whichness of the why and the things get fully developed. I am also interested in this mod. The S40 I have was "ported" by the previous owner and runs very well except for occasional backfiring. I imagine the jets were modified but I have no idea nor record of what is in there now. The parts breakdown I am using (http://www.suzukisavage.lt/upl/file/manual/PDF07-ls650-parts-list.pdf) shows spring #31 inside the diaphragm cover. Spring #35 is on the choke side of the carb. Since several discussion threads talk about the difficulty in removing the three Phillips screw on the diaphragm cover, can I assume we are talking about screw #31? |
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Title: Re: Backfires & Afterfire reduced somewhat Post by RanDaMan on 07/12/12 at 12:22:39 Cookie, On the first page of this thread it says spring #35 not #31. :) edit . . .but i dont know if theyre using the same schematic or not. :-X going by your break down image i assumed it would be spring #31, BUT. the link that was posted for ordering the new part shows a soring length of only 1.58" leading me to believe its spring #35 ?? :-? I plan on doing this mod as well so hopefully it will get cleared up as to which spring should be trimmed. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by renegade1 on 07/12/12 at 14:55:02 spring 31 the TEV is the spring you cut 10mm |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/02/13 at 12:59:51 Tried replacing the stock spring with a somewhat weaker spring I found on eBay. (1.85" long, but thinner wire than the original spring.) Once the bike is warmed up, it now has no backfires or shutdown afterfires. The idle is slightly uneven. However, when I first started it, the idle was too low, and the bike would almost stall at stop signs. I'm going to try riding it again, cold, with the idle speed turned up a bit and the idle mix screw turned in one turn, from 3 to 2 turns out. I think this method will eventually work on my bike, which is completely stock and running at sea level. If I can't get a decent cold idle with the idle mix screw, I will try a spring somewhere between the stock spring and the one in there now. The backfiring was getting to be too much in group rides, where people kept saying they thought someone was shooting at them until they realized the sound was coming from my bike. (And I wasn't shooting at them.) |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Gyrobob on 11/03/13 at 11:15:36 4A4C4141454C47404A4B5C2E0 wrote:
A low idle will damage the motor. Not enough oil gets up to the cam. I have my idle set per the many old flatii recommendations here. On the RYCA tach it is set at about 900 rpm. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Dave on 11/03/13 at 15:53:17 Well if the bike idles differently.....You have put a weak enough spring in so that the TEV is operating all the time.....not just during high vacuum. This will probably make the bike run too rich.....as the TEV is supposed to only work when the throttle is closed abrubtly and the vacuum is really high and the mixture really lean. I am expecting that your fuel mileage is going to be much worse. The good news is....if this doesn't work out you know how to put it back where it was......or you can try and find a spring with tension somewhere between the two. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/03/13 at 20:14:18 The helpful thing I've learned is that if I can get a spring that's just strong enough to keep the TEV closed at idle, but that allows the mix to be richer on decel and shutoff, I should be able to eliminate most of the backfiring. I'll ride it as is for a couple of days this week to verify the idle issue. I have a spare stock spring I can trim down a little at a time to see if I can close in on the right length. |
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Title: TEV and overall "richness"? Post by DavidOfMA on 11/04/13 at 04:33:33 One question: If the best backfiring setting does result in the TEV being somewhat open at all throttle settings, is it likely to have a major impact when the throttle is fairly open? Or will it function somewhat like a too-large pilot jet and affect mainly idle and low speed? Thanks! David |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Dave on 11/04/13 at 04:59:09 I don't have a stock carb here anymore to look at....but my guess is that the TEV circuitry works only when the throttle butterfly is nearly closed. When the butterfly is open the vacuum is stabilized by the CV slide and a really high vacuum condition will not exist....however if you have a very weak TEV spring there may be enough vacuum in normal operaton that the TEV is operating whenever the engine is running.. I don't know how much extra fuel the TEV suppilies...and how much that might affect the mixture at throttle settings other than idle. You are exploring new ground and only time will tell. For some reason your bike backfires more than normal.....so you might be trying to compensate for some other condition that causes your bike to backfire. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/04/13 at 06:27:32 Maybe so, but I have wracked my brains trying to find a cause for the backfiring. According to my brother, who bought the bike new, it backfired more when he got it than it does now, so it's possible there's a manufacturing tolerance (though it's not in the pilot jet, as I replaced that). The carb is clean, TEV is clean, no air leaks, stock everything except for Raptor petcock. All I have left to play with, I think, is the TEV. I'll run it a couple days as is, if it's running boggy or gas mileage is awful, I'll try a slightly cut down stock spring, and if that fails, I guess I'll live with the backfiring. It's not bad if I'm riding solo, but when I ride with a group I'm frequently hitting the brakes and quickly backing off the throttle, as these guys ride a lot harder than I usually do! Thanks for your advice and insights, David |
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Title: Re: Backfires & Afterfire gone completely!!! Post by latony007 on 11/04/13 at 10:37:48 I wouldn't buy another one of these bikes for no other reason than the backfiring, its annoying and embarrassing and should not be "norm" for any bike. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/04/13 at 17:08:53 1970s technology, mostly, that has to meet 2000's EPA requirements. It's amazing they haven't updated the design to conform more to current conditions. I can see how a 1986 Savage would have problems, but mine is a 2007. Hopefully, though, I'll finally get it fixed. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/05/13 at 08:59:03 Did another test run with the new spring and bike behavior is not optimal. No backfiring, but it's a little boggy from idle to 30mph, idle drops briefly when I blip the throttle, and idle is a little uneven when bike is warmed up. Clipped half a round from the stock spring and will try that tomorrow. Hopefully there's a spring strength that will eliminate backfires without the undesired side effects. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Serowbot on 11/05/13 at 09:37:21 If the TEV is affecting anything other than full throttle chop, decel... it's purpose is essentially defeated... I'd be adjusting the slide,... which is also controlled by engine vacuum... As it is,.. the two are interfering with each other... JMHO... |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/05/13 at 09:59:07 How do I adjust the slide? I did reposition the needle, with the white spacer mod, and that cleaned up the midrange, but I wasn't aware you could adjust the slide itself. What kind of slide adjustment would richen the mix on rapid decel or shutoff? |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Serowbot on 11/05/13 at 10:34:46 That's what we do... needle spacer... ... but,.. if you're into experimenting,... (which it appears you are) ;)... there is an airjet above the rubber diaphragm accessed from the top... (making it larger or smaller will change the amount of vacuum pulling at the slide)...(not sure which way does which)... Adjustment of enrichment at full vacuum decel,.. is the TEV's job... but by playing with the spring, you are only adjusting when it activates, which will make it activate when it shouldn't... Not sure how,.. but you need to adjust how much fuel it adds, rather than when... I believe the TEV is not really doing much incremental fuel control... more like the vac-pet,.. it's open or closed... ...(a tapered needle, is incremental... a flat stopper, is on/off)... |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/05/13 at 11:06:47 My hope is that by getting it to activate a bit earlier, I'll get more fuel during decel. What I'd really like to do is slightly enlarge whatever the TEV squirts fuel through, but looking it over I couldn't figure it out. I'll look into your suggestion if I can't get the TEV mod to work. I'm not into experimenting, but I would like to eliminate the backfiring and the air screw adjustment doesn't do it. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Bubba on 11/05/13 at 11:14:55 What I find that eliminates backfire is throttle. I've gotten pretty good at controlling the backfire while riding by smoothing out the way I get on the throttle. As a matter of fact, I can decide pretty much decide when I want it to backfire...cuz sometimes it's just a matter of letting people know where you are... ;) Awhile back I messed with the TEV and it made my bike run horrible, smoke like a diesel and it did actually get rid of the backfire...i put it back to the stock spring... |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Dave on 11/05/13 at 11:34:40 Yep......throttle application (or de-application) can make a big difference. When you close the throttle all the way....it will backfire. If you can keep it just slightly open (fast idle), it makes alot less noise. If you chop the throttle while shifting gears.....your gonna make some noise. The TEV does operate through some brass jets.....we just need to figure out which one you want to be richer. The key is not in making it run sooner.....it needs to be a bit richer. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/05/13 at 11:36:50 I can mostly control backfire when I'm riding alone, but when I'm in a tight pack of 20 bikes hurtling through the twisties, I have to open up or jam shut the throttle frequently and often abruptly. And that's when I get a lot of backfires and some annoyed or startled fellow riders. |
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Title: Update Post by DavidOfMA on 11/07/13 at 05:15:17 I think I'm closing in on "no backfires." I trimmed about 1/8" off the length of the stock spring (half a full round) and took the bike on a couple of short rides. This small reduction in spring tension had no apparent effect on idle, but I had only one backfire and shutoff afterfire between the two rides. I went out of my way to rev and chop the throttle when I could. I need to take it out on the highway and then aggressively ride some twisties to be sure, but it does seem like I'm heading in the right direction, and that a little less spring tension, which holds the TEV open just a little longer, should finally fix this problem on my particular bike, a stock 2007 at sea level. YMMV but I think this technique is worth another look by anybody with a similar problem who has already tweaked the idle mix and idle speed and cleaned the carb, including the TEV. |
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Title: I think I've got it working -- no backfires Post by DavidOfMA on 11/09/13 at 10:47:55 Quote:
:D I think the yellow warning at the head of this thread needs to be revised. I took the bike out on an hour-long ride that combined highway, back roads, and town driving and tried to simulate the kind of ride that would make it backfire, gunshot style. I got a couple of little pops from time to time, but no gunshots at all while riding. I still get a gunshot crack on shutdown at least half the time, but I think that's a different issue. I believe this is a good technique to try if simply turning out the idle mix screw doesn't get rid of backfires. Reading over the earlier, locked thread, I think the problem most people had was using too weak a spring or taking too much off the stock spring, so the TEV was engaged all the time. The 1/8" I took off the length only slightly weakens it, but it seems to allow just enough additional fuel to flow on high-vacuum decels to prevent backfiring. At some point I may trim another 1/16 or so off the spring to see if it helps with after fire, or if the backfires come back on an actual group ride, but for now I'm happy. The bike is much more fun to ride without having to monitor my throttle use to keep from backfiring. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/10/13 at 15:11:59 003B3621303C27213A323F20530 wrote:
Just took a quick look at the TEV again. I assume by "operates through some brass jets," I gather there are jets that are underneath the TEV plunger that aren't called out in the exploded diagram of the carb on sites like this one? http://www.suzukipartshouse.com/oemparts/a/suz/506b36c3f870022ba8af9e73/carburetor It would be nice to do it "right" by installing a slightly larger jet, if that's so, rather than nibbling away at the spring. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Dave on 11/10/13 at 17:08:42 The parts list doesn't help much - somebody with a carb in their hands needs to look closely at the TEV circuit....and see where it pulls the fuel and air from. It may be that it uses the Enrichment lever circuit. The parts list shows part 40.....No. 2 air pilot jet????? What does that one serve...the enrichment circuit? |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/11/13 at 06:27:19 09323F2839352E28333B36295A0 wrote:
Hmmm... that would make sense, that it uses the enrichment circuit. I do have a partial spare carb but I'm not sure what to disassemble in order to see where the fuel and air for the TEV come from. Also, if that's the case, then changing a jet to enrich the TEV could make the enrichener too rich to properly run the bike cold, couldn't it? |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/13/13 at 09:53:46 Been riding for a while now with the slightly-clipped TEV spring and I think this is a pretty good workaround for an S40 that backfires a lot at sea level, for which turning out the idle mix screw is not sufficient and that has no air leaks. It's gotten cold here, but the backfires are still gone and otherwise the bike runs the same. I'd like to see it back in the tech section. The trick is to remove only a little of the spring at a time until the backfires stop. It might be a different amount for different years or altitudes, but it probably won't be more than I had to clip, since I'm literally at sea level, where it's running leaner than it is for folks in the hills and mountains. My two cents, anyway. Made the difference between I bike I decided to trade toward something else and one I'll hold onto a while longer. |
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Title: Re: Backfires & Afterfire gone completely!!! Post by Bubba on 11/14/13 at 09:32:37 If it works for you then that's great... For me I don't think it would ever work...it's not uncommon for me to change elevation by 4-7,000 feet in the span of 30 minutes... My bike can run perfectly fine with no pops, cracks or booms and then I ride over a pass and it all goes out the window... BUT, I wouldn't trade my rides through the mountains for anything... |
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Title: Re: Backfires & Afterfire gone completely!!! Post by DavidOfMA on 11/14/13 at 09:46:17 I bet it would work for you, too. It just makes the decel a little richer. Too rich at 4000,' probably, but only briefly, and only a little longer than the TEV richens the mix anyway. If I ever get up to 4000' I'll let you know if there's a down side to the fix, such as idle dropping too low on decel. Still too early to see the effect on gas mileage, but I'm fine with trading a few mpg for a quieter ride. |
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