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Post by ancorder on Aug 23, 2010 11:36:56 GMT -5
No, it's not a new scooter muffler. It's the lawnmower muffler variant discussed elsewhere on the forums. 5-8 hp briggs & stratton muffler welded onto the end of the stock header pipe. My stock muffler had loose vaffled and the weld holding it onto the header pipe was cracked, so I just decided to ditch the heavy old bastard anyway.
I had thought that a backfire on deceleration from the exhaust would be a result of a lean condition. I feel like I read that somewhere. Oh well. Since the original diagnosis (as close as I could get to one, anyway) was that the scoot was running too rich, I'm assuming that's still the case.
It might be time to ditch the airbox in this piece of crap anyway. Half of the screws/bolts that hold it in place and hold the cover on are stripped or jerry-rigged together. I know it's not smart to try to do any mods while fighting an engine running problem, but if I can't figure out the carb issue in the next few days I'm just going to go ahead and get the uni filter and some new jets.
Sigh. Pouring money and time into the thing, while scooter season is nearing its end...
I've got the carb off right now, so if I get home in time I'll pull the carb off the Schwinn and open them both up and compare the two. If I see a difference in jet size or clip setting I'll make the necessary changes. At least with the Schwinn's carb on it it ran up to full throttle; I think I'd rather deal with the backfiring at this point than the throttling issue.
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Post by sprocket on Aug 23, 2010 14:56:04 GMT -5
I posted that about the lawnmower muffler. But you must understand that is only a temporary fix to prevent engine damage. I recommend you get a properly designed muffler on that before going much further...
You are probably getting backfiring due to no back pressure on the muffler.
Many things cause backfiring, it could be as simple as the air/fuel mixture.
But try different throttle needle settings, you might get one that is just right!!
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Post by ancorder on Aug 23, 2010 16:24:17 GMT -5
Ah. I didn't realize it was only a temporary fix. It seemed like people were using it as an everyday solution.
So now I'm not sure if it's worth doing anything to it in the meantime.
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Post by sprocket on Aug 23, 2010 17:00:29 GMT -5
I don't know perhaps people are using those lawnmower mufflers permanently. I bet they don't last long. I think they are just a small 'glass-pack'.
Not sure what the current cost on a muffler and pipe is, around $65.00??? on ebay...
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Post by ancorder on Aug 23, 2010 18:16:26 GMT -5
Looked like about 90 after shipping. Hrm. I really hate trying to troubleshoot multiple problems at a time, but I also hate spending money. I'm going to go home after work and inspect everything under the hood, so to speak: intake manifold & gasket, airbox, vacuum hoses, PAIR system, etc. I doubt anything'll turn up, but I feel like I need to be trying. Then I'll take a close look at the carbs & throttle needle positions.
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Post by ancorder on Aug 23, 2010 22:56:48 GMT -5
Well, I tried all five needle positions, and the only appreciable difference was that when I moved the clip up (leaner) the flames coming out the muffler were a little more vibrant. I hadn't seen them before, but I was out there until after dark tonight.
When I got home I took a look at all the lines and whatnot. Lines are were good, pliable, correct size (so far as I can tell). They were all replaced last year, so it was expected that they would be good. Intake manifold is in good shape (was also replaced last year), but the o-ring and gasket were not in very good shape. I don't think they were killers, but I am ordering replacements. Airbox, aside from two stipped screw holes, was fine. seals as good or better than my other scoot's.
I am still pretty stumped. I'm debating whether the next step is to start changing jets or buy a new (probably stock) muffler. I'm leaning toward the muffler, because even though I'm not made of money, I suspect that anything else I try to do will just lead me astray down a different path. Probably best to just buy the darn muffler and get it over with.
I had planned to eventually put a pod on this; ought I to go ahead and get a "performance" muffler? Or should I just go stock and pray that it even works?
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Post by sprocket on Aug 24, 2010 10:52:39 GMT -5
I think you need to take care of the muffler problem first. Do a few searches on this forum at the bottom of the page. There have been people that have used standard tractor mufflers etc with some success apparently.
Personally I would get a stainless muffler and pipe or a standard muffler and a stainless pipe. It you change out the pipe now, then you can add a performance muffler later. It would be a 'half-way' measure for now...
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Post by ancorder on Aug 25, 2010 13:30:50 GMT -5
I broke down and spent a bunch of money last night for parts for th eTNG (and also a couple of spare things just to have around).
Ordered:
1x OEM exhaust (all the stainless ones I could find were either "performance" or ludicrously expensive, so I figured I'd just get the stock one for now and worry about upgrading later)
2x high-quality exhaust gaskets
1x intake manifold spacer, o-ring, and gasket
1x EGR blocking plate (because it was cheap and it's something I plan to do later)
1x center stand spring (for the Schwinn; hasn't had one since about a week after I bought it)
1x kickstarter kit (for the TNG, on which the threads had stripped out)
1x ignition coil (for spares; might just put it on the TNG anyway)
1x gas cap (to replace the one my key broke off into last year; tired of sticking the nub of the key into it to open)
1x new air filter for the TNG, because it just didn't look good, and there had been some gas through it on account of not winterizing)
The air filter, exhaust, intake gasket/o-ring, gas cap, ignition coil, and kickstarter will all go on the TNG when they get here, and then I'll start trying to troubleshoot this whole thing again. So this thread won't be updated (probably) for a few days.
Hopefully my next post will be something along the lines of "Oh, hey, I put all those parts on and it runs like a champ!"
Wish me luck.
In the meantime, I've got an inline cutoff valve that I'm going to mount in place of the vacuum fuel valve, assuming I can find a damn adapter with the right threads to thread onto the fuel tank...
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