Brmorgan
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So, I have this 371XP that I've talked about in a couple other threads before. Got it from a pawnshop last summer for $150. It's an older one ('96 by the serial number) and isn't in perfect shape, but has always run reliably. Back around Christmas I needed to do a good teardown to make sure it would be in good working order to use for a tree-spacing job I started.
Here's what I found during that teardown:
http://www.arboristsite.com/showpost.php?p=1895796&postcount=44
The new ring and getting rid of the base gasket got my compression up to right around 150 PSI after break-in. A good saw got a lot better between that and the bit of port work I did! Tonight, I replaced the gaskets and diaphragms in the carb and cleaned out the filter screen (it had a fair amount of sawdust trapped there). I also fixed the kill wire, which had broken off the coil a couple days ago at work (it had been replaced before and soldered directly to the coil instead of using a spade clip), and re-tapped a couple holes that had stripped out.
My question here is regarding this though: It's always needed to have its carb opened up 1-3/4 to 2 turns on both needles to tune right, even with the muffler mod and being ported out a bit. Otherwise it falls on its face if given throttle and revs out WAY too lean. Does this sound right at all to anyone else? I've had some picky Walbros before but this makes me really leery. Is it possible that it's a smaller carb from a 362 or something that just can't deliver enough fuel at average settings?
I've pretty much ruled out an air leak; the case held pressure OK (no vac test yet) and it's always held a nice smooth idle, and it has near-instant throttle response and runs like an absolute champ when the carb is opened up as described. After seeing the junk built up in the carb screen, I thought that would have fixed the problem since I figured it just wasn't getting enough fuel through the screen at "normal" settings. It did however take care of a warm-start issue - if I shut it off for even 15 seconds, it always took 3 pulls to get going again. Figured the check valve diaphragm wasn't closing but the plugged screen wasn't helping either.
I never rebuilt the metering lever/needle, just the diaphragm, and I didn't pull the welch plugs either since I figured I'd see if the easy stuff worked first. Do you guys think it would be worth the work to do that, or that either of those would have anything do do with it? I do have the remainder of a full rebuild kit left.
Here's how it sounded during break-in right after I did the initial port work and teardown (before the carb rebuild):
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That's with an old skip chain on an 8-pin; I'm now running a full-house on that 24" bar that's been filed with a Carlton FOP; I have to hold that chain back a little bit on the 8-pin rim in the softwood if I dog the spikes in, but man is it a fast firewood and limbing setup! I've had that saw at work with me the last few weeks - my boss and another guy are both using 575s and they both seem to look for an excuse to borrow mine when they can if I'm busy skidding with my ATV at the moment. One guy calls it my "Harley" because of its idle note. I have to say it is the best sounding saw on the jobsite at any rate! I just want to make sure that I'm not going to kill it at work with the suspect carb settings. I'm going to try to make an updated video of it sometime this week for comparison since I'm sure it'll do quite a bit better now.
Here's what I found during that teardown:
http://www.arboristsite.com/showpost.php?p=1895796&postcount=44
The new ring and getting rid of the base gasket got my compression up to right around 150 PSI after break-in. A good saw got a lot better between that and the bit of port work I did! Tonight, I replaced the gaskets and diaphragms in the carb and cleaned out the filter screen (it had a fair amount of sawdust trapped there). I also fixed the kill wire, which had broken off the coil a couple days ago at work (it had been replaced before and soldered directly to the coil instead of using a spade clip), and re-tapped a couple holes that had stripped out.
My question here is regarding this though: It's always needed to have its carb opened up 1-3/4 to 2 turns on both needles to tune right, even with the muffler mod and being ported out a bit. Otherwise it falls on its face if given throttle and revs out WAY too lean. Does this sound right at all to anyone else? I've had some picky Walbros before but this makes me really leery. Is it possible that it's a smaller carb from a 362 or something that just can't deliver enough fuel at average settings?
I've pretty much ruled out an air leak; the case held pressure OK (no vac test yet) and it's always held a nice smooth idle, and it has near-instant throttle response and runs like an absolute champ when the carb is opened up as described. After seeing the junk built up in the carb screen, I thought that would have fixed the problem since I figured it just wasn't getting enough fuel through the screen at "normal" settings. It did however take care of a warm-start issue - if I shut it off for even 15 seconds, it always took 3 pulls to get going again. Figured the check valve diaphragm wasn't closing but the plugged screen wasn't helping either.
I never rebuilt the metering lever/needle, just the diaphragm, and I didn't pull the welch plugs either since I figured I'd see if the easy stuff worked first. Do you guys think it would be worth the work to do that, or that either of those would have anything do do with it? I do have the remainder of a full rebuild kit left.
Here's how it sounded during break-in right after I did the initial port work and teardown (before the carb rebuild):
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/5MEJ98Ajtw0&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/5MEJ98Ajtw0&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
That's with an old skip chain on an 8-pin; I'm now running a full-house on that 24" bar that's been filed with a Carlton FOP; I have to hold that chain back a little bit on the 8-pin rim in the softwood if I dog the spikes in, but man is it a fast firewood and limbing setup! I've had that saw at work with me the last few weeks - my boss and another guy are both using 575s and they both seem to look for an excuse to borrow mine when they can if I'm busy skidding with my ATV at the moment. One guy calls it my "Harley" because of its idle note. I have to say it is the best sounding saw on the jobsite at any rate! I just want to make sure that I'm not going to kill it at work with the suspect carb settings. I'm going to try to make an updated video of it sometime this week for comparison since I'm sure it'll do quite a bit better now.
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