Out of curiosity, I would re-pressure/vac test while its still "melted" on. Just because the seals were good a year ago don't mean they still are. Lots of stuff that is bad now WAS ok at some point prior. Test things in isolation of other things when diagnosing. Your assumption of the MM causing the meltdown may or may not be related. Just because you find "A" fault doen't mean you found ALL the faults. That's why most shops will replace All the rubbers instead of trying to find the bad one. Not worth the tech time. Once you pay for the vac tester its cheap insurance to use everytime.
seized my 660, What did I do wrong?
- Thread starter tex
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saxman
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Tex, I withdraw my advice as you did everything that can be done to keep debris from entering the cylinder. Well it was a shot anyway. I am glad to see someone else went down the wrong path with me.
Steve
Steve
NORMZILLA44
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Steve, that was good advise dude, because you never know somebody could have done the muffler job on the saw. The only bad advise ever I think, is that not given. I think in the unknown all options should be explored!
tex
ArboristSite Operative
Thanks for all the thoughts guys. I was figuring on starting from scratch as far as re vac testing etc. At this point I'll figure on going through the carb as well. As far as my tuning experience, lesson learned i guess. First engine I've smoked of many I've tuned. Saws must be a little more sensative than motorcycles and snowmobiles?
NORMZILLA44
Addicted to ArboristSite
Tex, sounds like you are off to a good start as where to go. We have all had hard lessons and learned.
Being on the third cylinder now even if the case does check out good it would still be a good idea to tear down the bottom end and throw new seals in the crank bearings should really be rolled to check there status after 2 blow ups anyways. Just my way of doing things though I always tear them all the way down when blown up.
NORMZILLA44
Addicted to ArboristSite
Good advise:msp_thumbsup:
tex
ArboristSite Operative
Update
Just did a vac test. Very slow leak down. About 1 in/hg per minute. I'm pulling vac from impulse line with rubber "plugs" squished between muff/cly and carb/boot to seal it off. This should incorporate everything? When I tear it down further, I'll isolate the components to see where I'm leaking.
Just did a vac test. Very slow leak down. About 1 in/hg per minute. I'm pulling vac from impulse line with rubber "plugs" squished between muff/cly and carb/boot to seal it off. This should incorporate everything? When I tear it down further, I'll isolate the components to see where I'm leaking.
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tex
ArboristSite Operative
silver lining
At least with it sezed up tight I won't have any trouble getting the clutch and flywheel loose.:biggrin:
At least with it sezed up tight I won't have any trouble getting the clutch and flywheel loose.:biggrin:
roostersgt
Addicted to ArboristSite
Before tearing everything down, first pull off fuel filter and insert pressure test line to fuel line. Pressure line to 5lbs and spray soapy water / windex on carb. Check for bubbles and bleed down on your meter. Might just be a simple problem with carb. Your slow leak you described would barely be noticeable, if at all while running saw, and I doubt it wouldn't let you tune it to 4 stroke.
NORMZILLA44
Addicted to ArboristSite
All rela good advise:msp_thumbup: Even though a lot of us have been down this road, some not as far threads like this are good for all of us. It is a great way I think to learn, and or improve what you do or don't know. There are always different angles and approaches.
tex
ArboristSite Operative
The carb was out of the equation on the vac test. I installed a piece of flat rubber between the carb and boot. No vac to the carb itself. Good idea though.
tex
ArboristSite Operative
Dunk it with pressure I'm assuming. How much pressure? I like the idea of greasing the seals better i think. I'm cringing thinking about dunking anything but a tire in water to chase bubbles. :eek2: And no, she won't turn.
Also a good idea though!
roostersgt
Addicted to ArboristSite
Good idea to check everything. Your "leak" may be a combination of small leaks.
ol'homey
ArboristSite Operative
On any saw start at factory settings to get it running then open the low speed mix screw until it loads up and stalls. If opening the low speed screw has no effect or you can't get it to load up and stall stop right there. You've either got an air leak or a blocked low speed circuit. After you confirm enough fuel available to stall it out from the low speed circuit then turn it back in enough so that you have a decent idle with no loading up and no leaner. Then go to the high speed screw and open it up another 1/2 turn or so from factory setting. Go to WOT and it should be 4 stroking, if not open it some more to make it 4 stroke. If you can't make it 4 stroke stop you've got a problem with the high speed circuit, fuel pump, filter etc. not able to deliver enough fuel. Once it's 4 stroking turn it in until you find the point where it no longer 4 strokes and then back it out again 1/8T or more until you've got a nice clear 4 stroke burble going on. When you cut with it lift the saw in the middle of the cut and listen for the burble, if you don't hear it stop and back the high speed screw out a little more. Many times a saw will burble cold but not when it's gets hot during hard use in the middle of a long cut. The extra fuel will keep the saw from melting down. A lot of guys like to tune to hit a high rpm WOT and they may run it like that for years. Then one day they run into a big hard wood trunk where it's fully loaded WOT for a long period of time and then uh oh, another melt down! Too lean. Also note that you get the low speed circuit is set first and then shouldn't have to mess with it. The reason is fuel is delivered from the low speed circuit at ALL speeds idle, low, mid and high and therefore the low speed mix setting affects everything. The high speed setting only affects mid to WOT throttle and shouldn't affect idle as the throttle plate is nearly closed and only pulling fuel from the low speed fuel ports located behind the plate. Hope this helps!
If the saw had a major enough air leak that he couldn't get a properly working carburetor to compensate for it he never would have been able to get it to idle down.
ol'homey
ArboristSite Operative
Exactly Zero! I mess with a lot of older stuff that might have a very slight vacuum leak due to worn seals etc. If the low speed circuit can deliver enough fuel to compensate and load up the saw then no problem. If it can't then I've got work to do. Last one that did that had a bad clutch side crank bearing that allowed the crank to move around radially. Don't know if a bad seal took out the bearing or a bad bearing took out the seal but replaced both and problem solved. The way I make sure that a saw is always able to get enough fuel is make it run rich everywhere. After that I dial in it to where I'm always close to loading up at idle and clearly 4 stroking at WOT. If it starts to lean out and not want to idle down or not burble out of the cut then I know to stop, inspect, adjust etc.
