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Husqvarna 450 e series I just cannot figure out whats wrong!!

floatingkiwi

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Hi All

I have my 2012 450 E series (I) here that was new to me originally. It's been a part time saw with not a lot of running each year and kept well tuned and sharp etc by me, an engineer.
The beginning of a long story: Well, about 8 months ago it started doing what I can only describe as weird things in the cut after warming up (like literally 5-10 mins into cutting), which kept getting worse and worse. it would start to falter and stumble in the cut and would slightly idle up when on its side. Tuning wise (with my Tach) you could tune it perfectly really easily. as soon as you start cutting it would do these weird things. This thing has run like a sewing machine since I bought it - until now.
Crankcase leak right? sure, ok lets go down that road...
1) first visit to the doctor - supposedly pressure and vac checked, new fuel hose. Its all good mate!! NO. Brought it home, worse than ever.
2) second visit - carb kit installation. (charged me for a full kit and only installed the seals, but thats another story). Its all good mate!!. NOT EVEN CLOSE. Got it home with a terrible low speed bog - you couldn't touch the trigger for about 5 mins on startup. I pulled the carb to bits to find what he'd done - diaphram was damaged/bent, metering lever hadn't been checked, only seals had been done etc. AND he'd upped the idle to mask the bog.
3) third visit - (insisted on the better technician) Found supposed carb pump side seal leaking. new carb installed for free, full pressure and vac tested, tuned. Its all good mate!! Well, got it home and sure enough, as soon as I get it warm it starts doing the same thing.
4) I borrowed a new coil and installed that. FIXED!! Well, for about a day then starts doing the same thing again.....ARRGGGHHHHH.

So, I've now stripped the thing down fully and pulled the jug off the plug. It looks really good as it should for having done not much work. Crank side seals dont appear to have any issues but I'm throwing a kit at it anyway. the new zama carb has the larger 5mm 20 spline needles/jets which is a pain - no tool for that yet so I've used a bit of plastic tube.
Lots of oil inside the crankcase.
bit of carbony residue on top of piston, looks like it's been very rich.
bore is very good, tiny bit of random scoring but nothing of note.
Bearings are good and haven't spun in the housing.
no housing cracks or any evidence of invasion by oil or air.
Intake boot good, no cracks.
impulse line seems fine, good tight fit.

WHAT AM I MISSING????? The problem is it runs fine during tuning but then goes bad in the cut after a few mins.
 

timg

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Possible poor combustion and running under load due to plug or possible blocked spark arrestor screen on muffler outlet. Is the gasket on the correct side of the diaphram?
 

heimannm

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Based on my most recent experiences I would still be focused on the ignition. I have worked on several of the 4 Series saws and had multiple coil issues. Saws would either run very poorly, or fire but not run at all. Simply testing for spark showed good spark, but in one case it was intermittent and the other the timing was off.

In my limited experience, cheap replacement coils have worked as well as OEM for those saws.

Mark
 

David Young

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a little outside the box.

make sure you have fresh mix.

most saws have a vent to draw warm engine air in for the winter time. make sure it is closed.

I would not have believed this with out seeing it. make sure there is an oem fuel filter!
 

pbillyi69

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im third on air leak because of it changing when turned on its side. does it stumble when you turn it on both sides?
 

lehman live edge slab

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The air leak may not present itself cold that’s why it starts to change after a warm up. I tore a ms 250 down 4 times before I got it fixed. After re sealing the pan and new crank seals ran good so I sent it back. Came back weak later running well cold but started to suck air when hot. Resealed it all again good for couple weeks again same issue. Last time I pulled it apart I checked the pan for flat and wasn’t flat and when it got hot it moved enough to pull air at case seam. Changed pan out an no issues for last year and a half
 

floatingkiwi

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Possible poor combustion and running under load due to plug or possible blocked spark arrestor screen on muffler outlet. Is the gasket on the correct side of the diaphram?
AS above, I've completely stripped the thing and it has a new carb. It started doing randomly a few months ago.
 

floatingkiwi

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Based on my most recent experiences I would still be focused on the ignition. I have worked on several of the 4 Series saws and had multiple coil issues. Saws would either run very poorly, or fire but not run at all. Simply testing for spark showed good spark, but in one case it was intermittent and the other the timing was off.

In my limited experience, cheap replacement coils have worked as well as OEM for those saws.

Mark
yes it now has a new coil (updated part number) but no change
 

floatingkiwi

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The air leak may not present itself cold that’s why it starts to change after a warm up. I tore a ms 250 down 4 times before I got it fixed. After re sealing the pan and new crank seals ran good so I sent it back. Came back weak later running well cold but started to suck air when hot. Resealed it all again good for couple weeks again same issue. Last time I pulled it apart I checked the pan for flat and wasn’t flat and when it got hot it moved enough to pull air at case seam. Changed pan out an no issues for last year and a half
Pan??
 

pbillyi69

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i think the 450s the bottom half is plastic and the bottom of the saw or tank
 

pbillyi69

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i repaired a 455 once and im positive i had more in parts than it would have cost to just buy another one new. at the time they were still on about 350 bucks but i got for free and let someone borrow it who thought it was a good idea to wash it and not dump the water out and run it when he was done. i didnt discover it for about 6 weeks when i was prepairng everything for winter. the bearings were almost rusted in place.
 
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