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Makita DCS500 Misfire

Jonno

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Hi and greetings from Oz, I have a Makita DCS500 (same as Dolmar PS510 ?) the saw will idle fine but from about 1/3 throttle upwards it has a high speed miss and loss of power, it won't rev out.
I believe it to be ignition orientated as it is too clipped and precise to be a fuel issue.
I replaced the plug in the vain hope I'd get out of it painlessly but to no avail.
Removed and cleaned carb also, but my gut told me I was dreaming but tried anyway.
I noticed a reply on this forum to a post in Oct '22 that mentioned this issue and replacing the coil, but there isn't a lot on the internet that I could find otherwise.
The OEM coil is $230-$300 in Australia 🤦‍♀️ however I see a few stores (Inc Amazon) carry the Chinesium (Haishine) one for around $40.
I'm not one to fire the parts canon or to buy junk, but I'm looking at replacing the coil.
Any input would be appreciated on this issue.20231107_073922.jpg
 

Wood Doctor

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I just ran into this same misfire issue with a rather new Stihl 194T brought in by a tree service company. Like you, I replaced the spark plug to no avail. It is likely a bad ignition coil (I checked the gap with the flywheel and that's OK), but I am not sure either. It could be a fuel delivery issue (carb problem, etc.) instead. What says the OPE forum?
 

Fun2Cut

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Can you verify with a tachometer that your ‘misfire’ is ignition related? Or do you have an inline spark tester? That would give you a visual on your coil output.

I’d echo check the coil to flywheel gap. Is your flywheel compromised in any way- lost a magnet? shorn key? etc…

I don’t know these saws like some other fellows around here. Nor am I the smartest cookie (or cookie cutter 😀). But a few things I’d check myself I think before I’d throw a new coil at it.
 

Jonno

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Can you verify with a tachometer that your ‘misfire’ is ignition related? Or do you have an inline spark tester? That would give you a visual on your coil output.

I’d echo check the coil to flywheel gap. Is your flywheel compromised in any way- lost a magnet? shorn key? etc…

I don’t know these saws like some other fellows around here. Nor am I the smartest cookie (or cookie cutter 😀). But a few things I’d check myself I think before I’d throw a new coil at it.

Can you verify with a tachometer that your ‘misfire’ is ignition related? Or do you have an inline spark tester? That would give you a visual on your coil output.

I’d echo check the coil to flywheel gap. Is your flywheel compromised in any way- lost a magnet? shorn key? etc…

I don’t know these saws like some other fellows around here. Nor am I the smartest cookie (or cookie cutter 😀). But a few things I’d check myself I think before I’d throw a new coil at it.
Ignition related is my take on it, like I said it's a sharp cutout like a rev limiter at work, no a slow surge like fuel starvation, have even sprayed a little aerosol around and nothing changes.
I have a digital tacho but my ear can provide the feedback needed on rpm.
The inline spark tester is a good idea but I don't possess one of those but imagine I could rig something up to get a visual maybe, I'll check.
Flywheel is fine, cleaned and inspected and gap is ok,
Saw was working one session and started misfiring the next, I'm 99.9% sure I need a coil but was just seeing if anyone has had experience with the issue, if not it will be good when I sort the problem and post the solution as it may help others down the track.
High summer here, so saw not needed much but I will sort it out soon.
Thanks for you input
 

Vintage Engine Repairs

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Can you upload a video? Sounds like you’ve diagnosed it already, but would be keen to hear it out of interest. What state you in in Aus?
 

Wood Doctor

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My Stihl 194T with the same misfire symptoms as Jonno's saw is now running fine with a new coil. The dealer I talked to said these saws have a history of coil failure, so I ordered a new one and installed it. Engine started right up and the misfiring was gone at all speeds. Fixed.
 

qurotro

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Run the saw at really dark place and see if the wire is arcing? I have a husky 372 that did that and found out coil wire is arcing.
 

Jonno

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My Stihl 194T with the same misfire symptoms as Jonno's saw is now running fine with a new coil. The dealer I talked to said these saws have a history of coil failure, so I ordered a new one and installed it. Engine started right up and the misfiring was gone at all speeds. Fixed.
Thanks for the advice
 

Jonno

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Sorry for slow reply I've been away, here is a video of the chainsaw misfire, I am aware that the saw has an electronic rev limiter but this saw is missing in the mid range as well.
Great idea, shall try that
I've been away but got a chance to run the saw last night in the dark, no visible spark leakage so I will order a Chinesium coil!
 
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