Help needed.

B

Britmobil

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Hello from Norway. 😊 I have a Dolmar PS5105 chainsaw, a good saw i have had for years. For some time ago it wouldnt start, ended up being the coil since there was no spark. (There was still no spark after i disconnected the wire from the switch) So i bought a new coil off eBay, and now it has spark. But the saw refuses to start, not even near at all. The plug is checked okay, i have tested it in another saw. Any tips? (The new coil is a non OEM chinese-made one)
 
Forgot to say: 185psi compression, spark plug gets wet when trying to start the saw.
 
Not at all familiar with Dolmar/Makita type saws- they were/are not that popular here.
But if we treat it like any 2-stroke and everything else is in order, you need spark, air/fuel mixture and compression for a 2-stroke to run- you claim all 3 are good in this case.
Failing a massive air leak in the system somewhere, IF you trust the Chinese coil- about all that is left is timing of the spark and a possible sheared flywheel key.
If the key has sheared and the flywheel moved in rotation relevant to the crank rotation- spark timing can be far enough out to be sparking at the incorrect position to the piston and the compressed combustible mix, result being- fuel mix getting to chamber, good compression when measured by gauge, good strong spark from plug- but the 3 are not timed to happen in harmony and the saw will not fire.
 
Thank you for your input. I took off the flywheel, and the key and slot is all good. As you mention, it has good compression, it has spark, it gets fuel. The fact it was running very good before it out of nothing wouldnt start, makes me belive the impulse-line is okay too. (I have had air leaks before, then the saw have started, or shown signs of nearly doing it. Now it is completly dead. 🤔 I am starting to regret i bought a non OEM-coil, does not trust it now. Would love to get it running again, i have many Stihls, ranging from 010 to 880, but this Dolmar is the one who has been the most popular saw for me.
 
Honestly, I am not at all familiar with the brand, but would be keeping an eye out for a 5105 or the Makita equivalent parts saw, one with another issue like has had straight fuel run through it.
 
Bob Hedgecutter said:
Not at all familiar with Dolmar/Makita type saws- they were/are not that popular here.
But if we treat it like any 2-stroke and everything else is in order, you need spark, air/fuel mixture and compression for a 2-stroke to run- you claim all 3 are good in this case.
Failing a massive air leak in the system somewhere, IF you trust the Chinese coil- about all that is left is timing of the spark and a possible sheared flywheel key.
If the key has sheared and the flywheel moved in rotation relevant to the crank rotation- spark timing can be far enough out to be sparking at the incorrect position to the piston and the compressed combustible mix, result being- fuel mix getting to chamber, good compression when measured by gauge, good strong spark from plug- but the 3 are not timed to happen in harmony and the saw will not fire.
Click to expand...
Same thoughts.
 
That 50cc frame has a few different coil/flywheel combos that won’t mix. I’m betting you have a mismatch. Check the part numbers for compatibility
 
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