Dolmar ps510 won’t rev intermittently

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Guest

• Jan 19, 2020

• #1

new to Dolmar saws. Picked up a cheap ps510 from pawn shop that ran great. Ported the cylinder and cut the base down. Running 210psi cold .017 squish. Saw runs like an animal until it doesn’t then it hits rev limiter as soon as you pull the trigger. Kill it starts right up no problems. Pull the trigger and rev limiter???? Wtf???!! it has the black ignition coil. I tried retarding the static timing 4 degrees thinking it didn’t like that much compression. Same thing. Any help would be appreciated! Thanks in advance!

 

cuinrearview

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• Jan 19, 2020

• #2

I've heard of a few tank vent issues with these. Guys pull the duck bill and trim the corner a little.

 

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• Jan 19, 2020

• #3

Man that’s a good suggestion and I will try it. However it’s not bogging like starving for fuel, it’s literally bouncing repeatedly at an exact rpm like the coil is limiting it somehow. I have removed the ground to the killswitch at the coil Incase it was arching. I have also tried the plug from my stihl 260 with the same results. I’ve read there are coil issues with these but have not found anything saying which is the fix. Red coil green coil black? Gold jacket green jacket who gives sh*t ‍‍

 

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• Jan 19, 2020

• #4

Ok so I’ve got some new information. It’s arcing from the plug boot to the metal on the plug thus bypassing the electrodes, And it’s no matter what plug I put in it. I am using the plug recommendations from the manual. Is there a higher resistance plug needed. Gap opened that I’m not aware of? I do not see anything abnormal on the plug boot. Or is the coil just shot? This is one finicky bastard!

 

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Terry Syd

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• Jan 20, 2020

• #5

It appears the plug boot is faulty, it's conducting electricity. You could put another boot on it, or perhaps trim the boot back away from the metal on the plug.

 

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• Jan 20, 2020

• #6

Good idea. When I get a chance to d$&k with it today I will pull a plug boot from a junk saw and see what happens! I’m really liking this forum. There are a lot of great minds on here!

 

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• Jan 20, 2020

• #7

Welp....no go on the plug boot being the problems. I guess I imagined it arching to the grounded metal on the plug. I’ve tried trimming the boot, no boot, new boot. Still same thing. Thing runs like an animal then 2 seconds later won’t rev at all and bouncing at the same low rpm. Gotta be the coil. Anybody know what coil is the correct replacement for these that is an updated coil. Red, green, black? Surely it’s nothing to do with the higher compression and tighter squish??! It would not run at all if that were the case.

 

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• Jan 20, 2020

• #8

I did put the timing back to stock since I ruled that out and it made no difference

 

cuinrearview

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• Jan 20, 2020

• #9

It may well be the coil, but I still wouldn't rule out fuel starvation. See if it still does it on it's side with the fuel cap off.

 

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• Jan 20, 2020

• #10

I actually tried that and yes it does

 

M2theB

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• Jan 20, 2020

• #11

Have you pressure/vac checked it?
Could be lean

 

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• Jan 20, 2020

• #12

Yes holding both

 

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• Jan 20, 2020

• #13

It’s also spitting out fuel from the exhaust when this happens so it’s definitely not lean

 

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• Jan 20, 2020

• #14

2 seconds later runs great and might run fine for a few hours

 

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• Jan 20, 2020

• #15

It’s not acting like a fuel problem it’s bouncing at a specific rpm every time just like the rev limiter does. I tried to upload a video but my internet is bad here in the woods

 

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• Jan 20, 2020

• #16

Idk if it’s coincidence or not but it only has done this when it’s cold outside. Squish too tight? .017 should be fine but maybe the timing curve doesn’t like it. Wish I had a coil to try on it before buying one.

 

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• Jan 20, 2020

• #17

I would think if the squish were too tight it would run bad all the time

 

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• Jan 20, 2020

• #18

Oh and I’m about 15’ above sea level if that could effect the squish/timing curve when cold I doubt it but not going to say impossible

 

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• Jan 21, 2020

• #19

C’mon where’s my Dolmar experts here!!! lol

 

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• Jan 21, 2020

• #20

So just got off the phone with makita and they said to correct the problem I have to change the flywheel and crankshaft? Umm no I’ll throw it in the trash. Anyone need a 510 for parts for free!