Dolmar PS510 won’t start

[fordf150]

Speaking from experience... don't bother rebuilding the carbs on the 510/5100/5105/5000 saws if they aren't holding a tune. Just replace them. They are around $40... and use the c1q-dm14 carb no matter which carb your saw has. It's the cheapest and it's from before the carb change that have these saws the flooding issues

 

[Old2stroke]

Start with basics, make sure it isn't flooded, drain tank and pull fuel line off carb, remove plug and muffler and pull over a zillion times (ignition off) until you can see there is no fuel squishing around top of piston viewed through exhaust port or being sprayed out. Stick in a dry good plug and squirt some fuel above the piston through the exhaust port and pull some more, if it doesn't fire, the spark is too weak or occurs at the wrong time or compression is too low. Squirt some oil on top of piston and let it work around piston, then try again, might improve compression enough to fire. You have confirmed that flywheel hasn't slipped on the crank so now the coil is suspect, see if the coil will fire a plug gaped to 0.050" in air, if it does, it should fire a normal gap under compression but try a plug gapped to 0.015" in the engine. Coils are always a problem, if they are suspect, there is no meaningful test that can be done on an electronic module and replacement is all you can do.

 

[Lee192233]

Makes no difference in compression readings.

I stand corrected. Still might cause a no start condition though? I'll step out of this thread and let the experts figure it out. There are others with tons more experience with 2 strokes than I have. Good luck getting it running OP.

 

[fordf150]

I stand corrected. Still might cause a no start condition though? I'll step out of this thread and let the experts figure it out. There are others with tons more experience with 2 strokes than I have. Good luck getting it running OP.

It will most definitely cause a no start but will have zero affect on compression readings.

 

[J D]

You have confirmed that flywheel hasn't slipped on the crank

The flywheel turns so I aSumer the key is intact.

I wouldn't call that definitive at all... Given the saw was running when you last put it away it's unlikely that's the issue anyway.
I'm guessing you've still got a fuel delivery issue & the compression tester is reading low. Still worth confirming the compression too

 

[Old2stroke]

I wouldn't call that definitive at all... Given the saw was running when you last put it away it's unlikely that's the issue anyway.
I'm guessing you've still got a fuel delivery issue & the compression tester is reading low. Still worth confirming the compression too

Yeah, you are right. I wasn't reading carefully enough and thought he had pulled the flywheel to check the key. A good "ballpark" test for a slipped flywheel is to check if the magnets line up with the coil legs just before the piston reaches TDC.

 

[Old2stroke]

You can waste a lot of time chasing down possible air leaks, faulty carb issues and a lot of other things that won't let the engine run right, but if you can't get it to even fire at all, you have to concentrate on which of the basics is the problem. Compression, flooding or spark that is too weak or occurs at the wrong time.

 

[Fatherwheels]

I hadn’t started it for about a year but prior to that had no running problems. The carb has limiter caps so I’m not sure how to answer that question. Also, I didn’t remove those H and L screws while cleaning and rebuilding the carb and I’m not sure if that’s significant. I will take the muffler off and inspect the exhaust port and piston but won’t be able to do this till next week as I’ve gone out of town. Thanks for your help.

The carb could be gummed up if you didn't get the needles out to clean them and their seats.

 

[Ambrosia]

Speaking from experience... don't bother rebuilding the carbs on the 510/5100/5105/5000 saws if they aren't holding a tune. Just replace them. They are around $40... and use the c1q-dm14 carb no matter which carb your saw has. It's the cheapest and it's from before the carb change that have these saws the flooding issues

The carb could be gummed up if you didn't get the needles out to clean them and their seats.

The limiter caps don’t look like they are removable. Can you just break them off? Thanks Whinbush

 

[Ambrosia]

The limiter caps don’t look like they are removable. Can you just break them off?

The limiter caps don’t look like they are removable. Can you just break them off? Thanks Whinbush

Ford-Thanks for the tip on the carburetor. I’ll look for the c1q-dm14 carb.

 

[Fatherwheels]

The limiter caps don’t look like they are removable. Can you just break them off? Thanks Whinbush

@fordf150 , any info on the type of restrictors used in the 510, how to remove them.
EDIT, just seen you answered above.

 

[Ambrosia]

Yeah, you are right. I wasn't reading carefully enough and thought he had pulled the flywheel to check the key. A good "ballpark" test for a slipped flywheel is to check if the magnets line up with the coil legs just before the piston reaches TDC.

If I remove the recoil mechanism, shouldn’t I be able to evaluate if the flywheel key is intact?

 

[user 122190]

If I remove the recoil mechanism, shouldn’t I be able to evaluate if the flywheel key is intact?

You have to pull the flywheel. The chance that that is the problem is remote.

 

[a. palmer jr.]

It was stated earlier but I'll restate it, you don't have enough compression. 110 is too low for a piston ported 2 stroke, 150 or higher would be much better. If your saw has a catylitic converter change it to a regular muffler after you rebuild the top end and it will run cooler. I've tore these down and all they needed was a new set of rings because the originals lost tension, I assume from becoming overheated.

 

[Ambrosia]

It was stated earlier but I'll restate it, you don't have enough compression. 110 is too low for a piston ported 2 stroke, 150 or higher would be much better. If your saw has a catylitic converter change it to a regular muffler after you rebuild the top end and it will run cooler. I've tore these down and all they needed was a new set of rings because the originals lost tension, I assume from becoming overheated.

Thanks, a.palmer. I will recheck the compression with another device. Where would you look for a new set of rings? Any suggestion there?

 

[a. palmer jr.]

Thanks, a.palmer. I will recheck the compression with another device. Where would you look for a new set of rings? Any suggestion there?

If the piston and cylinder are okay you can pick up a set of Caber rings from ebay, they're not too expensive, around $10 or so...

 

[Ambrosia]

If the piston and cylinder are okay you can pick up a set of Caber rings from ebay, they're not too expensive, around $10 or so...

Thanks

 

[a. palmer jr.]

Thanks

If you want the new rings to last awhile don't neglect to change the muffler for the older style. You can tell the difference by looking at the top of the muffler, the new style cat converter has a circle on the top and the old style is flatter with horizontal lines across it. If you want to see what one looks like there is a Dolmar 510 on ebay with one on it, it's the saw that costs $250.

 

[Ambrosia]

If you want the new rings to last awhile don't neglect to change the muffler for the older style. You can tell the difference by looking at the top of the muffler, the new style cat converter has a circle on the top and the old style is flatter with horizontal lines across it. If you want to see what one looks like there is a Dolmar 510 on ebay with one on it, it's the saw that costs $250.

Hey, thanks. I‘ve checked it out and I have the older style with the horizontal lines. I appreciate the heads up. I also see where that saw on eBay has 165psi compression. Mine is so much weaker! I’ll have to bone up on YouTube for the top end rebuild. I assume if the piston looks decent I’d just replace the ring (it looks like there is just one ring), and if the piston is scored, replace it as well. Again, thanks for your time in this.

 

[a. palmer jr.]

Hey, thanks. I‘ve checked it out and I have the older style with the horizontal lines. I appreciate the heads up. I also see where that saw on eBay has 165psi compression. Mine is so much weaker! I’ll have to bone up on YouTube for the top end rebuild. I assume if the piston looks decent I’d just replace the ring (it looks like there is just one ring), and if the piston is scored, replace it as well. Again, thanks for your time in this.

Another thought: Dolmar parts, other than the Caber ring are not cheap like Stihl parts. You can buy pistons and cylinders for Stihl saws for 25 dollars or so but not Dolmars, because there's not much aftermarket for Dolmar parts. New OEM parts for Dolmar are kinda pricy..