Dolmar 510 not responding

[isaaccarlson]

I am working on a Dolmar 510 that wouldn’t run anymore. It was so packed with crud from 10+ years that the clutch and flywheel were barely able to turn. I stripped it down, cleaned it, ported it a bit, gave it a new bar and chain, did a muffler mod, and it fires right up, idles great, revs up, but doesn’t seem to cut much better than stock. It is running a 3/8 chain, since that is what the owner wanted and he has spares for it.

Compression is almost 200 psi, and it pulls over like a tank. New clutch and rim.
Ignition timing looks to be around 25-30*, but I have to put a light on it tomorrow. Any ideas? I have has excellent results from every saw I have worked on so this is driving me nuts.

 

[Dub11]

Maybe the coil is week from over heating after all them years of being overly insulated.

 

[Fruecrue]

Timing numbers?

 

[isaaccarlson]

74, 105, 127

 

[Fruecrue]

Is that before or after porting?

 

[isaaccarlson]

Both. I didn’t change the timing, just opened up the intake and exhaust.

 

[Redfin]

Tuned well?

 

[Termitebuffet]

They fairly hot anyhow, might not be a huge difference just opening up...

Sawhawgz, ruining the internet since 2012...

 

[isaaccarlson]

Yep, tuned well. It cuts better, but not night and day different like I’m used to. I’ll try running a couple of tanks through it and see what it does. The owner said he couldn’t keep it running before he brought it, so it will be a big improvement for him.

 

[Simondo]

I am working on a Dolmar 510 that wouldn’t run anymore. It was so packed with crud from 10+ years that the clutch and flywheel were barely able to turn. I stripped it down, cleaned it, ported it a bit, gave it a new bar and chain, did a muffler mod, and it fires right up, idles great, revs up, but doesn’t seem to cut much better than stock. It is running a 3/8 chain, since that is what the owner wanted and he has spares for it.

Compression is almost 200 psi, and it pulls over like a tank. New clutch and rim.
Ignition timing looks to be around 25-30*, but I have to put a light on it tomorrow. Any ideas? I have has excellent results from every saw I have worked on so this is driving me nuts.

The ps-5105 saws i have and work on for others dont really feel so good on 3/8 (full size) so I think the 3/8 chain is not helping in the first place.
The ps-510 gives back about 1/2 a hp over the Ps-5105 (is it open or closed port by the way as iv never looked inside a 510 ?) in standard condition by my information ...thats a lot to make up just to get to the performance of a stock Ps-5105 and if the 3/8 already dulls the performance on a stock Ps-5105......well you get the picture im painting .

 

[Ronaldo]

The ps-5105 saws i have and work on for others dont really feel so good on 3/8 (full size) so I think the 3/8 chain is not helping in the first place.
The ps-510 gives back about 1/2 a hp over the Ps-5105 (is it open or closed port by the way as iv never looked inside a 510 ?) in standard condition by my information ...thats a lot to make up just to get to the performance of a stock Ps-5105 and if the 3/8 already dulls the performance on a stock Ps-5105......well you get the picture im painting .

Interesting reading.....Iv'e tested my 5105 with both .325 and 3/8 and found the 3/8 cuts faster and it pulls a 16 inch bar very well on the full size chisel chain. Has to be the smoothest chainsaw that I've ever had hands on and lots of torque for a 50cc. I only wish the air filtration was a better system similar to my Jonsered/Husqvarna saws. The 5105 is my first saw with heated grips and is that ever nice!

Sent from my SM-S320VL using Tapatalk

 

[Simondo]

Interesting reading.....Iv'e tested my 5105 with both .325 and 3/8 and found the 3/8 cuts faster and it pulls a 16 inch bar very well on the full size chisel chain. Has to be the smoothest chainsaw that I've ever had hands on and lots of torque for a 50cc. I only wish the air filtration was a better system similar to my Jonsered/Husqvarna saws. The 5105 is my first saw with heated grips and is that ever nice!

Sent from my SM-S320VL using Tapatalk

The slightly higher gearing of 3/8 I find can pull the rpm down sooner in the average situation /wood sorts unless the operator has a sympathetic hand and keeps a sharp ! chain.
Start dogging the saw through the bigger stuff rather than self feeding and the saw is running lower RPM easier than on .325. Its a compromise thing with lots of variables but .325 1.3mm and a 15" light bar is still the set up I suggest . We do run 15" on saws in UK a lot .

 

[merc_man]

Maybe the coil is week from over heating after all them years of being overly insulated.

I second the coil. First thing that popped into my mind. If its a limited coil going south it.may not let it go past certain rpm.

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[isaaccarlson]

This is an open port cylinder. The thransfers looked like they had plenty of area so I left them alone. I will run the saw again and see how it does. The last piece I was using was super hard and may have pulled the rpm’s down a bit. I will get it on video and see how it looks. I’m used to my ported 350, which turns really really fast. If it’s a bad coil it will get replaced.

 

[Simondo]

This is an open port cylinder. The thransfers looked like they had plenty of area so I left them alone. I will run the saw again and see how it does. The last piece I was using was super hard and may have pulled the rpm’s down a bit. I will get it on video and see how it looks. I’m used to my ported 350, which turns really really fast. If it’s a bad coil it will get replaced.
View attachment 150076

Thanks for the pic of the cylinder .
A family favourite open hex port cylinder design Dolmar/makita use as well with the ps 32, 35, 420 (421 ) . Here is a pic of a ps 420 for comparison.

 

[drf256]

74, 105, 127

May wanna try more intake. Maybe use a piston skirt mod first, so you can go back easily.

I agree on the transfers. They look great, too bad that aren’t closed.

Just opening the intake and exhaust port doesn’t always do much. Making either too big can hurt performance. With the intake, you’ll lose velocity and vac signal. With the ex, you can go too wide and short circuit charge out of the chamber.

If you made the ports really big , you shifted the powerband up and the limited coil may defeat that.

You made no mods, but the saw is “blowing 200 psi”? Are you sure you didn’t have a lot of oil in the cylinder?

Where is your squish?

Personally, I’d take 40 out of the band, drop the jug to a squish of true 15, use 105 EX, 78 IN. Then go 127/128/129 on the 1/2/3 transfers. 1 being the one closest to the ex port.

A popup may be even better here. You’ll gain intake and compression and not have to play with those beautiful hex transfers.

Just my gut feeling. I’m not familiar with the model. Is it the one with the coil bolted to the cylinder?

 

[Dub11]

May wanna try more intake. Maybe use a piston skirt mod first, so you can go back easily.

I agree on the transfers. They look great, too bad that aren’t closed.

Just opening the intake and exhaust port doesn’t always do much. Making either too big can hurt performance. With the intake, you’ll lose velocity and vac signal. With the ex, you can go too wide and short circuit charge out of the chamber.

If you made the ports really big , you shifted the powerband up and the limited coil may defeat that.

You made no mods, but the saw is “blowing 200 psi”? Are you sure you didn’t have a lot of oil in the cylinder?

Where is your squish?

Personally, I’d take 40 out of the band, drop the jug to a squish of true 15, use 105 EX, 78 IN. Then go 127/128/129 on the 1/2/3 transfers. 1 being the one closest to the ex port.

A popup may be even better here. You’ll gain intake and compression and not have to play with those beautiful hex transfers.

Just my gut feeling. I’m not familiar with the model. Is it the one with the coil bolted to the cylinder?

Coil on the case. It's a "detuned" version of a 5105/5100 and will accept their p/c too.

 

[isaaccarlson]

Squish is at .017” with paper gasket. I widened the ports as far as the piston skirt would allow, which was not much.
A muffler mod didn’t seem to do much at all, which seems strange to me.

 

[Dub11]

Squish is at .017” with paper gasket. I widened the ports as far as the piston skirt would allow, which was not much.
A muffler mod didn’t seem to do much at all, which seems strange to me.

The 510 I had it looked like some one took a torch to the baffle going in from the cylinder side blowing a whole though it.

 

[Dub11]

Bump