Dolmar 5100S "To rebuild, or not to rebuild"

[smokediver351]

I have a Dolmar 5100S with a scored cylinder. While the saw was cutting, it was cutting great. I got about 4 hours out of it. Next time I pulled it out, it wouldn't crank. I have since learned about the probles that are associated with this particular saw. I'm trying to make up my mind on whether to rebuild the saw, or not. The cylinder kit looks to be about $175 at the cheapest I can find, and I feel pretty sure it will need some carb work- it's been sitting for a while. This is my first Dolmar. I heard great things, but my experience hasn't matched the hype. Any feedback?

 

[a. palmer jr.]

I've always had good luck with them. Make sure the saw actually needs a p/c before ordering one. Sometimes you can get by with just a piston or a set of rings. I haven't seen any aftermarket kits for them but I'm sure there will be before long. If you decide to rebuild it you should check everything in the intake system and probably run the carb a bit on the rich side.

 

[JustinM]

I vote rebuild without a doubt.

I have at least 5 saws in the 50cc class and my 5100 is definitely one of the first 2 I grab on a regular basis (my 346 probably beats it out just slightly). To me i like it more than any stihl in that class i have (or have used) - although really ALL of them are great saws. I have had my 5100 for 5 - 6 years and I dont know how many hours - never a problem. The issue with this model has more to do with then coming lean from the dealer than anything else I believe. Rebuild and just make sure you richen it out a little & I think you'll be happy.

Is the cylinder actually scored or does it just have transfer from the piston? More often than not if the saw has died from leaning out the softer piston material ends up transferring to the cylinder. I dont think there's aftermarket pistons for this model but I see on ebay you can get an OEM Mahle for under $100usd. Worth trying to clean the cylinder with some muriatic acid & at least see.

Good luck.

 

[Poleman]

Rebuild...nice little saw.

Like stated earlier check the P/C...I bet you will only need a piston. I've done four that sound like your...one even ran although poorly. Seems those cylinders a tough....at least in my case. I just removede the transfer ansd installed new piston and made sure there were no air leaks etc. or any issues.

Good Luck

 

[a. palmer jr.]

I've done two this year and neither needed anything but rings. I had assumed that maybe Dolmar made a run of soft rings or something.

 

[nstueve]

If you have visible scoring you'll need to do one of the following.

Option 1: I would contact your regional Dolmar rep or local dealer and ask just for the P&C to be covered under warranty (if it's still under warranty). I have had 70% success with this request however they will void the warranty after the P&C crosses the counter since you aren't a Dolmar certified mech to replace the parts.

Option 2 - if your not under warrenty:
Here is what I have done for others if you are not covered under warranty.
You pull the top end and send it to me. I will try to clean the cylinder for you with a Fordom and Mandrel set up (not acid- don't do it!). If the cylinder cleans up without being through the chrome I charge $40 for the clean and hone job. New OEM piston kits are $70. You can usually get them shipped for $5 each way. So you would be into the cleaned cylinder and new OEM piston for $120 instead of $175 ($197 is my dealers price for new P&C).

That being said, It's a gamble... I can usually tell before final finish and hone if it will be usable or not. So if it's bad I charge $20 for the time. So worst case this way is you're out $25 for my time and shipping.

Option 3: Find Mastermind's thread on how to clean cylinders with the a mandrel and emory cloth and do it yourself. I have heard of guys doing it with a variable speed drill, split mandrel and emery cloth. Keep in mind you need several different grit emery cloth's and I use a red scotch brite with WD40 for final clean and hone. This way you have nothing invested but time and parts (which could be $10-$30 in parts). If you have 1/4" steel rod (for mandrel), emery cloth and red scotch brites laying around already it cost you very little.

If you want more info. PM me and I'll send you my cell # so I can walk you through any questions.

 

[blsnelling]

Tear it down before you order parts. Make sure the PTO side crank bearing isn't spun in the case.

 

[SawTroll]

As with other saws, you need to find the reason it failed, and fix if needed, before replacing/fixing the top end.

However, based on the fact that it is a 5100S, chances are that the reason is somewhere in the area of running hot (marginal engine cooling) and/or a lean factory carb setting - so you may not be able to pinpoint the reason. I would start with removing any limiters on the carb adjustment screws, and check how far from lightly seated (all the way in) they were when the saw failed.

 

[shorthunter]

Just send the saw to me and I will fix it. Then you can put the money toward another saw

 

[fordf150]

As with other saws, you need to find the reason it failed, and fix if needed, before replacing/fixing the top end.

However, based on the fact that it is a 5100S, chanses are that the reason is somewhere in the area of running hot (marginal engine cooling) and or a lean factory carb setting - so you may not be able to pinpoint the reason. I would start with removing any limiters on the carb adjustment screws, and check how far from lightly seated (all the way in) they were when the saw failed.

first step....figure out why it failed. Yes with it being a 5100 the most likely cause is lean carb settings but that isnt set in stone. preferably pressure and vac test before tear down. If you determine that it was just lean settings try cleaning your cylinder up and replace just the piston. Others have had good luck doing this but i have only had about a 25% success on 5100/5105 cylinders cleaning up. If it doesnt clean up you are at the point of how much money do you want to invest in it. OEM piston kit is $70. OEM 5105 cylinder kit is around the $185 mark. Option #3. 510 cylinder kit for $125. 510 cylinder kit is a direct bolt on but does sacrifice some power. http://performanceoutdoorequipment.com/collections/piston-and-cylinder If it also needs a carb you will be into it for another $10 for a kit or $45 for a complete new carb.

 

[dugide]

fordf150--is that carb after market?

 

[fordf150]

fordf150--is that carb after market?

Nope http://performanceoutdoorequipment....r-and-fuel/products/zama-c1q-dm13b-zmc1q-dm13

 

[dugide]

$45 is a cheap price, i'll have to get carbs from you, my cost is much higher, not far from double.

 

[fordf150]

$106 is list price on the carb from Dolmar IIRC

 

[dugide]

my list price here is the same.

 

[SawTroll]

$106 is list price on the carb from Dolmar IIRC

What venturi size are the 5100 carbs?

 

[fordf150]

What venturi size are the 5100 carbs?

13.5mm

 

[SawTroll]

13.5mm

Thanks, what I suspected - sounds like they need a larger one!

 

[fordf150]

we got into that discussion a few months back. Can't remember what thread it was in though and tried searching but nothing is coming up

 

[nstueve]

I have a Dolmar 5100S with a scored cylinder. While the saw was cutting, it was cutting great. I got about 4 hours out of it. Next time I pulled it out, it wouldn't crank. I have since learned about the probles that are associated with this particular saw. I'm trying to make up my mind on whether to rebuild the saw, or not. The cylinder kit looks to be about $175 at the cheapest I can find, and I feel pretty sure it will need some carb work- it's been sitting for a while. This is my first Dolmar. I heard great things, but my experience hasn't matched the hype. Any feedback?

To OP,
pull the muffler and look at the piston through the exhaust port. if the piston looks like below pic it's lean seized.

If piston doesn't look like above you'll have more poking around to do. 90% of these saws torch themselves on a lean condition. You don't need a bigger venturi carb so don't let Troll scare you off the saw. They just need carb adjusted properly to get more fuel through to help keep the saw cool. Most good Dolmar shops (like Ford150) know to make this adjustment right out of the box. Some don't and you end up with a torched saw. I know tree services running 5100/5105's with richened up carb settings for several years and they beat the snot out of their saws.

Pull the muffler off... it will take you 5mins to check for lean seize. If you look good there come back and will work you forward from there.