Dolmar 5100s wont start thread

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atvdave

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OK.. Like it says, my 5100s wont crank over. I've been having some problems with it shutting off when it gets hot, but it will fire back up after several minutes.

Now I cant get it to crank over at all, not even a burp.

Tried different plugs, Comp at 150psi, getting gas, good spark,.... what else should I check.

I know most will say pull the muffler off and look for groves, but with 150psi should it matter?

Thanks
Dave
 
OK.. Like it says, my 5100s wont crank over. I've been having some problems with it shutting off when it gets hot, but it will fire back up after several minutes.

Now I cant get it to crank over at all, not even a burp.

Tried different plugs, Comp at 150psi, getting gas, good spark,.... what else should I check.

I know most will say pull the muffler off and look for groves, but with 150psi should it matter?

Thanks
Dave

If you have a good spark is it happening at the right time? Check the flywheel key.

Is it flooded? Maybe it has gotten too much gas when trying to start it.
 
......
Is it flooded? Maybe it has gotten too much gas when trying to start it.

That is the only thing that has kept mine from starting - make no more than 3 pulls with the choke on!

....but cutting out when warm indicates a coil problem, as an earlier poster said.....
 
Good points... I did tune it with a tach in early spring and set it to 12,500 RPM to it would be a tad rich. I have ran it a few time's but like I said it would die after it got hot.

As to check for bad coil.. I can't start it so I can't check for that yet.. I may play with the carb and see if it will help.

Thanks
Dave
 
OK.. Like it says, my 5100s wont crank over. I've been having some problems with it shutting off when it gets hot, but it will fire back up after several minutes.

Now I cant get it to crank over at all, not even a burp.

Tried different plugs, Comp at 150psi, getting gas, good spark,.... what else should I check.

I know most will say pull the muffler off and look for groves, but with 150psi should it matter?

Thanks
Dave

Check the clutch side crank seal. I've seen a few of these come out/fail and will act like that.
 
That is the only thing that has kept mine from starting - make no more than 3 pulls with the choke on!

....but cutting out when warm indicates a coil problem, as an earlier poster said.....

These saws are easy to flood and hard to hear pop when you should turn the choke off. Trolls three pull rule is good advise but I think there is more to the problem in this case.
 
Thanks for the help..

Here's what the plug looked like the last time I ran it.

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I worked at a Dolmar dealership last summer, I cleared out and started a lot of flooded 5100s, also saw several with bad coils...
 
OK.. Like it says, my 5100s wont crank over. I've been having some problems with it shutting off when it gets hot, but it will fire back up after several minutes.

Now I cant get it to crank over at all, not even a burp.

Tried different plugs, Comp at 150psi, getting gas, good spark,.... what else should I check.

I know most will say pull the muffler off and look for groves, but with 150psi should it matter?

Thanks
Dave

Pull the exhaust off and have a look, it takes nothing to do so, if the P&C look good, it could be a bad coil. Also check for carbon buildup, that can cause overheating.
 
If there are a lot of carbon in the engine, from running way rich, some tanks of alkylate fuel at normal rpm settings will clean it out - but by all means don't do it, as the loosened carbon may score the engine! :potstir:
 
These Dolmar engines are so finely tuned and like any racing engine susceptible to flooding if anythings not set bang on right, go back to basics: make sure you have a good strong spark, set L to 1 turn out set H to 1.5 turns out and set the idle screw in, start with no choke then introduce slowly a bit at a time until she starts to fire
if the carbs primed should fire after three or four pulls
you might have to pull the plug to check for flooding

once running set the L screw turn out till it runs ok then in till it starts to falter then back 1/4 turn. then set H screw so it runs well (as saw trol 14 to 14.4k) now repeat L screw setting lowering the idle screw till the chain stops moving, BTW setting should be done hot.

Tip, you can warm everything up with hair dryer, to get it going so you can set it up. (just don't let the misses see)
 
Thanks for the info guy's. I'll look into all your suggestions. However it will have to wait, I'm going out of town for a few weeks, so when I get back, I'll look into it.

Dont think the hotel maid will like me working on a saw in the room?:blob2:

Anyone in Waterloo, IA good at fixing saw's??

Dave
 
Ok.. got back in town this week and took a look at the saw today. I tried all kinds of settings on the carb. H all the way in, H all the way out, H in the middle, same with the L screw.

I took off the plug to dry out the cylinder in-between changes. I even put in a new plug. I'm pretty much convinced that this thing keeps flooding. I got good spark, 150PSI comp, and took off the muffler to have a look, looks good.

What I did notice is that after a few pulls, and no start, I would remove the plug and turn the saw over and a few drops of fuel would drip out, about 4 o 5... even out of the muffler.
I'm used to working on 2 stroke carbs on dirt bikes and ATV's, but have never taken apart a saw carb. Do they have some kind of float valve in them? or what should I check/do next?

Thanks
Dave
 
These Dolmar engines are so finely tuned ......

As it looks to me, the basic problem was that they were tuned too lean for EPA reasons from the factory for import to the US ( not "finely"), and Dolmar USA failed to tell all the dealers that they had to correct that, before they were handed to the costumer. I don't believe the really good dealers had many complaints, but there were a lot of dealers that wasn't in that category.........:msp_wink:
 
Ok.. got back in town this week and took a look at the saw today. I tried all kinds of settings on the carb. H all the way in, H all the way out, H in the middle, same with the L screw.

I took off the plug to dry out the cylinder in-between changes. I even put in a new plug. I'm pretty much convinced that this thing keeps flooding. I got good spark, 150PSI comp, and took off the muffler to have a look, looks good.

What I did notice is that after a few pulls, and no start, I would remove the plug and turn the saw over and a few drops of fuel would drip out, about 4 o 5... even out of the muffler.
I'm used to working on 2 stroke carbs on dirt bikes and ATV's, but have never taken apart a saw carb. Do they have some kind of float valve in them? or what should I check/do next?

Thanks
Dave
No float valve, they have a metering diaphragm system replaces that
impulse from the engine pushes on the diaphragm and lifts a metering needle, the hight of that setting (metering lever to diaphragm ) governs the amount of fuel, sounds like that might be wrong??? connect the fuel input up to a foot pump (with gauge) give it a pump 10psi it should hold there for a wile (might creep down slowly) then actuate the diaphragm (theres a small hole in the plate) you can blow (or push it with something blunt) and the pressure should drop off, that shows its working, take the pressure up a bit on more 22 psi it should hold pressure then drop off and then re seat at about 6 psi
I think that setting might be causing you problems
get me the carb make and modal might be able tell you more.
 
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