Dolmar 6400 restart problem

[tbrickner]

Hi all,

I am having a problem with my Dolmar 6400.  I was having trouble starting it initially.  It had bad gas changed the gas and tuned the H,L,Idle screws.

Saw seemed to run ok.  About a month later started it up.  It started fine cut for about 5 minutes and it started bogging down.  I turned it off waited 5 minutes and tried to restart it again but couldn't get the saw started up again.

Any help on what may be the cause of this?

Thanks,
Tom

[oldsaw]

If you are cold starting okay but can't warm start, you may either have the mix too rich or coil issues.

[tbrickner]

Oldsaw,

Would this be causing the bogdown I experience in the first 5 minutes?  I have a 50:1 mix on the gas.

I am a little conservative on the carburetor so I don't burn up the saw.  Could this be causing the problem with the bogging down and would it cause a problem with the warm start?

or Would you lean more towards a coil issue even if it is firing up?

Is there also a posibility that the muffler is clogged.  I bought this saw used so I don't know how much use it has had.

Any thoughts of what to check first and in what order would be helpful.

Thanks,
Tom

[oldsaw]

Check the screen on the muffler, it's on the list of things I check on any saw I buy.  However, that usually gets you low power and hard starts all the time.  The best way to set your mix is with a tach.  It doesn't take a lot more "rich" to cause some problems starting.  If you can find someone with a tach, you can take care of that problem, the coil is going to be a "swap and see" sort of thing.  For some reason, nobody wants to quote a price on the internet for that coil.  You will have to do some looking.

[tbrickner]

Thanks Oldsaw,

I'll take a look at all those things and let you know what I find out.  I really appreciate your help.

Tom

[oldsaw]

Was just thinking today too.  May need to rebuild carb.  A bad metering needle or diaphragm could do this.

[tbrickner]

Thanks again Oldsaw,

I took off my muffler and it looked fairly clean.  Also the cylinder looked good so I am ok there.  Old spark plug fired ok but I replaced it with a new one just in case.  I will try to fire it up again tomorrow and see if it cuts.

I do have a tachometer and I had it set last to 11500 RPM on High setting.  I will replace it with fresh gas and mix and try to re-tune it again.

I guess I will have to look at the coil and if that is ok look into the carb.

Thanks again.  I do appreciate your advice,
Tom

[tbrickner]

Hey Oldsaw,

So the muffler was ok,  new spark plug is ok.  I filled her with some fresh mix and reset all the carb adjustment.  Went back and set the low, Idle and high.

Found some odd stuff when adjusting the carburetur.

The L=Low adjustment when high rpm when screwing it in and went low when screwing it out but I could get about 4 full turns out and the speed didn't change much from 3700 rpm screwed in to 3200 rpm screwed out 4 turns.  When I turned the screws further out on the Low setting it didn't really change much from 3200 rpm.

The Idle was adjustable and was able to get the saw to rev up then back it off to about 2700 rpm idle speed.

The high was adjusted to 13000 rpm running full out without a load and the saw in a load of oak ran between 8000 to 9000 rpm seemed to pull strong and didn't bog down like it did before.  I originall was a little conservative and had the high set to no more than 12000 rpm which may have been one of my problems.

Also found that after you pull out the choke to get it to start you have to push the choke back in to get it to fire up.  I thought that the choke had a half way setting which seemed to be part of my problem when starting the saw.  Is this the case where you pull the choke out start the saw.  Stop then push the coke in and start it then tap the throttle to get it started?

Any thoughts would be appreciated.

Thanks,
Tom

[sharkey]

What kind of carb? 

I recently had a problem with my Echo 670.  One time it would run good, then next time it wouldnt want to idle, bog on transition and so on.  It required constant adjustment.  It would run lean and then rich etc.  Found that the Walbro HDA carbs develop air leaks at the main jet nozzle check valve.  The older model HDA carb cannot handle the alcohol fuel apparently and the membrane in the check valve shrinks causing an air leak.  The bad idle is the first sign.  You can check the carb with a vacuum tester to see if its good.  Mine was leaking air and needed to be replaced.  Once the new one was on there its running good again.