Makita 7900 flooding EVERY cold start

[karld]

Afternoon gents

I have a new Makita 7900 that has been an absolute basta to start from the very beginning.

If I use the choke it floods, it has never popped once with the choke. If I also have the decomp button pushed in it will spit fuel out and the wrap handle will be covered with fuel within 2 or 3 pulls.

I did the mm so taking it back to the dealer with the issue will be awkward. It had the same problem before I did the muffler mod.

It will eventually start from cold without choke (up to 20 pulls), but that kinda ruins the saw for me. Once running it is fine and with a 22” bar it keeps me smiling.

Dolmar is my favourite brand but with this issue I hardly pick the saw up anymore, which is not good. I’m thinking it must be a carb issue but that’s just me guessing?

Any ideas guys?

As all posts are better with pics and vids:

 

[Czed]

@huskihl
@Stump Shot
Thoughts ?
I never ran dolmar much

 

[jacob j.]

Sounds like the inlet needle is either being pinned open or not seating correctly. Go through the carburetor and check to see
if the metering diaphragm is installed correctly, and if so, if the inlet needle lever is too high. If both of those look ok, check
the inlet needle seat to see if the opening is even. In the picture below, the inlet needle is #1 and lever is #2.

 

[Stump Shot]

@huskihl
@Stump Shot
Thoughts ?
I never ran dolmar much

Same as any other saw running a diaphragm carburetor.

More likely than not, there is something going on with the inlet needle and seat. A quick pressure test will confirm this, should hold 7 psi( .5 bar ) if not...
It's either sticking or a wood booger keeping it from closing or sometimes(more rare) a tip failure. Disassembly will be required to decipher just what goes on.

 

[SOS Ridgerider]

The flooding issue has been an intermittent problem throughout the 64-73-79 series.
The fix, from the dealer, has often been to replace the oem spring in your carb with the one in the pic below. This usually takes care of it. I keep a few of these on hand for just this purpose. This is advice I’ve gotten from the oldest Dolmar dealer in the country, and they’ve never steered me wrong.

Keep us posted on how things go, so we can all learn from it.

 

[karld]

Thanks guys...that has given me a very clear direction forward. I will check out the carb and update the thread

 

[huskihl]

Common on this whole series. I’ve only experienced it on a used one that I bought so I assumed it needed a carb kit. The new kit with spring fixed the problem

 

[Wilhelm]

Try first cold pull without using the DeCo and without choke, my PS-7900 almost always "pops" when I do this - she just as often floods if I don't do that.
No matter whether she pops or not next 1-3 pulls with choke, mine always sound off.
Utilizing the DeCo on my PS-7300 & PS-7310 makes them harder to start, as such I NEVER use them.

Relieving fuel tank pressure prior to trying to start them also seems to help a little starting this saw family.

I did not know about the carb spring, one always learns something new here on OPE.

 

[mark_kershner]

Following. Looks like it could be an awesome saw.


Sent from my iPhone using Tapatalk

 

[huskyboy]

The popoff has been kinda low on a few of these I tested. Even with a brand new kit and spring. The restrictive tank vent design doesn’t help the problem either (tank builds a lot of pressure). I just stretch the spring out juuust a bit more or lower the lever just a tad. Both achieve the same thing. I clean the needle seat with a q tip with toothpaste and carb clean it after. Usually holds 15-20 psi after that. The walbro spring that Sondre mentioned is stiffer, thats probably the easiest thing for you to try first...

 

[Wilhelm]

Following. Looks like it could be an awesome saw.


Sent from my iPhone using Tapatalk

It's the best saw there is since 2000.

 

[Wilhelm]

Since nobody suggested it, PUSH THE KILL SWITCH TO "ON" POSITION!

 

[David Young]

In addition to what Has been shared already...
Take the fulcrum pin out hold it between your fingertips. Put the lever on the pin and hit the lever it should spin around on the pin freely. Any sticking will show up as a problem.