makita woes... another 6401 issue.

[jerseyjeff]

I put this in the wrong place, and need to delete the post in the manual thread.


After Sandy I realized that I needed a bigger saw to go with my little redmax 4500, and I stumbled on a dolmar/makita 6400 at Home Depot for 100, and picked it up. I discovered the piston was installed backwards, and the off switch was more of a suggestion, but, in general it has turned out to be a nice saw, and it is very light, and will run a 20-24 inch bar all day. My buddy had an NWP piston kit and I could not resist turning it into an 84 cc saw. After putting in the kit, checking compression (127 psi) I fired it up without a bar, and then discovered the e-clip was missing when the drum fell off, and the clutch went into low orbit. Oops.
I replaced the the clutch, drum, sprocket and needle bearings, and a brandy new e-clip too. The saw ran great, and pulled like mad. I did a few test cuts in some 6 inch oak (all I had) and was happy.
I read about the HD filter kit and liked the idea of additional filtration, and ordered one up, put the black humpback on the saw, a new bar and chain, and headed up to my in laws to drop a bunch of ash (yeah ash borer). The saw started on 1/4 choke, went straight to WOT, and revved a little and then stalled. I could not get the saw to run on or start on anything less than 1/2 to 1/4 choke, and it went from full speed to off. I ended up running 8 tanks of gas through the redmax this weekend, and it handled everything like a champ, but the teal paper weight is making me a bit grumpy.
I am thinking I may have a carb issue based issue based on reading the old threads, and my plan is to start messing with the L screw, but, because I only know enough to be dangerous, I wanted to ask before I make it worse.

 

[dsell]

127 psi is low, especially new. There are so many things that could be wrong that you have to go back to the basics. Plugged impulse port, losing spark, pinched fuel line, plugged tank vent, plugged fuel filter, air leak which could be seals, intake, gaskets, carb, and fuel lines. Plugged Spark arrester, bad ignition switch, water in fuel, bad decompression valve, sheared flywheel key, internal carb screen plugged needs a bubble bath and kit. New parts can be bad too.

 

[huskihl]

What is 1/8, 1/4, and 1/2 choke?

 

[jerseyjeff]

127 psi is low, especially new. There are so many things that could be wrong that you have to go back to the basics. Plugged impulse port, losing spark, pinched fuel line, plugged tank vent, plugged fuel filter, air leak which could be seals, intake, gaskets, carb, and fuel lines. Plugged Spark arrester, bad ignition switch, water in fuel, bad decompression valve, sheared flywheel key, internal carb screen plugged needs a bubble bath and kit. New parts can be bad too.

Whoa boy... I think the decomp valve is good, and i have a new, clean, and appears good fuel filter I can put on. The flywheel key is still good (well there and intact) I will check the spark arrester this afternoon, I am OCD about fuel and it has only ever had ethanol free premium, with the husky premium 2-stroke mix. I would be shocked if there was water in the fuel.

 

[jerseyjeff]

What is 1/8, 1/4, and 1/2 choke?

There is a choke lever on right of the handle, and fully out is fully choked, and I found I could start the saw with it 3/4 by travel in, but not fully in. That still might be clear as mud.

 

[dsell]

Reading through again, how much have you cut with the new cylinder? I would pull the muffler off and check for scoring on the piston and cylinder. 2nd use a mity vac brake bleeder or syringe, remove the fuel line from the carb and connect there to see if you can draw fuel easily. If fuel hits the syringe rubber, it will be the last time it works. If you use the mity vac, use the bleed container to catch the gas.

 

[wanab]

The way I start my 6400/7900 is full choke until it pops. Then open the choke by pushing the lever all the way in. Pull until it starts on high idle. Once it's running blip the throttle to release the high idle. First time I even heard anybody call a 14 1/2# saw light.

 

[Wood Doctor]

With a big bore kit on board, this saw truly amazes me. I have had no trouble with it except for a slight bar oil leak when shut off. So, I drain the oil out for extended storage. Regardless, at a GTG one year it outcut every Stihl 460 it ran against with a 25" bar on board. I've used it in big red elm with a 32" bar:

 

[jerseyjeff]

Reading through again, how much have you cut with the new cylinder? I would pull the muffler off and check for scoring on the piston and cylinder. 2nd use a mity vac brake bleeder or syringe, remove the fuel line from the carb and connect there to see if you can draw fuel easily. If fuel hits the syringe rubber, it will be the last time it works. If you use the mity vac, use the bleed container to catch the gas.

Ok, I have more data

1) Daylight savings time blows. I had 30 minutes between getting home and lights out to work on the saw.
2) The syringe/vac test is a bit terrifying, either you pull fuel and are SOL or it is ok. (lucky for me, I am ok, I hooked a 40 ml irrigation syringe to the fuel line, and did not pull anything)
3) I looked down into the exhaust port sans muffler, and did not see any scoring.
4) I made about 4-5 cuts with the new piston and cylinder, made zero cuts with new p+c and the HD air filter kit.
5) After looking at everything, I put it back together, turned the L screw till it bottomed, and then backed it out 1.5 turns. The saw started, and was idling high enough to spin the chain, I then turned the L screw in till the chain stopped. When I gave it the beans, it bogged and stalled. It also still started better with the choke pulled out a little.

 

[jerseyjeff]

With a big bore kit on board, this saw truly amazes me. I have had no trouble with it except for a slight bar oil leak when shut off. So, I drain the oil out for extended storage. Regardless, at a GTG one year it outcut every Stihl 460 it ran against with a 25" bar on board. I've used it in big red elm with a 32" bar:
View attachment 940567

You have exactly what I want, I was hoping the HD airfilter would give it more clean air Your muffler looks modded too, did you do anything to it?

 

[wanab]

If the saw is racing at idle you need to turn the L screw out, not in.

 

[jerseyjeff]

The way I start my 6400/7900 is full choke until it pops. Then open the choke by pushing the lever all the way in. Pull until it starts on high idle. Once it's running blip the throttle to release the high idle. First time I even heard anybody call a 14 1/2# saw light.

I sometimes mill with a friend that has a stihl 088. After getting that going and in a log, everything else seems pretty light to me! My redmax though is crazy light, and with the muffler mod is a tiny little beast. It did a hard 2 days work with the dolkita being a non-starter.

 

[dsell]

Ok, I have more data

1) Daylight savings time blows. I had 30 minutes between getting home and lights out to work on the saw.
2) The syringe/vac test is a bit terrifying, either you pull fuel and are SOL or it is ok. (lucky for me, I am ok, I hooked a 40 ml irrigation syringe to the fuel line, and did not pull anything)
3) I looked down into the exhaust port sans muffler, and did not see any scoring.
4) I made about 4-5 cuts with the new piston and cylinder, made zero cuts with new p+c and the HD air filter kit.
5) After looking at everything, I put it back together, turned the L screw till it bottomed, and then backed it out 1.5 turns. The saw started, and was idling high enough to spin the chain, I then turned the L screw in till the chain stopped. When I gave it the beans, it bogged and stalled. It also still started better with the choke pulled out a little.

Was that a typo on the syringe test? You should have pulled fuel into the syringe. Then, you should be able to push the fuel back in.

 

[jerseyjeff]

Was that a typo on the syringe test? You should have pulled fuel into the syringe. Then, you should be able to push the fuel back in.

Yep, my bad, I was able to pull 15 ml into the syringe, and push it back in. It dribbled a bit when I took the syringe out. I think I then flooded it, and am tabling it for the evening

 

[Wood Doctor]

You have exactly what I want, I was hoping the HD airfilter would give it more clean air Your muffler looks modded too, did you do anything to it?

I did practically nothing to the muffler. I just allowed it to breathe a little easier -- outside work and only because of the new and larger top end. Some chain saw users will not go near this saw today because it's mostly blue and not orange. I bought and serviced a Makita 6420 for one of my friends who cuts hardwood slabs with it using an Alaskan sawmill. He also has no complaints:

 

[dsell]

When you changed the air filter I assume you had to pull the carb mounting screws. Have you double checked to make sure the carb mounted to the intake correctly? Any chance there is an insert in the intake that slipped? Screws too long, bottomed out or poked the intake boot?

 

[jerseyjeff]

When you changed the air filter I assume you had to pull the carb mounting screws. Have you double checked to make sure the carb mounted to the intake correctly? Any chance there is an insert in the intake that slipped? Screws too long, bottomed out or poked the intake boot?

Just went back to the garage, and took off and reinstalled the boot. and, I may have found the culprit. The fuel line is cracked at the cylinder. and there is definitely a drip of fuel under the nipple where fuel should be getting into the cylinder.
now i just need to get some fuel hose, and try again in the daylight tomorrow. Here is hoping that is it...

 

[dsell]

Just went back to the garage, and took off and reinstalled the boot. and, I may have found the culprit. The fuel line is cracked at the cylinder. and there is definitely a drip of fuel under the nipple where fuel should be getting into the cylinder.
now i just need to get some fuel hose, and try again in the daylight tomorrow. Here is hoping that is it...

I think you are referring to the impulse line which would certainly give your symptoms.

 

[dsell]

46 is the impulse line.

 

[jerseyjeff]

46 is the impulse line.

View attachment 940602
View attachment 940603

that is it! The crack was on the bottom of the line, I am going to try to replace it tonight. I am getting 7/64 od, and 1/8 id, and I may see if I can get something at the local mower shop or home creapo.