6401 Big Bore won't fire Over

[rsbhunter]

level

I don't know how to check the metering level, i read on the forum where it should be set, but it wasn't for a Dolkita, and i don't know if they are the same....Was this a straight C&P replacement, or was the carb pulled to do limiter caps and such? There again, i can't think of what would cause such an excess of fuel...(my lack of 2 cycle experience) Does the diaphrams being cracked or split lead to this? If a carb is a carb , then the needles shut off fuel when closed, unless dirt gets under them, or they have been seated closed really hard alot...if like you say, you're getting fuel with both needles closed (with limiter caps trimmed or removed) then i would focus on the carb/fuel system...but again, this is based on general principals, not 2 cycle...good luck, i know this can make ya crazy...rsbhunter

 

[mstang1988]

I don't know how to check the metering level, i read on the forum where it should be set, but it wasn't for a Dolkita, and i don't know if they are the same....Was this a straight C&P replacement, or was the carb pulled to do limiter caps and such? There again, i can't think of what would cause such an excess of fuel...(my lack of 2 cycle experience) Does the diaphrams being cracked or split lead to this? If a carb is a carb , then the needles shut off fuel when closed, unless dirt gets under them, or they have been seated closed really hard alot...if like you say, you're getting fuel with both needles closed (with limiter caps trimmed or removed) then i would focus on the carb/fuel system...but again, this is based on general principals, not 2 cycle...good luck, i know this can make ya crazy...rsbhunter

Ok, quick tuned it all they way back in and then one turn out. See the fog that comes out of the compression release valve?

[video=youtube_share;XD0jzynmbhU]http://youtu.be/XD0jzynmbhU[/video]

 

[DB43725]

Like Brad said it apears to be flooded,,,Take plug out turn upside down and pull rope 6 or 8 times,,reinstall plug and start.

 

[rsbhunter]

Flooding

Ok, believe me, i'm not questioning any of what you say, that IS weird...try pushing off the choke and starting at half throttle??? you dang sure don't need choke on with that kind of fuel...also where is the "L" screw set?, or if your getting fuel at closed screws, then it's time to really get the experts on here to answer....it's not even trying to pop....rsbhunter

 

[mstang1988]

Like Brad said it apears to be flooded,,,Take plug out turn upside down and pull rope 6 or 8 times,,reinstall plug and start.

I agree that it seems to be flooded or behaving like it's flooded. This thing is driving me nuts!

 

[mstang1988]

Ok, believe me, i'm not questioning any of what you say, that IS weird...try pushing off the choke and starting at half throttle??? you dang sure don't need choke on with that kind of fuel...also where is the "L" screw set?, or if your getting fuel at closed screws, then it's time to really get the experts on here to answer....it's not even trying to pop....rsbhunter

I've tried with the choke off but I'll try again. The L screw was 1 turn out but I can put it all the way back in. Yes, still getting a lot of fuel all the way in. The needle is fine though, I took it completely out to inspect. The H needle was flat on the end but it didn't look like it was user impact to me. The limiter cap was still on it when I got the saw and I'm pretty sure it has never been pulled. The limiter cap keeps it from going in more then 1 turn.

This AM I pulled the carb completely and inspected everything. Looks fine but I cleaned it up (internally and externally).

I also took it up to my local echo dealer (was dropping off my string trimmer for warranty work) and had them test the compression. They said it was 100PSI. I'm not sure I believe them though as they also said normal is 90-120PSI.

I tested the squish, right around .030".

 

[WKEND LUMBERJAK]

How many times did they pull the saw over to get the results for the compresion?

 

[w8ye]

I couldn't find where you said that you have removed the limiters or at least the tabs on the carb needles?

 

[rsbhunter]

Big Bore

I can't remember if you posted, is this a factory or aftermarket c&p? You said you used the "factory" gasket...New or original? Metal or gskt material? Is the compression high with the decom pulled out? Nothing is making sense as to why it won't at least pop....Can you have someone hold throttle wide open while you pull the start rope with the choke off(just to see if it pops, not but a second) Not to be funny, but i'm glad it's not mine, it would be close to becoming a "flying object"...rsbhunter

 

[Sapo_feo]

I have the same problem. Got a BB kit from Bailey's and put it on a 6401 and it was excellent. Sold that saw and got a different 6401 at an auction, ordered the same kit and it won't fire. The saw was running when I did the swap. Floods out after 2 pulls. The compression is 120 and has good spark, the other saw was 150. I thought it had a bad intake boot, but after dumping money into it I just shelved it and never got a new boot.

 

[cuttinscott]

In Your Video the Saw is FLOODED Big Time!!!!!!! Also in You Pics I see You have the WRONG SPARK PLUG!!!!. You need to pressure test the carb to be sure its not letting unwanted Fuel into the piston/cylinder. I have seen the welsh plug come loose on that model carb and that will also FLOOD the saw to a point where it wont run.


The Correct spark plug is a NGK BPMR6A not the ????4A in your pic.


Scott

 

[rsbhunter]

BB kit

I know you feel frustrated already, but did you keep the old P&C? If this is an aftermarket kit, i would consider sending it back and getting an OEM 79cc kit....No, i'm not made of money, but when i started researching this swap for my own saw, i read alot of posts about "the after market kit" being siezed, low compression, etc. If i was going to spend the money on a kit ($109.00 vs $189.00) a HD kit, and other parts i needed, i decided that i didn't care about the extra 6cc's, or the $80.00 difference, as this was my first EVER work on a chainsaw, and i wanted to put the odds in my favor for it to turn out ok....I am NOT bashing aftermarket kits...there's thousands out there that work great...but i didn't want my first attempt to end up not working, and not know whether to blame my skills (or lack of:bang or think "could it be the kit".....anyway, i'd almost be willing to reassemble the original p&c on it, and see if it runs??? Alot of work, but alot less asprin and liquid pain relievers (BEER!!!!!!!!!!!!!!!!!time) rsbhunter

 

[Logger4Life]

I think that the BB kits aren't quite as good as the OEM kits . But the first saw I rebuilt and ported was a third hand HD rental 6401 that I had a total of $275 in finished and that was 2 yrs ago and it is still running strong and wears a 28" bar with a full-comp chain I actually think that it has a more user friendly powerband than any of my other ported saws and its got around 190psi for compression. I am also building another one so I don't think they are all that bad . I am actually impressed with my 066 BB kit from Bailey's.

Back to your saw it has way to much fuel getting into the cylinder somehow if I where to take a guess I would say rebuild the Carb or at least the main needle jet it has a little piece of rubber on the tip of it and either it is gone as in eaten off by ethanol or it is sticking open and dumping fuel into the cylinder just sitting there .As the tank pressurizes from evaporating gas it will push fuel right through the carb and cause it to be flooded before you even try to start it as the fuel will just be sitting in the crank case of the saw . I had it happen to me on my ECsaws 7900 I let it sit for about a month and went to start it and a bunch of fuel come running right out of the exhaust I changed the carb to a new Walbro HD-12 for a 372XP and took out the spark plug pulled it over until it was dry again put a new plug in it and new fuel and it fired right back up. Now I am haveing problems with getting my ported 7900's and 681's to start after refueling and can't figure it out. But if you can't get it figured out I take it off your hands for a fair price.

 

[mstang1988]

And the answer is... flooded! I assumed burning the excess gas with a match or torch out of the cylinder would do the job. Heck, I even pulled the cylinder but again, I first choked it, Bleh. Turning it upside down and cranking it over a few times and starting it without choking did the job. I started at 1 turn on each and went up until it was stable. Woohoo!

This thing seems like it's really going to run. I had a wedding to go to so didn't get to finish it. I might look at putting a new clutch in as well.

As far as the 100PSI compress goes he pulled it over 3-4 times. I suspect it's more then that as it feels just as stout as the original P&C when cranking it over (not that that's a great test).

Now I need to figure out why the choke floods the motor so easily. I also pulled a dumb ass trying to get it tuned up and got the clutch pretty warm. Hopefully not much damage.

 

[mstang1988]

Thanks for the help everybody! I love this community because the people are such good and helpful people.

 

[w8ye]

I inspect the clutches.

When you remove the B&C, I also take off the clip and rim.

Then I check to see if the clutch bell rocks on the shaft? If it rocks very much, I'm considering a new bearing.

I then remove the bell or drum and feel for a groove where the shoes ride. If there is a groove or ledge at the edge, I replace the drum.

If I replace the drum, I always replace the bearing.

Look at the shoes for wear. Nose around at pictures on the Internet to get a idea what new shoes look like and compare yours.

If your shoes are badly worn, I would replace the whole clutch assembly. It has left hand threads!

Clean everything out while you are in there and oil the bearing if it is dry.

 

[rsbhunter]

Great!!!!!!!!

Glad to hear it was something fairly simple to fix....let us know what the problem ends up being, as one of us will probably run into it at one time or another...are you considering opening up your exhaust outlet? I know it really helps with pushing out the exhaust!!rsbhunter

 

[WKEND LUMBERJAK]

And the answer is... flooded! I assumed burning the excess gas with a match or torch out of the cylinder would do the job. Heck, I even pulled the cylinder but again, I first choked it, Bleh. Turning it upside down and cranking it over a few times and starting it without choking did the job. I started at 1 turn on each and went up until it was stable. Woohoo!

This thing seems like it's really going to run. I had a wedding to go to so didn't get to finish it. I might look at putting a new clutch in as well.

As far as the 100PSI compress goes he pulled it over 3-4 times. I suspect it's more then that as it feels just as stout as the original P&C when cranking it over (not that that's a great test).

Now I need to figure out why the choke floods the motor so easily. I also pulled a dumb ass trying to get it tuned up and got the clutch pretty warm. Hopefully not much damage.

That is a trait of this series of saw. one pop cold push choke in and make shure the on off switch is in the right posititon. Don't ask how I know.

 

[rsbhunter]

Glad i wasn't the only one

Yeah, what he said......i was about halfway to frustrated ...til i looked at the switch!!!!!!!!!!:bang:

 

[mstang1988]

Yeah, what he said......i was about halfway to frustrated ...til i looked at the switch!!!!!!!!!!:bang:

I had done the switch thing before the big bore kit and new I flooded it. Tuned it up and put it in some wood today. Great upgrade. I still have a bit more tuning to do and the clutch is letting the chain creap a bit. It's tuned around 12,800RPM without hitting the rev. limiter. Right now I have to have it at high idle to start (pull choke out, push back in). Other then that seems to be perfect. Vs my Makita/Dolmar 9000 I feel it has noticeably less torque but it still has so much tq./power that I couldn't stop the chain with the 20" bar burried and being force fed into seasoned pecan. If I had one saw to keep this might be the one now, even vs my 346xpne by nmurph.