346XP. "H" screw all the way in and only ~11,000 RPM, no load. Need some serious tuning advise!

[grizz55chev]

Air leak at the boot is my guess, pressure vac test.

 

[Cycledude]

To late now but You should always clean the area around the spark plug before removing it

 

[rustyb]

Air leak at the boot is my guess, pressure vac test.

How do I do that test, and what tool do I need?

 

[grizz55chev]

Search the threads, it all here on arboristsite. The guys here have taught me a lot and theyre always ready with good advice. Lookup pressure vac test!

 

[rustyb]

Here's the latest:
1)I got the stripped screw out of the carb. Whom ever had the idea of using a flat screwdriver....well, that worked. Thanks!
2)I took a knife and removed that stuff thought to be varnish. It came off in a flake, with ease. Looked like some kind of adhesive...but I don't know. It was brittle and easily cracked.
3)I took the metering valve out and the low and high speed screws. I put my cheater glasses on, got out in the sun and could see no varnish or anything else...anywhere. This carb is super clean as far as my eyes can tell! There was one exception....several very fine grainy looking things caught in the small cupped screen on the bottom end of the carb.
4)I couldn't get the intake boot off so decided to take the cylinder off to get a better look and to also get a better look at things inside. I have looked and looked at that boot and I see no split/crack. Of course, I can not be 100% certain that I didn't miss something. There is nothing obvious though, that I'm sure of.
5)Small amount of scoring at the top of the piston, muffler side. See the pics.
6)I'm doubting this could be related but.......this saw leaks bar oil too. Makes a heck of a mess in the saw case and leaves oil where ever I sit it.

I really appreciate the input, everyone! I'm just still at a loss as to what I can do with the minimal tools I have .....and minimal enthusiasm to be a mechanic any more. I used to thrive on this stuff in the 80's while racing MX. Not these days.

I'm sorta leaning towards a new carb or kit as suggested. Not sure what to do. Perhaps send the saw to someone here on AS?

 

[MS260 Fan]

Does the ring move freely within the groove? Not bound near that scratch is it?

 

[MS260 Fan]

It looks like something got in the cylinder. Maybe a small metal shaving during reassembly after your muffler mod? Is there evidence of anything embedded at the top of the cylinder in line with the scratches? Or at the top of the exhaust port? Hopefully it ejected it out into the muffler. I'm certain someone on here has seen that before.

I really thought the carb review was going lead somewhere. Are the gaskets still nice and flexible?

 

[rustyb]

It looks like something got in the cylinder. Maybe a small metal shaving during reassembly after your muffler mod? Is there evidence of anything embedded at the top of the cylinder in line with the scratches? Or at the top of the exhaust port? Hopefully it ejected it out into the muffler. I'm certain someone on here has seen that before.

I really thought the carb review was going lead somewhere. Are the gaskets still nice and flexible?

The ring moves freely and there's nothing stuck in the cylinder. It, the crank, and everything else looks clean! I took the muffler off during the mod and am reasonably certain nothing got in then. I'm quite anal about keeping stuff out of my engines. Perhaps something came off the plug...like some metal from the the plug's washer, or something of that nature. Seems I've seen that happen before in the past, maybe on another saw.... or weedeater, MX bike....

Re the carb gaskets....yes, they are nice and flexible.

Attached are some pics of the boot to answer your earlier question regarding the clamp.

 

[lone wolf]

My coil is blue and stamped 14,100. So, I thought I'd set the RPM at 14,000 with the tach and go from there.

I warmed it up first by cutting for a few mins. I knew it was rich. I then tached it and she was around 8000 RPM, no load on the bench. So I kept turning it in, 1/4 turn at a time, checking the RPM with each turn. I did this until.....until it wouldn't turn any more....and it was only turning in the 11000 range....perhaps 12000. The screw was all the way in! I don't recall exact numbers but I do know it never hit 13000.

Knowing something wasn't right, I backed the H screw out about 3/4 of a turn and started cutting wood. Honestly, this saw had never cut so good and so fast. After a bit though, it began acting like it was running out of gas....even on a full tank. Thinking that was due to being too lean, I backed the H screw out ~1/4 turn and started cutting again. No problems after that. Saw runs really, really good.

I didn't tach it....but I did shut it down while wide open in the cut....then I pulled the plug. Please see the attached photos. ALSO, for what it's worth, I looked in the plug hole with a flash light....and the piston top is covered with black stuff......except for a small section that would be towards the air filter side....and that was just bare metal.

Can anyone tell me what's going on.....besides of course that I don't know what in the hell I'm doing?

Saw may have had the limiter caps cut off and it may have had the muffler opened up.View attachment 470663 View attachment 470664 View attachment 470665 View attachment 470666

Well you did a lot with the H screw but what did you do with the L?

 

[MS260 Fan]

Good to hear everything is free. Whatever it was never got under the ring.

I light the inside with a little flashlight in a dark room and twist the boot every which way. You can do the without removing the clamp now that the cylinder is off.

I've never taken off a clamp like that. It loosens when you pinch the ends together? The boot it molded to match a step in the cylinder. It takes a little pressure and wiggling to get on or off even without the clamp.

What was the throttle response like from idle when you were tuning?

 

[rustyb]

Well you did a lot with the H screw but what did you do with the L?

I turned it in until it started to stumble then turned it out to max RPM then went half way between the two. I did this each time I messed with the H screw as I recall.

 

[lone wolf]

I turned it in until it started to stumble then turned it out to max RPM then went half way between the two. I did this each time I messed with the H screw as I recall.

That's sounds about right especially if it is holding idle.

 

[rustyb]

I've never taken off a clamp like that. It loosens when you pinch the ends together?

What was the throttle response like from idle when you were tuning?

Yes, it loosens the clamp. However, I get the distinct impression there's a more specialized tool for this job than needle nose pliers. I quit trying to get it off in fear of screwing up yet another thing. ;-)

Throttle response was great....except, at times, it seemed to stumble. But really, that's been months ago and I made so many adjustments, and was so frustrated, that I can't remember all the details now.

 

[Chris-PA]

Small amount of scoring at the top of the piston, muffler side. See the pics.

That looks a lot better than I feared it would!

I turned it in until it started to stumble then turned it out to max RPM then went half way between the two. I did this each time I messed with the H screw as I recall.

That would put it between lean enough to stumble and max idle rpm, which means L is set lean. Normally you want L set to the rich side of max idle rpm, or if it has an accelerator pump then L should be set at max idle rpm. Still, it's hard to see why this would cause the other issue you had.

 

[lone wolf]

Pull the needle jets out and look at them under magnification and see if the ends have been distorted from over tightening.

 

[MS260 Fan]

Yes, it loosens the clamp. However, I get the distinct impression there's a more specialized tool for this job than needle nose pliers. I quit trying to get it off in fear of screwing up yet another thing. ;-)

Throttle response was great....except, at times, it seemed to stumble. But really, that's been months ago and I made so many adjustments, and was so frustrated, that I can't remember all the details now.

I hear you on the clamp!

I was thinking along the same line as lone wolf and the L screw when I asked about throttle response off idle. Sounds like you had it set pretty close. The h needle could be damaged or there could be something on the seat. I pull most of the cotton of a qtip and dunk it in there after filling it with carb cleaner. Something to wet any debris at the bottom. Then rotate the qtip a few times

 

[rustyb]

Ok. I'm relieved.... but not sure whether to feel embarrassed and foolish as well.

Before and during tearing it down, I couldn't help but believe it was something really simple. After all, though I know things happen to newish saws, I knew I had treated this one gingerly from the start. I am anal about taking care of these things! And it had few miles on her. But what the heck???

When I had the carb apart, I blew it out as best I could with compressed air...even though I couldn't see anything but a few tiny grains of something in the screen. The boot looked great. I couldn't imagine any seals could be bad. So, I held my breath and reassembled, turning the H and L screws one full turn out.

She started right up. Warmed'er up and she tached at a bit over 11k. I kept turning in the H screw, tiny bits at a time until she tached at 13700. I stopped there as I felt bad holding it wide open long enough for the tach to read each time. This is where I feel a bit embarrassed. I think one of the problems before was that I wasn't letting the tach catch up with the RPMs. I had never used a tach before...and this was a cheap $10 ebay unit. Embarrassed again!

Plenty of H speed screw left to get the RPMs up to 14100.

I cut some wood sideways and couldn't get it to act as if it were running out of gas like before. Something in the carb? A frustrated operator hastily adjusting the L screw and not getting it right? I don't know but she seems to run awesome now!

This was today. When I resurrected this thread, someone planted the seed in me to investigate the 550xp. Baileys had a great deal on them....PLUS $50 off! But, that was ending in one day! And I didn't have time to assemble my 346xp to see if she ran better. So, I ordered the 550xp. It got here yesterday. I ran both back to back today.

I can't afford/rationalize keeping both....so someone is going to get a very clean, low mileage, awesome running 50cc 346xp. Will be posting it on the "Trad'n Post" when I get some time....within several days.

Thanks for the help, everyone!

 

[Gypo Logger]

Im having the same problem with one of my modded 346's, runnig fat with H seated on a defeated fix jet AM carb.
Wish I knew more about carbs, but not a real biggy in the whole spectrum of things.

 

[rustyb]

Not sure it mattered, or matters....but, one thing I forgot to mention is that I removed the guts of the tank filter as was referenced in post #37....the "mastermind" mod. However, I didn't drill a hole.