066, new carb, H bottomed out to run ~ok

[keen99]

replaced the carb on the 066 (stopped running, put two kits in the stock carb, neither of which exactly matched the stock parts, gave up and went new) - Tillotson HS-320A. This was february or so.

Did a quick tune on it at the time, didn't note where the H screw ended up, but it seemed to run appropriately with a bit of 4 stroking in the cut and strong out of the cut.

Tried to start it yesterday to take down the rest of a fallen tree and cut up the part on the ground to get it out of the way (saved me cutting it down, it was going to be pretty sketchy the way it was split and rotted) and it instant-flooded. Gave up before I tossed it in the pond and used the cs400.

Got it started today - still flooded fast. Got smart and leaned out the L a little bit and that seemed to do it (eventually. un-flooding a 90cc saw is not for the weak of heart...) ..but not before I paid too much attention to the tillotson manual for the HS that indicated the H/L screws were the wrong way around and turned the H.

So, went back my tuning stump (6 foot tall oak stump I cut with the big bar, knocked over with the tractor, and...never moved further because it's too damn heavy... plenty wide enough to bury the 24" in) and tried to tune the H....and anything over about 1/4" turn out loads up like crazy out of the cut, and stalls in the cut. 3/4 just stalls out on throttle. Bottomed out seems to get closer to the right place, but it still isn't smooth.


So - obviously, something isn't right. But what? My finger memory suggests that the H was close to bottom last time, definitely not around 3/4 out. The carb was new in the box - and it's certainly possible I fouled up the seat, but I dont really remember wrenching hard on it.....how sensitive are these seats? I'm not ready to drop another $50 on a carb unless I'm sure that'll fix it. I'm open to throwing a proven chinese knockoff (if there is such a thing) on there if it's in the 10-15$ range, though, maybe.

What -else- would cause too much fuel at WOT? L is in the 1/4-1/3 turn ballpark so I wouldn't expect it to be contributing too much fuel....

thanks.


....david (not a 2 stroke expert at all, but tuned plenty of carbs by ear over the years...these days though I prefer to use instrumentation!)

 

[Ozhoo]

Those knock off Tilly's are $12 carbs in a $20 dollar box. Pressure test the carb and you'll find the source. Sounds like the welch plug is leaking. You can see below how a leaking welch plug would contribute to flooding.

 

[HarleyT]

Take the carb apart and clean it.

 

[keen99]

Those knock off Tilly's are $12 carbs in a $20 dollar box. Pressure test the carb and you'll find the source. Sounds like the welch plug is leaking. You can see below how a leaking welch plug would contribute to flooding.

thanks - I can definitely see how that plug could cause a problem!

When you say "knock off tilly's" - do you mean that the tilly's are walbro knockoffs? I thought I'd read that tillotson is one of the OE suppliers for some of stihl's carbs? Or are you suggesting that there are knockoffs of genuine tillotson carbs out there?

On that topic - I wasn't able to find a source for new genuine walbro carbs at any price when I was searching before. what's the deal with supply on these? (I did find some take-off wj-67's, but they were the limiter-cap versions which, if I'm paying money for, I'd rather not have to deal with...) Or should I be looking for 1122 120 0621 (or 122 120 0618 for the wj69) instead? (...and that is, indeed, turning up better results at OE prices I'd expect)

 

[Ozhoo]

Tilly made some of the best, most reliable carburetors ever, but every one of these HS-320's that I've run into has ended up in the bin. I have one sitting on the bench from a 660 that wouldn't tune right. I just checked and the H needle is 1/8th turn out but that's where the guy said it ran best. I'll tear into it when I get a chance.

Post up i the wanted ads here for a used WJ-69 or 67. Sure it'll set you bad 40 bucks or so but it'll be worth it.

 

[Ozhoo]

Or better yet, send me your original carb and I'll go over it, test it and send it back.

 

[blsnelling]

I would NOT run your saw in this condition. The H should not be near bottomed out.

 

[keen99]

I would NOT run your saw in this condition. The H should not be near bottomed out.

agreed - I've only run it to tune it (and to start it!)

 

[Rockjock]

I do not have a listing for that carb on the 066 on the dealer network. The few that I have are outfitted with a walbro carb. I would go over it again, cost of a new one here in Ontario is about 175 $


- WJ41 WALBRO 1122 120 0616
. WJ35 WALBRO 1122 120 0616
. WJ48 WALBRO 1122 120 0616
. WJ51 WALBRO 1122 120 0621
. WJ67 WALBRO 1122 120 0621
. WJ69 WALBRO 1122 120 0618

 

[keen99]

thanks - I've got a known working used wj69 on it's way thanks to a generous AS member to try out, and my wj67 is on it's way up to him.

I'll get that swapped in place of the tillotson as soon as I can get a chance when it gets here and update you guys - and maybe apply some fuel+pressure to the 320 to see if I can figure out if something goofy is going on with it.

hopefully that works out - saturday it was "f$!k it, get it started, clean it, sell it"...

 

[Ozhoo]

I pulled a WJ69 from a running saw and sent it to him

 

[Ozhoo]

...get it started, clean it, sell it"...

Dibbs if you sell it

 

[keen99]

ok - installed working used wj69 from @Ozhoo a few minutes ago. no changes made to it. 4/5ths full tank. (fresh red 50:1 trufuel. I dont mess with pump gas anymore in the small tools.)

4th pull with full choke popped the decomp. half choke, decomp, fired on first pull.

started to warm it up (sounded rich, but florida room temp saw and all, so no real judge, and after about ~~1 minute it stalled. idle (off choke) was a little high, enough to turn the chain with reasonable speed. cheap tach seemed to be indicating around 2500rpm at idle but I wasn't watching it close.

won't refire now. (no choke initially a dozen pulls, then tried half choke for a few for the hell of it). wont pop the decomp, and won't fire w/o decomp either. (and no kickback on the pull)

so where do I look next?

 

[HarleyT]

Did you try full choke?

 

[keen99]

Did you try full choke?

other than the initial start, no. my general experience is that would guarantee it to flood. I would only expect to use full choke in florida to start it with an empty carb - though I suppose if it stalled because if failing to pull fuel, that would be an empty carb...

I returned 20-30m later and half-choke pull started it. 30-60s later, stalled and wouldn't refire again.

I'll try it again, and if it stalls, I'll pull the plug and see if it's wet like it has been.

 

[keen99]

(a few hours after the 2nd time) 3rd time: started first pull no choke. idled up around 3k, didn't touch the throttle for a minute or so. a few revs, then it lost power and stalled out again (can't catch it with the throttle when it happens)

pulled the plug (and boy are my fingers happy about that), it was damp but not wet. installed a new plug (new ngk).

2 pulls no choke, fired right up. idled a bit smoother, and closer to 3200 now. it sat for maybe 2 minutes before it started to stutter and idle started dropping - hit 2800 and it tanked. grabbed the throttle, but couldn't recover it.

 

[keen99]

would an over-rich idle cause it to flood-while-running (wet plug)? I haven't tried to adjust this carb to match what this saw wants at all yet, just in it's known running state.

and I didnt pull the new plug to confirm it was wet - my fingers are still unhappy about that first one.

 

[Ozhoo]

Yep, close the L side a 1/8th an retry. Sounds like it's loading up.

Here's a common way to adjust the L side.
Once you get it idling, start slowly closing the L side, as the mixture leans out the saw will speed up. When the mixture gets too lean the saw will start to stumble. Quickly back up the L screw 1/4 turn. Jack the throttle a couple times to test throttle response (no wide open, just throttle response). If it hesitates to come off idle open up the L side a tad and retest.

 

[keen99]

post-hurricane update, finally got a chance to adjust out the flooding idle.

same **** different bucket. or same bucket. they all look the same when they're filled with ****.

sitting a few weeks untouched with 3/4 tank of fuel (and tank marked) - and first fire was already flooded. 1 pull on full choke kicked the decomp, then no other fires at all no matter what. had to flood clear it (knee on the top, brake on, no decomp, full throttle, pull until it fires. 10-15 pulls and it started to spit, then a few more and it fired - barely ran as it puked raw fuel out the exhaust in a wet cloud.

one other symptom: the handle gets oil-wet sitting. new caps (new china from ebay dave, those puked fuel, so new stihl), so they're not leaking (those were installed right before parking it a few weeks ago). presumably the body/tank seam. but is it something else? there's no way that body/tank seam would feed fuel into the combustion chamber, right? thought it was just the cap, but I've kinda ruled that out now.


got it cleared and running, started to adjust idle, and then it flooded out before I got far. cleared it again (not as many pulls needed, not as much wet smoke), turned the idle screw in a bit to run the idle up above stall, adjusted L to half between rough rich and rough idle, started to turn the idle screw out - and it stalled again. and again wouldn't fire.

I think I've burned enough time on this thing - I could have bought two new ones with the time I've spent since I got it.

 

[keen99]

back out to it - got it started again w/o clearing it. continued dialing in the idle until I stalled it. again, wouldn't restart. opened up the L a bit, and ~5 or so pulls later it fired up like nothing had happened. (I was heading toward lean on L when it stalled). got the sweet spot again, backed the idle out a bit more, now it's just kicking the clutch on and off, so it's close. stalled. another ~5 pulls and it started. trying to find that L happy idle happy spot, hands off at about 2900rpm spiking up to 3100, and it stalled -again-.

these stalls really felt more like "out of fuel" stalls, then a few pulls to reload the bowl, then another minute or so of run, then a stall.

so - what's wrong with the fuel delivery system? bowl not maintaining enough fuel at high idle? (haven't gotten it to a real idle. and haven't done anything more than throttle blips to settle idle back down after an adjustment)