Odd (maybe) 359/hda199 issues. Is this typical?

[wcorey]

I've been lucky enough to pick up a couple cheap, clean-but-toasted 359's over the last couple months, been anxious to have a go at porting one.

First one the cylinder cleaned up ok and I was even able to use the piston.
Turned the base, opened up the lower transfers and did a typical 160 ex, 160 int and 20 blowdown.
Did a once over on the carb, looked clean inside with no obvious issues.

Seems like a real ripper, idles steady, instant throttle response, holds nice in the cut.

But... it goes lean at wot at random intervals, richen it up a bit then it's fine for a few cuts or so until it goes rich and I have to lean it out again.
Cut and repeat, back and forth...
Did a pressure/vac test and it's fine there.
Decided not to chance frying it, got frustrated quick and put it on the shelf for now.
Too many other saws begging for attention...


The second one I put one of wastsonr's Hyway kits in, unmodified other than a muffler mod.
This one idles fines, great throttle response, spools up smoothly but at wot 4-strokes nicely for a couple seconds then goes lean.
Consistently every time I pull the trigger.

Doesn't respond to high needle adj past one and a quarter turns or so out.
Passes pres/vac test.
Completely dis-assembled the almost new looking carb including having the accel pump piston and main jet out.
Damned if I can find anything that appears out of place.
Untrasonic'd, re-assembled/re-installed, now runs even worse!

Frustrated again, just put it aside and finished a rat 288xp port/build instead, that one made me feel much better...

I've done some reading on the hda199 issues and it seems the typical symptom is a stumble or bog between idle and wot, not what I'm experiencing at all.
Is the lean/rich flakiness at wot also a typical issue with these?
Are these candidates for the Tree Monkey fix or something different?

I'm a bit disappointed in myself for not being able to figure this one out, it's pretty rare (virtually never) for me to have to have someone else fix anything I've ever owned...

 

[w8ye]

With my HDA-199 I experienced a lean out in midrange without advancing the throttle. If you wiggled the trigger, it would recover because of the accelerator pump. I increased the idle mixture setting until it went away.

I never had anymore trouble with the HDA-199.

A fellow gave me a Dolmar 111i because it would go lean or rich on you at full throttle. It was the high speed nozzle check valve and I put a new carb on the chainsaw and the problems went away. That was three years ago.

 

[buck futter]

Understand your frustration.

I posted some problems I was having with my 359 carbs. They were the older 175 but one of he carbs had a similar problem. I installed a kit in one but haven't tried it yet. If you figure anything out let me know please.


Also I had one carb that would go lean and one that would go rich so I knew it wasn't a vent or filter. You may want to check those out.

Good luck bro.

 

[Ronaldo]

The 199 can be touchy.
I do know the Tree Monkey fix works and is not too costly.
I have two that he has fixed and they work great.

Ron

 

[Justsaws]

Those do not sound like AC pump issues.

Did you clean the carbs.

1. Did you pull the welch plugs? Fuel tank vent system. Fuel line/ filter.

2. Fuel tank vent system. Fuel line / fuel filter. Main jet.

The AC circuit charges the fuel flow as the trigger is being pulled. Typically if it is "bad" it will bog and require trigger feathering or choking to hit WOT. If the circuit is leaking it will run rich unless leaking past the o-ring which might cause it to lean out at WOT, supposedly very unlikely. Most often the long thin circuit is simply plugged with crap rendering the AC pump non functional.