Need strato help

[Saw Dr.]

OK, so maybe it is not a saw, but I am finally stumped. Husky BT-380 strato backpack blower. I cannot get this thing to tune properly or run out. It has LOADS of compression, the muffler screen is clean, and the carb is in good order. I can get it to idle all day long, but it is horrendously rich on top (at factory carb setting.) If I lean it out, it will run somewhat better on top, but not idle at all. There is significant air coming BACK through the strato port when I try to rev it up. This does not seem normal to me. The blower has never been apart, and has been in landscape service for its life. Infrequent filter service, as is the norm for landscapers. Piston is a little noisy, but better than most used pieces. Any ideas?

 

[jus2fat]

You didn't mention how old the blower was...

If still under warranty..then definitely back to the dealer..

Maybe this blower just has a faulty carb..??--That's my best guess.

But then..you have probably forgotten more about 2-stroke carbs than I know..!!

Please keep me and other readers informed on what you discover the problem turns out to be..!!

J2F

 

[Saw Dr.]

I'm thinking that I will just try a new carb. This one is a stupid RB series carb, but it is double barrel. I really don't care for those carbs in single or double venturi. I initially thought the main jet o-ring might have been leaking, but I checked it and flipped it over. No change. If the carb does not fix it, the engine is coming apart. It seems to idle too well to be an ignition timing issue. I do not know if it is normal to have air kicking back out of the strato port on these. It is coming out very strong. It can be felt several inches away from the throat when you go to full throttle. Maybe the piston skirt is worn and that is my air kicking back. That would be very strange since it has such good compression.

 

[LegDeLimber]

I'm curious about how that strato port reacts also. have seen the theory video, but wondering how it really behaves in real life.
seems the carb/port linkage would need to be staged with care and the springs on my weed beater
are pretty darn stiff. Could see that as wearing things to be out of time, hanging or leaking.
..But, all I've got to go by is..
...I've got a new 33cc, strato, poulan pp330 that I'm wanting to learn a bit about before gassing it up.
stripped and looked in the ports , nasty mold flash left hanging and some poor fastener work
have made me put it on hold till I'm ready to do a full teardown and bit o port cleaning.

 

[morgaj1]

I'm not an expert by an means, just a backwoods hack. But looking through the schematics on a strato engine and the dual throat carb, here is my guess. I would guess that you have trash blocking one of the air passages. This would explain the unusually high pressures through the strato port. And, it would make sense, given that the previous owner did not clean the air filter. My 2 cents, although probably not worth that much :msp_biggrin:

 

[Chris-PA]

I'm thinking that I will just try a new carb. This one is a stupid RB series carb, but it is double barrel. I really don't care for those carbs in single or double venturi. I initially thought the main jet o-ring might have been leaking, but I checked it and flipped it over. No change. If the carb does not fix it, the engine is coming apart. It seems to idle too well to be an ignition timing issue. I do not know if it is normal to have air kicking back out of the strato port on these. It is coming out very strong. It can be felt several inches away from the throat when you go to full throttle. Maybe the piston skirt is worn and that is my air kicking back. That would be very strange since it has such good compression.

I had never looked into the RB, but I just looked into the Walbro WY and it looks similar. They clearly developed those to try to get around the problems inherent with a fixed venturi/fixed jet carb that has no air bleed system.

These barrel valve carbs are variable venturi/constant velocity carbs, so in theory they could provide a mixture that is controlled with airflow (unlike the standard carbs). I've been wondering if any saws used the WY - and now the RB too - and how they've worked out.