rideon67

My Feedback: (1)

With a new electronic ignition the old Sachs seems to run OK at any throttle setting and has good throttle response EXCEPT when going to full from idle very quickly. When slammed wide open the engine sags and will die unless throttle is immediately backed off. It will go to wide open OK as long as the transition is a little slower (like 1 sec).

Is this normal? I tried riching up the LS needle 1/4 turn but saw no difference. The way this Walbro carb is setting it's impossible to turn the needles while the engine is running, so fine tuning is kinda tedious. What should I try? I have not flown the plane yet, so don't know it it tends to lean out when unloaded in the air. I'm trying to error on the rich side at the HS needle.

RTK

My Feedback: (1)

Here is a quick and simple way:

Both needles 2 turns out.

set high and back off a few hundred
set low (keep leaning) so it will not transition then richen till it will
re-set high and back off a few hundred.
Done

TLH101

My Feedback: (90)

You cannot "slam" the throttle on a gasser. It will need be advanced smoothly. Those big props won't spin up that fast.

RTK

My Feedback: (1)

If you slam it and it dies you are lean.

I slam my throttle on all my engines ranging from 26cc to 110cc with no problems of dieing and no hesitation per say.

Antique

My Feedback: (4)

Electronic ignition engines with syncro spark rely on crank rpm to change the timing..If the low speed needle is too rich the engine will accelerate slowy, so the spark advance is slower...Richening the low speed needle makes it worse...It's a fine line between too lean and too rich....

T-one

Rideon67 there are several considerations here
timing may be retarded.
what model walbro carb
what size engine do you have.
It should be able to transition smoothly and fast (slam).

rideon67

My Feedback: (1)

OK, the Walbro carb is a HDA 22 F4 which has a phenolic spacer between it and the 3.7 Sachs engine with zinger 22-6/10. HS needle is approx 5/8 open, LS is approx 7/8 open. I had the carb partly disassembled to look for dirt/problems and found nothing out of line.

When putting the carb back together I couldn't remember how the aluminum cap with with one screw and molded in name (WALBRO) went, so I placed it so the WALBRO can be read from the air inlet/choke end. Since the engine runs OK except for the transition sag I assume it is assembled right.

T-one

OK rideon, First I suspect that is one very old 3.7 with the orignal carb.
second, with the engine upside down, the walbro name should be next to the phenolic (intermediate flange)and readable.
third, Start with the needles a 1 & 1/8 to 1 & 1/4 open (both)
fourth, check the timing, if it retarded it will lag when slammed. should be 28-30 degrees BTDC.
Fifth, an offer you can't refuse, if it is not in a plane, box it up good, insure it and send it to us and we will make it run right at no cost unless it needs parts.
But try the above if you feel you can. Otherwise consider the option.
I have one of those old black case 3.7 that is all orignal.
good luck

Antique

My Feedback: (4)

28 to 30 BTDC only works for fixed timing and C&H Syncro Spark..Pro Spark starts at about 4 and advances..Don't know for sure about Reichmuth (D&B) and Air Hobbies, I suspect they also start at 4 degrees...

T-one

Right about C/H,
Pro Spark Is/was 5 BTDC from the manual
Reichmuth quotes "ignition timing is not generally critical, will start and idle very well with 5 degrees advance of TDC, most gas engines will run between 24 and 30 degrees with most at 28 degrees" from the manual.

GeraldRosebery

My Feedback: (14)

Clearly the Low end is lean. If the needles have no effect, the carb may need cleaning. The engine should respond instantly (I assume you mean a side carb cylinder.)

T-one

Gerry it is a side mounted carb, and yes the low end might be lean, but it may also have a retarded igniton that will also react the same.

rideon67

My Feedback: (1)

Whoooah. That is a generous offer indeed and one I may take you up on. We spent 3 hours and a gallon of gas at the field today with our clubs best gas tuners-- one thinks it's the ignition and the other thinks carb. Turning the HS needle back and forth while wide open (do NOT do this at home) would occasionally find the sweet spot but if the throttle was backed off and reopened it would not repeat and if the engine was shut off it would not repeat. Also, the midrange was usually very rough and also was not repeatable but would ocassionally run smooth. Low speed and idle responded to jet setting as expected and were generally good. When LS needle was right the idle was repeatable but transition was not. Transition could also be adjusted for within a given run, but would not repeat and always sag after restarting at the previous good setting.

Yes, it is an old (low time) Huskavarna orange Sachs engine with orig carb. The Walbro name is next to the phenolic and readable. Firing occurs approx 5 deg BTDC when turned over by hand. Also, I've been running a .035 plug gap which may be too big.

There is also a thread on my glitching problems in the giant forum. So far nothing has worked and even if the engine was right the plane would still be unflyable.

I plan to talk to Air Hobbies tomorrow and am to the point of cutting my losses on this setup. With what I've spent so far a new engine would have been pretty cheap. If they can't help you may be getting a package.

T-one

Rideon67, Like I said send it to us if you want. We've been doing that sort of thing for many,many years including the Zenoahs,Quadras and on and on. I'd like to try it just for kicks.

Antique

My Feedback: (4)

That's a very good engine, but after 15 years the carb diaphragms might be too stiff to respond...Any of your gasser gurus suggest a diaphragm kit for the carb ?

rideon67

My Feedback: (1)

After talking to Air Hobbies today it looks like something is happening on the plane that does not happen on his dyno. He ran the engine extensively and found it to run great only needing initial setting and then repeatable. (also with no extraordinary RF emmitance) When he Sent it back to me - I put it on the plane and zoop, the settings were way off and not repeatable. He is generously sending me a new ignition to try so I'll try that next with a new batch of gas. I didn't expect this kind of customer service and believe me, I really appreciate it. I'll also try a new spark plug

I had a little runout (wobble) in the spinner backplate that may have been inducing vibration and of course the dynamics of vibrations on the plane (with isolation mounts) with a 22-6/10 would be different than on his dyno with a 24-10. With all the nasty applications these carbs see, I can't imagine they would be sensitive to vibration frequencies and amplitudes. Dam these gremilins.

T-One -- since the engine works on AH's dyno but not on my C Eagle, I'm guessing the troubleshooting will need to be done on the plane. We can cross that bridge when all other routes are closed. Thanks

rideon67

My Feedback: (1)

Yes, one of the guys thought it was the carb. This is a Walbro HDA 22 F4 and I couldn't find any place that listed it or spare parts for it. The engine ran good at AH but I had the carb apart after that. Found no dirt and all the guts looked good and felt plyable. If I could find a rebuild kit I would try it.

Antique

My Feedback: (4)

The HDA series Walbros all take the same carb kit, D10 HDA, about $5 for the diaphragms..
Lock the ignition at 28 BTDC, borrow a C&H snycro spark ignition from someone, and test again...If you can't find a syncro spark use a starter or a BIG glove..You might just be surprised...

rideon67

My Feedback: (1)

Found the rebuild rubber kit. Will order if other tests don't pan out.

How do you "Lock the ignition at 28 BTDC" with an electronic ignition?

Antique

My Feedback: (4)

The sensor is mounted on the case, usually on a delrin or nylon ring...They were linked to the carb by a 2.56 rod that rotated the ring for advance and retard...If there's no link to the carb it's already been taken off and the ring locked at 5 degrees for an ignition that advances with rpm..If you can't locate a C&H ignition you'll have to leave it where it is...Take T one up on his offer, you can't go wrong...

GeraldRosebery

My Feedback: (14)

OK, that's interesting. Bill Oberdieck, who has chipped in here had a look at my Taurus 62 which also is a Sachs cylinder with side carb. It was running like a absolute dog in the air. He found nothing wrong with it on the bench. It ran perfectly. To make a long story short, the problem was never with the engine, but with the plane. Somehow the airflow through the cowl was wildly influencing airflow into the carb as well making it behave very strangely. The incredibly simple solution to the entire 2-year problem was to install a baffle at the cowl inlet to stop the air blast from prop and airspeed from flowing past the carb at all. Instant fix! No further mixture problems! Study your installation!

rideon67

My Feedback: (1)

Unable to stand a day without trying I had another go today. Changed gap from .035 to .028, removed heavy spinner plate, made a new batch of gas with Klotz 50:1 instead of Lawnboy. Vibration was worse -- evidently the spinner plate mass took some of the oomph out of the single cylinder excitation, but everything else was the same.......still ran like crap.

Gerry -- will try to disrupt the airflow tomorrow to test your theory. The lousy running done here and good performance at AH were both done with a prop and no cowl so not too optimistic. I wish I knew how it ran in the air but with the glitch gremlin still waiting to be found there's no way this thing is gonna fly.

mglavin

My Feedback: (31)

How is the fuel system setup on the model?

Antique

My Feedback: (4)

Next time you take it to AH take your ignition with it..
Spark plug gap is vastly overrated, going from .035 to .028 would make a difference only if the ignition was too weak in the first place...

rideon67

My Feedback: (1)

Fuel system is 32oz tank on CG at carb level. Two lines - one vent and one to carb with T with dot for filling. Have not seen bubbles and when held vertical can see no difference in motor perf. (still crappy)

RCIGN1 - if the replacement ign doesn't work that's my intention. Been shipping thus far, but road trip is coming I think.