With 50 years of engine tuning experience between my friend and I, we find ourselves stumped with the Webra 1.45 pattern engine. The set up is in an Entrophy, with Hyde style soft mount OS Max "F" plug, and Graves Pipe. We have run both fresh Byron's 15% nitro/16% oil and Omega 15% nitro fuel in the engine. Approximately one gallon has been burned, and we have never touched the pump adjustments. Here are the problems:

1. detonation at idle, especially on a cold start.... the engine is slapping around inside the cowling so much so that it has knocked the engine cover holding blocks off of the fuse.

2. Both high side and low side needle valves don't seem to seem to be doing anything, i.e., what should be a blubbering rich setting on the high side results in the same tached output (around 7,600K on an APC 17X12) as having the high side one turn from being fully closed. The idle needle sometimes seems rich, then on the next start, it seems lean.

3. At half throttle, there is rpm surging up and down. It has a "lean" sound to it, but I am not sure if it is really lean. When the engine is run up from half throttle after thirty seconds at mid throttle, it seems to load up, and may or may not return to full throttle, quitting. It has flamed out as well as come back to full throttle with this problem.

4. Finally, the most frustrating part of all of this is the engine never seems to do the same thing twice in a row. Yesterday, it seemed we had the engine running just right, with proper transition, acceptable idle, although the surging mid throttle was still there. This morning, when attempting to run the engine, it was as if all adjustments were completely off again, especially when transitioning from mid to high throttle

My friend and I would be most grateful for ANY AND ALL suggestions!!!

Thanks!
GPB

P.S. We checked all the usual stuff, like pin holes in the fuel line, fuel tank stopper tight, etc......

I ran this engine awhile last fall; it was very reliable, and adjusted fine. Assuming this is a NEW motor...my first guess, based on your symptoms is crap in the pump. If it's possible, find someone who has one and swap backplates. Betcha almost anything it's pump issues.

If you're not timid, you can tear into the pump, being careful to disassemble things, clean everything up, and try NOT to tamper with the adjustment, unless you need to. Probably in the inlet nipple channels on the "IN" side of the regulator diaphragm.

There is also a pretty high probability that something got through the pump and is in the carb. Disassemble it completely, you're looking for little pieces of plastic, aluminum, "nitro fuzz", ANYTHING in the mixture channel will create many of the symptoms you have.

Finally - DON'T run Omega with castor in it; that motor needs 18% oil, and I didn't run mine with more than 15% nitro. Castor over time will cause a lot of buildup inside the engine.

Hope all this helps some; I know how frustrating carb related problems can be; I had my own to solve this weekend.

I am beginning to think it might be a pump and/or carb problem as well. Never having had one of these Webras before, I was wondering if it was a geared or diaphram pump, now I know. Any particular procedure for disassembling the pump, so as not to screw it up?

Thanks
GPB

I want to be straight - LONG ago, on the old OS Hanno pumper days, I disassembled the ONLY backplate pump that I ever will. Call me a coward; but like Eastwood "A man has to know his limitations"....and tearing into those fragile environments with small parts...well... I screwed up ONE. So I won't do another.

Perhaps someone who HAS will post shortly, then we'll BOTH know....

I'm sorry I can't be of any more help on this.

I agree with Bob P. on possible crud in the pump or carb. The carb is easy to check out. The pump is a bit more challenging.

One of mine got some specks of something that snuck through my triple filtered fuel. Cleaned and it is sweet now.

It is a system of diaphragms and a spring. The only really tricky part is not to flip any diaphragms front to back or do a 180 degree flip while reassembling. There are some holes on one side and not the other.

My rule during cleaning of the pump is to make it the only thing on the bench and to finish it the same night I take it apart.

Make a sketch of top and bottom, left to right as you disassemble, if it makes you more comfortable.

BTW, I just tested a Perry 9700 pump carb on my Webra 1.45 today. It is staying in the plane. The pump is backed out two turns to get the pressure right for the carb. Now it will hold any RPM I want for any length of time with no flats spots. Just what the doctor ordered for FAI.

Another key with the Webra is not to run it peaked to the max. It will heat up in the air and start to get erratic. Find your peak, richen it, squeeze the line to get a small rev up sound. Then fly. You will likely not have to adjust at all from that setting as the conditions change.

Thats the truth. The motor DOES NOT like to be lean, you must leave it a few clicks, 4-5 from what I have found, for the motor to run well in the air.

Best fuel I have found is Ritch's Brew 15% Pylon. I tried several others and the 145 like this stuff the best down here in Texas. It took an easy 2 gallons for the motor to really turn on. Now during that time, I played with props and fuel to find the right combo.

Also I am amazed at the difference the prop will make in the adjustments. Mine likes the APC 17-10N the best.

Reduce your pump pressure buy turning the pump adjusting screw one full turn counter clockwise.

I've had two Webra 1.45 engines now and both of mine required the pump pressure to be reduced 3/4 to 1 full turn out. Both ran terrible before doing this and both ran great, and I mean GREAT, after reducing the pump pressure. Depending on the location of your fuel tank your adjustment may vary slightly.

I've seen guys spend weeks going around in circles on the NSRCA mailing list trying to get these engines working trying everything except the pump. I suggest trying the pump first then if that doesn't work do the more complicated things.

Based on my experience with this engine, if the pump pressure is correct there is no reason for special regulators, etc., etc. It should run great.

Disclaimer: It is possible that like Bob Air BS you could have something stuck in the pump, especially if you aren't using a fuel filter, but before going there just try the pump adjustment.

Best of luck,
KeithB

YNOT, I have not experienced the finickiness that you describe regarding the Webra. Mine ran great from the start as soon as I adjusted the pump. I'f you're still having to leave it rich then you may also have a pump adjustment problem.

I'm also from Texas and mine's run fine on Witches Brew, Cool Power, WildCat and Morgan (all 15%).

KeithB

I'll throw in my 2 cents. I have not run a WEbra, but I have run 4 UAV Bully engines. I had a similar problem and discovered that the rubber 'O' ring on the high speed needle was leaking a little air. REALLY aggravating and very easy to fix.
I've never 'adjusted' the pump on any engine (OS .61RF variants, Bullys, OS 1.40RXs) since the OS .60FSR with the old Perry backplate pump. Those came with the pressure set WAY to high and had to be reduced significantly.
Good luck - and remember: filter, filter, filter!!!
-Will B.

YNOT,

Were you at the Jetero Pattern contest. If you were I remember what a time you had getting your Webra to run. This is accually my engine we are talking about. Glowplugboy started the post for me since I was still at the fied flying Sunday. My engine is acting just like yours. We have been chasing the setup for a week or 2 now. I think BobAir's post hits the nail on the head. The pump pressure must be reduced in order to tame this beast.

Mike A.

I have been looking at the webra 1.45 for my new pattern ship, and have been reading here about the problems with the engine. Has anyone also tried a higher nitro like 25% coolpower? I fly with a person that uses the OS140 not the FI and uses 25% with all kinds of power... For those who use the pump adjustment to fix the problem, how far back was your fuel tank from the engine? and one last question what is the length from glow plug to the first baffle?
Thanks
scott

"F" plug? Sounds a little hot for the application though I will admit I do not have experience with this particular engine. Wouldn't one of cooler Rossi #7 or #8 or even an OS #8 be a better choice for your Webra? Everything you list as a problem points to detonation which is usually caused by too much nitro or too hot of a plug in a high compression engine.

Just a thought.

John

PatternPilot,

The increase in nitro can help the transition and it can also help the engine run cooler because it allows the needles to be set to a richer position.

But the Webra will run fine on 15%. And this is the goal of some flyers because Nitro=$.

Which pipe are you asking about the baffle distance? I have tried Bolly, Asano, and Greves on the 1.45. Many like the big ES pipe for the Webra. I have not been able to get my hands on one so far.

The setting I like for the Greves (Webra)1100/260 pipe is 780 mm from the face of the exhaust flange to the end of the 40mm part of the tube (right before the stinger). This is a great set up for 17x12, 16x14, 17x13 in the 8000-8100 range. It will peak for more RPM than 8100 but keep it a bit rich to keep it cool.

JWN,

The OS-F plug is very close to the recommended Webra #7 in running temp.

I have tried the Rossi 7 and 8. Both are very difficult to get through the mid-range.

And the OS-8 is actually a pretty warm plug if I recall correctly.

But yes to the detonation question. That is what we are trying to avoid here. It does not show up with a bang or a pop like in a 4-cycle. The Webra just gets hot. Usually it evens keeps running and you will notice it when you land.

My rule is that if the engine (2 or 4 stroke) is barking. It is trying to detonate. Tame is down with a richer needle.

Well, I do now the OS F plug is considerably hotter than an OS 8 and the Rossi 8 is much cooler than an OS 8. It just sounds like they are going the wrong way on plugs in trying to eliminate detonation.

How about lowering the compression? My BGX behaved exactly as you describe when I had a pipe on it until I installed 3 additional head shims.

John

Yea, I was at the Jetero contest and the motor ate my lunch all weekend. Had a dead stick and zeroed half a flight.

Interesting thing. I changed props to a 17-10 and the motor just sings. Took 2nd at the Nederland contest, never had a problem, flew it 10+ times over the 4th of July weekend and never had an issue. However, last week, changed to a 17-8 and it got hot and died again.

My biggest problem is overheating. I can smell it. Will tunning down the pump help with this?

YNOT,

I believe backing out the pump may help you. One of the experiences I had was, in my effort to get the midrange working, I over leaned the HS needle. This would clear up the richness left after the engine came across the 4000-6000 RPM range. THAT IS NOT THE THING TO DO. It will still flood in the midrange and even worse, overheats the engine when wide open.

On a nearby thread Tony F stated that the Webra is easy to run lean. Very true, it doesn't complain like other engines when lean, it still runs.
Backing out the pump a turn or two may allow a richer HS needle and prevent heat up. And hopefully leaning the midrange in the process.

BTW, Tony F and Stefan Fink helped me get my Webra's running sweet.