Quadra 52 won't run under 3500 HELP
 

I have a new Quadra 52. It is very difficult to start even with electric starter. At first I though it was ignition so I have installed a CH ignition jump start system which provides a strong at zero rpm, just moving the prop.

With the jump start on and using 24 v electric starter spinning over it is very difficult to start and will not start at low throttle.
I have a prime bottle I use to prime the carb and with the throttle 1/2 open if my batteries arent down in the starter it will start. When running it won't go below 3500 rpm without dying. This is with the CH ignition on. The plug is clean/gapped and dry when removed. I am thinking low speed on the carb preventing fuel below 3500 rpm. The engine is strong turning a 20 x 6/10 prop and has about 18# of thrust. There is no issue from 3500 rpm to full throttle. I have pulled both needles, cleaned the carm (remember this is a new out of the box I bought when Q52 were the biggest you could find). The engine sat new in the box for 7 years until I had a plane for it.

The carb:

The carb is a ZAMA and I have opened it up.
The filters are clean,, needle and seat free to move.
The ports from the L needle through the very tiny ports in the throttle barrel are open and flow easily.
All the internal porting is clean and free.
There is NO damage to the metal parts of this carb.

I have attemped to adjust the needles to get good starting. I used the reco. settings from the Q manual and they don't work. They do work for the high speed, but nothing below 3500 rpm. I have attempted everysetting I can think of on the L needle and no idle. The compression is strong and the engine is almost run in from the higher running.

I really think this is fuel delivery and have ordered the "rubber" carb parts from a Huskavara chainsaw part supplier. I found a H chain saw that uses the same ZAMA body and the diaphrams appear to be the same.


Fuel,, spark air it has to run, There is air,, I know there is spark,, just can't get the fuel. Also is there a substitute carb I can use on this engine.

My current plan is to replace the "rubber" parts and if this doesn't work to adjust the lever arm from the needle to allow more fuel to enter the carb.

Is there any help out there in R/C land that can tame the starting idle on this beast. I am about at wits end as the wife would say.

RE: Quadra 52 won't run under 3500 HELP
 

Check the following: Long shot, but possible.

IN the first picture you see the needle control lever. The diaphragm in the second picture pushes down on the lever causing the needle to open and allow fuel to enter.

Turn the carb sideways so that you can look across the base of the carb. The needle lever handle should be dead level with the base of the carb. Not the little knob, but the lever on which the little knob that the diaphragm pushes down on should be level. If it is below the base of the carb, sighting straight across from one sie to the other, it will not allow fuel to enter at low RPM. The reverse is true if the lever "handle" is above the base, it would die at idle due to too much fuel. You can bend this whichever way you need to go. In your case it would have to be below the base for the starvation at idle.

I lay a straight edge across the carb over the lever and you can see which it is, High, low or just right. It should tourch the straight edge just barely.

RE: Quadra 52 won't run under 3500 HELP
 

You are correct. I did check this and the point is about .015 below the level of the machine surface. That is a good observation. I plan to bend the tang to make it exactly level with the machine surface. Attached are figures of 2 types of carbs one type showing .012" below and the other flush. Currently my carb is set as in Figure A. When the new "rubber" arrives I will plan to adjust the lever as you suggested and give it a whirl. Thanks for the suggestion. I wasn't exactly sure which Figure A or B would apply to my carb.

RE: Quadra 52 won't run under 3500 HELP
 

I would check for an air leak in the induction track.

RE: Quadra 52 won't run under 3500 HELP
 

?? Do you mean the adaptor plate between the carb and the engine,, or internal to the carb?

RE: Quadra 52 won't run under 3500 HELP
 

Some where between the carb and the engine. I'd look right under the carb to make sure there's no leak there. I don't remember what a Q35 looks like, I got 75s and 100s the carb sits on the side and inducts into the crankcase with reed valves under the carb. If the Q35 is like that that's where I'd check first.

Also check that the crankcase seals are good, if they leak or the bearing seals leak it'll give you the same problem.

RE: Quadra 52 won't run under 3500 HELP
 

Another thing to test is if it will run with the choke fully closed you definitely have an air leak.

RE: Quadra 52 won't run under 3500 HELP
 

That would be a great test,, but there is no choke on this engine only my thumb over the carb intake. Don't know if I want to get that close to the 20"er turning.

RE: Quadra 52 won't run under 3500 HELP
 

Just a suggestion...if it were mine, I'd get a Walbro carb....I've had the same problems with the ZAMA carb......Switched, and the old Quadra came to life and ran like a champ...

RE: Quadra 52 won't run under 3500 HELP
 

I'm ok with switching to Warb carb,, but which one? My carb bore is 11/16" Don't know which to use.

Today I replaced the pump lever arm. The arm is adjusted flush with the machine face. This time the motor will choke and start using electric starter. The Low speed needle valve now does affect lower speeds. But no way will this go below 3100 rpm. Nothing I do with the needle will keep it running. I would believe I now have the low speed about right because any turn left or right will cause it to die. I checked and the needle is exactly 1 turn open which happens to be the Q recommendation. But it still won't go below 3100 rpm. I change the plug with new one checked the mag gap and no change. I pulled the old and new plug after running with the engine dying at 3100 rpm and the plug was wet. The engine is inverted. I am considering rotating the engine but that is a "lot of work" to rework the entire front end on this bird. :(

RE: Quadra 52 won't run under 3500 HELP
 

The Walbro WT-201 This is the correct size for the 50cc engines..

RE: Quadra 52 won't run under 3500 HELP
 

Eugene,, any idea who might be a supplier?

Today I spent more time on the Q 52 w/Zama carb.

I added a slideplate choke. Wow what a difference this made in starting. I also adjusted the float valve pivot arm to allow more fuel. The engine is turning 7300 rpm with a 20 6x10 wood prop. So it is strong turning up.

I still can't get idle below 3100 but what I noticed was that with the choke partially closed I could idle lower. With the choke 2/3 open I could get 2700 rpm with leaning the LS needle. So I made an Adaptor plate. The carb dia is 11/16" but the choke slide plate is 1/2" so this is effectively a restrictor plate. By closing the choke increases the velocity of air through the carb. So,,, with this observation I made a restrictor plate with 3/8" hole. Basically sheet metal with hole at inlet side of carb. But before I could try it,, my tank ran out of fuel and have to go buy more. My starting 24 v battery also ran down,, so more tomorrow.

One thing I also noticed is by reducing the opening from 11/16 to 1/2" I had a lower idle but only lost 200 rpm on top end. So higher air velocity might help.

I will shop around for a W Carb. to see what's out there. Thanks Jim

RE: Quadra 52 won't run under 3500 HELP
 

http://www.brillelli.com/brillelli_engines_004.htm
I'd go with the WT201b.

RE: Quadra 52 won't run under 3500 HELP
 

Thank you Rich,, I have a few more steps on the Zama and if they don't work I will order the wab carb.

Interesting though the WT210B carb intake is almost 1/2" compared to the 11/16 on the ZAMA. My current testing is using a restrictor plate to reduce the intake to 3/8 then 1/2". I have found better idle with the restrictor plate and only 200 rpm drop off of top end. Thanks again. Jim

RE: Quadra 52 won't run under 3500 HELP
 

The WT-201B is the standard carb on the DA-50 and Brillelli 366 plus many other engines so its plenty big enough. It does have an external pressure pulse line that should be noted. You could also use a WT-76A or B which is very similar but has the pulse port drilled to the carb mounting flange. That carb was used on the Taurus 52 and several Brison engines.

RE: Quadra 52 won't run under 3500 HELP
 

Rich theQ52 w/Zana carb has a hole through the base of the carb to the crankcase for the pressure to operate the pump system. Is this WT-76A type. I was going to post a pic, but the upload is down currently. Perhaps tomorrow I can post a pic. Jim

RE: Quadra 52 won't run under 3500 HELP
 

I'm not Rich and I hope I'm not stepping on someones toes but here is some more info. If your carb has the mounting bolts spaced at about 31.5 mm and the pressure port is through the carb flange, the WT-76 series should work. You should be able to get a new one from Brillelli as they have used that carb before and probably still do on some engines. I have also recently seen them at that EB-- auction site for $12.99 in a buy it now site. Look for WT-76A. I have engines that use both the WT-76A and B version and both work well. Hope this helps ....

RE: Quadra 52 won't run under 3500 HELP
 

Back to basics..... Remove the carb, check that the buttery is installed correctly. The butterfly is NOT round but oval and has beveled edges for correct sealing at low speed operation. Unscrew the idle speed screw untill the throttle arm does not touch. Hold carb up to sun and see if any light leaks past the butteryfly, light leaks = air leaks = fast idle.

RE: Quadra 52 won't run under 3500 HELP
 

The Walbro WT-144 was the original carb for the Quadra 50 and 52. It is no longer made, however you can buy one here: http://www.m-and-d.com/WL-WT-144.html (I bought one from here last August). I had similar problems with a very old Quadra 50 last summer. I replaced the carb, all the gaskets, bearings and seals (I knew there was an air leak somewhere, but I couldn't trace it down) so I replaced everything at once (mostly to save time) and that fixed it. I tried a Zama carb but I couldn't get the pulse port to line up perfectly, it was slightly off.

Grizak

RE: Quadra 52 won't run under 3500 HELP
 

Ok,, latest update. I added a choke plate to the inlet of the carb. With the choke I can close it fully spin the engine over until it pops,, open the choke 1/2 and start the engine. This is repeatable and easy to do,, Then once it is running I open the choke and it will go to full power,, but,,,,,,,,,,,,,,, It will idle slightly slower,, [X(] So I measured the throttle opening in the carb at 11/16 and the choke plate at 1/2. So this means a smaller opening improved the idle. So I decided to do a test. I made a plate of sheet metal with a 3/8" hole and mounted it under the choke plate at the air intake. Started and retuned the engine. The engine lost 400 rpm top end,, which didn't suprise me. What did was that it would now idle at 2900 rpm and even as low as 2700 rpm. So I decided to fly the bird. Take off showed the rpm loss but it flew well until the choke plate vibrated closed and killed the engine. So the brick bird (read really heavy plane) deadsticked into a 15mph wind. and landed in the briar patch at the approach end of the runway. Minor puncture in wing was all. I ordered a rebuild kit for $4.85 for the carb which is all the rubber parts. I will install it tomorrow and confirm if this makes an idle difference. I will also check to see if the throttle plate is correctly installed. I plan to install the choke plate minus the restrictor plate (woo woo sounds like nascar). to see if it will idle and perform with new rubber internals.

If this doesn't work I am considering the WT76A I saw on ebay at roughly $12.00 as a test replacement that truck racer found. I am not above buying a new carb such as the others mentioned but I am getting a bit frustrated with the no idle situation. Given this really is a new engine. What about mounting the plug vertical vs down. think that would make any difference possibly plug flooding inverted.

Well tomorrow will be another day and we will patch the wing and try again. The wing would not need patching if I had a reliable engine. Jim

RE: Quadra 52 won't run under 3500 HELP
 

I am a little unclear about your idle problem. Will it just not throttle below aprox. 3000 with the carb set to idle position or does it die below 3000? If it just won't throttle to below aprox. 3000, then it is probably an air leak problem that has been suggested by several. If it dies below 3000, then it is probably a fuel delivery problem and maybe just replacing the rubber parts in the carb will help .... restore the pump volume, etc. If the engine has set for some time, the idle fuel passages in the carb could be blocked by gum and solidified oil cutting off fuel at low throttle. Several possibilities here. Too bad you don't have somebody nearby with a similar engine you could borrow a carb from.

RE: Quadra 52 won't run under 3500 HELP
 

Hey Jim,

I don't want to sound obnoxious but tkg suggestion (see above) is a very good idea. I had the exact similar problem with a ZDZ 40 with a Bing carburetor and after messing with all the internal adjustments and trying to "re-design" the carburetor it came down to a simple reversed butterfly.

Most folks (I included) remove the idle stop adjustment screw. What happens (in some carburetors) is that the butterfly doesn't have a detent to stop rotating and the throtle lever may flip 180 degrees. In that case the carb will work just fine when you go full throttle but will not idle and die when the butterfly is closed. The reason being as tkg well explains is because the butterfly is not round but oval and beveled around the edges so it seals properly. Make sure to reverse the servo direction because when you flip the butterfly the full open and full closed directions get reversed too.

Trust me I seen this happen on several other engines. I friend picked up an almost new ZDZ (this time a Walbro carb) from this guy on the classified adds and when we tried to fire it up the same thing happened. The seller "swore" that the engine was running fine when he had it, and that he never touched the carb. After all he sold a dud and he wasn't ready to admit it. Take a break and start all over from the basics. You may find out your problem is much simpler than you think.

RE: Quadra 52 won't run under 3500 HELP
 

Today first thing I will check will be the butterfly valve. Hope it is that simple.

RE: Quadra 52 won't run under 3500 HELP
 

Ok I went back to basics. Pulled carb closed butterfly fully and no light passed around the edges. There are 2 notches and 1 lines up exactly with the low speed fuel inlet. So my assumption is the air through this notch is what draws the fuel at low speed idle. "if it had an idle" :(

So on with the rubber replacement and more testing. If this doesn't work,, new carb will have to be next, or replace engine.:(

RE: Quadra 52 won't run under 3500 HELP
 

I am sorry to ask a few more questions from you, if you don’t mind?. Does your throttle arm rotate a full 180 degrees or just 90 degrees? Did you bought this engine used or brand new? Has this engine ever run O.K. before?

I am very intrigued with your problem and will like to help if possible.

RE: Quadra 52 won't run under 3500 HELP
 

AirTech I bought it new in the box from the hobby shop when they were selling new. So it is a new engine. There was never any fuel stored in the engine after running. I have about 15 flights on the plane but only 1/2 to full throttle. The throttle arm is only a approx 90 degree arm and does not go 180.

I have checked the butterfly and it makes a tight seal and has a detent to prevent if from being installed incorrectly.

Today I put in all new "rubbers" and tried again. Once again.. 3000 rpm to 7200 rpm was solid. But I can't land at 3000 rpm unless flying the wheels force touchdown. Yesterday I attempted to fly with the restrictor plate and it did fly but on idle back it shut off and dead stick against a 15 mph wind with a 19# plane. Didn't make the field landed 6' short but enough to hit the briars and punch holes in the wing and crack the canopy.

So I am a bit frustrated with this carb/engine. I have examined the engine and found no damage the piston still looks like new and it is just beginning to break in a bit even if it is at the higher rpm. There is no mechanical binding. I am using 50 : 1 Belray full synthetic oil then switched to different conventional oil at 40:1 still no idle. Fuel from friend who flies gas burners would not get it to idle eventhough the fuel worked in his gas burner well.

The choke I installed makes it easier to start as it mounts on the intake only and does not restrict normal air flow. All the passages in the carb are clear and have been flow tested. The float lever arm was replaced / adjusted as per ZAMA instruction.

So far nothing has worked and I am arriving at the conclusion this is the wrong carb for this engine. I can't believe it was sold and won't get idle below 3000. I also have the C&H jump start for easier starting. If I leave the jump start on the engine has very solid ingnition and still no idle below 3000 rpm. Plugs changes to different brands/types/gap have had no effect on idle.

I have tried EVERY suggestion but no idle. There are no air leaks I can find on the crankcase as there is a good vac at the air intake on my thumb when turning over by hand.

So I am about to give up on this one unless there is some magic wand to wave. [&o] Jim

RE: Quadra 52 won't run under 3500 HELP
 

Jim,

Hang in there buddy and give me some time to consult with a couple of experts on these brand engine. For better assistance could you send me the S/N if there is one stamped on the case.

You say this was a brand new engine when you bough it. Taking in consideration that it's quite hard to start there is the possibility the pump diaphragm may be too hard from lack of use, but that is just my best guess.

After I talk to my friends I'll send you mail.

RE: Quadra 52 won't run under 3500 HELP
 

I changed the pump diaphragm and it had no effect. I agree with you it really takes excessive starting to get it to run. Only with add on choke will it run.

I did have a brain dump today and found B&B still warranties and sells Quadra. I called them just to see if they had carb parts or what carb they were using. Spoke to Dick Bennett owner. He wanted to know if I bought it from him,, I told him local hobby shop and engine was new but didn't have papers. We discussed all the issues and he reco. send it to them as they had some issues with Walb carbs. I told him mine was Zama and he said he never had an issue with them but to send it to him for a look and test run. Since this really is a new engine just been in the box for a while I sent it to him to see what he can do. I have never touched the engine only the carb and he will see it is a "new" engine as the exhaust isn't even blackened yet.

So I am still interested with what the "brain trust" might come up with for options as this story continues. Considering I actually paid the LHS close to $500 for this engine I would hate to sell it on ebay for $75. I would expect it to run. But if I get it back and still have a problem I'll take more action to see if it will run properly. It is a very solid engine just can't imagine it won't idle down. Dick did say he recommended a 20x10 prop and I have been running 18,, but that should not kill the engine at 3100 rpm. I suppose you can read the frustration on this Quadra. Let me know what the brain trust recommends. Sorry I didn't get the SS # before I sent in this morning. Jim

RE: Quadra 52 won't run under 3500 HELP
 

Hey Jim,

Seems like you are on track to solve your problem. Talked to Dick at B&B Specialties and he told me your engine is on its way there. If Dick can't fix it no one can. BTW he runs one the most honest operation in the hobby and is a real gentleman to do business with.

He seems to agree with me that probably the pump diaphragm membrane may have hardened after such a prolonged time in storage. I'm sure Dick can easily overhaul your carb but if I were in your place I will consider upgrading to a Walbro that fits. Dick will be more knowledgeable than anyone to set you up with the correct model Walbro.

Good luck and happy flying.

RE: Quadra 52 won't run under 3500 HELP
 

From my short conversation with B&B Dick seem to be a straight up guy. So all is in his hands. I just hope he can find the problem and correct it. I would really like to know. Remember I did replace all the diaphrams with new ones and this did not correct the problem. SO fingers crossed. Jim

My only regret is I can't be there to see what he finds and that I waited so long to return it. I bought it at the local hobby shop and looked today closer and it showed B&B as the warranty service. Didn't know where the hobby shop got the new engine from as he is no longer in business. Finding B&B as warranty is how I decided to call because I just have to believe the engine will run better that this. The local hobby shop closed after Katrina shut down most of the hobby stuff and wasn't around to ask.

I have converted many weed eater motors to r/c and never had this much issue with a conversion running. So I was a bit suprised to find a commercial r/c engine not running correctly.

RE: Quadra 52 won't run under 3500 HELP
 

I missed the fact you had replaced all the diaphragms already. That make it very interesting to find out what the cause of your problem may be. Please keep me informed as to what Dick diagnoses the cause of the problem turns out to be.

I reiterate, Dick is a very professional gentleman and he will let you know exactly what's the cause of the problem is and how to better fix it. I am sure he will have the engine back to you in very short time.

RE: Quadra 52 won't run under 3500 HELP
 

Please, keep us posted as to the outcome. This has been very interesting. I appreciate your sharing this problem. I can tell by your posts that
you are somewhat knowledgeable. persistent and thorough. Now, I am anxiously awaiting your report. I know the problem is going to be solved.

RE: Quadra 52 won't run under 3500 HELP
 

If your absoluty sure the carb is closing all the way and has no leaks then you have a air leak in the engine.
No way an engine is going to idle at 3000 rpm with no air.going through the carb.

RE: Quadra 52 won't run under 3500 HELP
 

I agree, what I found was that the low speed needle had little effect on the rpm as I could not get below 3100 rpm. Since this was a new out of the box engine if there are any leaks that aren't from the carb perhaps B&B can find them. It would not run any with the intake fully closed so I really don't suspect a leak on the engine itself.

RE: Quadra 52 won't run under 3500 HELP
 

Don't remember seeing a Zama carb on any Quadra unless someone changed it. Where is the throttle butterfly when it's running at 3200 rpm or when it shuts off. Cyl. gasket could have a piece out of it but should spray fuel out if it is.

RE: Quadra 52 won't run under 3500 HELP
 

This one came new with the Zama. Dick at B&B told me they could have either the Zama or the Walb.

I think the carb it too big for the engine and at low throttle there isn't enough airflow over the ventura to keep the engine running. I measured the carb opening and it was 11/16" with the actual barrel at ~5/8". I have never seen one that large. I experimented with restrictor plates and with a 3/8" plate on the intake the engine idle went to 2700 rpm,, from 3100 rpm with no restrictor plate. The restrictor plate allowed the engine to pull more vacuum on the ventura to test my theory of too large a carb intake. For every 100 rpm lower in idle the top end also came down 100 rpm. With no restrictor plate and a 18x10 prop top end was 7200 and bottom 3100. With the restrictor plate the top end was 6800 rpm and bottom 2700 rpm. The recommended prop is 20x10 so I would expect higher rpm with smaller prop. Given the 18 " prop is a tad bit lighter you might think that would affect idle but it did not have any significant effect. When the engine would shut off at idle the low speed needle valve was totally ineffective in changine rpm. Which lead me to the thought of too low a vacuum in the intake at low rpm. So we will see what B&B finds to make it run as design. This is why I sent it to them to check out.

RE: Quadra 52 won't run under 3500 HELP
 

[quote]ORIGINAL: jimcork1


This is interesting, I would not have thought a restector plate would have any effect on the idle. The only effect I could see it having is turbulating the air/fuel mixture so it was mixed a little better, but at idle the engine shouldn't "see" it.

RE: Quadra 52 won't run under 3500 HELP
 

Stock carb is a Walbro WA 144. Venturi bore size is 1/2 in. As you say, stock prop is 20 -10. Should swing it in the low 7s. Mag. ign. should idle at around 2100 rpm. Rebuilt one last summer for a club member converting it from 50 to 52 and rebuilt bent crank. Second flight he rolled it at about 200 ft. and the batt. fell out. Full throttle straight down. Buried the motor about a ft. Firewall was molded to the back of the motor. Bummer. I'm sure yours will run fine with a good carb. To late now but you should be able to take the low needle out and blow air in and it should come out the three holes you see where the butterfly closes. These are only pinholes. If the last hole is plugged, it will shut off before the butterfly closes. At full throttle, it is still going through those three holes.

RE: Quadra 52 won't run under 3500 HELP
 

Not too late that is one of the first thing I did and it confirmed all 3 passages were open.


I actually found a ZAMA manual on line that gave all the test for the carb and did all of these test as the first step.
The carb basically checked ok but the engine still would not idle,, that's why I went to restrictor plate. If you notice the correct Warb carb has a smaller throat than what I measured on the zama.

RE: Quadra 52 won't run under 3500 HELP
 

What is the difference between the 50 and the 52 Quadra? Thanks Rich