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Quadra 52 won't run under 3500 HELP

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Quadra 52 won't run under 3500 HELP

Old 03-03-2008, 07:03 PM
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jimcork1
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Default 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.
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Old 03-03-2008, 08:16 PM
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Default 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.
Old 03-03-2008, 10:14 PM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: Safebet

Check the following: Long shot, but possible.

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.
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.
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Old 03-04-2008, 08:45 AM
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Default RE: Quadra 52 won't run under 3500 HELP

I would check for an air leak in the induction track.
Old 03-04-2008, 09:30 AM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: soarrich

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

?? Do you mean the adaptor plate between the carb and the engine,, or internal to the carb?
Old 03-04-2008, 09:48 AM
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Default 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.
Old 03-04-2008, 10:09 AM
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Default 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.
Old 03-04-2008, 10:47 AM
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Default 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.
Old 03-04-2008, 11:07 AM
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Default 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...
Old 03-04-2008, 12:22 PM
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Default 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.
Old 03-04-2008, 01:33 PM
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eugene
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Default RE: Quadra 52 won't run under 3500 HELP



The Walbro WT-201 This is the correct size for the 50cc engines..
Old 03-04-2008, 04:47 PM
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Default 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
Old 03-04-2008, 05:59 PM
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Default RE: Quadra 52 won't run under 3500 HELP

http://www.brillelli.com/brillelli_engines_004.htm
I'd go with the WT201b.
Old 03-04-2008, 06:21 PM
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Default 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
Old 03-04-2008, 06:40 PM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: jimcork1

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
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.
Old 03-04-2008, 07:45 PM
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Default 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
Old 03-04-2008, 08:23 PM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: jimcork1

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
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 ....
Old 03-04-2008, 08:42 PM
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Default 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.
Old 03-04-2008, 09:28 PM
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Default 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
Old 03-05-2008, 08:13 PM
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Default 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
Old 03-05-2008, 09:26 PM
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Default 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.
Old 03-06-2008, 12:01 AM
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Default RE: Quadra 52 won't run under 3500 HELP

ORIGINAL: tkg

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.
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.
Old 03-06-2008, 07:11 AM
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Default 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.
Old 03-06-2008, 09:55 AM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: tkg

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.

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.
Old 03-06-2008, 11:03 AM
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Default RE: Quadra 52 won't run under 3500 HELP


ORIGINAL: jimcork1


ORIGINAL: tkg

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.

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.
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.

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