Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
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.
Posts: 654
Joined: 9/25/2004 From: Diana,
TX, USA Status: offline
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.
Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
quote:
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.
Posts: 2372
Joined: 2/1/2002 From: Middletown,
NJ, USA Status: offline
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.
Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
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.
Posts: 572
Joined: 6/5/2002 From: Indiana| USA, IN, USA Status: offline
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...
Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
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.
Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
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
Posts: 934
Joined: 1/29/2002 From: Slidell,
LA, USA Status: offline
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
Posts: 562
Joined: 4/3/2004 From: Des Moines, IA, USA Status: offline
quote:
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.
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Quadra 52 won't run under 3500 HELP - 
