+ Reply to Thread
Page 1 of 2 12 LastLast
Results 1 to 15 of 16

Thread: cuynua 430 thro problems with air filter

  1. #1
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    cuynua 430 thro problems with air filter

    hi guys, have a question about my cuyuna 430, i bought this on a b1-rd awhile back and she runs/flies great. engine has a fresh overhaul however i nor the orig owner can get her to thro up with various airfilters installed. for one..............

    all stock 430 with a mic 28mm carb.
    panzoil 40:1 dino oil and 87 octane gas. non corn gas

    what it does................

    start it up with foam filter installed, idles great and will start to rev up but once you hit a few thousand rpm she simplies falls on her ass. wont die but the rpm just starts to drop. i remove the filter and she revs right on up. w/o the filter im getting 5000rpm max and i cruse right @ 4300 rpm. yes i have been flying w/o the filter and i know its a no no but..........

    when i bought the plane it had a k&n cone style filter on it and the guy told me about what it was doing. so i bought an all foam filter per cuyuna's recomendations and well it still does it.

    now i did talk to some ppl that know this engine brand and they also said it needs a 32mm carb and that might be my problem. also could be jeted wrong. well if it is jetted wrong im not sure which way to go here, lean or rich.

    i can say if she sits over night i have to pull the plugs and either them out due to being mounted inverted and filling with fuel. once dried she will fire right up and run great with no air filter.

    so it is a jetting prob, carb too small 28 vs. 32mm or what????? this is driving me nuts here and i would like the engine to last me a long time, and please no preaching to me about not using the breather. i know its not good on them at all, i have been a mechanic for over 20 years and a moddeler for 27 years. i know what im doing is not good on the engine. please help me get this figured out guys. thanks steve
    Attached Thumbnails Attached Thumbnails cuynua 430 thro problems with air filter-2011-05-28-20.17.05.jpg  
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  2. #2
    Registered User mstull's Avatar
    Join Date
    Jun 2005
    Location
    West Texas
    Posts
    1,263

    Re: cuynua 430 thro problems with air filter

    Steve,

    Yes, it sure sounds like a jetting problem. The foam air filter chokes the carb just enough to make it run too rich... which points to that it's tuned too rich or it's flooding. Make sure the carb's vents are open to the air. I just helped one guy who had connected the two vents with a piece of hose, without cutting a hole in the hose. It ran super rich, almost instantly flooding the carb. Some Mikuni carbs only have one vent. It/they are a little nipple on the side/s of the carb about 1/3 of the way from the top. It is common to have a short piece of hose connect to the vent/s, but they can just be left open. They must be vented to keep the float bowl at ambient air pressure.

    First off, I'd get a viton tipped float needle with 1.5 seat for your carb. It is common for vibration to shake the solid needle off its seat and flood the carb. And I'd replace the rubber boot that the carb mounts to. Those tend to get hard with age and can vibrate the carb too much. Vibration is a huge deal on U/L engines. You might want to replace the rubber engine mounts too.

    If those things didn't fix the problem, then buy an EGT probe and gauge and tune in the carb.

    Your 28 mm carb is the right size. Rebuild it, and make sure vibration hasn't worn anything, particularly the slide and where the needle can vibrate against its needle jet.

    The Mikuni part number for a Viton tipped float needle with the smallest (1.5mm) needle seat for the VM series carbs is Mikuni # VM28/511-1.5 or Sudco #
    002-233. I buy mine from Sudco, the Mikuni distributor for the USA. Use the smallest (1.5 mm) seat if you're using a pulse pump. For gravity fuel
    systems, use a larger seat.
    Mark E. Stull
    mstull@wtxs.net

  3. #3
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    Mark,

    thanks for the reply, ok first things first, my vent lines are open with small tygon tubes going down about 3 inches long. thjere is 1 on each side. havent ever opened up the carb to look inside. came with the plane. my carb boot is getting hard bacause i see some surface cracks in it . also my carb is safty wired to the intake. now i flew about 2 gal thru her last evening. here is what i noticed. 10 to 15 pulls full choke finally started up.

    i flew for 15 min while my freind was putting his trike together. i was just going to stay up but i landed and helped him with the last bit. so engine shut down for 15 or so min. well he took off and her i am trying and trying to get my engine to start. thought it wass flooded so i take out the plugs...................they look like a nice dry tan color. just like my models do when tuned close. well i choke and pull and choke and pull and finally i get my model 50:1 gas oil mix(not nitro fuel) and pump a few squirts in the carb. i pull some more and then finally its off. well we flew for awhile and everything seems to be fine but i have a feeling im running a tad on the lean side sence i switched oils. i was running belray mc-1 full senth.

    i now have been using penzoil 40:1 conventional. 16 ozs per 5 gal vs 8 ozs of senth per 5 gal. when i switched oils was when i was also having warmed up engine starting problems.
    now i have always had air filter issues.

    as for a pirometer i do have one and it used to work but for some reason she stopped working . i did find some bare spots on the probe wire but that wasnt the problem. the guage seems fine. i bet there is more spots grounding out. if and when i get my piro to working what exaust temps should i be seeing. the probe is mounted just past my y exaust going up to my muffler. the plane is all stock(b1-rd) if i would have to guess i would say about 10 inches from the heads.

    on my engine my max rpm on take off is 5800
    cruse is 4500 +- 100. ill pulll the carb today and have a look see with the enternals. i am an auto and diesel mech and i have worked plenty on small 4 and 2 strokers so that is why this is very puzzleing

    oh i do have a mic pulse pump
    Attached Thumbnails Attached Thumbnails cuynua 430 thro problems with air filter-2011-08-18-12.51.24.jpg   cuynua 430 thro problems with air filter-2011-05-28-20.16.55.jpg   cuynua 430 thro problems with air filter-2011-05-28-20.16.47.jpg  

    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  4. #4
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,252

    Re: cuynua 430 thro problems with air filter

    I see two problems. First, the 430 series engines used the VM32 carburetor, not the 28. Second, it sounds like you're overpropped (unless the undersize carb is limiting it)... max rpm should be up around 6500.

    I have a K&N filter on mine, with no trouble, except for once when I put too much oil on it. Bogged at full throttle, when I cleaned it an re-oiled it more sparingly, it ran fine.

    I also use 91 octane gas in my Cuyuna, not 87.

    You can download the Cuyuna manuals (which include jetting information) from the files section of the Cuyunamotor Yahoo group.

    -Dana

    Space isn't remote at all. It's only an hours drive away if your car could go straight upwards.

  5. #5
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    hey Dana, thanks for the info. i have a 32mm carb and boot comming for my engine. also the correct air filter as well. as for the fuel,.............can i use corn gas in my 430? the reason i use 87 oct. is that is the only fuel avail. in my town that isnt corn gas. i have heard alot of bad things about the corn stuff eating up seals and o-rings. so im not really sure there. ill have to go out and measure my prop tomorrow to compare it with the b1 manual. if it is over proped i can simply change the pitch sense it is a ground adjustable and that will compensate for an oversize prop or should but my bet is the 28mm carb.

    another thing i have a concern about is my pirometer. or egt.........it no longer works. how can i test if it is the probe, or the guage? and what should the temp be about 8" from port? thanks guys
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  6. #6
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,252

    Re: cuynua 430 thro problems with air filter

    I've been using 10% ethanol gas because it's the only thing available in CT. No problems that I know of, but it runs about 1/2 jet size leaner than avgas (which I use when I have to fill up away from home, and before storing it for the winter).

    8" is way too far away for the EGT probe! The readings at that point will not be meaningful. The Cuyuna manual specifies that it should be 1.5" from the exhaust manifold gasket, on the #1 (rear) cylinder pipe.

    -Dana

    Invalid thought detected. Close all mental processes and restart body.

  7. #7
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    Dana, you have been a huge help. thank you.
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  8. #8
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    ok back to the egt probe/guage.

    how do i test mine out to see which one is faulty? while shopping for a new west tach probe i noticed in the discription that they are grounded, so is that why i get no reading when off the engine, trying to test it on my bench? or are they saposed to be like the mechanical probes used in........say a car water temp sensor? i remember when i was into drag cars, to test the wts i simply held a bic lighter under the probe and watched the temp go up and down. if thats the case then i bet my egt probe is no good as it hasnt worked in months and i get no reading when tested like this.

    also measured the prop and i have the correct size and pit. 72x36

    and pulled the carb which will be replaced and everything looks as it should. so im almost positive that the 32mm carb will get my rpm's where they should be. and that the 28mm is choking my engine down.
    Last edited by corvettercr; September 30th, 2011 at 06:51 AM.
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  9. #9
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,252

    Re: cuynua 430 thro problems with air filter

    One thing to remember about the thermocouple wires used in EGT and CHT probes is that the wire is very brittle and fragile... easy to break from vibration. Naturally, if it's broken you'll have no reading or an intermittent reading. Yes, you can test it with a lighter flame. Between where the wire is anchored on the non moving aircraft frame and the soft mounted engine should be a large loop or coil to take up the motion.

    Also EGT gagues are notoriously inaccurate; the true test is plug color, then note what the EGT is actually reading when the plugs are the right color.

    Next, and you probably already know this, but the GSC prop protractor measures the blade angle in degrees, which is not the same as the prop pitch which is measured in inches. If your prop is supposed to be a 36" pitch, you have to convert the angle to inches based on how far out from the hub you're measuring the angle.

    -Dana

    If cars had followed the same developmental path as computers, a Rolls Royce would cost $100, get a million miles per gallon and explode once a year, killing everyone inside.

  10. #10
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    yep, i had the large coil just as you mentioned. i did take everything apart and i had tons of bare spots from age and vib.

    tested with a lighter and nothing so i just ordered a new probe and guage from chief. lots cheaper than spruce.com

    Dana, thank you so much for taking the time to help me with everything. and everyone else that has replied to my threads. im sure we will talk again.
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  11. #11
    Registered User texas-buzzard's Avatar
    Join Date
    Jun 2005
    Location
    san angelo, tx
    Posts
    100

    Re: cuynua 430 thro problems with air filter

    Try to stay away from the import egt probes as they are very inaccurate. egt's are not reliable for tuning but come in handy when something changes suddenly in flight such as a cracked carb boot, etc. plug color is the best indicator of how a 2-stroke is eating its lunch.

  12. #12
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    got her tuned finally and running great with the 28mm carb. i still have the 32mm comming and will upgrade later but for now it works great. my problem was i was running a bit on the rich side so i moved the e-clip up from the middle groove to the 2nd from the top. also set the screw per cuyuna's carb tuning manual and she will rev to 6000 rpm static with a egt reading of 1100f . i know thats not optimal but for my weight but it seems to be working great. the engine starts as it should now and will run great with the filter on it . im so happy. thank you guys for all who replied and for the help!!!
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  13. #13
    Registered User corvettercr's Avatar
    Join Date
    Jun 2011
    Location
    erick oklahoma
    Posts
    53

    Re: cuynua 430 thro problems with air filter

    oh forgot to mention...........the plug readings are a nice tan color and dry

    no soot no oily residue and not burnt. i think im good to go............., for now
    "For once you have tasted flight, you will walk the earth with your eyes turned skywards,For there you have been and there you will long to return" Leonardo da Vinci

  14. #14
    Registered User
    Join Date
    Aug 2010
    Location
    Plymouth, MN USA
    Posts
    322

    Re: cuynua 430 thro problems with air filter

    You can not test an EGT probe with a small flame like from a cigarette lighter, not hot enough. The yellow flame is most likely about 300 to 400 degs. Most likely will not even register on the display. You can test your probe/display very easily using a propane torch and a accurate volt meter.

    1. Remove the probe connections from the meter.

    2. Use an ohmmeter to check the probe and meter

    With probe at room temp, it should read about 2.5 ohms at the connector.

    Measure the meter terminals with the ohmmeter, you should read 8 to 12 ohms. If you have the ohmmeter polarity correct, the EGT meter needle may move some.

    3. If no problems found above, then reconnect the probe terminals to the EGT gauge.

    Connect the volt meter, set to the DC millavolt range, to the terminals of the EGT gauge.
    Remove the probe from the exhaust pipe. Slowly bring the propane torch close to the tip of the probe. Watch the voltmeter and gauge. You should get the following results.
    Probe temp(degs F) voltage(MV DC)
    200 2.87
    600 11.91
    800 16.58
    1000 21.31
    1200 26.03
    1400 30.70

    If you get voltage but no gauge deflection, try reversing the connections at the gauge. If none of this works, either your gauge or probe is bad. Most likely only one. Would be rare for both to go bad at the same time.

    Richard

  15. #15
    Registered User mstull's Avatar
    Join Date
    Jun 2005
    Location
    West Texas
    Posts
    1,263

    Re: cuynua 430 thro problems with air filter

    That's great info Richard. I have been using a cheap digital multi-tester set to DC mV for many years like that. An EGT or CHT gauge is really just a millivolt meter with temperature numbers instead of millivolts printed on the dial.

    The probes tend to break right where the wire starts to flex at the probe... particularly on engines that vibrate a lot. I saw one probe fail before the engine was even broken in on one very high vibration engine. It helps to tie down the probe's wire so it can't vibrate there, and route the wire towards the engine's center of vibration, attaching it to an exhaust port stud or engine cooling fin for example. Analog type gauges are extremely fragile, and can also be quickly and easily ruined by vibration.

    There are a lot of things that can affect the accuracy of the probe: How far out the header pipe from the engine is the big one. Farther out will read hotter, even though that's counterintuitive. Whether you extend the probe's wires is a another one. Every place you change the kind of metal of the wire, you're creating another thermocouple. At least one of the probe's wires is not copper. So ideally, the only change of material will be where the probe's wires attach to the gauge.

    There are 2 different types of probes that different brands of gauges are designed for, that put out different voltages. So it's best to buy the same brand of probe and gauge. Because it is easy for the readings to be off, the readings should be considered more relative than absolute. There was a good article about that in a recent EAA magazine.

    So tune the engine to have a fairly consistent EGT from 1/4 throttle through full throttle, and read the spark plugs to determine if that's a good temperature. Rather than leave the probe attached to the engine where it will break and fail, I only attach mine when I'm tuning in the engine on the ground. You can cover the little hole with a hose clamp the rest of the time.

    For my Kawasaki 440/340, around 24 mV is where it needs to be... which sounds right with Richard's scale. The temperature is roughly 46 times the millivolts. It is impossible to tune the carb to hold the exact same temperature at every throttle setting. Just get it as consistent as you can and make sure there are no overly hot throttle settings. Try to get it perfect at commonly used throttle settings like cruise and climb.

    Below 1/4 throttle, there may not be enough exhaust to fully heat the probe. So at very low throttle settings, just tune the engine to run smoothly.

    It will change a lot with altitude and temperature, running cooler at higher altitudes and air temperatures.
    Mark E. Stull
    mstull@wtxs.net

+ Reply to Thread
Page 1 of 2 12 LastLast

Similar Threads

  1. cuyuna 430 30 hp on a b1rd u/l
    By corvettercr in forum 2-Stroke Aircaft Engines
    Replies: 10
    Last Post: June 26th, 2011, 12:32 PM
  2. Murphy Rebel Oil Filter
    By rebelbuilder in forum Firewall Forward / Props / Fuel system
    Replies: 1
    Last Post: November 25th, 2008, 06:46 PM
  3. Lifetime Cleanable Oil Filter
    By Lee Schaumberg in forum Firewall Forward / Props / Fuel system
    Replies: 6
    Last Post: October 17th, 2008, 08:21 AM
  4. CUYUNA 430 prop
    By mogren in forum For Sale / Wanted
    Replies: 0
    Last Post: December 17th, 2003, 08:47 PM
  5. Cayuna 430?
    By mogren in forum 2-Stroke Aircaft Engines
    Replies: 0
    Last Post: September 8th, 2003, 10:43 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts