MetallicaJunkie

I have a 3w 80xi that has never run right. Let me start out by saying... i recently put a new carb on it(from aircraft intl.), i recently over hauled it and put a new ring in it, new bearings, and decarbonized the motor. i also installed a new rcxcell ignition a few days ago. i get about 6350 rpm with a 26x10 mezjlik prop...so the top end numbers are ok. it idles fine on the ground. i have the low end set just right in my opinion. any leaner and it will bog when i throttle it up. here is what the problem is the motor idles fine on the ground, but when it comes time for me to land, the engine takes too long to idle down. i have to go wayyy out to bleed off enough airspeed to land and to give it time for the idle to come down, or i have to go around and lower it a couple of clicks to finally get it to idle down...and by the time i get it the ground the idle just fizzles out and the engine dies. it happened three times in a row today. some one told me the low end might be lean... so i richened it about a 1/4 turn or so, to where the mid range was thick and burblely. same thing happened.

i have ruled out just about everything i could... new carb, overhauled the engine, new ignition...whats left, the timing? not that it would matter, im also using stihl hp ultra 40:1 lol

speedracerntrixie

My Feedback: (29)

Sounds like it could be too lean on the bottom and rich on the top. I would leave the bottom alone as you have already richened itand lean the top slightly. How did you set the timing when you converted to RCXL? After trying the needle settings you may want to try advancing the timing just a touch. If none of that helps it may just be a charictaristic of the engine with a deep pitch prop on it. The airflow through the prop keeps it spooled up until you are on the ground and slow. My DA 150s used to do the same thing until I learned to slow the airplane down for landing at a slightly higher idle.

BadAzzMaxx

High end to rich.

Milton

MetallicaJunkie

i just wish it would idle down on a dime like my dl/dles and every other gas motor ive seen fly


i didnt, i just dropped in the rcxcel hall sensor in place of the stock 3w sensor, it has plenty of room to shift in either direction.... im gonna investigate what its set at when u say advance the timing, looking at the engine standing infront of the plane, would i rotate the hall sensor clockwise or counter CL?






i was under the impression the high end needle did not effect the idle at all....but i guess there is always next weekend to try it out, because like i say, it always runs great on the ground

bcchi

Rotate the hall sensor clockwise when viewed from the front,to advance timing.
BCCHI

MetallicaJunkie

thanks BCCHI..... one thing i did notice, there was more black oily residue than normal, unless i was being more observant than usual

tkg

My Feedback: (1)

The XL ignition needs 24-26 degrees BTDC on a 3W. Using the stock XL sensor in the 3W holes gives you around 5 degrees BDTC . If you have a one magnet motor. With a two magnet motor the timing can be correct or 5Deg BTDC depending on which magnet your triggering off.

bcchi

Hello TKG,
Are you still in HI.
No snow here got to fly the DL 20 on Fri & Sat,Yes on Christmas day
BC Still buildings for 3-W
BCCHI

MetallicaJunkie

i have a 2 magnet set up on my 3w(newer style?) what does the "B" in front of top dead center mean(BTDC) i guess it would make sense to set the timing with first magnet

jerdavis

My Feedback: (3)

Before. Before Top Dead Center. BTDC. Make it spark 26 degrees before the piston reaches top dead center.

pe reivers

Depending on hall sensor orientation, there normally is only one magnet that will fire. Use that, or the first magnet that fires to set the spark to fire at about 26 - 28 degrees before top dead center.

MetallicaJunkie

ok i found some good videos on youtube, sometime this week ill check to see what the timing is set at

if i follow this video i will be fine http://www.youtube.com/watch?v=GBXFpxWg7vY

how much before TDC are we talking?... since im new to this(timing) it seems vague at the moment. how about if i have the piston at TDC how many degrees do i set it to spark?

pe reivers

between 26 and 28 like posted before. You need to have a degree disk fitted instead of the propeller.

MetallicaJunkie

ok thank you, i found a nice on on the C&H Ignition website

All Day Dan

My Feedback: (5)

This video has been a big help for all of us. Dan.
http://www.youtube.com/watch?v=GBXFpxWg7vY

mwhar760

My Feedback: (18)

also check for an air leak when you close the throttle,i have had several people bring me engines they have rebuilt but didn't get a good seal when they put it back together aluminum does and will warp when heat is applied from prior running !!!!! and you take the engine apart it will tweak that is why when you rebuild automotive,motorcycle, engines with aluminum heads, blocks ect. they machine them resurface them!!! i have had 2 dle 55 that i had to resurface the crankcase to the cylinder, also if you split the crank case and there is no gasket you need to reseal the case with anerobic gasket maker from permatex!!!! do not use silicone!!! a closed throttle should go to idle with a sealed engine,also you may re kit the carb the diaphrams are only good for so long !!! this to will also give you eratic running...,engine timing only affects rpm and power!!!! if you still have problems i would gladly take a look at it!!! for free!!!! i do have references if needed!!!! also the low speed needle only affects the idle and transition for full, the high side is just that only high rpm. i also accept that everyone has an opinion and weather right or wrong i hope my info. will help you!!!!!! mike

MetallicaJunkie

thanks for the reply mike, i appreciate your kind gesture. im the kind of guy that loves to fix things on my own even if someone has to guide me through the steps, thats the way i learn ...if i dont do things on my own ill never learn.....im not at the point where i wanna send it off yet...


OK here is where i need your advice.... i did find TDC and set it at zero on a degree wheel. sitting in front of my engine, i rotated the hub clockwise and it sparked at 43.......set at zero, i rotated the hub counter clockwise it went all the way around and it sparked at 32.5

what do i need to do get it to the ideal RCXL degree setting?

tkg

My Feedback: (1)

Set at 0, then rotate CCW until it sparks. Move sensor so that it sparks 26-28 Degrees BTDC.

tkg

My Feedback: (1)

Ain't snowing here either, be home on 2 Jan

Tony Hallo

.
I have experienced this same issue on a GT80, I've been told that replacing the stock Walbro WJ64 with a SDC80 will correct the problem. I haven't tried yet, I am currently building a plane to accept the GT80 and have the SDC 80 for the install, I will know next flying season. The WJ 64 appears to a high speed check valve assemblywhile the SDC 80 looks to a screen type check valve.

What carb is on the 3W 80xi?

MetallicaJunkie

My 80xi has a Tilotson carb

I have a friend that has a stock Evolution 80, and it runs strong and doesnt seem to have any bad characteristics.

so do you guys think i will bet a better idle down going to 27 degrees, from where it was initially,32.5 degrees?

mwhar760

My Feedback: (18)

you are gonna have to move the hall sensor!!! <div>in the direction of the prop rotation till you get a spark at 28 to 30 degrees before top dead center!!!</div><div>32.5 it may start or pop but it really needs to be closer to 30!!!!!</div><div>here are a couple of pic's of a a&amp;m 4.2 that had the throttle coupled spark ignition that i converted over to an rcexl!!!</div><div>with the engine inverted you can see where i sank the magnet in the hub before tdc !!!</div><div>the magnet will always be before the hall sensor at tdc and should spark at the desired time when you rotate the crankshaft</div><div>in the direction of the prop rotation!!! the picture the engine is at tdc and unless its a twin i always mount the engine inverted!!!</div><div>if all else fails don't get discouraged!!!! you can send it to me!!! i would be glad to set it up you free!!</div><div>or even better you can come to my shop and i can teach you!!! your call!!!!</div>

MetallicaJunkie

i think i got it figured out, i got a good idle of about 16-1700 or so, and top end of 6100 with a mejzlik 26x10... it doesnt kick back any more when trying to start it, and its not spitting as much oil out of exhaust.... but i will find out if i fixed the problem when i fly it, i dont mind losing 200 top end, when it has the power to hover at less than half throttle, what i do want is it to idle down on approach

thank you to all those who helped

mwhar760

My Feedback: (18)

good deal!!!keep us posted if you need any more help!!! mike