Why does it do it?
 

I have an RCSSV50 from TBM on a CMP 74in Extra330L. Has about 3/4 gal at 40:1 through it, but still blowing black oil. 22x8 prop. Starts great, responds to the throttle well. I'm using the ignition that came with it, but I chunked the no name plug that came with it and used a CM-6. 1400 4.8 vdc Nimh battery. My problem is that it doesn't want to lean out properly. It will miss and sputter but keep running. When I try to lean it out, it will go lean before it quits sputtering. I have checked all the tubing connections for leaks, cleaned the carb screen, and checked the plug cap for tracking. No help. HOWEVER, when I pull it vertical, it will smooth out and climb right on out of sight. Goes right back to sputtering when returned to level flight. We thought maybe the added prop load while vertical helped so I installed a 22x10, but it didn't help any. Anyone have any thoughts?

RE: Why does it do it?
 

You didn't talk about the Low Speed Needle Valve

RE: Why does it do it?
 

We tried leaning the low speed and got it low enough that it died on the throttle advance. Then we bumped it up until it responded properly. Then we leaned the top end until it sagged after a few seconds at full throttle. Then we opened it up until that smoothed out. BTW My helper is an experienced giant scale flyer. He is familiar with the tuning. I also put a tube on the carb hole and ran it into the fuselage. The way it is blowing burnt oil, I'm wondering if it just doesn't need more break-in . I've had several gassers but this is the first one that didn't at least run reasonably smooth when first run. This is also the first non name brand motor I've had. My other are Taurus, 3W, ZDZ, Quadra.

RE: Why does it do it?
 

If it doesn't exibit this on the ground after properly tuning, investigate your reference pressure fix a bit further. If you cannot reach a properly tuned condition on the ground, dig further into the carb, reeds, block, gaskets, something has been missed. Oil choice alone could account for the residue. If you are using a good oil, its doing its job, and the residue should dissipate with more time on the engine.

RE: Why does it do it?
 

I'm using Pennzoil air cooled. It will blow a black spot on the grass when running. The instructions say to run about 6gal for full break-in. I soldered a brass tube on the diaphragm hole and ran the tubing thru the firewall hole( it just has about a 2in hole through the firewall) to about the wing tube. I'm going to try to do more adjusting and then pull the engine and remove the carb to check for dirt and inspect the reeds. It is a rear induction engine. BTW I also tried to tape up the top cowl vents to change the airflow to no avail.

RE: Why does it do it?
 

As Jim, W8YE, said, it sounds as though the engine has a way to go before it is broken-in. If the problem persists after a couple of gallons of fuel, then I would become concerned.


Ed Cregger

RE: Why does it do it?
 

Check the ignition timing. It should be between 27 and 29 degs. Any more and it will run rough, any less and it will not make the power it should.

RE: Why does it do it?
 

Your high-end needle is too rich. Just because it seems tuned to run on the ground, doesn't mean it will work in the air. The needle settings on the ground are a rough adjustment only. Once you get it in the air, see how it sounds, land and adjust and repeat until it runs good.

RE: Why does it do it?
 

are you sure the cm6 plug is suitable for that engine? I tried a different plug in a china 52cc motor as suggested by some guys here on rcu but the throttle glitched bad and even stayed wide open. A couple other guy in our club experienced the same problem until they put the original plug back in and problem solved. Also some engines require 6v on the ignition...at least the Turnigy engines from china suggest that you use 6v and 93 octane gas. I'm using Penzoil air cooled also...good oil and I dont have to have 2 or 3 different gas cans sitting around with different mixes. my 2 cents

Ron:eek:

RE: Why does it do it?
 

Hi Check the timing as already suggested, just to eliminate it out of the problem.

RE: Why does it do it?
 

Sounds like the same thing my SV90 was doing. Ran great on the ground, pulled a 35% Giles 202 (27lbs) in the air like a truck but had a strange rich sounding 4 stroke burble in the air. It kept pulling great, never dead sticked and i got tired of messing with it to get the burble out. After about 5 gallons it got better and better and a few small tweeks and it runs great. If it doesn't dead stick and pulls good try just flying it. Good Luck

RE: Why does it do it?
 

The black stuff is talking to you. Over and over it's saying it isn't broken in yet. That experienced giant scale guy needs to do a better job of listening. Look for a tiny leak around the base of the carb and the insualtor block, then spray some soapy water in the same area and look again. Worst case is you remove the insulator block and fine sand it flat if there is a leak. Get those put of the way and we'll work another area if the sputtering problem doesn't go away. The black stuff will go away when it completes the break in.

RE: Why does it do it?
 

I was already planning the timing and leak checks, but I got home from town too late to get started on it. Somehow, as I was headed to the shop, the couch jumped in front of me, and I landed on it. ;-) Good night, Irene! (I'm giving away my age with that song title.)

RE: Why does it do it?
 

No worries. If the timing is off, it's prolly not enough to be a big deal and would not cause the sputtering anyway. Later in the troubleshooting process you can pull the carb and check that the reeds are seating correctly. There have been a few reeds from every reed maker that of late have not been seating on one side or the other.

RE: Why does it do it?
 

The reeds were going to an "item of interest" as the police say of suspects. When I turn the prop back and forth, I hear a sort of sound like the reeds are vibrating in the air backing up through the carb. Like they aren't sealing off against the reverse pressure. Sort of a saxophone reed sound. I was saving that to look at if I had to pull the engine to get to the carb. Don't know if it is doing it at high RPM. The way it starts doesn't indicate a low rpm reed problem. I've read that bad reeds will make one hard to start. Always starts great.

RE: Why does it do it?
 

Pat, I have to disagree with you here. More than one DL50 was having sputtering problems at our field and after finding the timing advanced 11 degs too far on one we set it back to 28, retuned, and it's ran great since. We later found a couple of others off by roughly the same amount and they were running quite bad as well. Setting the ignition timing and then retuning them fixed the problem with them as well.

In each case with the DL's they sounded horrible in the low and mid range and ran pretty good at WOT. With you having so much dyno time running these engines maybe you can help explain why the 11 degs of extra advance would cause them to run sooooo rough in the low and mid range and then they clear right up after setting the timing and retuning the mixture.

P.S. Pat, I am also curious as to whom might you might be refering to as "That experienced giant scale guy". Could you enlighten us? I've read and reread the posts and I can't find any mention of "experience" other than your post #12. It appears, IMHO, that everyone was trying to offer suggestions as to how the OP might be able to solve his problem and trying to do so without "degrading, insulting or embarrassing someone".

RE: Why does it do it?
 

More than one DL50 was having sputtering problems at our field and after finding the timing advanced 11 degs too far on one we set it back to 28, retuned, and it's ran great since. We later found a couple of others off by roughly the same amount and they were running quite bad as well. Setting the ignition timing and then retuning them fixed the problem with them as well.

In each case with the DL's they sounded horrible in the low and mid range and ran pretty good at WOT. T.O.M., with you having so much dyno time running these engines maybe you can help explain why the 11 degs of extra advance would cause them to run sooooo rough in the low and mid range and then they clear right up after setting the timing and retuning the mixture.

RE: Why does it do it?
 

Detonation.

That was the short answer but there are several other factors that combine and contribute to creating detonation. There are ways to run dramatically advanced timing but the average modeler does not have the machine tools or knowledge base to measure and modify various head dimensions and piston relationships.

RE: Why does it do it?
 

After rummaging around the shop last night I found a plastic proctractor to check the timing. It appears to be about 45deg. That would explain the problems. I am going to re-check and set it this evening and run it if I get a chance. It gets dark so darn early here. About 4:45. By the time I get home from work time is short for much work outdoors.

RE: Why does it do it?
 

Shoot, sounds like a good reason to take the day off. :):):)

RE: Why does it do it?
 

Appears to have been the timing. I finally got time to try it today. The timing was about 45deg. I moved it to 28deg. Had to extend the slots in the pickup to do it, but I finally got it where I wanted it. Fired right off and ran great after it warmed up. No missing or sputtering. Didn't seem to burn as oily either. The final test will be flying it, but that will have to wait til at least Thanksgiving day. No time off til then!!! Thanks for the help.

RE: Why does it do it?
 

The slot thing troubles me. Seems that every Chinese engine manufacturer does one of two things wrong on their engines. The first is failing to use the right math to determine the correct location for the timing magnet. The second is to use a sensor bracket with adjustment slots much too short to achieve the correct timing. There's also a third. Failing to establish the correct hole positions for the sensor bracket screws.

RE: Why does it do it?
 

I second that Pat. I gets to be a pain in the butt when they do it over and over and never seem to learn.....

RE: Why does it do it?
 

I slid it over and it stopped about 31 or 32deg. To get where I felt like it should be, I had to take out about 3/32 of the plastic. Somewhere there has to be an engineering drawing for the machinist to use. They had to set it up in some sort of jig to drill it. Just as easy to set it up right as off a little. Maybe they are on piecework. TBM says SV make all kinds of motors for snowmobiles, chainsaws, etc. Must be some crummy running snowmobiles over there.

RE: Why does it do it?
 

Finally got a chance to fly it on Sat. The timing was the problem. The SV50 screams with a 22x10. I might try a 23x8 to slow it down some on final. All it needs is a little breaking in and carb adjustments as I go along. Starts great and the 74in Extra will leave the ground at half throttle. Seem like they should put the timing check in the instructions that come with the engines. Something like: "Our manufacturing methods are sort of hit-and-miss. Please adjust the timing before running. We hope it falls somewhere in the adjustment range of the switch." Actually I had made a mental note to check it, but when it halfway ran on the ground, I let it go.