Air leak test (bubble found around flywheel bearing)

[militarymaxx]

I did an air test where I plugged the carb, the exhaust port, hooked up some fuel line to the HSN side and blew. I get very tiny bubbles coming out around the center of the bearing behind the flywheel. Compression is great and I never get any oil blow by from this bearing. I am running a little on the hot side (260 ish)
and thought I was sucking air from somewhere. I've heard of this bearing sometimes leaking oil normally and if so, that would make it 'non air tight', but what about the small air leak ?

 

[SkyMaxx]

Sometimes that bearing does leak oil. If the system were a dry system, then it would also produce an air leak. The problem with your test is that you plugged all outlets for the engine. The air you put in will go the path of least resistance. In this case, it forced itself out the main bearing. You must have blown pretty hard to make this happen.

Note, 260 is not on the hot side of anything. 250 - 270 is generally thought of as a sweet spot for most engines. So you are actually running just fine. Any cooler and we would have recommended leaning it out a little to get more performance. Any hotter and we would have suggested to richen it up.

My question is why conduct this test? Is your engine not performing as it should? Do you have any other negative symptoms that imply an air leak? If not, then tune and go.

 

[militarymaxx]

Over the last few weekends I have been chasing a slightly hi temp. It would start up just fine, run like a raped ape, temps would be around 250ish and then they would jump up to 300 as the tank emptied. I know that as the tank empties it creates a lean condition, and I never let it stay at those temps for more than a few seconds. Maybe it was a spike, maybe it's just lean because the tank was nearly empty. The HSN is perfect. I get a good launch, good smoke, good speed. So I have been richening up the LSN to the point that the needle is out past the end of the collar. The track I run on requires 0-25% throttle. I vary rarely get into WOT. So I figure any overheating problems I have are related to the LSN. So I open it up some more, and more and more. Is it common to have the LSN turned out past the collar end, past flush ? What's the worst that can happen ? I'll richen it up too much right ? I'm looking for temps around 250 at or near the end of a tank. Maybe I'm asking for the impossible.

 

[SkyMaxx]

The only reason you would have the LSN driving a temp issue is if you were continually starting and stopping the engine, continually pumping the throttle between the 0-25% throttle that you mentioned, and the vehicle never moved so a lack of air flow over the cooling head.

I rarely adjust my LSN beyond the factory preset (flush with the collar). If I do it is usually only small amounts in either direction (talking like 1/16 - 1/2 turns at the most).

What engine is this?

Yes, a temp spike is common as the fuel tank empties itself. As you noted, this is caused by the engine going super lean as the fuel flow decreases. What percent nitro are you running? Perhaps you need a change.

The only other cause for concern here is the outside running temps. If you are hitting these temps in the current conditions around Hampton Roads (colder than normal), then you may have your needles a little hosed up despite the performance.

 

[militarymaxx]

I am on and off the throttle quite a bit but the buggy never stops moving. Maybe it needs to move more through the air for better cooling. The motor is an RB Concept economy 1003-E. It's their basic entry level engine. I want to run something by you, tell me what you think. My fuel tank cap is wearing out and on medium to hard landings it will open enough to spill fuel out. I'm thinking that when the lid opens I lose most or all of my pressure and the loss of pressure is giving me a lean condition. I've looked at the track and where the jumps/bumps are at and I'm thinking that the cap is opening enough to where pressure never really builds up enough in the tank to give good flow. What do you think ?

 

[Chevy-SS]

woohoo! Methinks you found a problem, no doubt. If the tank ain't got the pressure, then the engine ain't got the fuel. That means LEAN. That pressure acts like the fuel pump in a real car.

Fix the cap seal problem and then post new running temps here so we can all see if that was the cure.

 

[NooP]

Thats got to be a no brainer. If the cap is openeing from time to time, its probably not even holding pressure at all. Get a new tank and bash away.

--NooP

 

[militarymaxx]

Got some good news and some bad news. The good news is that I installed a new tank and with the LSN/HSN settings I had, I was very, very rich on both needles. That supports the loss of pressure/lean condition theory. So things are tight now. The bad news is two-fold. In the process of trying to start things I flooded it real bad, over and over. My fault for not going back to the factory settings and starting from there. In the process I drained my starter box batteries. My fault again for not bringing spares. So, I'm back at the house charging batteries (my fault still for not bringing the charger and using my car battery to charge). I'm going back out, with the factory settings, and plenty of stick packs for the starter. More to come.......

 

[SkyMaxx]

Glad to hear that you isolated the problem. Sorry to hear about the other issues. Call it the domino affect. At any rate, once you have nailed down the other issues you should be good to go.

The track you speak of...is it the one at NAVSTA Norfolk? If so, gonna be there this weekend (Saturday)? I was thinking about running out there tomorrow or Saturday...if the weather holds. Perhaps we can hook up and compare notes.

 

[militarymaxx]

Yes, the track on base just up from the hobby shop. I got things running, at least close. No fuel spillage at all, so I have that fixed.
I'm still trying to get that 240-250 temp range but it just seems to hover between 275-300. The high end seems good. From a standstill I punch it, get a puff of smoke and off she goes with no hesitation and good power right up to peak RPM's. So I leave it alone and kept playing with the LSN. Since I'm using only 1/4 throttle for most of the track I'm guessing my temp solution can be found in the LSN. I know I'm close because when I first started this evening the temps would get over 300. As I richened the LSN they would come down some. I guess I just need to open the LSN up some more. Another thing I have to address is the idle. The idle screw is set for the .8 to 1 mm opening but after running a few laps on the track it will idle for maybe a few seconds and then the RPM's just slowly drop off and it dies. It fires right back up but it won't idle like it use to. I can't remember if that means the LSN is lean or rich. Anyways, hope to catch you out there either tomorrow or Saturday (weather permitting).

 

[SkyMaxx]

What time you planning on running?

As for the LSN, I'd seriously consider leaving that needle alone. Your solution is most likely going to be found in your HSN. As for the idle set screw, I run mine a little wider of a gap and things seem to be okay.

If you get good acceleration off the line, the LSN is probably just fine. You get more temp control out of your HSN adjustments.

 

[militarymaxx]

Friday is typically an early day (noonish). I'm usually out there shortly after 3, but if the weather is good, I might be out there earlier. I really want to get this thing resolved.

This is what I had for settings at the end of today:
HSN - 1.5 turns out
LSN - 7 turns out

The factory settings (which RB says is on the rich side) are:
HSN - 3.5 turns out
LSN - 5 turns out

I put everthing back to factory. I think you're right. I was trying to richen everything up with the LSN when the HSN was probably a bit restrictive at 1.5 turns out. It makes sense. I can't richen up the LSN side when the HSN is almost closed. So I will start things off with the factory settings and go from there.

 

[SkyMaxx]

So, you will be at the track around noon? Or you get off work around noon and will be at the track around 1500?

Trying to narrow down the window for my own play time.

 

[militarymaxx]

Noon sounds good. Might as well make a long day of it. There's another guy that works for me that should be there as well. He has a T-Maxx with this .18 sirio and a new MBX he just picked up.
The track is a little dusty and my carpenter crew just built a nice table next to the stand. We also sprayed some weed killer to keep the growth down. If it wasn't for self-help, I think it would just overgrow and be forgotten.

 

[SkyMaxx]

You work in the hobby shop? Cool. Seeya around noon.

 

[militarymaxx]

No, I work at SIMA (1st LT Dept.) so I have access to just about anything. Mowers, trimmers, weed sprayers, lumber, etc. Since I consider maintaining the track a self-help project, I can justify the materials. Rgr, see you at noon.

 

[Chevy-SS]

Cool that you guys can get together like that. Be sure and post the results. I'm curious to see.

 

[militarymaxx]

Just want to wrap this thread up. Don't want to leave Chevy-SS hanging. Yes, the leaking tank was the culprit. No tank pressure caused the engine to starve for fuel and that had me chasing a lean condition. So, with a new tank, factory settings in place, (and a little help from SkyMaxx), I'm golden again.

 

[Chevy-SS]

Thanks for reply mm. I will file that under "troubleshooting". Glad to hear it's fixed.

 

[Waste Land]

240 to 270 is peak performance? Oh yeah more power for back flips I'm runnign like 210 or 220