No CHT, high EGT, and a fuel leak

Thu, Aug 25 2016 10:31am CDT 1
Josh Jones
Josh Jones
10 Posts
Hi folks,

I'm currently testing my Simonini Mini 3 engine (Bing 54 carb). This engine had only 6.5 hours on it when the trike it was on crashed. Since then, I've had the engine dismantled and checked out, installed a new prop (identical to the old one), and hooked the engine/carb up to the new trike. No settings have been changed from the previous installation. The cables, wiring, fuel lines, EGT/CHT sensors, prop, etc are all new, but it's virtually the same setup I was running previously without issues.

But now, I'm running into a few snags as I do my ground testing. I contacted Bing and Simonini a couple weeks ago and have not heard back. Perhaps the Trikepilot community at large can help point me in the right direction.

First, I'm not getting a reading on my Falcon CHT gauge. I've tested the resistance of the gauge (good), the millivolts on the wire terminals coming from the sensor to the instrument when heating it with a torch (good), and the temp goes through the roof when I have it hooked to the instrument and heat the sensor with the torch. But after putting the sensor back under the spark plug and running the engine for 10-15 minutes, the needle barely goes over 100 degrees. I'm about ready to give up on it. I've read in multiple places that for two-strokes, the CHT reading is basically worthless and unnecessary. Is this true?

Secondly, I'm getting high EGT readings in the mid-range during ground testing. According to Simonini, EGT temps should never exceed 1100 F. I've hit 1100 easily and 1150 when backing off the throttle. It seemed as if I would hit 1150 consistently had I stayed on the throttle in the mid-range. At full throttle, it cools down to 1000 F.

I tried moving the clip on the jet needle. This lowered temps in the mid-range to 1000 to 1050 or so, but it also seemed to run a little rougher and built up carbon on the spark plug. Also, when running this test, I noticed a steady drip/almost a stream of fuel running out the bottom of the air filter and coating the prop.

I have since put the jet needle clip back where it was. This slowed the fuel leak to a slow drip. I noticed when I cleaned the air filter before I ran the engine that the bottom side was stained, so I guess some leaking had gone on last year before the crash. Is some minor fuel leakage out of the air filter something considered acceptable and normal or is it indicative of the problem with carberation?

I'm not sure what to do about the high EGT. I suppose the first things to do would be to test the EGT probe and read the spark plug. Sound right? To test the probe, I plan to use a digital candy thermometer and a propane torch. I'll compare the reading of the thermometer against the probe/gauge. When it comes to reading the spark plug, I'm definately not an expert. So here is a link a few pictures of the plug after running for fifteen minutes or so and at times reaching/exceeding max temps on the gauge.

https://www.dropbox.com/sh/m4o8296lfbgok6r/AAAJoUZZihknRHgrxjrO9KTua?dl=0

Thoughts anyone?
Thu, Aug 25 2016 12:23pm CDT 2
Doug Boyle
Doug Boyle
168 Posts
Hi Josh, You're on the right track for 2-stroke troubleshooting; although, I know nothing about your particular engine! Some things to remind yourself of are: reading the plug is the only sure fire way of knowing what's happening inside your engine. To be accurate, don't let the engine idle before you shut it off to read the plugs.

Also, too much/little pitch can send your EGT's one way and the CHT's the other. Gauges/senders are notoriously problematic/inaccurate, but do provide baselines and trends. Old floats can leak and get heavy/soaked and throw off the float bowl levels (fuel should be about halfway with floats removed). Dirty air cleaners will make your engine run rich. Always verify all of the numbers on all your jets, and check the charts for proper sizing for your environment. Carb cleaner is tough on o-rings, so don't subject them. Sometimes it is necessary to use weld tip cleaners to return the orifices to original dimensions after storing wet, but be careful when using. Verify compression and seals; the engines dislike air leaks. Don't assume the plugs have the correct gap; Ducati ignitions have weak sparks and work best with small gaps (.014-.018). Don't use screw on caps, but rather, solid caps on plugs. Use air-cooled oil, not outboard oil. Synthetic oils are wonderful but provide no corrosion protection for your crank. Consider mineral oil rated to API-TC or JASCO -C. Fog your engine/carbs when storing for any length of time and seal off the intake and exhaust.

Thu, Aug 25 2016 09:24pm CDT 3
Josh Jones
Josh Jones
10 Posts
Thanks for the reply, Doug. Lots of good advice.

Before I took the pictures (click on dropbox link above to see plug), I shut the trike off without idling. So the pictures should provide an accurate representation of what is going on in the engine.

My prop shouldn't be part of the problem. It is identical in size/pitch as the one that I ran with before the crash. My floats are virtually brand new (the engine only has a little more than 8 hours on it). Perhaps it's possible that something was jarred and messed up inside the carb during the crash? Part of my air filter is wet with fuel/oil, but if it was causing a rich mixture, I would think my EGTs would be lower. I need to take apart my carb and confirm the numbers on the needle jet and jet needle to make sure they are what Simonini recommends. Compression and seals should be good as compression was checked and seals replaced by the mechanic when he checked out the engine.

I only use Pennzoil 2-cycle air-cooled engine oil. But I think that has been discontinued. Aircraftspruce is selling Quaker State air-cooled engine oil in its place. I assume this is a suitable replacement, but I still have some Pennzoil left. I need the corrosion protection considering my hangar can get awfully humid. I'm planning to fog the engine and plug the intake and exhaust. I've learned a lot by watching the 2-stroke videos on EAA's website.

I discovered that the candy thermometer doesn't go above 400 degrees, so I my previously mentioned idea to test the EGT thermocouple and instrument won't work. But I found this link.

http://www.mglavionics.com/kb/article/AA-00228/0/Is-my-EGT-probe-reading-correctly.html

I like their idea of using a candle to test the EGT. I'll try that tomorrow and post the results.
Thu, Aug 25 2016 10:54pm CDT 4
Bill Chance
Bill Chance
19 Posts
First, you shouldn't ever have fuel dripping from the air cleaner. Need to fix that problem first. Probably a float problem. Float may be stuck allowing fuel to flow back into the intake part of the carb. Raising the needle allowed more fuel into the cylinder causing a drop in temps. Dropping the needle back down keeps less fuel from entering the carb throat and running back into the air cleaner. You have to address this problem before working on the others. Pull the bowl and make sure the float needle is not stuck or has some trash under where it seats. Check to see if the floats are good and floating in the bowl. Run the engine to get it good and warm then shut it down. Carefully pull the bowl off. The fuel level should be about 1/2 inch from the top edge of the bowl. You can see fuel buildup on a 2 stroke engine air cleaners after they have been ran awhile so that part was normal but they shouldn't be saturated by fuel.

When you run the engine at full throttle you're running on the main jet. If you're seeing 1000' F I would go up to one size bigger.
At 1/4 to 3/4 throttle the mixture is controlled by the needle and the needle jet. Some 2strokes can be jet sensitive. Even if your buddy hadn't dropped it in, what worked last year may not work now because changes in temp, humidity, air density, etc.

Be careful with that torch. It's best to test the probes in heated oil. CHT's can be an good general indicator but usually aren't fast enough to save a piston. By the time you see a dangerous big rise in CHT a few seconds later you have a holed piston. Go by what the EGT reads.

Because of the additives in modern fuels most experts don't put much faith in plug readings anymore but they can get you close. Watching the EGT temps can get the mixture right.

The only Simonini I've been around didn't have a Bing on it and the initial jetting chart I have for Simonini is for the type 84 Bing. Call the Pro Carb Shop in Council Grove, KS. 800 309-2464 to order some jets after you see what jets you already have. Order their tuning & parts manual. It's cheap and will help you alot. They also have a tech help line 620 767-7844. They charge for info but if you order parts on the 800 number they will usually answer your questions.
Fri, Aug 26 2016 06:39pm CDT 5
Josh Jones
Josh Jones
10 Posts
I just got back from doing some more engine testing.

First, I used a candle to test the EGT gauge. It wasn't a very big candle (the flame was pretty small), but I got the EGT gauge to read 890 F or so. So I'm guessing my EGT gauge is representing my actual EGTs pretty accurately.

I pulled off the float bowl and confirmed that the float arms were parallel with the carb body. I also removed the float needle to confirm that it wasn't worn or that dirt was preventing it from sealing.

Next, I removed my main jet (185), needle jet (2.78), and jet needle (11K2) to find out what sizes they were.

After this, I put everything back together. I also confirmed that my vent hose wasn't plugged.

Finally, with the air filter removed to observe the inside of the carb, I warmed up the engine and ran it from idle to just over half throttle. The EGTs stayed around 1080 to 1100 from 1/3 to 1/2 throttle, but once I went beyond 4000 RPMs, the temps started creeping up above 1100. At this point, I throttle down enough to bring the temps to 1080 and then shut down the engine. The spark plug looked identical to the pics linked to above.

Concerning the fuel leakage, from the seat I was able to see a small, intermittent stream of fuel running down and dripping out of the vent hose around 1/4 throttle. As I throttled up higher, this seemed to slow considereably. My dad was watching the carb throat and was able to see fuel running out where the air filter would have been. This too seemed to slow as I throttled up.

I pulled the float bowl off. The fuel level was a little more than 1/4 inch below the top of the bowl and about 1/2 inch below the top of the bowl with the floats removed. Is it just a case of having too much fuel in the float bowl? If my float arms are parallel and the floats are moving freely, shouldn't the fuel level be fine?

I ordered the tuning and parts manual from Pro Carb Shop a few weeks ago and have been referring to it. I've emailed Simonini about which needle jet, jet needle, and main jet should be in the carb under normal circumstances. Hope to hear back from them soon. I may need to change my needle jet or jet needle. Perhaps I'll give Pro Carb Shop a call and see what they recommend.

Bill, you said if my full throttle temp is 1000 F, you would go bigger with the main jet. Do you mean smaller? I believe the ideal temp range is 1020 -- 1080 F. Wouldn't a smaller main jet lean the mixture and increase temps in the 3/4 to full throttle range?
Fri, Aug 26 2016 10:03pm CDT 6
Bill Chance
Bill Chance
19 Posts
Bigger jet=richer mixture=cooler temps. 1000'F is awfully close to 1100'F. Keep in mind the gauge is calibrated for 70'F at the cold joint of the probe so rising and falling air temps throws the actual EGT temps off from what the gauge reads. I err on the running richer side.

From what your describing you still have a fuel level problem. I bet your father was awfully nervous with that prop spinning so close. One of those " how about I sit in the seat and YOU look" moments. Bend the float tang and get the fuel level correct. With the air cleaner off you will get a leaner mixture.

Do you have a choke or do you prime it?
Sat, Aug 27 2016 11:22am CDT 7
Josh Jones
Josh Jones
10 Posts
Bill,

I'm sure you have more experience than I do, so I respect your opinion. Please bare with me. You mentioned previously that the EGT temps could be used to get the mixture right. Considering how fine-tuned the mixture needs to be, EGT readings would have to be considered quite reliable if they are to be used to get the mixture perfect. But then, you stated that in your opinion, a reading 100 degrees away from max temperature is not to be trusted and justifies going to a richer mixture. Seems to me that if an EGT gauge is assumed to be at least 9% inaccurate, it should not be used to fine tune the mixture.

Forgive me if I'm wrong, but isn't it ideal to run a two-stroke as hot as possible without exceeding max temps? If you are too rich/cooler, won't that cause carbon buildup and all the related issues? Isn't a two-stroke's happy zone pretty narrow and hotter rather than cooler?

Don't worry...Dad could have gotten a better view, but he was stayed a safe distance from the prop. I figured having the air cleaner off would make noticeable difference in EGT, but it didn't seem to. I did notice that the carb is parallel with the engine, which is angled toward the nose of the aircraft when parked on the ground. In flight, the engine/carb would be horizontal and the carriage angled upward. On the ground, perhaps this foward angle of the carb (thus, fuel level higher on the one side of the float bowl), combined with vibration and perhaps a slightly high fuel level, is causing the fuel to leak out of the air filter and vent hose. But like it says here ( http://www.trikepilot.com/magazine/read/adjusting-the-bing-carburetor_755.html ), when I removed the floats the fuel was very close to 1/2 from the top of the float bowl. If I lower the fuel level in the bowl, this will cause a leaner mixture. Not something I need, considering my temps. And why did the leaking get worse when I moved the jet needle clip 1 notch richer if the problem is with the fuel level in the float bowl? Hmmm...dunno. I'm game to try adjusting the float arms though.

I do have a choke. When I was running hot in the mid-range, I tried giving it a little choke, but I had a hard time accomplishing that. It started running rough almost immediately, almost like the choke was all or nothing.

Pro Carb Shop sells a Colortune spark plug. Does anyone have experience with that? Perhaps that would be the best way to get the mixture right.

What I'm leaning toward doing now is adjusting the float arms slightly to reduce the amount of fuel in the float bowl and installing the next size larger needle jet (2.80) to reduce temps across the mid-range.

Sat, Aug 27 2016 02:12pm CDT 8
Bill Chance
Bill Chance
19 Posts
No problem Josh, I'm not offended at all. The EGT is all most of us have so that's what we have to use. If you have motorcycle or snow sled and you have engine trouble you can just pull over. But I err on the rich side of things with my plane as I can't pull over, I can only go down. Plugs are cheap to replace and a little carbon build up is going to occur over time anyway. Your right, max power/ HP out of a 2stroke is when the engine is running as lean/hot as it can stand. But max power temp and kaputski temp are very close so that's what I meant when I stated 1000'F would make me nervous. Actually the 1100'F number from Simonini is conservative as damage occurs/can happen beyond 1200'F.

Your on the right track as the first thing you need to do is address the fuel leaking per page 14 of your Pro Carb Shop manual. Fix one thing at a time. Bend the tang, not the arms. The tang is the flat piece the float needle hangs on. The leaking got worse when you went richer because raising the needle (lowering the clip) allowed more fuel to enter the throat out of the bowl. For now don't worry about the fuel level in the bowl being to low causing a lean mixture (Unless you go to far with the tang bending). Your not going to use use fuel at a rate running at 1/2 -3/4 throttle that the pump can't keep up with.

Rule of thumb. When you pull the choke at any engine speed/throttle setting and the engine runs better your too lean. Its really not a choke, its an enriching circuit, but commonly called a choke. When the engine sputters it's too rich or running right at rich. When it was running hot, pulling the choke should have made it better.

With such low time on your motor I assume there is no gunk buildup in your carb. All the air and fuel passage ways are clear? The guy I bought my trike from had several trikes and claimed he had never flown mine. He bought it on a whim I guess. The one time he tried to fly it he cranked it up and fuel was pouring out the air cleaner so he shut it down. I cleaned the carbs and never had any problem. The engine ran rich for months and couldn't get any heat buildup. Like you I was worried about carbon build up. Kept jacking with the mixture to get the EGT temps. The weather changed and finally got the midrange temps too high and couldn't fix it by moving the needle. Had to fly around at WOT to cool the engine as the main jet was right but burned lots of fuel and had to pull in all the time to keep it from climbing until I changed the needle jet.

I thought about the Color Tune but you have to look down into the thing to see the flame. And for me that meant standing on a stool or ladder with my head 12" from a spinning prop with someone sitting in the seat with their foot on the brake. No thank you.

As far as plug reading. When I use Iriduim plugs they always look black and sooty no matter what the mixture. When I use regular plugs I can see some color change even though so called experts state you can't always go by color any more. But they also use engine analyzers which are pricey to own.

Fix the fuel leak first then work on the jetting problems. Good luck and report back you findings
Sat, Aug 27 2016 02:22pm CDT 9
Bill Chance
Bill Chance
19 Posts
Josh also check that the needle clip is under the plastic plug inside the slide. As many as I have worked on I can't believe I did that once.
Mon, Aug 29 2016 12:03pm CDT 10
Josh Jones
Josh Jones
10 Posts
I sent the pictures of my spark plug to Chuck at J-Bird, and he thought it looked like the engine was running a little on the rich side. He questions the accuracy of my EGT gauge. He was also surprised by how low Simonini's max temp is, saying most engines max out at 1200 or higher. One of the first things he would have tried was moving the clip on the jet needle, which I did. This effectively lowered the temps, but also caused symptoms of excessive richness. If the engine was truly lean, would moving the jet needle clip one notch make it too rich? If the engine is too rich when the temps read okay, then my gauge must be reading too high. Right?

He agreed that adjusting the fuel level in the float bowl will probably fix the leaking problem. He said he dismantled and cleaned the carb when he had it this spring, so it's doubtful that there is any gunk plugging up the carb, especially since I flushed the fuel lines and fuel pump before hooking up to the carb.

I ordered a Colortune sparkplug. I don't think I have to worry about getting a haircut using it. It comes with a plastic tube that fits over the sparkplug. This tube has a angled mirror at the top allowing you to see the flame from the side and keep away from the prop. I'll just have to make sure this tube stays on and doesn't get sucked into the prop. Also, I'll have the trike tied down and braked so it can't go anywhere. Perhaps I'll have a better idea what's really going on in the cylinder once I try this gadget out.

Sun, Sep 11 2016 11:39am CDT 11
tom speirs
tom speirs
59 Posts
What oil ?what ratio ? I always run motul 800 at 1.5% /66.1 never had a problem I fly ppgs as well . More fuel cools thing down more oil heats up and fouls the plug so most lean it out to get it to rev and then pop goes the weasel . Agree that EGT is the one to watch
You could always try some of true Ppg sites for info ...and learn how to read a plug
Ps color tune never helped me out
Sun, Sep 11 2016 05:40pm CDT 12
Mark Pansing
Mark Pansing
4 Posts
Let us know how the Colortune works out. Like most everything on the Internet, some say it works and others say it's a waste of time.
Thu, Oct 13 2016 02:36pm CDT 13
Mark Pansing
Mark Pansing
4 Posts
Any updates on the Colortune?
Mon, Dec 5 2016 01:51pm CST 14
Nick Axworthy
Nick Axworthy
9 Posts
Josh hope you dont mind me butting in on your post.

I fly a British Mainair trike with a 503 dcdi.

Hi guys trying to sort out a high EGT temp on an old British 2 stroke motorbike single cylinder.

This bike is near 45 years old.

Fitted an egt to help me decide if the carb is doing its job and I am not going to melt the piston...only got the bike a few months ago.

Anyway the prob I am having is the EGT if fine up to 45mph on aproching 50mph if I ease back on the throttle the EGT rises rapidly and will go over 650c if I let it...

This is on about half throttle...if I lift the needle one slot the engine will stutter a bit and tend to 4 stroke and defiatly shows signs of being rich...and the engine still has this high egt on easing down on the throttle at higher speed.

I did try pushing the engine hard past 50mph and as long as its working hard the egt is fine...gently ease down and the spike...the piston did nip up last time I tried this...so it confirms I am working with high temps.

Any ideas guys....I have tried all I know from tuning my twin bings on my trike but I have run out of ideas.

Nick.

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