1QwkSport2.5r

I'm not familiar with guitar tuning, but what I'd get from that is basically tuning from a loose string tighter?

In any event, it's always better to start from a rich needle setting and work leaner. And yes, I've heard of flooded mufflers causing the engine to run backwards. That's one of many reasons why I never hand start 4-stroke cycle engines. Getting whacked by the prop hurts; an electric finger prevents that from happening to me.

avinut

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This thread is overworked. Go back to my original post and DO IT. All the other stuff, though true, is academic. You will throw props lean, rich, inverted, or any other way until you do the over tightening trick.

Hobbsy

My Feedback: (102)

Perzactly.

LarsL

Nothing academic about "the other stuff." Dave's real issue was that he was too lean. The result was that the engine would spit the prop. He said the engine would start to knock and that he had the high speed needle leaned to only one turn open. You don't get knocking from being too rich and one turn open is not too rich. Dave can tighten the prop until the cows come home but his engine still won't run right.

Lars

cublover

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mounted inverted??... your mix is to rich.. the fuel getting in the cyl is to much causing the lock.,... I love saito,, and all have run a bit lean.. 15% nitro 16% oil...OS F... PURRRRFECT combo...

Tommy_Gun

The ONLY reason you will throw a prop from a rich mixture, is by using and electric starter on an engine that is hydraulic locked. The electric starter then works to loosen the prop nut. The other really bad thing that can result in this situation is bending the connecting rod.

This is a totally different problem from the prop coming loose WHILE running from a LEAN condition.

I swear, some of the 'tude conveyed by a few in this thread is beyond belief.

Good Luck to the OP, I sincerely hope he is able to separate the wheat from the chaff with respect to the different bits of advice he is getting here.

BobH

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I have the Saito 150.. inverted.. it runs Perfect!! just set the carb right and that takes care of any issues.. Doing that is pretty elementary.. run it until its peaked and back of a few hundred rpms. Easy peasy.

Red7fifty

My Feedback: (73)

I had an O.S. 91 Ducted Fan engine wayyyy back.....new, I ran a tank of 10% Nitro (If I remember right) and it ran great on it's first tank. Took it out to the field, and filled tank with 15% Nitro, and after start, it would do the same "Bang STOP" thing the OP described. I figured out, this engine was not tolerant of the extra 5% nitro. Dropped the nitro content, and problem went away.

avinut

My Feedback: (2)

Finally ! a reasonable post. (Red750)

1QwkSport2.5r

I think a lot of the posts in this thread are reasonable. I don't think over tightening a prop is reasonable. The sensible thing to do would be to get the prop good and tight and use a lock nut, or actually a jamb nut. Harry Higley & sons make thin jamb nuts for 4-stroke cycle engines like what I pictured below. This is what I use on my 4-stroke cycle engines and have not had a prop come loose on me since I started using these.

1rcelectric

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I have several Saito 150 engines and never had what you are describing happen. First, check the valve clearance. it should be no more than .002. Additionally, change your fuel to 20 or 30% nitro. 30% preferred. If you do this, I think you'll be without any problems.

Hobbsy

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The Saito supplied gauge is .0039". That's all I use. 10% nitro methane in the fuel is plenty and both 5% and 0% are good too.

Red7fifty

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How do I unsubscribe? lol

2walla

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A disabled friend of mine loved saitos and i was the one that always started and tuned them. I have broke in at least 10 120-180 sized saitos for him and own 3-4 myself. It is too lean period. Recommend you run it on the rich side until it is broken in or you will deadstick. After a gallon or two it will loosen up and you can lean it more and the fuel consumption will drop noticeably .


Amazing how many will offer bad advice and stick to their guns till the end.

jeffEE

My Feedback: (5)

And as to the nitro %. Saito recommends 20 % nitro with at least 18% oil. And suggests that up to 30% heli fuel be used to help with the cooling. More oil, more cooling. This is what Saito recommends. At least in the big motors, 150,180, 2.20. I have owned all 3 of the big motors and am still running 2 of the 2.20s. The idea of peaking the rpms and then backing off 500 rpm is good, but on most 4 strokes, it is hard to hear the rpm drop. Use a tach, get it correct. And if its throwing props after its running, its too lean. But I think that has been established.

cublover

My Feedback: (47)

So... let me get this straight.. when its to lean, it throws a prop?.. is this because of a "backfire" That's the only way I can think it would throw the prop... I am or would like to think a hell of a Saito guy'... When it comes to 4 strokes.. I have run them all!!.. I love em.. but it seems like a good 90% of you guys are saying lean...just wondering what I have been missing here.. I have never had a real lean run..Id like to think I set them right.. but I have seen them lock because of to much fuel."Inverted mount",.even when running... and throw a prop,"loading up". I had a YS that did it all the time... not happy..... went back to Saito..lol as far as nitro goes..I know a TON of people who say high nitro content is needed... welllllllllllll,,, not true...unless your at 8000 ft alt. High nitro HELPS power,, but does not make ALL power in your engine.. Nitro brings in Oxygen to the mix, helping combustion. I might be lost here,, so I thought id get all the pros here to help out... When fuel got to the point it was getting to spendy to buy, and needing race fuel, I mixed my own.. So Id like to think I know somewhat of what Im talking about. Why is that Heli's run 30-45% nitro? bet most of you will say it needs more power.. well,,,,Most of us would disagree with ya.. they need cooling!! the engine doesn't get to much air blowing over it, and nitro cools as well as bring in oxygen, or these types of engines would FRY right there inside about 3 min. cars need the same,, as do boats... but back to original post... I'm wondering if he is having a backfire, because nobody asked, and he never said it runs backwards for a split second, and die's. If that was the case,,, then yup... LEAN would cause it... if not,, then the engine would be rich.. if it just locks... it is filling the cyl to much for it to burn and be expelled from the exhaust. Or am I just simply wrong here?

LarsL

Goodness gracious, do some of you people not read any of the OP's posts on this??? He said he has gotten it running in his words "perfect but when he gives it throttle, it stops spitting the prop. So there is no way on God's green earth that there is a hydro-lock of fuel (by the way he has also posted that his engine setup is in an upright position).

Dave must be laughing at all of this right now. I do hope that you let us know how you have gotten on with it when you are done Dave.

Lars

Hobbsy

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None of the advice above is bad, just different because everyone's experience is different. If you use the back flip method of starting and get a Saito rich, when you flip it backwards and it's too rich it will fire forward and then kick back removing the prop or loosening the nuts as surely as too lean will. It has happened to me on more than one occasion and others as well. So, don't burn your halo too bright or you'll burn it out.

[email protected]

My Feedback: (29)

Saito 150 great engine. Don't use 10%. It will knock and run like crqp. I use 30% Helicopter fule .
Also invest in a true turn spinner for 4 stroke engines. They have that extra knurling to grab the engine and prop. .
With mine I also run a perry pump. (The fuel tank is lower then the engine ) needle settings. Start rich on the low end high end. I know the high end on mine is 3 3/4 turns out. When mine fund through the air it looks like a smoke stream especially from mid to low end.
Good luck !!!
Van

LarsL

No halo here, I just read all of Dave's posts and paid attention to the information he provided. He let us know he has been in this hobby for 36 years so he has experience and is not a newbie. He told us about his fuel, his glow plug, his engine orientation, his high speed needle position and what happens just as the problem occurs. He specifically asked for help on where to start his needle positions. He didn't mention anything about back flipping the prop or hydro locking, but he did add that the engine "cranks up perfectly every time" which tells me he gets it running just fine.

The two biggest clues he provided were that he indicated his high speed needle was one turn open from closed and that he was experiencing knock. Those spell lean. If however he had said that the needle was something like 5+ turns open and that the engine was sputtering, I would have thought rich.

As others including I believe yourself have stated, on the high speed he should start out 3 1/2 - 4 turns open. On the low speed the top of the screw should be even with the top of the throttle arm. From there at full throttle, he should slowly lean the high speed needle out and I suggest using a tach as with a 4-stroke it can be more difficult to hear the rpm's drop when it is starting to get too lean. Richen it up 200-300 rpm from its lowest point. Do all of this on a test stand as you also suggested. When he knows it is running great and transitions well with no backfires and spitting of props, transfering the engine over to his plane, he should only need to perhaps make some small tweeks. I myself would start over as I described above.

Lars

jeffEE

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And stand well out of the prop path...jut in case.

Hobbsy

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Dave mentioned kick backs but called it locking up, I mentioned scenarios where kick backs can happen, that should be a good thing.

Sport_Pilot

Sounds as though it is knocking, eventually bad enough to throw the prop. A richer mixture may or may not help but even if it does that is not the best solution. Better to do one or more of these basic three things.

1. Use a colder plug.
2. Use lower nitro fuel.
3. Use a smaller prop.

flyerdave

My Feedback: (212)

Finally had time to get the engine out of the plane and on a test stand. I backed the high speed needle out to 3 1/2 turns and started the engine, ran a little rich but NEVER kicked the prop. I leaned it just a little and it is now running like a dream, doesn't kick the prop and goes from super low idle to full throttle instantly. You all were right, I was trying to run it way too lean. Thanks for the advice. Now I can't wait to get it back in the WACO and try it out.

[email protected]

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No Use 30% I have used 50 also a bit overkill but 30 works best