RE: Saito 125 poor performance problem
 

Hi Guys,

Oooo, it's a feisty one!

A quick recap on what I have done.

Firstly, yes I have tapped into the carb body just below the inlet manifold O ring. This puts the nipple probably about 5mm-10mm closer to the throttle barrel than toga toga's. I put it here so that it wasn't an additional mass on the manifold itself, which had previously caused me problems on an 82a. The inlet manifold has a little nick filed in it to clear the end of the nipple, but this is all on the "sealed-side" of the O-ring.

Secondly, the problem isn't a lack of raw power. From a cold start or after a lengthy idle, the engine pulls 8800rpm on 16x6 or 9800 on a 14x8. If the inlet air flow was being significantly affected, it wouldn't be able to do this. Its the fact that it dies off by upto 1000rpm after >5seconds that is bemusing, and that once it has died off, HS needle adjustments will richen or lean the engine as expected but won't restore the performance.

Yes, I've gone back to the original muffler and run with and without muffler pressure. I've also removed the nipple and blanked the tapped hole with a bolt cut to length to be flush on the inside face. No change in behaviour. You're right I should try a new carb assembly and inlet manifold - I'm sure JD Haytree to whom I've sent the engine will do this if he can't find anything else wrong!

I agree with the need to adjust Saitos properly, which I argue is actually another way of saying that Saitos actually respond manageably to HS and LS needle adjustments which is more than some other engines. Also, it amazes me how long it takes a Saito to bed in - I had to keep gently adjusting the LS needle on my 82a for about the first 10 hours of running to keep it set sweet. Some of this I attribute to me running in on synthetic oil fuel rather than a predominantly castor-based fuel. John Haytree also advised on the needle interaction, and I have tuned the LS needle as well as the HS.

The one mistake I made, and it's a big one, is not running in before modifying the engine. I guess I have just become complacent with how good these engines always are and how well they run out of the box. Lesson learned!

So now I wait. Not sure when John Haytree is working over the festive period, so it may be the new year before he has a look at it.


Finally, I have one more experiment. Can someone run a tank through their Saito and put a pot under the breather tube to capture the oil? That'll tell us how much of the total oil in the fuel consumed actually makes it past the ring and out of the breather. I can't do this on my 82a as it currently blows a bit out the front bearing so it wouldn't be accurate. Or I can do it with the 125 when it comes back.

HS

RE: Saito 125 poor performance problem
 

This is not correct. Fuel is injected after the crankcase. Only blow by oil lubricates the YS engines crankcase.

It will still be messy at low throttle settings without a velocity stack. It also assumes that there are dynamics designed into the intake systems of our engines. unless you are talking about highly refined racing engine, that's doubtful.

RE: Saito 125 poor performance problem
 

Y-S engines have a double barreled carburetor. The air inlet side only controls air and as Greg says, the fuel is added as the air leaves the crank case going out the second side of the carb.

RE: Saito 125 poor performance problem
 

Quote:

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ORIGINAL: w8ye

Y-S engines have a double barreled carburetor.
The air inlet side only controls air and as Greg says, the fuel is added as the air leaves the crank case, going out the second side of the carburettor.

---

And this means current YS engines get their bottom-end lubrication, just like other R/C four-stroke glow engines; i.e. using the oil in the blow-by gas, that passes by the piston and the ring.

The intake air could, however, be 'contaminated' by burnt oil and post-combustion gases.

It does not seem to negatively affect the 'physical abilities' YS engines have, though.


And we've all gone off the far end... We're way off subject...



HighSide,


The piston ring gap in your engine seems to be OK for its piston diameter.

I don't think this is the reason for the substandard performance you are seeing from your Saito.


I guess we will all have to wait, until John Haytree can see your engine...

RE: Saito 125 poor performance problem
 

I too have a Saito 125a that has only a couple of gallons of fuel run through it. The vibration is excessive and the prop nuts are very hot after only a few minutes of running the engine. Taking it apart revealed the bearings to be very dry and even a little rusty! I can only assume the crankcase port being in the back plate is causing the oil to be ported out the back and not properly lubricating the bearings (causing the overheating and rust). Could be be a design flaw??? Oh yeah, I too can only get 7900 rpm with an APC 15x8 prop. Should have gotten the OS engine and saved some money!

RE: Saito 125 poor performance problem
 

The hot prop nuts are SOP for fourstrokes of any brand, are you sure you're not seeing 9,100 with the APC 15x8?

RE: Saito 125 poor performance problem
 

What I recommend for all the backplate-breather Saitos is that before the flying season starts, you tip them on their nose and fill the crankcase with oil.

Once the oil starts leaking out the front bearing (and it will), turn the engine so that it's still nose-down but at a 45-degree angle with the cam-box facing down. This will encourage oil to flow into the cambox area and lube the gears, cam and lifters.

It also pays to use a *long*breather tube on these engines so that it's harder for the oil to simply vanish out the breather when the engine is running. This will ensure that *some* of the oil in your fuel makes it to the cambox area.

I've heard of a number of the backplate-breather Saitos running so dry that the camshaft bushes start squealing. My Saito 100 started doing this until I began the start of season oiling procedure I outlined above.

And don't be fooled into thinking you can just dribble some oil down the pushrod tubes the lifter fit is so good that virtually none of that oil will make it into the cambox. The only way to get oil into the cambox is using the method I described or by lifting the cam-cover and oiling directly (a real PITA).

If you ever hear your Saito making a kind of "chirping" noise when idling odds are that's dry camshaft bushes. If it really squeals you've got problems :-D

RE: Saito 125 poor performance problem
 

The method I use is to pump oil into the breather line until it moves the piston to TDC. Pinch off the breather and turn the motor over several times by hand. That will pump the oil into the front half of the case. Open the breather back up and turn the motor over several more times to pump out the excess oil. Works like a charm.

RE: Saito 125 poor performance problem
 

That's one reason I use the Corrosion X Aerosol, it goes everywhere inside the engine as a foam, it even comes out the front seal. No way to have a dry cam, ever. Having had the CX come out through the front bearing on several engines for several years has never caused any front bearing to leak other than while injecting the CX.

RE: Saito 125 poor performance problem
 

Where do you get the CX? Is it something from a cycle shop or a hardware store?

david

RE: Saito 125 poor performance problem
 

I've always noticed that the RPM's come up higher at the first throttle up and then sag down after a few seconds. There is also a post somewhere here on RCU that explained this condition. Ive owned 2 Saito 125's and they would never turn a 16x6 with any authority, not even a 15x8. APC 15x7 works best on this motor.

RE: Saito 125 poor performance problem
 

Would you be interested in trading your substandard Saito 125 to an OS Surpass 120 with pump?

Send me a PM and we'll discuss it.

RE: Saito 125 poor performance problem
 

http://www.corrosionxproducts.com/corrosionxpage.htm

I used to get it from Sheldon's in Calif. but they got bought out, now I get it from CorrosionX.com, same price.

RE: Saito 125 poor performance problem
 

Thanks for the link Hobbsy.

David

RE: Saito 125 poor performance problem
 

This thread made me question the wisdom of buying a Saito 125, after much pondering of sell it off or run it I decided to run it and see what I had.
The engine still has less than 1 gallon of fuel through it but right now here are the numbers
Saito 125, 16x6 MA K series, 8910 peak (sustained) backed off to 8370 for operation.
Before the LSN was set the rpm would surge ~1k over the HSN set point then gradually settle back to the set point.
Once the LSN was set going from idle to WOT produced consistant rpm change with out the overshoot and settling back.
Not sure if this info is of any use to you at all but thought I would post it anyway.
I am at 500ft el, 60 deg F, 24% rel hum.

RE: Saito 125 poor performance problem
 

Quote:

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ORIGINAL: chashint

...8,910 RPM peak (sustained) backed off to 8,370 for operation.

---

Charlie,


This is really unnecessary...

Richen 100 RPM from nose-up peak.


Richening 540 RPM loses you a whooping 17% of the output... Really!

And there is no gain in any criterion!


I have seen four-stroke engine throw the prop, while being adjusted way too lean on the ground...
...I have never seen it happen in flight, after being adjusted properly...

RE: Saito 125 poor performance problem
 

Hi Dar,
I am still just playing with the engine on the test bench, when I said "for operation" I guess that really means I just backed the rpm down to that number for sustained WOT running.
With multiple reports in this thread suggesting that a 16x6 prop is too much for the engine to handle I just had to see for myself. I have always considered a 16x6 as the benchmark prop for 120 class four-stroke engines and if the Saito 125 would not handle it that would have been a real disappointment.
I am very pleased with the engine, I ran it more this afternoon and the rpm was even better than the morning runs.
Towards the end of the day I peaked the engine again and it easily hit 9k, I think it had more to give but I stopped at 9k. I backed the HSN off and finished the run around 8k.
Right now I don't see anything to not like about this engine, it idles below 2k and transitions smoothly to WOT with slow or quick throttle changes, there is no lag when transitioning quickly from idle to WOT. Another nice thing about this engine is how linear the throttle is, small changes on the high end actually affect the WOT rpm, lots of engines really don’t have much sensitivity to minor throttle adjustments near the high end.
I did find it interesting that when the LSN was at factory settings I saw the same rpm surge and settle that the OP has reported. Chances are it is only coincidence, but perhaps a clue is here about his problem.
I will not be able to play with the engine tomorrow but when I run it again I will reset the LSN to factory and see if the rpm overshoot at WOT returns.
Hopefully my rpm figures give the OP assurance of what this engine should be capable of with a 16x6 prop.
I will take your method of HSN setting under consideration, it sounds interesting although somewhat awkward to execute.
Take care.

RE: Saito 125 poor performance problem
 

Sounds like you are getting very close! I do think that your engine will vibrate less if you get the LSN leaned out a little bit further. I posted something about that on the Saito thread.

RE: Saito 125 poor performance problem
 

Charlie, be sure and post some #'s with a 16x6 and tell us what brand the prop is. I am using a MA Scimitar 16x6 right now. My 1.25 will turn it 900RPM more then a APC 16x6. Not to metion the spool up with the wooden MA prop is instant. During flight test the APC 15x6 was better then the APC 16x6.

David

RE: Saito 125 poor performance problem
 

I've not seen one actually throw a prop, but I've seen backfires that loosened the props in the air. The props windmill until the plane lands.

RE: Saito 125 poor performance problem
 

I saw my buddies Saito 1.00 powered Hellcat throw the prop. He changed from 10% PM to a YS20/20 blend without changing the needles. I was test flying it and it threw the prop on the second pass. It landed fine and we actuall found all the parts. That will never happen again. At least not the finding all the parts part.

David

RE: Saito 125 poor performance problem
 

A friend had a Y-S 91 on a L-19 that was smoking a little so he turned the needle in a couple clicks.

Bang! and we were scratch around in the grass looking for the prop nut. Finally he found a prop nut but it had 1/4-28 threads.

He got a new nut and poorly fitting washer at the bolt and nut store the next day.

RE: Saito 125 poor performance problem
 

Hi David,
I almost feel like I am hijacking this thread and I don't want to.
The problem the original poster is having is very interesting and I would like to know what the final resolution is.

I am still just playing with this engine, every time it is run there is an increase in the WOT rpm.
Fuel is 15% Omega and the prop is a Master Airscrew 16x6 K-series.
The last time I tuned the HSN I stopped at 9k, it ran without stress for several seconds at 9k before I backed it off. I think there was more to be had since the rpm was going up consistantly with each click on the HSN, but I am being very cautious about avoiding a lean run.
Tomorrow will be another opportunity to run the engine, I will finish off the Omega and when I switch over to my everyday fuel I will put a real tune on both needles and post the figures in the Club Saito thread.
If I get a different prop (unlikely on New Year's Day) I will post those numbers here and in Club Saito.

RE: Saito 125 poor performance problem
 

Thanks Charlie. I will keep up over there.

David

RE: Saito 125 poor performance problem
 

Hi guys, all interesting stuff. I haven't forgotten the thread, just waiting for the engine to come back with a verdict!

:-)