Tick over on a Saito 100

[flying daddy]

Just brought a brand new Saito 100 .I have I run it now with 3 tank full of fuel  so it should be kind off run in .It does not tick over very well .It is an unven then cuts out .I am a bit reluctant to mess about with the slow running jet .It must of been set at the factory .Should I turn the slow running needle  half a turn at a time clock wise or anti clockwise to get it turn over correctly  ,?

[GrumpyGnome]

Could you post a video of you starting it, letting it idle with the glow stick attached for a few seconds, letting it idle for a few seconds without the glow stick, then whacing the throttle open?

 

The LSN may be too lean, too rich, or you're just aiming for too low an idle.....

 

In any event, half a turn is far far too big an adjustment -  it will be close to correct as it came from the factory.

[flying daddy]

Thank Grumpy Gnome  will do but I am layed up at the moment Just come home from hospital with a new knee replacement .Once I am able I post a video up 

[Paul De Tourtoulon]

Try an electric starter, but out of interest, can you photo your technic using your Knee to start it ?.

 

 Good luck with your Knee.

[jrman]

Saitos generally have the slow running needle set very rich out of the factory.

[GrumpyGnome]

Yes, seem to want them to run slobberingly rich!

 

@flying daddyhope the knee recovers soon.

Edited April 2 by GrumpyGnome

[Jon H]

3 hours ago, GrumpyGnome said:

Yes, seem to want them to run slobberingly rich!

 

Engine manufacturers ship engines with very rich slow run needles to guarantee the engine starts. They do this as they know that modellers really struggle to deal with engines that wont start (should the needle be a smidge too lean for the fuel/setup the customer has) and the return rate would be very high. Its just a faff they dont need. During my time at laser i had countless engines back that 'wouldnt start' and not a single one failed to start first time when i tired it. Maybe its a procedural thing? im not sure, i just know it causes problems. 

 

As a tangent, i did post some videos a while back of some chaps struggling with an engine that wouldnt start and challenged the folk here to diagnose the problem. To cut a long story short it became clear most were diagnosing with their eyes and not their ears, and i did find that quite interesting as it mislead a fair few in the wrong direction. 

 

7 hours ago, flying daddy said:

I am a bit reluctant to mess about with the slow running je

 

It wont bite you. The worst thing you will do is go too lean and the engine will not start any more. If that happens, you know what you did to break it so you also know how to un break it. Just undo whatever you did. If in doubt, close it completely and open it a bit at a time until the engine starts, or the needle falls out. If it falls out, the carb is blocked anyway so it needs a clean. The biggest mistake people make with slow run needles is turn them too much. 1/8 turn at a time is the absolute maximum you should be moving it. My suggestion would be to fire it up, peak the main needle (you cant set the slow run with the main set too rich) then come back to idle. With the engine running lean the slow run 1/8 turn and slam the throttle open. If the engine makes it to full power do it again, and again... Keep doing this repeatedly until the engine bogs down and no longer accelerates to full throttle when you jam it open. When that happens, tweak it back the smallest amount possible until it picks up cleanly and its job done. From engine start to perfect tune should take 2-3 minutes tops. Its very quick and simple once you get the hang of it. 

 

I forgot. Do you have a tacho? They are handy but do not use it to tune with. They react too slowly to be of any use so just use your ears. They are however good reality checks and for a saito 100 on 15x6 or 14x7 i would be looking for around 9000 at top end and an idle of 2000rpm. If you cant get a stable idle at 2000rpm the slow run needs a look. 

Edited April 2 by Jon H

[Jonathan M]

@Jon H Great description as always, totally clear!

[Antony R]

All the saitos I've had from new needed far more than 3 tanks to be run in, the symptoms you describe are what I've experienced. It needs much more running in and then you can lean the bottom end.

[flying daddy]

T

12 hours ago, Jon H said:

 

Engine manufacturers ship engines with very rich slow run needles to guarantee the engine starts. They do this as they know that modellers really struggle to deal with engines that wont start (should the needle be a smidge too lean for the fuel/setup the customer has) and the return rate would be very high. Its just a faff they dont need. During my time at laser i had countless engines back that 'wouldnt start' and not a single one failed to start first time when i tired it. Maybe its a procedural thing? im not sure, i just know it causes problems. 

 

As a tangent, i did post some videos a while back of some chaps struggling with an engine that wouldnt start and challenged the folk here to diagnose the problem. To cut a long story short it became clear most were diagnosing with their eyes and not their ears, and i did find that quite interesting as it mislead a fair few in the wrong direction. 

 

 

It wont bite you. The worst thing you will do is go too lean and the engine will not start any more. If that happens, you know what you did to break it so you also know how to un break it. Just undo whatever you did. If in doubt, close it completely and open it a bit at a time until the engine starts, or the needle falls out. If it falls out, the carb is blocked anyway so it needs a clean. The biggest mistake people make with slow run needles is turn them too much. 1/8 turn at a time is the absolute maximum you should be moving it. My suggestion would be to fire it up, peak the main needle (you cant set the slow run with the main set too rich) then come back to idle. With the engine running lean the slow run 1/8 turn and slam the throttle open. If the engine makes it to full power do it again, and again... Keep doing this repeatedly until the engine bogs down and no longer accelerates to full throttle when you jam it open. When that happens, tweak it back the smallest amount possible until it picks up cleanly and its job done. From engine start to perfect tune should take 2-3 minutes tops. Its very quick and simple once you get the hang of it. 

 

I forgot. Do you have a tacho? They are handy but do not use it to tune with. They react too slowly to be of any use so just use your ears. They are however good reality checks and for a saito 100 on 15x6 or 14x7 i would be looking for around 9000 at top end and an idle of 2000rpm. If you cant get a stable idle at 2000rpm the slow run needs a look. 

 Thanks Jon I found that very interesting and useful .You explained well After reading your instructions. I feel confident to tackle it now .I will run a few more tanks to make sure it is run in 👍

[Paul De Tourtoulon]

Saito's are long to run in, so don't look for silly HP and rpm numbers to start with, 2.500 rpm is a more than acceptable idle whilst running in.

[Christopher Wolfe]

17 hours ago, Jon H said:

 

The biggest mistake people make with slow run needles is turn them too much. 1/8 turn at a time is the absolute maximum you should be moving it.

 

If slow run needles are so finicky that they require such tiny adjustments then why don't the manufacturers use a finer screw thread?

I can remember back to the days when my Cox Tee-Dee engines were transformed to easily tuned engines when fitted with a KK (Kustom Kraftmanship) 128TPI needle valve carburettor assembly.

[Tim Donald]

I had this problem with my new Saito 82.  It needed the slow running needle turning in a lot.  I thought something must be wrong with it at first as I would have expected it to come in approximately the correct setting from the factory. I can't remember now how much it needed leaning but it wasn't a few degrees,  more like a couple of full turns.  It has run and idled perfectly ever since.  

[Andy Stephenson]

I recently sold a Saito 62 for a friend but needed to show a video of it running. I had it mounted on a test stand ready for the video but it simply wouldn't start although it had run well before. On investigation I noticed the needle had a slightly different taper and a blunter end than a spare I had. On fitting the spare, it started and ran perfectly. I was assured that the needle it came with was a genuine part. So what is normally the high quality of Saito engineering can sometimes let us down.

[Jon H]

On 03/04/2025 at 14:36, Christopher Wolfe said:

f slow run needles are so finicky that they require such tiny adjustments then why don't the manufacturers use a finer screw thread?

 

Not an unreasonable question. I have no real answer beyond a guess that they want to make their parts using standard pitches and threads rather than completely reinventing the wheel. Also 1/8 turn is not an insignificant adjustment. I am pretty pedantic with mine and 1/64 of a turn is not an uncommon level of adjustment for me. An easier method is changing the needle taper and i think OS used to include a 2nd main needle for some engines with a different taper to suit....something, i cant remember why they did it. 
 

 

On 03/04/2025 at 06:27, Antony R said:

It needs much more running in and then you can lean the bottom end.

 

No you must set the slow run needle early doors as the slow run is better named the 'everything under 60-70% throttle needle'. The slow run is responsible for metering fuel up to around 60 or 70% of the throttle travel so if its miles out the engine will handle horribly. 

 

On 03/04/2025 at 09:21, flying daddy said:

.I will run a few more tanks to make sure it is run in 👍

 

Dont worry about running in. There is a massive amount of paranoia and general hysteria connected to run in procedures and 99% of it is absolutely not required. 

 

If you take your brand new engine and fit the smallest prop possible, then start it and immediately firewall it while tuning it for its absolute peak performance...it will be fine. It will not throw a tantrum, or break, or die in any shape or form unless you decide its a good idea to leave it at full power for the next half hour while wrapping it in a blanket to see how hot it can get. I have no idea how many engines i test ran at laser, thousands probably, but every new engine i ran was screaming its heart out within 30 seconds of it first turning a blade. I tuned them for peak performance on the main, throttled back and set the slow run. Each engine was test run for less than 3 minutes, rpm and performance checked, and it was all over, done, boxed, off to the customer. 

 

Why did we do it this way? First, heat. Heat is good for your engine. Oils perform better, build up of harmful combustion residue is reduced, and in the case of a new engine especially all of the parts have expanded to their full dimension. Clearly too much heat is bad, but so is too little. Run the engine in too cautiously and very cold the components will not expand correctly and the engine will run in to those in service dimensions. Once you run it harder and hotter later, perfomance will be lost as the parts have worn to fit a different engine in terms of its dimensions. In any case engines should be hot. I would cautiously give a guide of 90-120'c on the head, 70-90 on the crankcase. that sort of thing. Basically if you can touch it but not hold it for longer than a second its probably about right. If you can pick it up and hold it then its too cold. If you can fry an egg....

The next reason was RPM. High rpm at light load is great for bedding in the rings and valves. In the case of the laser specifically the high rpm did a nice job of work hardening the ali valve seats. in the head. 

 

Corrosion. Run the engine rich/cold and you leave raw fuel in the engine. Methanol loves water, and you get rust soup in your crankcase. 

 

Lubrication. As discussed heat is good for your oil, but running rich is bad for lubrication. The accepted wisdom is that rich means better lubrication as you have more fuel so more oil. Makes sense, kinda, but its wrong. In a 4 stroke in particular, if you do not burn the methanol off it migrates down into the crankcase where it dilutes your oil and reduces its effectiveness.

 

Finally, from the point of a view of a manufacturer, it was important to stress test the engine to confirm its performance and reveal any issues. 

 

Like the slow run needle, run in instructions are extremely conservative to cover off the guy who just rags the thing from the get go with zero cooling and the lowest quality fuel he can find. 

 

The run in procedure i would recommend for any model 4 stroke on the market is to first take off the rocker covers (all) and cam cover (OS and OS clones only) and give the engine a shot of 2 stroke oil. Anything not an OS or a clone give a good squirt up the crankcase breather instead. Turn the engine over to distribute the oil, then drain most of it out. Pick a small ish prop for the engine. 14x7 for a 100 is perfectly fine and fire it up. Run for about 30 seconds at 3000 ish rpm. open to 5000rpm and remove the glow (adjust throttle to keep the 5000), leave it like this for another 30 seconds. Then open to full power, and tune for about 90% of peak. This should take no longer than 5 seconds. Once you have done this throttle back and adjust the slow run to be half decent. Run like this for about 5 minutes up and down the full rpm range with some short 5 second bursts at full power, and plenty of idle to full power accelerations as well. Once bored set both needles for as close to peak as possible, pinch off the fuel, let the engine cool and have a cup of tea. 

 

With that out of the way refuel the model, start the engine and check peak on the main needle. You can now fly the model and use the full power of the engine but use common sense. Dont just peg it flat out and hope for the best, just fly it normally. A lazy aerobatic routine is great for running in an engine as you are at half throttle most of the time, full power up hill, back to idle on the way down, back up to half. The engine gets a full work out but also gets a breather with the near idle throttle setting while diving out of a loop.  

 

There are plenty of reasons to do it this way but the headline news is its better for the engine. No dirt or sand blown up while on the ground so debris ingestion is far less likely. Our engines are air cooled and there is more air in the sky...Its more fun to use the engine rather than just look at it...i could go on. 

 

A project i always wanted to do was a video where i would assemble a brand new laser engine, fit it to a model, set it up, and then completely wring its neck in the air all in one continuous take just to demonstrate how much exaggerated fuss is made about running in.   

 

The short version of all this is that the traditional 'run it in slow and rich while cool to the touch' is wrong. It always has been and the procedure above will work just fine provided common sense is employed. I was actually sent a brand new saito 82 to run in and i used the same method with that. It didnt melt, or explode, and by the end of the 5 minute run it would hold full power for the 5 second burst without sounding distressed in any way while ticking over reliably at 2000. Were it mine and in a model i would have refuelled and flown it without hesitation. 

 

Bit of a long one, hope its useful. 

Edited April 4 by Jon H

[Cuban8]

Thanks Jon - a very informative and entertaining read.

[Jon H]

No worries cuban. 

 

One point i forgot was fuel. Much is talked about fuel and oil and blah blah. 5% nitro, 15% oil for any 2 or 4 stroke bog stock fixed wing engine. It will be fine. You need no more or less. Tuned pipes, helicopters, club 20, ducted fan...requirements may differ, but for sport,scale and aerobatic fixed wing normal stuff, its fine. I run ASP/SC, Saito, Enya, RCV, Magnum (the old british one) and OS on this mix, never use on board glow* even on multi cylinder engines and have suffered just one non fuel starvation related deadstick in the last 20 years, and i think that was my fault anyway and not the engine.   

 

You also do not need more oil in the fuel for running in. In the latter years after its development i ran in all of the new lasers i built on the new 7% oil fuel (not recommended for saito!). 7% was always my starter for 10 and i intended to continue development with 5% oil being an easy win and a target of 2.5% with further testing to confirm reliability. Alas things didnt work out that way with the demise of model technics and then laser itself, but we use way too much oil and i run '20% castor only' engines on 15% synth oil without problems. I also ran my ASP160 twin (18% oil recommended) on 10% oil for a full season before i ran out of it. As i have said before and the teacher used to tell you at school. Quality is more important than quantity. If you dont have enough oil in the fuel the conrod will seize and fail in 2-3 seconds. Not hours or weeks or 'in 10 years your engine will....something', no, 2 seconds. If the engine didnt seize up almost immediately, you have enough oil.  

 

Lower oil and nitro fuel offers improvement in economy and reliability as the engine will run slightly hotter with low nitro and this is good as it keeps the plug alight. I did start to write something about high nitro and its impact but came across an apparent contradiction which isnt one, but its too late in the day to write an essay explaining so we can shelve that for now. 

 

 

 

*really pants sc400 5 cylinder radial needed onboard glow to prevent it giving up the ghost. That was until i changed the pistons for twin ring laser 75 pistons and the increase in compression removed the need for the glow. That was until it threw a rod bearing for the 5th time and the valves made of cheddar started leaking again. I think the crank pin is under size for the needle roller master rod bearing. This play causes impact loads the bearing cant handle so it breaks up. I should have nicked a PB102 bar end for laser and just made a bush for it...one day, when i can be bothered to rebuild it again. 

 

 

 

 

 

 

 

[Tim Flyer]

I regularly need to readjust the slow running needles on my engines(all makes)  . That has always been the case (probably every few months) sometimes more if heavily used. The slow run needles gradually unscrew with vibration sending the mix too rich. I always think about adjustment in “clock minutes “ which makes it simple. 

Yesterday my OS 120 ax needed a  big 15 minutes turn on the idle screw, as I had left it for some time due to sheer laziness and time pressure. After readjustment the reduction in wasted oil over the bottom of the fuselage was dramatic. 

[Nigel R]

4 hours ago, Tim Flyer said:

OS 120 ax

 

I applaud your dedication to glow flying 💪 👏 

[Tim Flyer]

Thanks Nigel.  I have 9 glow engined planes that I keep ready to fly, and for me running the engines is a good part of the enjoyment.  If I had very large models I’m sure I might consider petrol (there are some amazing engines out there) but cost and practicality and performance keeps me using my glow engines. Despite having bought my first glow engine in the 70s the fun still hasn’t worn off! 
 

So far my small petrol engines are confined to garden tools but admittedly I also enjoy running and servicing them too. 

Edited April 5 by Tim Flyer

[flying daddy]

Took my Saito 100 to the flying field today  (installed in my model ) No intentions of flying it just wanted to set up the Saito has explained in this thread .Hit another snag .The Saito 100 is inverted .The engine would fire but would not start and it kept throwing the prop before it would start .I suspect it was getting fuel lock has the carp is below the centre line of the fuel tank .Had to give up due to the start battery and glow battery ran low .Spent tonight repositioning the Saito up right .Fingers crossed that will stop it locking up everything I try to start it 

[Martin Harris - Moderator]

Easier way to prove it would have been to invert the model.  That's where a cradle helps but with help, it's pretty easy to have it held upside down...and saves a lot of work if it proves not to be flooding!

[Jon H]

1 hour ago, flying daddy said:

I suspect it was getting fuel lock has the carp is below the centre line of the fuel tank

 

why not lower the tank? Its likely a full flip to upright has the tank low now so i would look into its location as you dont stand much chance if the tank isnt in the right place. 

 

Always align the top of the tank with the middle of the carb for the best results. 

[Paul De Tourtoulon]

8 hours ago, Jon H said:

 

why not lower the tank? Its likely a full flip to upright has the tank low now so i would look into its location as you dont stand much chance if the tank isnt in the right place. 

 

Always align the top of the tank with the middle of the carb for the best results. 

If that doesn't do it, 'maybe' your Saito 100 is like both of my ones, they also just threw props, so I shimmed the heads ( 0.4mm) and since then they haven't thrown one.

[Nigel R]

On 04/04/2025 at 17:44, Jon H said:

Bit of a long one, hope its useful. 

 

Slight tangent. Would you also advise the same basic method for a glow 2 stroke? Small ish prop, tune a bit shy of peak, run it for a tank going up and down the rev range... then go fly?

 

As far as I understand it, the main work hardening is on the conrod bushings, and there is slight wearing in of the piston/liner fit, but that's about it for 2 strokes...?