Gabrielsande

Hey Guys! listen the engine is the only 4st petrol in the market, ifDLE does one for sure, will be more reliable!
the main problem to me is the carburattor, Ihave two problems:

1, the engine behaves like a glow one, you let it idling for too long and then hesitates on a quick throttle change, it seems to get rich when cooling ,this is not a problem is just a matter of flying it on the happy side, you have dead sticks if you try to achieve a very smooth idle making the transition to weak, so at idle my one os a bit rough and after few minutes idleing will amost stop if you dont keep it happy on rpms, but neverit let me down in the air.

2, that exporadic cough! and based in all my attempts( needle settings spark plug gap and change carburattor adjusting) Ibelive is something to do with the fuel delivery and the sudden chages in directionm high cg manuouvers, on take off will do it if I go full throtlle, because I think if is like a car inlet manifold when the throttle is closed there is a lot of vacuum,but when wide open no much vaccum, and if the pump works on the one way pulse of the dif in vac of the inlet ,it will change a lot with the throttle variations so Ithink at some point there is not enough pressure to feed it, unlike 2 st engines which takes the pulse from the piston going up and down in crankcase, I have seen some guys adapting normal walbros and even using a T junction in the crankase vent to feed the pump.

I never had a problem with the ignition, Ihave removed the metal cap since the first day I do this in all my gas engines because is a matter of time to the spark jump inside,from the connection clip on top of the plug through the silicone to the metal shield due to damage for the vibrations, and frying the module with time, (how many cars you see with metal shields on the plugs,there are some and they gives problems with time), so I remove the shield and then cut with care the mesh half inch up the cable, and solder the mesh to a cable to attatch later on to one of the engine mounts bolts, so you end with a normal ht lead, the silicone cap fits the plug perfectly and being lighter it does not vibrates lasting more without giving you any problems. it will do the cough time to time with no warning when fast changes of the plane attitude ex, going straight and pulling up nearly in 90 deg like going in a wall,or going leveled and moving fast to knife edge, but when it does it then i try to replicate the same fault and Icant, is just random!


Engine sounds really nice, Ithink still a converted glow engine, so thats why we have to use that heavy engine mount to keep the engine cool ending with a 1.4 kg engine which delivers 2.8 hp when a dle 30 weights 1.2 kg and delivers 3.7!.

Anyway still a good looking engine which is small enough to fit in any cowl, and if you gona use it on a scale/sport plane will be perfect, on a piper cub! will be the best engine! Idont see any problem with that, just follow the manual instructions to tune up, and dont go too lean on the needles,rather having a rough idle when cold than a dead stick in the air!!, and before taking off, warm the engine properly they takes few minutes to reach temperature.

After all still fitted in my mx2 and still being the talk about in my club and meetings "is that a saito? is it petrol?.... it sounds really nice! and this is what makes my plane especial,despite Im not exploiting the 3d airframe which is designed around the dle30 if I had a bib Piper cub it will go in for sure!

Hope this helps! dudes!

nudger

Hi Gabrialsande
I also have the same carb symtoms and the ignition problem on both saitos.3 ignition packs ive used and every mixture possible tried.If it was just me trying to sort the engine out then Id say it may be something I was doing wrong.But at every step of the way Ive had a life long areo modeller and time served mechanic helping me to no effect.

All I want is to fly without the worry of it stopping,I thought saito would give me this but I was wrong.

Nudge

Gabrielsande

Hi there as Isaid in mine, I never had any dead stick just caughs time to time, check you are using the right propeller Im using a 17x6 apc to brake in and an agile flying,Itried once a 18x6 and it was loading the engine too much, these engines overheats if they are too enclosed, thats why the alloy mount to help with the heat,something good to do is to use the pc microprocessors conductive paste between the engine and mount, You can't "not use" the alloy mount as is explained in the manual .

So just make sure you are using a good fuel installation,bubble proof, I use a kind of felt filter clunk but the one which does not loses fibres,and one of those glow alloy filters with a metal mesh inside you can clean time to time,try to put the tank at the same level as the carb and not too far from the engine again as a glow engine.

And then, just adjust the top end for max rpm and once there back off a bit, the same as with the low end close the needle until the engine gets very smooth, and then turn the needle anticlokwise to get it reacher, just turn little by little, throttle up to warm the engine again and leave it idle again it has to be on the rich side so it will idle a bit rough if you leave the engine idling for too long, in mine if I leave it too long as a glow one it will stop after few minutes idling and this is right, if you try to leave the perfect idle later it will starve in the air at mid throttle.

I still using the original ignition since I bought it in 2009, with just a standard 6v 2600 mah nihm.

let me know how is doing,and how your setup is!

cheers!

ya33a

Hi.
I have an FG20 which has the same issues. I believe our local importer has supplied replacement carbies under warranty to fix one of the problems. The new FG21 has a rexcel ignition and the updated carby. If that helps? with my engine I just use it in a 1/4 scale Taylorcraft and put up with the rough running as character when flying.

velottatv

I have the Saito FG-36 and it has the same issues that everyone mentions. Very frustrating. Some times it runs perfect and others it won't even start. This weekend I took the cowling off(PAU Extra 330L) and the engine ran perfect. Put the cowling back on and it wouldn't start.

I'm thinking there might be an air flow problem. The plane has an air chamber tunnel under the fuselage to route hot air outside. I've noticed when I go from idel to full throttle, the cowling pulls inward. The routing for the airflow is in through the prop and intakes, over the cylinder (invert mounting), then out of the cowling through the air tunnel on the bottom.My theory is the airflow is causing a venturi effect sucking air AWAY from the carb intake and starving the engine, thus the cowling top portion pulling inward,

I'm thinking about putting some sort of hole in the cowling top to allow air flow over the carb intake. Any ideas about this??

ya33a

Hi,
I thought about the venturi effect, as well early on, I have an H9 Taylorcraft, that I did a build report on in this site, I used a venturi 'extender' which is a nozel off a silicone sealant tube and fitted a velocity stack to the top so the carby woul dbe getting cool fresh air from the hole I drilled under the scoop on top of the cowling. I also blanked off one of the inlets and opened up the out let air so there wouldn't be an issue with hot air expanding and boiling the engine through no airflow. I've run the engine with and without the cowl, with and without the stack extension, fresh and old batteries, exhaust extensions and no extensions.... And all I get is grief.

I've found that premium gas 98 Ron is better than the 91 or ethanol blend and good quality oil is a must. plus I filter the mix a couple of times before putting it into the engine, once I've gone through this ritual I seem to get 2 good flights before the gremlins return.

velottatv

ya33a,

Thanks for the information. You just saved me a lot of time experimenting! So now...on to the next theory. I was thinking about the battery voltage on the ignition. I normally use a 4 cell NiMH but a week ago Iaccidently hit the ignition switch and the battery ran down. So I put in a 5 cell NiMH and the plane ran great that day. No problems at all. Next time to the field I went back to the 4 cell and nothing but problems.

I was thinking about putting a 6.6v FiFe on the ignition to see how it would go. Any thoughts?

Thanks!

ya33a

Hi again,
Make sure the battery is ONLY 6v max, the original SAITO ignition modules were very sensative to high voltage spikes and went to lunch at anything approaching 6.5v, a fully charged 5 cell pack could be as high as 6.7v straight off the charger. I tend to use a high capacity 4 cell pack which lasts about 3 hours of running, - mid to low with the occasional WOT, just for the heck of it.

Gabrielsande

Hi again,well If you look back in to the thread, I had my saito since nearly they came out, tried all, still using the original ignition on a 6v nihm 2600 mah pack ,thought the same about inake problems on the mx2 so,opened the bottom hole,closed on of the scoops, and also made a thin alloy scoop which directs the fresh air in to the carburator, stripped the carb twice cleaning and adjusting the pump lever, for max flow, still the same.

I found the carb very sensitive to needle changes, so the best is just to do little changes when hot and throtlle it up 2 or 3 times and let it idle before doing an other change,mine behaves like a glow one if idles for too long it goes rich and then stops,the idle is set on the rich side I went for a very smooth idle and then opened the needle a bit,this seems to cure the problem in the air of starving when applying full throtlle similar to glow engines.

I tell you something guys, Im very happy with my engine, Is being nearly a year now flying the mx2 time to time with no problems starts up striaght away using an Align starter, I found it takes few minutes to warm up and release its full potencial,so Im easy on it for the first minutes, despite having les power than a dle 30 and being heavier, the plane now hovers and pulls away from there not like the dle but it does,making mild 3D flying possible with no problems, it looks and sounds great!, stillthat cough time to time allways when doing sudden changes off direction ,but time to time,but is just a miss and still running,so at the moments is giving me more pleasure than problems.

But if you try to get a smooth idle running then you will get more problems in the air even dead sticks, my theory of the problem is simple:

This is a 4st engine, so you dont have a negative and positive pulse from the crankcase to feed the fuel pump as in a 2 stroke,so this carburator works on the negative pulse from the intake and a spring which makes the positive pulse,but my guess is hey! Im 38 years old but I had a nice 56 chevy belair coupe time ago (sadly was stolen and never recovered) in which the wipers were working from the vaccum of the intake and I remember they going very fast when idling and going slow when flooring the engine, this is becasue the lack of vacuum when the throtle is wide open, so I think the same applies here, if the pump works from the negative pulse only and you have the throttle wide open for a wile,how the pump works? to me at that point the engine is relaing on the fuel accumulated in the regulator or the venturi efect like in a normal aspirated carburator, so this could lead time to time to have an uneaven fuel flow causing those problems.

I think saito should use a mechanical geared pump.to feed the carburator lets see how they do the newer versions

I found some threads of guys adapting normal walbros to the engine and feeding the pump from the crakcase with a T junction from the breather nipple,with succes, I thought about probaby using a ocsilating perry pump to feed the carburator together with its pump,but I have to find were is the best place to add the nipple,it should be before the regulator somewere,I never tried using one just in the fuel line before the carb,could be a good test to do,but as I said, mine is running good and does not worth to still wasting more time.

Let me know if somebody try a perry pump, might be an easy solution!

take care guys and have nice flights!!

AM6

Hi all
Anyone experiencing high end misfires and generally inconsistent running,particularly when loading the engine, could try a rxcel ignition swap.
Been there...
Happy Landings.
AM6.

Gabrielsande

Hello!

Did you check the valvles gap?,if they are ok could be fuel starvation so you have tostart from the tank clunk,trough the fuel lines,filters,carb filter,carb itself,and needle settings.

on the ignition side Im using the original ignition,never gave me a trouble,I have a dle 30 and a cheap crrcpro 26.they are all running on they original ignitions too, one mod I do on them from new,is removing the metalcap from the cable,I had my first gas engine giving me all sorts of misfires and problems,and once wouldnt start and then I heared the spark jumping between the connector and the shield,through the silicone,this was because themetal capbeing so heavy it vibrates a lot,so at the end the silicone wears and the spark jumps there, also the ground is done by the same shield which vibrates on the plug and could do bad contact

so what I done since is remove the metal cap,then I cutt the metal mesh,along the ht cable with care,,twist the mesh and then solder a cable,which goes in to one of the engine mount bolts as ground, this makes the silicone cap to fit nice in the spark plug,it has lessmass so it vibrates less,and the ground is always doing good contact, the same as a ht cable on a car or bike ,they dont have armoured cables.I also add an extra ground cable ,just at the exit of the ht lead from the box, I just turn tight a cable around the mesh,put some good tape on it and the end goes to an other engine bolt.

Make sure to not turn the engine with the ignition on ant the ht lead removed from the plug,this could damage the module,the same as using a bad or old plug.
Hope this helps

See ya!

velottatv

Update on the FG36 troubles. Spent the week going through the plane checking everything. Pulled the exhaust apart and cleaned the carbon although it wasn't too bad. Switched from 4.8v to 6.0v NiMH battery on the ignition. Reset both low and hi needles to factory recommendations.

Took awhile to dial in but finally got it. Left hi alone and made small adjustments in the low until it ran good. The engine ran great but idled high at around 2300 rpm. Anything below this and the engine coughed and sputtered at mid and high range. Twice I lowered the rpm's by a few clicks on the radio. Both times the engine reverted back to the coughing. So for now, I'm going to keep the idle up.

I was doing all sorts of manuevers and the plane ran better than it ever has. Hopefully it will stay that way!!

MercerAUST

I've been running the FG-20 (original version) for about 40 hours now and it idles reliably, transitions well and is smooth on WOT. I originally had irregular running due to several problems. I had initial fueling problems (my vent line was too long/restrictive and the weak carby pump could not adequately transfer the fuel). I fixed this up, but then had problems with overheating. Going back to the recommended prop fixed this. After all this mucking around, the engine still wasn't quite right, but replacing the spark plug fixed this. It's been good for the last 20 hours.

I haven't had any problems with the original ignition model to date (or with a FG-14 with nearly 80 hours).

charlvnk

I think I may have found yet another design problem on the FG-30. I modified mine to take a OS GT33 ignition and hall pickup. That made one hell of an improvement, but it's only good for about 1 minute at full throttle and then the engine starts to lose power and gets very hot even with the cowl off. If I adjust the high end needle more rich, it doesn't happen but then it causes a significant drop in power and runs very rough for the first minute because the mixture is actually too rich.

I noticed that when it's hot, the carburetor can be moved very slightly from side to side. It was the intake tube that rotated slightly where it attaches to the cylinder head. I tried to tighten the four little bolts but couldnt really because the tiny phenolic bush then broke and I had to replace it.

My theory is this : We all know how extremely hot a gas engine's cylinder head can get compared to a glow engine. Those 4 bolts are heated to the same temperature as well because they screw into the head directly. The steel then obviously expands so in effect they become slightly longer. The phenolic spacer between the tube and the head, which is there to prevent the tube and carb from heating up too, doesn't expand as much (if anything at all) as the steel bolts that hold it in place. So then the tension is released and those extremely thin paper gaskets don't seal anymore, and a tiny bit of air is sucked in with the mixture causing the engine to run lean. The hotter it gets, the wider the gap opens and the leaner it will run !

So yesterday I removed the two gaskets on both sides of the phenolic spacer and replaced them with high temp RTV silicone gasket maker. Today I will run it again to see if this was the cure for the problem.

Gabrielsande

Hi there, an other good theory!,but I never had any temperature problems, there are not many choices on propellers Im stuck with the 17x6 on the Goldwings MX2, tried a 18x6 once and engine stalled at some point,  And I thik it was temperature, you have to wear the alloy engine mount and is good to use some pc proccesor paste were they meets,to help to transfer the heat, Still using the sandard ignition  with a 6v pack and the metal cap removed,just the silicone plug and the mesh atattched to the engine as ground.

charlvnk

Ok - I tested it and was much better, but still started running lean and overheated after enough time. There were symptoms of fuel starvation -
almost as if the pump did not suck in enough gas.

So I found another problem - the phenolic spacer between the carburetor and intake manifold only had a gasket on the manifold side. On the carb side, which is not machined and therefore slightly rough and not 100% flat, there was nothing !  Just the metal against the phenolic spacer.

This will obviously affect the operation of the already weak fuel pump, and will also cause problems with it running lean.
I fixed this using more silicone RTV gasket maker, and today it ran almost perfectly - no dead sticks or overheating problems anymore, just the occasional hiccup at wide open throttle but it never loses power or cuts out an dies. Up to 3/4 throttle there's not even a single hiccup or anything. Perhaps the slight problem at wide open throttle can be improved by high end neadle adjustment - it's set quite rich at the moment because I didn't want to take chances with possible overheating again.

charlvnk

After fixing the problems with the intake manifold I took it to the field for a test flight.  It performed flawlessly for the first part of the flight but then started missing e beat now and then. With the second flight it was worse and I had a dead stick. Thereafter couldn't get it started no matter what - it only gave a few coughs and then died.

I decided I've had it with this engine and was about to throw it away, but the next morning something told me to just go and check again, just in case it's something small like a dud spark plug or something.  And sure as hell - it was !  Actually a combination of bad spark plug and some damage to the plug cap on the OS ignition module (it came off a GT33 engine that was split in two after a serious crash).  I could hear the spark jumping inside the cap and sometimes I could see it in the spark plug gap.

I fixed those problems and decided it's now make or break time.  I ran it at full throttle on the ground, with the cubs's cowl on, for four minutes constant end there wasn't even one single hiccup or anything.  And throttle response was still perfect as well.  I guess after doing that it's just luck I didn't kill it !

Time to take it for another test flight to confirm it's ok now.  I sure hope it is, because it's sound gos so well with the look of the Hangar9 25% Cub.  You ma ask "why put it in a Cub ?" - well, I guess it's one of the safest planes to fly when you are expecting a dead stick at any moment !

affas

I did a uprade on mine with CH ignition and Zama modified carb. the engine is like a complete new engine. Idles forever, smooth throttletransition and perfect on top rpm.

[youtube]http://www.youtube.com/watch?v=aCiJLDfwntQ[/youtube]

Inflight video will be posted as soon as I have a man to shoot the video

ya33a

It's a real shame you've had to go to these lengths to fix something which should have been right from the start, Saito haven't done themselves any favours by not fixing the faulty engines from the start and their service agents in most countries have ignored the problem hoping it will go away, if it was any other engine manufacturer they wouldn't get away with not fixing the problem, I'm glad you have something which works for you.

affas

Totally agree!

Saito have not shown that they can make a gasser that works. Could not be that difficult.

Gabrielsande

Hey guys!, just something to say, I know sometimes we think we can find the problem ourselves,we all think we are a kind of engine guru.
I use to not listen and bang my head against the wall before find solutions.

But now having this media to share information and experiences,I rather spend some time serching and reading a lot before put my hands and brain to work, because I know someone went trough a problem like mine before.

If you go up in the thread, you will find the plug cap problem explained, as I said before, is easy to the factory to just clamp a metal cap, than have a separate ground cable with a round terminal to fit in one of the engine mount bolts,saito also comes with an extra groud cable to avoid module damage if the metal cap fails to do good contact, but in mine I found it too tight to fit to close to the cylinder,and I had this problem in all my gas engines after few hours in the air. they started failing to start and misfiring in the air

Again, vibrations makes the metal cap to vibrate a lot on the silicone plug and at the end it chews the silicone making it thinner and alowing the spark to jump there from the contact to to the metal cap.

what Im doing in all the engines even new boxed ones is to get rid of the metal shield,cut the metal mesh along the cable, and leave the ht cable to one side and the ground mesh to the other, twisting it and soldering a round contact in the end to later attatch to the engine, also I turn around the mesh upper the cable against the box an other cable,to attatch to the engine mount just in case.

Doing this never had a trouble with any ignition,istill have all the original ignitions running with no trouble so far, the silicone plug fits tightand being lighter vibrates less lasting longer.
same as a car apart from some vw with metalcaps which gives the same problem the rest uses just a cable and the coil grounded to the engine,cars,motor bikes,chainsaws etc.

have a think and a look to the pictures you can see the bare plugand the ground cable in my mx2 and the sukhoi, I hope this will help.

cheers!

charlvnk

The first two minutes of my test flight went very well, although the slight "hiccup" when doing a roll or any other high(ish)-G manouver was still there.  And then - DISASTER !  It started sounding very unhappy and almost died so I switched ff so I tried to land. But the bird wasn't ready to land - she wanted to keep on flying ! The engine could not be brought to idle. So I did another approach and switched off the ignition to do a dead stick landing.

I didn't have my thermometer there but could feel the engine was EXTREMELY hot. There REALLY isn't anything more I can do for cooling - the cowl is already full of ducting / guides and a proper baffle setup. So I thought perhaps I set the needles waaay lean. The same thing happened with every subsequent flight now matter how rich I set the needle. The symptoms all looked like fuel starvation to me, and looking at the colour of the spark plug it was obvious that the engine was indeed running way too lean.

So I took everything apart AGAIN. There was NO dirt inside any part of the carburetor, and fuel flow from the tank was unrestricted.
One thing I did however notice was how much force it actually took to make the dome / bubble of the fuel pump membrane move against that spring. Perhaps the membrane hardened a bit over time but I can't get a service kit for this carburetor anywhere to check if that's the case. I decided the fuel pump is a poor design because the negative pressure pulses from the intake manifold are pretty weak especially at wide open throttle - can't see how that can really be sufficient to properly pulse that "fuel pump".

So I did a modification - blocked off the little channel under the carb that goes to the slot in the phenolic spacer whereby the low pressure pulses from the intake manifold is supposed to suck that dome against the return spring. I used epoxy for that. Then I drilled a hole halfway through the intake manifold flange and the phenolic spacer, right underneath the hole that goes to the dome of the fuel pump membrane on the carburetor. Next was another hole drilled from the side of the intake flange, just deep enough to meet with the first hole. I then press-fitted a piece of brass tube with some green high strength thread locker into this second hole. The return spring that pushes back the fuel pump membrane's dome was removed and tossed away, and the carb was bolted to the intake manifold flange again.
So now I was able to apply pressure to the fuel pump membrane's dome / bubble from the outside via that piece of brass tube sticking out.

Next step was to remove the rear engine cover and drill a hole to fit a second nipple (same as the one used for the vent, but with a larger hole through it). I then replaced the rear cover and connected this second nipple to the brass tube I attached to the intake manifold flange under the carb with a length of tygon tube. This mod makes the fuel pump work the same way as the normal Walbro carbs on the 2-stroke engines.

I tested this mod by turning the crankshaft with an electric starter, and the fuel inlet to the carburetor sucking fuel from a container 1 meter below. The new fuel pump setup pumped like crazy !  Next I ran the engine on the ground, and had to set both needles slightly more lean which tells me the carburetor was actually getting more fuel pressure from the pump.

I forgot to mention - another mod was to carefully cut off about 1mm length of the pop-off valve spring to slightly reduce the pop-off valve reseat pressure. In Walbro's service manual it says pop-off pressure must be 20 - 30 psi, but most importantly the pop-off valve reseat pressure must be 10 to 12 psi. Before cutting the spring, I tested about 15psi. After cutting 1mm off, it was just under 12psi.

I couldn't believe how good the throttle response was now (ZERO hesitation at any point), and how smooth it ran right throughout the range from idle to wide open throttle. I also picked up the plane and shook it around with the nose pointed upward at full throttle, and not a single cough or hesitation from it !  In other words - it now seems to be running almost PERFECTLY.

BUT as they say - "the proof is in the pudding" - so I can't say that all these mods have taken care of my overheating problem - will have to fly it first. One thing I CAN say however is that this is my very last attempt at getting this engine to actually run like an engine. You may ask why I'm doing all this effort, why not toss this piece of junk and get a proper engine ?  Well, I like a challenge like this and I will not give up until I can say I have tried EVERYTHING that I can think of.  Also, I'm learning a lot about gas engines in the process too !

Gabrielsande

Hey dude, well done!, if you look up in the thread I mentioned that might be the problem,the one way pumping action, I wasn´t brave enough to do the mod,please if you can post some pictures,and I will try todo the same!

In mine perhaps the tank is very close to the carb and at the same level, so doesn´t overheats, just the samehiccup at high g manouvres and not always, neverhad a dead stick, Im usinga 17x6 apc prop,I think your is the cure for the desease! well done again!

Curing that to me is one of the best looking engines,and the sound!......But never had such a problem with a normal gas engine,in a normal walbro just set the needles and done ,years without touching them.

Will see! tested the other daya friends extra with an OS 35 gas and I was impressed with the quality,niceand quiet,and the low vibrations, but these saitoshave that special thing which makes you go madonthemtrying to fix problemsthey designers left behind!! and wont admit! will be nice from them to admit the fault and publish how to made the mod or send the instructions and the kit to do it.

thank you for sharing your experience and keep posting!!

Luis Sande

ya33a

[youtube]http://www.youtube.com/watch?v=eoKG6mAYRt4[/youtube]

Here's my attempt with the FG 20, I spent most of the day getting it to run 95%....
I will try and work my way through the 'fix' before taking the plunge to try it myself, yes pictures or a diagram would be helpful.

Thanks

w8ye

My Feedback: (16)

When you get it in the air, you will need to do the needles over again?