Need Help with Saito 120 !!!
 

Hello People,

I was in the process of breaking in a brand new Saito 120, on my third tank of fuel, when I noticed oil/fuel coming out of the bottom of the cam gear housing. I broke the engine down to check out the gasket under the cam gear housing. The gasket appeared ok and I reassembled the engine. Now the engine will not start. I readjusted the valves and still nothing. I noticed that after I primed the carburetor and attempted to start the engine that the fuel would blow back into the tank. I changed fuel line and still nothing. As a last resort I removed the high speed needle, opened the carb up all the way, and then turned it over with the starter to see if there was any trash in the carb. Nothing. I did notice that when I did this, it felt like air was coming out of the carb. I'm no engine expert, but I do know that a carb is basically a vacuum and air should not be coming out.

Could it be that the cam is out of timing? And if this is the case, how can I get it back in timing. The valves appear to be operating in the right order. The exhaust valve opes just after compression and than the intake valve opens. Any and all help would be greatly appreciated.

Thanks in advance.

RE: Need Help with Saito 120 !!!
 

The cam has a timing mark on it. With the engine piston at top dead center, re-install the cam with the mark straight down.

Enjoy,
Jim

RE: Need Help with Saito 120 !!!
 

Gary,

Jim is right.......you have the cam in wrong or the 2 valves reversed!! On the Saito's, it's common for the new engines to leak when they get hot and they run REAL HOT! When this leak occurs, just snug up the hex bolts while she is hot...maybe 1/16 to 1/8 of a turn and NO MORE as you may strip her!

I wished you would have never opened her up!........anayway......

Anyway, reverse the push rods on the cam, IF THE CAM IS IN RIGHT; THEY SHOULD NOT "CRISS-CROSS"!

If you have the dirrections the breakdown is there; if you DON'T want to mess with it, then send it over to Horizonhobbys.com and they will put her back in shape with new gaskets and such. I dont recomend you use the same gaskets as there is a tremendous ammount of pressure and heat in these GREAT engines!! They are simply the best 4-strokes money can buy!!

Since there are only 2 rods and 2 cam lobes, you can't miss!!GOOD LUCK, let us know!!

Since she is NIB, you may want to send her to Horizon to have "piece of mind", on the other hand; it was issues like these that made us differ from the "not an engine guy" to AN "engine guy".......this is how I learned! And there were times when I had a KNOT in my stomach messing with a friends MERCEDEZ or WORSE a vintage 1930's car where parts were NOT obtainable, but I hung in there and now I can take these things apart with my eyes closed! If you took her apart, YOU CAN put her together again! LOOK AT THE "SCORES" on the parts! Meaning.........what rubbed on what? Example.........You can see which way a rod went into an RC engine because the shinny side rubs against the crank right? The other side is rubbing against NOTHING and does not shine! This is how I have been given a totally disassembled engine and used good common sence to put "humpty dumpty" back together again!

The Slip!!

RE: Need Help with Saito 120 !!!
 

Wrong again Slip, most rods rub the back plate and not the crank, there is a filet at the base of the crankpin that keeps the rod from rubbing the crank.

RE: Need Help with Saito 120 !!!
 

Gary:

Forget what was said about switching the inlet and exhaust push rods and guides, only a total klutz could do it, the tappet guides point to the correct rockers, it would be too obvious an error. See the first picture.

I'll assume yours is a FA-120S version, you can't use the timing pin on the S engine because the tappets have to go in the housing before the cam, you can't put them in from the top. This makes the S engines real bears to time the cam. What makes it hard is that it's almost impossible not to hit the gear on something as you set the assembly in place.

You said "...The exhaust valve opes just after compression..." This in itself says the cam is 90 degrees out of time.

Pull both rocker covers and the glow plug. Turn the engine in forward rotation, watch the rockers. You'll see the exhaust open, then start to close. As it's closing you will see the inlet start opening. When the exhaust is 1/2 closed and the inlet 1/2 open you are at the point of maximum "Overlap," stop there and use a toothpick or similar probe to feel the piston position. If the piston is not all the way at the top of its stroke the cam is out of time. Holding your probe on the piston rock the crank back and forth to double check the piston position, the timing gear teeth are coarse enough that even one tooth off will show up in this test.

If it's out of time lift the cam assembly out again, set the piston to TDC using the probe as you did in checking it, set the cam mark straight down, very carefully set the assembly back in place. DO NOT ASSEMBLE IT WITHOUT THE GASKET. The gasket sets the clearance in the timing gears.

Don't tighten the screws, just snug them and check to be sure the timing is right. You don't have to reassemble the valve gear, just set the push rods in place, with a finger on each one you can feel their position as you watched the rockers before. When you're sure it's right tighten the screws, and put the engine back together.

Bill.

RE: Need Help with Saito 120 !!!
 

Thanks for all the input.

I disassembled the engine again. I set the crank at TDC and aligned the mark on the cam gear at the 6 o'clock position. I carefully reassembled everything and made sure everything was tightened up.

Once she was back together, I primed her and attached the glow plug. She cranked right over on the first time with my starter. I ran the engine up to 3900 rpm for another 15 minutes. She ran just as good as the first time I started her yesterday.

I have about 30-40 minutes run time below 4000 rpm. Is it safe to start leaning her out? Also what kind of rpm should I go for with an APC 16x6 prop? I was thinking in the 9500 rpm range.

Thanks again. Your advice is greatly appreciated, especially since this is my first 4-stroke engine.

RE: Need Help with Saito 120 !!!
 

Gary:

With 40 minutes on the engine you can start leaning it, don't try for more than 8K to 9K until you are well over an hour, when you get three hours or so on it you should be able to spin the 16x6 APC over 11K rpm.

Glad you got it back together.

Side note: As the ring seats the oil leakage also will decrease.

Bill.

RE: Need Help with Saito 120 !!!
 

A little trick I use to keep the cam from rotating while reassembling, I pack the cam and housing with vaseline. This keeps the cam from rotating when you drop the housing into place. After the engine heats up, the vaseline just melts away.

RE: Need Help with Saito 120 !!!
 

Bill,

Thanks for the advice.

I started to slightly lean it out today. I ran it up to half throttle and it read about 6000 rpm on my tach. I leaned the high speed about 1/4 turn and the rpm increased about 300-500 rpm. This motor puts out a ton of prop wash. I used to .40-.50 size motors.

I thought it would be harder to tune than my 2-strokes, but aside from messing up the timing myself, I have had no problems. Saito's are freaking awesome. I don't know why I waited so long to get into 4-strokes.:)

Thanks again.

RE: Need Help with Saito 120 !!!
 

Gary:

Glad you like it, and welcome to the "Saito Sanitarium."

Now we have to diddle with your mind a bit more, and get you into flying twin engines and the "Twinsane Asylum."

Haw.

Bill.

RE: Need Help with Saito 120 !!!
 

Actually timing a Saito is quite easy. There is a small hole in intake cam which is the front cam on the left. If you take out that tappet you can turn the shaft until you see the little hole. I put one of the pushrods into the hole to keep the shaft from turning. Set to crankshaft at TDC and with the little hole visible exactly in the middle of the tappet opening set the assembly back on the engine. It is now timed correctly. Turn the engine two complete revolutions and look down the tappet hole. With the crank again at TDC you should see the little hole in the camshaft exactly in the middle. I rebuild these things so I have them apart a lot. I made a small tool to set the timing. It is a rod about 2 inches long exactly the size of the tappet hole with a *** on the end that is the same size as the hole in the camshaft. When inserted in the camshft through the tappet hole, the *** fits into the hole in the cam keeping it from turning and the cam can not move at all. Makes timing very easy.

Slipkid has some really screwy ideas. Go to his ebay auctions and look at the descriptions on some of the engines he sells. Does anyone here know what a "langed" engine is?? Read his descriptions to find out. He is daniel7450andthelion on ebay. Check his feedback too.

RE: Need Help with Saito 120 !!!
 

Loughbd:

Your timing pin should be 4 mm diameter, with a 2 mm peg on the end.

It works on all the mid block Saito engines, but wont work on the "High Cam" 120 engines and larger. These big block engines have tappets with enlarged heads, and they will not come out the top. They have to be installed before the cam is mounted in its carrier. See pictures. Small block and mid block use tappers as shown in the first picture, high cam big blocks use tappets as shown in the second.

Bill.

I am new to Saito 120 GS (my first 4 stroke). After running it for 40 minutes very rich, I leaned it a little, mounted the cowl, and went up flying. It all went well, except that it used some 12oz of fuel which I didn't expect, and the engine enclosure (cowl) was VERY messy with fuel (and or oil). I looked for leakage and after discarting some sources, concluded that fuel was coming out from an small hole drilled on top of the front bearing seating. I wonder whetther this is normal at this point of the break in process, or something is missing in that hole.
Otherwise the engine is great so far.

You should have only run it very rich for 10 minutes a 4,000 rpm or less. You wasted a lot of fuel running a cold engine. You need to place the engine on a test stand and set the needles properly. setting the high speed at peak first, then leaning the lo speed until you get a good idle and transition.