XJet

I've always run my Saito 100 with an APC 15x4W prop which is quite heavy and on 10% nitro it spins at just over 10,000 RPMs -- although I only use full throttle very occasionally (flying 3D you know).

So far it's been a brilliant motor and everyone remarks at how smooth it runs with an incredibly low idle and amazing power.

Well on Sunday I thought I'd try a different prop, to see what difference it made to a few maneuvers that need faster prop-wash over the tailfeathers (such as pinwheels, etc).

So I threw a Volk 15x6 wood prop on.

This prop is *way* lighter than the APC -- to the extent that I was also able to remove an ounce of lead I'd put in the tail of my profile in order to get the CG just right.

However, on starting the engine it became clear that it didn't like this prop at all.

The RPMs were about the same as with the APC but it wask knocking (almost detonating) quite badly at anything over about 1/4 throttle.

I richened it up quite a bit -- but that made little or no difference, even after I was 1000 RPMs down on full throttle.

After half a flight I took the wood prop off and put an MAS K series 14x6 (which is heavier than the wooden one but still lighter than the APC).

This significantly reduced the knocking -- but it was still there, even when rich.

The top-end RPMs on all three props was about the same (10,200 or so) so I assume that they all offer about the same aerodynamic load on the motor.

Throw the APC 15x4W back on and it's fine. Lean the needle out to 300RPMs rich of peak and it's still fine.

The problem is that I actually found this plane flies better with the 14x6 MAS prop but I'm concerned about the knocking at anything over about 1/2 throttle.

The valves are set exactly right, the fuel has only 10% nitro and a rich needle doesn't seem to reduce the knocking at all. There's no fuel foaming (all the props are balanced) so I'm stumped. I also checked that the propnuts weren't bottoming out on the threads and thus allowing the prop to slip on the shaft (I've seen that before). In fact both of the other props tried have a thicker hub than the APC 15x4W so that can't be the cause.

Is it just that these props are too light for the 100?

I could go to an MAS 15x6 (which is heavier than the 14x6) but then I'd lose spool-up which is important for 3D.

w8ye

My Feedback: (16)

After dropping your engine. You will have to feel of the cranks rotation and see if it damaged the bearings.

It's highly likely that it didn't hurt anything but you never know?

farminred

quick question.

for a 1/4 scale cub (sig)(somtimes floats) which engine the 180 or 220 want alot of power!

jb86

My Feedback: (8)

thanks for the advice. i will check that crank rotation and i am putting in new ceramic bearings later this week, before it runs again.
i was just worried that there may be a concern of the crank being damaged. and no way to check it w/o a dial indicator.

a 220 would be alot of engine (and size and weight) for a 1/4 scale cub. the 180 is about the same size and weight as the 120 (a little more weight). the 120 should be about the right engine. that a/c should weigh about 12 lbs. even w/floats 15-16 lbs. that is about what i would expect for 1/4 scale. the 180 would be good up to a 1/3 scale cub (moderate power).

jon

jb86

My Feedback: (8)

thanks for the advice. i will check that crank rotation and i am putting in new ceramic bearings later this week, before it runs again.
i was just worried that there may be a concern of the crank being damaged. and no way to check it w/o a dial indicator.

a 220 would be alot of engine for a 1/4 scale cub. the 180 is about the same size and weight as the 120 (a little more weight). the 120 should be about the right engine. that a/c should weigh about 12 lbs. even w/floats 15-16 lbs. that is about what i would expect for 1/4 scale. the 180 would be good up to a 1/3 scale cub (moderate power).

jon

w8ye

My Feedback: (16)

You can usually spot a bent crank if you look carefully while turning the engine over with the propeller off. It helps to have the glow plug out?

The cranks usually bend in the threaded area. Because of this, the engine may still turn normally but the prop will wiggle.

w8ye

My Feedback: (16)

You can usually spot a bent crank if you look carefully while turning the engine over with the propeller off. It helps to have the glow plug out?

The cranks usually bend in the threaded area. Because of this, the engine may still turn normally but the prop will wiggle.

scratchonly

I have a 15x6 on my saito 120 in a 10 lb pitts. I agree, it's perfect.

jktenor

Hi,

I wanted to update you all on the Saito 180 problem I was having. I sent it back to horizon repair. As it turned out the main bearings had been installed incorrectly at the factory and were spinning in their races. Horizon replaced the entire bottom end of the engine at no cost to me, as well as adjusting valves etc.

My Brother's 120 siato within two weeks was sent back as well as it turns out, it had a front bearing failure which Horizon repaired as well. Both engines are less than a year old. His engine was always very smooth.

I always wondered why it (the 180)vibrated so much and was so hard to start the first time. I will mount it back on the plane and see what happens and report back to you all. This is my first Saito, and I had no way of knowing anything like that ever happened.

My brother will mount his and we will probably test them with the next week or two. I have been working alot lately.

Hobbsy

My Feedback: (102)

Here is one "slooshin" that could help you out. This a TurboHeader plus Saitos 14mm, 90 degree adapter on a Saito 1.50.

Hibrass

My Feedback: (1)

w8ye,

Thanks for the advice. But the prop didn't work I'm still getting interferance against the backplate....

Any other ideas???

Thanks,

Hibrass

w8ye

My Feedback: (16)

Hibrass,

If you installed a new prop and tightened it for all you were worth I don't know what else without looking at it myself.

What is suspect is that the prop drive washer will have to be removed including the little cone.
With the crank all the way forward and not rubbing the back plate, then slide the little cone back against the front bearing.

Then to put on the drive washer - prop - prop washer - nuts and tighten?

Hibrass

My Feedback: (1)

W8ye,

Thanks that is the next step in the process. I still have to order a Manifold, Needle Valve and Velocity statck just to correct the know problems. Plus a muffler...

Thanks again...

More later,

Hibrass

RCWI

Hi all. I have a 1.25 and was wondering if I can paint the heads black? its not a golden night, but i'ed like to paint my heads black like the golden nights heads are gold. Can i do it? thanks

w8ye

My Feedback: (16)

The valve covers are chromed and paint will not stick to them very well

RPM1

My Feedback: (2)

You can powder coat them. I powder coated a few sets and have not had any flaking or problems with heat.

freeonthree

My Feedback: (1)

As long as it didn't break anything, it should be fine. I seriously doubt that it bent the crank. Fire it up, it will be just fine I bet.

Tbone4life

In the outdoor sections of home depot and lowes they have BBQ Grill Paints that can stand very high heats, wonder if they would work also?

Tbatt

My Feedback: (4)

I have loved Saito engines since they first came out. My first one was the rare 80 twin. It started on the first flip of the prop! It was love at first flip!

I now have quite a collection from one of the old FA45 (NIB) of course my 80 twin, 30, 56, 72, 80GK, 90 twin, 120, 150, 180, 90-R3, 170-R3.

I did venture down the OS path only to have lots of problems. My first OS was the 120 which broke it's crankshaft while starting one day. It was very prone to backfiring while starting. After the bearings gave out I got rid of it. My second (and last) OS was the 160 twin. It would either run great at idle and full throttle OR mid throttle but not both. I replaced the AIR BLEED carb with the carb from the 240 and it ran much better......until one of the connecting rods bent while in flight. I ordered a replacement rod and the new one was a different design which made me have to order another one to keep the engine balanced. Then the black coating on the cylinders started to come off. Next the bearings started to rumble. By the time I had gotten rid of the 160 twin I had put enough money in it to have bought a second engine (two sets of bearings, two rods, one carb, etc....).

blw

My Feedback: (3)

tbatt- are you a member of the Saito club?

WMB

My Feedback: (1)

Chief Aircraft had a monthly Saito special in the past that they would e-mail on request. I haven't seen this lately. Does anyone know if they still do that? It was good for a few dollars off.

I am ready to order my first new Saito. I want a 72 or 82 for very spirited performance in 40 size planes. I had a Saito 65 in a pattern/3D combo type plane. The cylinder broke so I put a ST51 on it. The ST51 pulled it much better. It will end up in a Midwest Zero that I'm am finishing up now.

I kept up with the Saito thread but still undecided. I'm thinking get the 82, are there any reasons to get the 72 over the 82? I wouldn't even mind the 91, but dont want the weight penalty.

Thinking ahead, I love the looks of the GP Revolver. I also have on the build pile a GP Tracer and GP 40 size Corsair. So this engine may end up pulling a few different planes.

Thanks all, MikeB

w8ye

My Feedback: (16)

The Saito 82 is superior in many ways to the 72. But it costs more

Have you considered buying one used on the RCU Market place?

blw

My Feedback: (3)

Mike,

The .72 is a little bit cheaper than the .82, and is happy with smaller props if clearance is an issue. Otherwise, it is only a bit more expensive, a wee bit lighter, and has more power.

WMB

My Feedback: (1)

82 it is then. I've seen them up for sale here in the past. It's slim pickens now.
Thanks, MikeB

nitrobeast

Hey guys

I just picked up a 40 size ultra stick with servos and a saito 72 for $100!!!. I flew it 4 times now and love the 4 stroke, this is my first one. My question is what should the rpm's be at idle? Now there at 3k which seems high to me but it doesnt pull the plane. Is that OK? Im running a 13x6 prop.

Thanks