ghendrix01

My Feedback: (1)

OK, this one has me stumped. I bought a used Saito 60T with very low time on it. Upon starting it, I cannot get over 7000 rpm with a 12-8 prop. I have found that the right cylinder does not seem to want to fire correctly. If I run the engine on just the left cylinder I get 6800 rpm. With just the right cylinder I get 4000 rpm and cannot get it to run past half throttle. If both cylinders are firing, I get the before mentioned 7000 rpm (yes, just 200 more rpm with both cylinders firing). I checked the valve lash and found it ok on both cylinders. The only thing I can identify is that the left cylinder seems to have more compression than the right. I have disassembled the engine and everything looks ok inside. The timing is correct. Any ideas as to where to go from here? I have other Saito twins (100 and 130) and all run fine on both cylinders.

Thanks for any help.

George

Kmot

My Feedback: (24)

Have you tried swapping glow plugs from side to side? If you do and then the left cylinder runs crappy you have identified your problem. Or maybe you just want to install two new plugs anyway and give another test run. Hopefully you don't have a mechanical problem on that right cylinder.

ghendrix01

My Feedback: (1)

Yes, I swapped plugs, tried new ones, nothing changed. Maybe I am hoping for too much. The prop range on this engine is 11-8 to 13-6. With a 12-5 I got about 8000 and with a 12-8, 7000.

In an effort to establish that the plumbing (intake runners and exhaust manifolds) were not affecting the performance of the right verses left, I disassembled the engine and swapped the right and left cylinder/piston assemblies. Left is now right, etc. I ran it again and found the same results with one exception. Neither side, when running alone, will rev beyond about 4000 rpm, but together I still only get about 7000 rpm. Again, the same cylinder as before still has more compression than the other.

Does anyone have the rpm figures for various prop sizes. This thing has a maximum rpm of 10000. I just don't know what prop would give that number.

Again, maybe I am expecting too much from this engine. I kind of thought it would at least equal a 40 of 46 size in performance and that is the size of plane it is mounted on (GP Cap232, 40 size). The plane just barely achieves flying speed. Nothing like what I would have expected.

Thanks,

George

William Robison

My Feedback: (3)

George:

Your FA-60T is an “Odd fire� engine, and the uneven firing impulses aren’t the only odd thing about it.

Let’s do a quick review of single cylinder four stroke engines, then get back to yours.

A tachometer will read a steady rpm, but it’s really an average of the engine speed and doesn’t reflect the instantaneous speed. When the engine is on the power stroke it accelerates the crank shaft, the engine speeds up. Then the crank coasts through the exhaust and intake strokes, then the load of the compression stroke slows the engine even more. When the cylinder fires again the rpm rises, and the cycle repeats. This equates, roughly, to 180 degrees of acceleration, and then 540bdegrees coasting. An “even fire� twin doubles the power strokes, having (again roughly) 180 degrees of power, 180 degrees coasting, then repeat.

An “Odd fire� twin has the power strokes one following the other, giving 360 degrees (180+ 180) power, then 360 degrees coasting. At first glance this looks like the even fire engine just stretched out, and that’s pretty much the case. But having one power stroke immediately following, the rpm changes are greater. We get a double kick on the prop, and then a longer coasting period.

Finally we come to the really odd part of odd fire. Losing one cylinder makes a greater rpm difference than losing the other. When the first cylinder fires it is pushing the second directly in its compression stroke, not using the flywheel effect of the prop, if #2 cylinder flames out it has less effect on the rpm than losing number one. If #1 has quit then #2 has to accelerate the prop, then the engine coasts, then comes on the compression of #1 and this slows the crank more, then the crank slows even further when pushing #2 piston up in its compression stroke.

So, getting an rpm difference between the two cylinders going out is perfectly normal. But it does seem you have more difference than you should.

Possible reasons for a greater differential include the glow plugs, as TomK said. It could also be that you don’t have the two HS needles adjusted properly. The odd fire twins have, in effect, two carbs so it’s also possible the throttles are not opening together. Another good possibility is an air leak in one intake or the other. Replace all the o-rings just in case.

Hope at least some of this will help.

Bill.

William Robison

My Feedback: (3)

George:

One more point - a 12x8 might be a little much. It should spin a 12x6 around 8500-9000 rpm.

Bill.

ghendrix01

My Feedback: (1)

Bill,

The 60T engine is not an odd fire as you describe. The old 90T and newer 100T and 130T are all odd fire engines. The 60T and newer 90TS are even fire as they both have two throws on the crank and both pistons travel out at the same time, giving one on compression and the other on exhaust. The firing strokes are 360 degrees apart. I have three 100Ts and know about adjusting the two carbs. The 60T has only one carb. Anyway, when I used a 12-5 prop, I only got about 8000 rpm. I would have thought I would have gotten aroung 9500 with the 12-5. I am probably expecting more from this engine than I should. The 100T in my Skybolt really pulls it nicely. Not as good as a 120 or 91 single, but respectfully. I just thought a 60 would be at least as good as a 40 2 stroke. Oh well, unless changing prop size improves the performance, I wil have to look into some other engine and find someone with a Cub or something like it that can use this 60T twin.

Thanks,

George

Ladyflyer

My Feedback: (2)

The 60t is a Boxer style opposed, alternate firing twin. The layout is as found on the old BMW cycle. The other odd thing is that the power is way down from a similar displacement single cylinder engine.
Me thinks you were a bit optimistic.

William Robison

My Feedback: (3)

George:

You're right. I looked at 60T and the dyslexia must have kicked in, I saw 90T.

Sorry.

Bill.

ghendrix01

My Feedback: (1)

Some new information about the difference in compression left verse right cylinder. It seems that the right exhaust valve may be leaking. When I turn the engine through the compression stroke of each cylinder (engine off plane, exhaust manifolds removed), I find that compression is leaking into the exhaust port of the right cylinder only. I place my finger over the port and turn the engine and I feel pressure leaking to the port. The left cylinder does not do this. The rocker arms were not installed when I checked this, so I know the valve is not open. I have removed the valve and upon inspection, I find that the seat area has a blackened section. I have attempted to seat the valve by lapping it using a polishing compound with no success. Any ideas on how to lap the valve to the seat? I feel that this is the problem causing the lower compression in the right cylinder and if I can get the valve to seat, things may improve.

Another thing, the manual that came with this engine lists larger props than the later manual on the Horizon web site. I will probably try a 10-6 or 11-5 prop and see if the rpm comes up. The largest prop recommended in the later manual is 12-5 as compared to 13-8 in the earlier manual.

Thanks,

George

ghendrix01

My Feedback: (1)

OK, I found the problem with this engine. Looking into the exhaust port, there is an pocket in the aluminum casting. Looking down the cylinder to the area around the exhaust seat, which is a brass insert, there is a small pocket in the casting which appears to go to the larger pocket in the exhaust port. This pocket is in the treaded area of the port which will not be sealed when the exhaust nut is screwed in. This seems to be the source of the compression leak. I guess I will have to order a new cylinder (55.96+7.99 shipping). This would be one of those manufacturing defects but since I bought the engine second hand, I have no recource except to order a new one. I sure am glad that I figured this one out. I will attempt to verify by trying to seal the pocket with some JB Weld just to see if it stops the leak. I'm pretty sure that this would not be a permanent fix as any leak at all would burn up the epoxy material in the JB Weld.

I hope this helps anyone else who may have similar problems although it would be pretty unlikely for something like this to be duplicated.

Thanks to everyone who answered this thread. I will update it with the final outcome after I get the new cylinder.

George

w8ye

My Feedback: (16)

You might call Horizon first. They may fix it for you eventhough being as it is a casting defect.

loughbd

A 10x6 prop is grossly too small for this engine. My old worn out saito 45 turns an 11x6 9000.

William Robison

My Feedback: (3)

Bruce:

Pardon me, but where did anyone mention a 10x6 prop on this engine?

Bill.

loughbd

Bill, try looking at post number nine. He said he was going to use a 10x6 or 11x5 prop.

William Robison

My Feedback: (3)

Bruce:

You're right. Post number nine.

Sorry.

Bill.

ghendrix01

My Feedback: (1)

In regards to the prop selection, as I stated earlier, the manual that came with this engine lists props from 11x8 to 13x6. The online manual on Horizon web site lists 10x6 to12x5 for sport and 11x5 to 12x5 for scale. Which should I use, the one that came with the engine (older) or what is shown presently on the web site? I was just going to see what I could get out of it as is using a 10x6. I have decided to just wait and get a new cylinder, transfer the parts (valves, etc.) and then see what it will do with a 12X5 to 12X8. That was what I wanted to use when flying. As is, I cannot expect much from this engine since it is really only a 1.5 cylinder engine with the compression leak in the right cylinder. I gave up on trying to do anything else with it after I found the leak.

No more used engines for me. This is the first and last one I will ever buy.

You know, getting 7000 out of it on a 12x8 is probably pretty good considering it is equal to a 40 four stroke right now with the compression leak (6800 on one cylinder, 7000 on two).

George

loughbd

There is NO WAY any 60 four cycle engine can be run on a 10x6 propeller. A 10x6 is about the smallest you would run on a 45 two cycle. A 45 two cycle will turn well over 13,000 rpm on a 10x6. A 60 four cycle would eat itself on one. I ran my original OS FS60 open rocker on a 13x6 and it ran over 8000. A Saito 80T twin on a 14x6 turns about 9000rpm.. Either Horizon has their stuff wrong or you read the wrong prop size.

A 25 year old Saito FA45 turns an 11x6 almost 9000rpm. I'm flying with one on a Pilot Skyloop 404 right now.

ghendrix01

My Feedback: (1)

Well, I would agree with you if it wasn't for the Horizon website. Go look for yourself. I didn't read it wrong. I also happen to have more than one actual printed manual with the same info. They came with my 100T and 130T Saito twins. The manaul that came with this 60T is older and has different info. I have yet to run it on anything smaller than a 12-5. Anyway, I got the new cylinder today and I will list the results of the tests as soon as I run the engine which now has about the same compression on both cylinders. Be assured I will start with the 12-8 prop.

George

iflyj3

My Feedback: (7)

George,

You may be throwing good money after bad. I have a 60T and it has the power of an OS 40 LA if that much. I had it on a Hanger 9 Cub and took it off and replaced it with the 90TS. A much better match.

The 60T is too heavy for the power it produces.

ghendrix01

My Feedback: (1)

Ok, I got 9500 with a 12-4, 9150 with a 12-5 and 7500 with a 12-8. If I had a 12-6, I would have tried it. This is more like what I expected. Do these seem about right? I may see a few more rpms when the new cylinder get broken in.

As for the overall performance, I know I won't be doing any 3D stuff with this engine, but since I never do that kind of stuff, that will be ok. I just like 4 cycle twins and I have 6 planes with them. They run smoother than a single and the sound is great.

Thanks to everyone who posted on this,

George

loughbd

Put a 10x6 on it and tell us what it does.

blw

My Feedback: (3)

Bruce- George said that he will use a 12x8. He was only telling us what he found in the Saito instructions about a 10x6, which was interesting. Are you really suggesting that he try the small prop?

loughbd

Why not?? According to him, Saito recommends a 10X6. How could they possibly be wrong???

blw

My Feedback: (3)

If you were to go to: http://www.horizonhobby.com/ProdInfo...n_cylinder.pdf you would see that Saito does recommend the 10x6 and 10x7 props for this engine. George was only stating what Saito is saying and was asking for helpful advice. "Helpful" is the key word here. He only mentioned using the 10x6 since his RPMs were way down in the first place....

ghendrix01

My Feedback: (1)

blw,

Exactly, I was looking for information from others that may have some experience with this engine.

Loughbd,

I scanned the pages from the manual for you to see. you may need to save and view it with a program that lets you zoom to see the text.

Btw, I never suggested I would try a 10-6, instead I stated I would start with a 12-8. I posted the rpm data from the 12-8, a 12-5 and 12-4.

The old manual that came with the engine listed the largest prop at 13-6. Based on the data from the 12 inch props, I cannot see using a prop that large. Also, I use a 13-8 on my 100T with great results. This prop size is listed in the scanned pages for the 100T. Other than the 10-6 and 10-7 listed for the 60T, the other props seem to be in the correct range. The 11 inch props may be too small, but since I am getting about what I expect from the 12-5, that is what I will be using.

Thanks for all the help,

George