Linkan2

Hi Tom
I recognize a lot of you have had the Dinna 7-35.
Compression was good at when I change the valve springs, the spring new higher and harder.
with Saito carburetor as the engine is stable in its adjustment,
an idle speed of 1350 rpm and peak at 7100rpm.
The oil in the time cap is now a little less and clear.
They can make a good engine of 7-35 also

tih

My Feedback: (1)

Just received my 7-35 today. It's the most beautiful object I've seen in a very long time.

A couple of observations:

I guess they've noticed that people are losing valve pushrods, because they've chosen to include a complete set of spare pushrods and pins with the engine.

The included glow plug harness seems like a joke. Those friction fit caps surely aren't going to stay on the plugs with the engine running?

My engine has been run for twenty minutes, according to the accompanying test report, so I guess I should hurry up and fill it with a good after run oil. Should I also open it up, though, and inspect the inside for rust? If they've shipped it out after running it, without properly protecting it, I'd like to know - and complain. I just pulled one of the pushrod pins, and dragged it along paper, where it left a black trace.

Based on Lars' experience, I've also purchased a Saito carburetor. Now to turn an adapter on the lathe... Metalworking is fun!

I'm going to use this engine in a Pica 1:5 WACO YMF-3, so it will be cowled. Thinking of the good old 1:3 rule for air flow, I'm wondering if I should make some baffles to mount on the engine, to force air flow through the cylinder cooling fins? I guess I could make them to be held by the bolts already holding the cylinders to the crank case, closing up the opening between the cylinders up to just below the exhaust pipe. Combined with a baffle within the cowl, to keep air from going 'round the engine above the cylinder heads and exhaust pipes, this should give good cooling, and help me achieve a proper ratio of in- to outflow. Sound reasonable?

Finally, I'm wondering: why do these engines want less oil than "regular" four stroke glow engines? Intuitively, it just sounds like a risky way to extract more power...?

-tih

Straightleg

These engines have needle bearings, ordinary four strokes do not.(you need less oil) You will NOT loose pushrods, if you keep rpm down.

Linkan2

Hello
I think they party of you turning into a busning without broblem.
The dimensions that I have on my sleeve OD 14,99mm and the carburetor has 11mm (ID)
The length is 13mm.
I drilled two holes M3 thread for Allen screws being ground down

Linkan2

tih

My Feedback: (1)

Thanks, Lars!

The Saito carburetor got to Norway today, so I should probably have it here Monday or Tuesday.

Meanwhile, I've mounted a propeller on the engine. It's rather hard to turn, and feels a bit rough, so I'm definitely going to take off the back plate, at least, to check for corrosion. Then, I'll wash it out with some glow fuel, and smother it in a high quality EP 90 GL4 gear oil, so I can feel better about letting it sit until I'm ready to mount it in the WACO.

Actually, I'd like to remove the front cover for inspection, as well. Has any of you gone inside the 7-35 from that side yet? I imagine it's just a matter of removing all the pins for the valve pushrods, and then pulling the cover off along the crank shaft? (I'm used to mechanical work, to the point where I'm comfortable with overhauling a manual automotive transmission unit, but wouldn't risk opening an automatic.)

-tih

Linkan2

hey TIH
you should not have gearbox oil in the engine is not made for the heat so no.
it's probably not mixable with methanol.
you look good if you take off the back cover of the rust, which I do not believe.

so if you now have to remove the front cover, you must loosen the lock ring at crankshaft

fast delivery of the carburetor where did you buy it?
take time on you during running-in.

j lauria

Personal observation of a UMS 7-77 in a 43 lb. corsair

Today I watched a 43 lb. Corsair fly with a UMS 7-77 radial engine. It flew beautifully, performing all of the usual aerobatic maneuvers expected of a Corsair. I questioned the pilot after the flight. When he first attempted to run the engine it would not start. After changing the glow plugs to Saitos from OS it started easily and has continued to do so for two seasons. He uses on board glow (Mc Daniels) and Cool power fuel. He also uses the original carburater. He has never removed a push rod or follower to inject oils into the crank case at days end. All of this information seems to be at odds with what I have read on this thread.

Maxam

My Feedback: (62)

He has been lucky. The 9-99 is far more prone to corrosion than the 7-77 due to the large volume crankcase. Sorry, OS type F plugs will last years over the Saito's The spring sockets for the OS plugs can be pushed on too far to a second notch thus shorting to the plugs ground. Is he using coolpower that is all castor?

j lauria

He uses Cool Power that is all synthetic

tih

My Feedback: (1)

Ah, yes -- on this one, the path from the carburetor passes through the crank case on the way to the cylinders, so after run oil has to be soluble in methanol, and be able to pass through the combustion chamber without ill effects. Didn't think of that... Thanks for the warning! Is there any suitable oil that I won't have to buy mail order? Something I could pick up at Biltema would be ideal...

The engine and the carburetor both got here really fast. I bought the engine from Horizon USA, and the carburetor from one of their neighbors: http://www.advantagehobby.com/

-tih

tih

My Feedback: (1)

You're right again, Lars.

...and after washing out the engine with some heli fuel I happened to have sitting here, with 22% oil content, it's nice and smooth.

-tih

Linkan2

when the engine is new from the factory, so they are in the front cover, there is the graphite grease.
On the cam and gear, they should EVER be washed away.
They disappear when you run the engine, lubricates good on the new engine.

to protect against corrosion in the engine (four-stroke), I have ATF oil when the engine is not running for a long time.

I think they are some good things in the manual there too

keep in mind that they are hanging cylinders shall be drained so that you do not get hydroloock

tih

My Feedback: (1)

That's certainly what I would do (and I keep LiquiMoly LM48 mounting paste on hand for just that purpose), but do you really think they do that after test running the engine?

Me, too, for "normal" four strokes. Hm, let me do a test ... nope, ATF does not mix with methanol: I can whip it into a suspension, but it separates again. Same thing with the mineral GL4 that I initially thought I would use. So what kind of oil plays nice with methanol (other than castor, which I'd rather avoid)?

-tih

Linkan2

TIH
what fuel you have, you are buying mixed in the hobby shop or you mix yourself?
And if so which oil do you have?
No you should not mix ATF oil and methanol, it should be right as it is.
as after-run oil.

graphite grease applied at the assembly of the engine, they will notice when you run the engine.
comes out as a dark gray oil, you should not use the now.

Good luck

tih

My Feedback: (1)

Ah, no, I was being unclear. I just meant that the after run oil perhaps ought to be both soluble in methanol, and able to pass through the combustion chamber without leaving a lot of carbon deposits.

-tih

j lauria

Update on my 9-99
Today the technician at Horizon advised mr that my engine needs new bearings. Cost $500.00. He also advises that the engine has low compression which accounts for it not starting. It may return to good compression after the bearings are replaced and it is run rich , some times it works. If it doesn't work the cylinders need to be replaced. Cost $200.00 per cylinder. They are sold in units I told him to return the engine to me. I give up!

tih

My Feedback: (1)

OK, that's quite a lot of money for new bearings, but there's a not insignificant amount of work involved, so I think it's acceptable.

Now, this sounds strange. If he's got the engine in front of him, and he's a service tech, he should be able to tell you what's going on. The "may return" bit sounds a bit like he's saying you may have stuck rings, but then he shouldn't be predicting cylinder swaps. IMHO, he should have pulled a cylinder, to observe the damage. Sure, that would have taken him fifteen minutes, but that's part of the effort he should put in before asking you to spend more money.

If it were me, I'd get the engine back (as you did), take it apart, replace the bearings, check, and probably replace, the rings, hone the valve seats while I was at it, and then run the engine nice and rich to prevent a relapse.

And if you do give up, at least sell the engine to someone who is willing and able to put some effort into saving it.

-tih

j lauria

The engine has been sold along with all of its accessories to a person who likes to tinker with engines and knows the history of this one. I recovered less than a fifth of what I had invested in this engine but equally significant I lost four or five days of flying because of it.

slskn

My Feedback: (4)

well, been flying my Ziroli Corsair with 9-99 all summer lots of flights, just have a question, the engine runs great starts good well oiled after wards bearings feel smooth, but seems I have very low compression, can turn prop easily by hand, my Stearman has 7-77 same amount of flights all summer but has more compression them my 9-99? just wondering why the 9-99 seems less compression, but runs fabulous, should I worry about it?...............Steve.

Maxam

My Feedback: (62)

Steve, Next time you go to run your 9-99 out at the field, Immediately after starting hold a folded paper towel loosely over the exhaust and run the engine up some for a minute. The towel should get really oily of course but only stain the color of the fuel. If it is a rusty color the rings are rusting some and compression would start to drop on some of the cylinders. Years ago when I was figuring all this stuff out I did not oil and dry the 9-90 properly and the exhaust was rusty! Since then with my after run techniques the exhaust is the color of the fuel dye and the compression is excellent on all cylinders. Yesterday the engine exceeded 200 flights on the old Robin Hood 99! -Tom

slskn

My Feedback: (4)

thanks for the info Tom, will surely do the test you suggest, I have been faithfully doing the run engine dry and oiling afterwards, like I said bearings are very smooth, just seems like low compression compared to my 7-77, wow!! I hope to get as many on my 9-99 as you have on your Robin hood that is fantastic!!! the Corsair has probably 250 or so flights on it, but with the the 9-99 on it I am guessing 60 or so on the engine, since I installed the Radial, before that it had the saito 450, which was a little under powered, the Corsair 36lbs. but the 9-99 flies it a bit faster although not as fast as it should go but am happy with the performance. thanks again for your input! happy flying!!!

eskiserkan

Today, I ordered Saito 120 radial carb. for my 7-35 also. I think it would be the best upgrade for this engine. What about 170 radial carburator ? Has anyone tried one on the 7-35 ?

Linkan2

Hello
no, do not think they will be better with the carburetor from Saito 170.
they both carburetors have the same spay bar, but the carburetor 170 has wider inside diameter.
it might fit on 7-77.
or carburetor from Saito 325r5, maybe it would work on 7-77 & 9-99 !!?

now I have two hours with new carburetor and has not touched the needles at all.
this is the best up dating of this engine right now.
good luck, now Autumn has arrived in Sweden.
so it will have to wait until spring
Lars

Maxam

My Feedback: (62)

The choke area is too large on the 170 carb.