Mein Duff

Interesting, Neil Tidey of Laser engines in England only recommends OS-F plugs for his engines which are designed to run on 0% Nitro...and he has been doing this for about 30 yrs.

RBACONS

My Feedback: (3)

Yeah, well I may have overstated that. It really depends on the design of the engine.

BobH

My Feedback: (2)

Don,
Two thing. A: its very difficult to start the engine before it's well broken with out a starter. That's been my experience from the beginning.
B: several of us are using an OS carb in this engine. The stock carb is basically junk. Difficult to adjust and you'll never get the engine adjusted properly.
CH ignitions sells a $30 adapter for the carb to engine mount.

Look in the engine forums under UMS Radial for more Information.

RBACONS

My Feedback: (3)

I received mine used so I can't speak to it being hard to start when new but it too had the carb replaced with an OS carb. I think it was a drop in replacement but then its an original Seidel engine, not one of the UMS models.

abufletcher

The Seidel/UMS manual is quite specific in spelling out that NO NITRO should be used. And "more than 6-7% oil can harm the run condition" of the engine. The fuel mixture I'm using is the same as the last time I had the engine running: 95% methanol and 5% synthetic oil.

abufletcher

I'm using the plugs that came with the engine, which look like standard OS-F plugs. The manual suggests replacing all the plugs at the same time (with plugs by the same manufacturer) after each flying season. I don't have that much time on the engine, but maybe that's something else to try.

abufletcher

Hmm...interesting (and yet sort of depressing at the same time). I'll check into this.

As far as being hard to start when new, once I figured out the priming procedure it started with just a few casual flips...in fact, I would have said it's almost "dangerously easy" to start.

abufletcher

Here is the relevant page on the UMS forum:

http://www.rcuniverse.com/forum/glow...ration-66.html

abufletcher

It was worth the hour's drive to talk with Osaka-san at his hobby shop. He has one of the EVO/UMS 7-35 engines and offered some sage advice. First, he had an interesting suggestion for fuel. He advised me to mix the methanol with my regular 10% nitro/18% oil 4S fuel at a 40% to 60% ratio. This will cut the oil down to an acceptable level and the nitro to around 6%. He said that his 7-35 runs great on that mixture. Second, it was interesting to see that his 7-35 has quite strong compression and he thought it was very strange that mine has virtually none. He also suggested that I remove each of the plugs and put 2-3 drops of Klotz oil in each cylinder (while rotating the prop). This isn't when trying to start it but just to condition the engine. Finally, if the engine does need an overhaul, he was able to provide a phone number for a company in Osaka that might be able to do it.

BTW, his EVO/UMS apparently came with a couple of neat refinements. One is a lever attached to the throttle arm that allowed the linkage to avoid the mount. I had to come up with my own work-around for that. The other is a nifty spring-loaded cap for the carb, which would do the same job as covering it with a finger. This cap is pulled forward by pulling down on another lever. Both levers are firmly mounted to the engine mount.

abufletcher

No progress on the Seidel, but I did have some fun at the field.

geezeraviation

My Feedback: (3)

The blue and yellow one is a Curtis, it and the Stearnan are nice models but somewhat ho hum compared to your Se 5a.How's your weather?
Doc

abufletcher

Alternating clear and cloudy with temps about 5C. The first picture is overlooking my flying field (yesterday). The second shows the first snows (also taken yesterday) on the mountain range on the other side of the valley.

geezeraviation

My Feedback: (3)

I flew Friday with a friend, clear as a bell, beautiful skies but cold wind at about 5mph from the north about 38 f when we started but got up to about 50 by the time we left. We don't get any snow here to speak of, twice or three times in the 33 years I've been in Texas. Moving to Tennessee soon, expect that to change lol
Doc

abufletcher

I had you pegged as a "native son of Texas" and now you tell me you're running off to see those "belles of Tennessee?" We don't get more than the occasion snow flurry in my town but there's enough snow to get stuck on the mountain roads.

TFF

You must be going to east Tn if you are going to get any consistent snow. Up in those hills.

geezeraviation

My Feedback: (3)

Looking near Greeneville or Morrisown, somewhere off east of Knoxville towards the tri city area. Yeah in the foot hills maybe. It's so flat here I can see the red light on the roof of the grain elevators 22 miles west of here. lol Coastal Plains I think they call this area.

abufletcher

BTW, here's a different version of the SE5a photo above. This one has "truer" white balance.

geezeraviation

My Feedback: (3)

Great photo.

abufletcher

I've exhausted all avenues and all hope of getting the engine started. I gave it one last try, having last night put a couple of drops of Klotz oil into each cylinder, and using the methanol+fuel mixture (for a methanol blend with 5% nitro and 9% oil). I had the tiniest bit of (foolish) hope since the oil seemed to give the engine the slightest bit more resistance on the propeller. But nothing.

Nothing left to do but to send it in for maintenance. I'm hoping the place in Osaka can do it. I'd hate to have to ship it all the way back to India.

Boomerang1

If it's been laying around for some time it could be the piston rings (if it is fitted with them) being sticky & stuck in the ring grooves, the valves sticking in their guides, the rocker arms being sticky or the cam followers sticking in their housings .

Easiest to check is the valve gear problems. With the pushrods removed (do one cylinder at a time, with the piston at top dead centre on the compression stroke you should be able to depress the rocker arm by hand to remove the pushrod) make sure the rocker arm & valve is free, it should spring back firmly with a click.

Check the cam followers, holding each one of those removed pushrods with light pressure where it fits into the crank case rotate the prop by hand, it should move up & down smoothly with full movement as it follows the cam rings. You should do these checks one cylinder at a time & don't get the pushrods mixed up otherwise you will have to check & reset the valve clearances. Don't forget, with each cylinder at top dead centre on the compression stroke you should have a little play in the rocker arms (valve clearance).

If the rings are sticky in the pistons about the only easy way to get them loose is to wind it over with a starter until the friction/fuel loosens them up enough for them to seal & make enough compression for the engine to fire. You could try removing the plugs (one at a time) & filling the cylinders with raw fuel to try to & wash away the sticky oil.

I guess the cold weather is not helping, I once had a friend with a sticky valve on an engine due to the (not extreme, perhaps 5 deg C) cold.
He poured boiling water over the head until the valve loosened enough for the engine to run, once run it was fine.
Do you have some way to heat the engine prior to attempting to start it (heat gun?).

Good luck!

John.

geezeraviation

My Feedback: (3)

Yeah gummed up rings or valves (or both) would likely be the reason for low compression and low compression would explain the no start. The valves are the easiest to check and correct but to free up sticky rings is more difficult and it will need to be flushed with some solvent and spun over briskly and as John suggested possibly heated up a bit.
Doc

abufletcher

We're heading into dark and frightening territory with those suggestions!

abufletcher

BTW, how would I know if the piston was at "top dead center on the compression stroke" if there is no compression?

abufletcher

Also explain to me (as if I were a child) how to "flush it out with solvent."

geezeraviation

My Feedback: (3)

Take out a plug, or all of them for that matter. Use a good light and peek in the plug hole and rotate the engine till you see the piston at the top of the cyl. You can use a small dowel if you like to help determine when it stops moving upward, fool with it, you'll get a feel for it. Use the top cyl to start with and we'll call this #1. If you're on the compression stroke both rocker arms will be loose. Rotate 360 (one full turn) and the exhaust rocker should be tight and the intake rocker should be beginning to tighten but no lash (gap). Then go 360 again and stop back at the top of #1. The firing order of radials is all odd then all even for a total of 720 degrees of operation, that is a requirement of all four stroke engines. ie on your 7 cyl. the order is 1-3-5-7-2-4-6. So, skip a cyl from where you started and go to #3 and bring the piston to the top and check the rockers as you did on cyl 1 then 360 and check that there is tension on both. I don't know the specific cam timing on this engine and am assuming that there is an overlap period at the top of the exhaust stroke causing both rockers to have no lash (gap) at this point. Overlap is typical on 4 stroke engines and serves to increase power, ie both valves being slightly open at the same time causes the exhaust gasses that are flowing out the exhaust port and into the manifold to help to establish flow from the intake tube through the port and begin filling the cyl with fresh fuel air mixture. Keep skipping cylinders till you have checked all seven for loose rockers at the top of the compression stroke. As far as flushing it out I'd put it on it's back on a bench (maybe even put a couple bolts in the mount to hold it) still with all plugs out and dribble a bit of fuel in each cyl. Plugs are prolly at the rear so now on the bottom and this wont be easy. No prop, maybe a spinner or something you can put your starter on. Your starter should turn it over with no plugs in it, and whirl away at it, I wouldn't use penetrant or WD 40 etc as I don't like the idea of rinsing the cyls with that sort of material. WARNING! Its going to spray the fuel all over the place so try to put some sort of shield up and wear an apron or you'll never get the oil out of that shirt. lol It should get warm just from the friction and I'd work at it for a while. Put a plug in and see if you can find a cylinder with compression if so take it out (the plug) and go around confirming the presence, or not, of compression on all cylinders. Doing this with fuel will leave things well primed, put one plug in and put a prop on and apply voltage to the plug and pull the prop through WITH A FIRM GRIP ON THE PROP and see if you get a bump, if so you've made progress and need to put it on the stand and do what comes next. I really wish you could just bring the darn thing over and we'd fool with it till we made it run.
Whew! Doc