os 37 help

[dal]

Ok, After sorting the fuel locking problem i have run a whole tank through on idle as recommended to run in. I have filled the tank again and onto stage 2 of running in, hovering for 30 secs and landing for another tank of fuel. This is where it go`s wrong. The engine runs fine up until about quarter revs, then starts to run rough and weak as if it is choking up.
i have noticed a fair amount of oil coming from the muffler and around the manifold area of the muffler! Will the engine be getting enough fuel if the muffler is leaking from the manifold area. Would this reduce pressure to the fuel tank?

Thanks Darren

[robgt]

If it's choking then it's probably too rich.
Try leaning off the main needle a couple of clicks at a time until you can spool it up and still have it running rich...

What muffler is fitted to the engine?
It could just be that you need to tighten the fixing bolts up a bit?
Or perhaps seal the muffler on using some silicone sealer or a thin layer of expoxy.

Cheers,
Rob

[Ade_Law]

getting engine tuning wrong can be expensive both in killing an engine and the resulting crash when the engine quits in the air if you cant auto.

find a local expert to help you get it setup and running sweet.

Ade

[dal]

If it's choking then it's probably too rich.
Try leaning off the main needle a couple of clicks at a time until you can spool it up and still have it running rich...

What muffler is fitted to the engine?
It could just be that you need to tighten the fixing bolts up a bit?
Or perhaps seal the muffler on using some silicone sealer or a thin layer of expoxy.

Cheers,
Rob

The muffler is the standard thunder tiger that came with the raptor 30 the engine is in!
I did try many different settings of the main needle but nothing made any difference.

Would a lack of pressure to the fuel tank have the same effect as described?

[David Drew]

I once had a naff exhaust on an SC engine and I could never work out how to get it to run well.

So I bought an OS37 & Zimmermann exhaust and touched nothing. Factory settings, MT fuel and a little running in & it's been just fine since.

Make sure the exhaust is not leaking. Silicone on the joint if needed & really the engine should run fine. Maybe get an expert to look at it. Mucking around with the settings may make getting to the real problem difficult. Best of luck

David

[robgt]

I did try many different settings of the main needle but nothing made any difference

Main needle changes need a minute to settle in, so if you changed the needle (by a couple of clicks) and then revved it up and saw no change straight away - that's what happens.

Lack of exhaust back pressure would probably see the engine run lean and cut out/blow a plug.

Best bet would be, as Ade suggested - get someone to have a look at it for you if they know what they're doing.

Cheers,
Rob

[dal]

Main needle changes need a minute to settle in, so if you changed the needle (by a couple of clicks) and then revved it up and saw no change straight away - that's what happens.

Lack of exhaust back pressure would probably see the engine run lean and cut out/blow a plug.

Best bet would be, as Ade suggested - get someone to have a look at it for you if they know what they're doing.

Cheers,
Rob

Ok, I have had a good look at the heli and discovered a small hole in the fuel tank. Could this affect the running of the heli?

Thanks, Dal

[robgt]

Absolutely!
Tank needs to be airtight in order for the pressurised fuel system to work properly.
Make sure all the fuel tube on the heli is in perfect condition too - replace any that looks suspect.
Cheers,
Rob

[dal]

Absolutely!
Tank needs to be airtight in order for the pressurised fuel system to work properly.
Make sure all the fuel tube on the heli is in perfect condition too - replace any that looks suspect.
Cheers,
Rob

Thanks for the help rob! Do you think this could be the reason for the engine running bad?

[robgt]

If it's not the sole reason, it's definitely a contributing factor without a doubt.
The system needs to be pressurised to work, and you have a hole in the system, so it's not getting enough pressure built up.

Cheers,
Rob

[choppertastic]

i had a weird problem with my os37, on a zimmerman can, in the it ran rich the lean then rich like it had a floating needle value. The tubing was replace and the tank checked along with the head, carb etc. Problem still occured...

I then tried header tanks, still had the same problem until I fitted a K&S header. Ever since it's been sweet.

[robgt]

Did you also run inline fuel filters between the fuel/header tank and the carb?
I've had no end of trouble with several types of inline filters.
One type that seems to work and cause no issues is the Sullivan Crud Catcher clear plastic double filter.

Cheers,
Rob

[choppertastic]

no filters. I filter when I fill the tank.

[robgt]

How about a filter in the back pressure pipe from the muffler to the main tank?
I have one there to catch the crud

Cheers,
Rob

[choppertastic]

I have thought about that but the clunk in the tank has a filter so I gave that one a miss