[Cougar429]

I finally was able to fire up the rebuilt 40FSR that came out of storage. Bolted it onto the nose of a trainer I bought uncovered. It came with an O.S. 40SF and a GWS 47, (more on that later).

Anyway, I tried for a couple of days to get it to run right, to the point I finally swapped it for the 40SF. With new 10% fuel it would not idle unless it was slobbering rich and any time I tried to give it throttle it would die unless the high speed needle was almost falling out, (I know you want it rich for breaking in a new ring, but this is ridiculous!). Even then, after a few seconds it would starve. Another thing was the fact I could see no draw when I held my finger over the carb and flipped it by hand. Unless I gave it a drop of prime it was hell to start. Once running you would see it draw fuel and even then it was minimal.

I checked the system for leaks, tore the carb down again and checked the crankcase for leaks. Nothing showed up and it has great compression.

Here comes the interesting part. The 40SF reacted almost identically. It seemed like the tank was going negative pressure, even though the vent line and fitting were clear and unobstructed.

Didn't get the chance to try the GWS 47 before dark, so no way to tell if this was a tank problem exacerbating the condition. The tank is slightly low, but I don't remember ever having draw problems like this, even when doing harriers with my Quickee 500 two decades ago. Yes, it's been that long!

Somewhere along the line it had been recommended to remove the internal baffle from the muffler for more power, so my suspicions were that the fitting was now in the wrong location for the pressure pulse to feed correctly. Sure enough, when I reinstalled it the whole game changed. I was now able to keep the motor running, although it is still a bit on the cantankerous side. Running O.S #8 plugs now, although different types, including idle bar style did not make that much difference before the baffle refit.

I just found the baffle from the FSR muffler and reinstalled it, so will try this tomorrow, weather permitting.

Almost forgot to mention the 40FSR ran with a tuned pipe and pump when it was stuck in storage so long ago, so no way to tell if that had anything to do with it. I can say I fit the carb from the GWS and it reacted the same way.

Anyone else heard of this one before?

[Luke Planemaker]

Sounds like you need to look inside your carb. Not familiar with your engine or carb, but I would check any internal screens and verify internal passages are not plugged with crud. Also check diaphragms are supple and not punctured if it has them. Maybe this link will help.

http://www.scotiabladerunners.ca/carbs.htm

[cassat]

Hmmmm Lukplanemaker,

I don't think the OS 40FSR had a diaphragm pump
Are you thinking of a YS 45 maybe?

Cougar
Please verify, you are running the OS with a pipe? or original muffler?

[Luke Planemaker]

Oops, thought it was bigger dual needle gas engine, when I read it was ringed and had high speed needle. Disregard my previous post.

[cassat]

The OS 40 FSR is one of the most reliable engines ever made in its class . I would suggest you bench mount it on a test stand and run it up. Give us more specific details.

The OS 40 FSR is one of the most reliable engines ever made in its class . I would suggest you bench mount it on a test stand and run it up. Give us more specific details.

No doubt about that. I have four of them. One in an airplane, one in the box ready to use, one needs bearings and one is spare parts. Mine are over 25 years old. definitely the best sport .40 ever produced.

If that engine does not run properly it is probably not the engine.

Ed S

[Cougar429]

O/K guys. A bit more info:

I'm running the stock muff and since the pump is also 20 years old left it off, plugging and sealing the port in the rear cover. It has the 4BK carb, (I don't think I changed it from stock, but the breakdown stops at the O-Ring part number, so hard to tell if that is the correct model).

Here's another strange one. As I said, I had the same reaction 3 different ways: with everything stock, with the GWS carb installed and on the completely different 40SF until the baffle went back in. I don't think the FSR had a baffle back then, so I filed one down to fit.

I want to test that rig and the 47 to see if the problem repeats, but with the abysmal weather outside that will have to wait. I also fit the FSR carb onto the 47 as another test item.

p.s. Ed, if you're looking for bearings, check out this source in Michigan. I just found sets for both the O.S. and GWS at under $10 CDN a set. I priced them out separately from our local bearing house and the front, (R6LLB) was $10.35 and the rear, (6902-2Z) priced at $18.21. We'll see how they hold up, but I ran the 40SF with them in there and nothing came apart, (yet!). These higher priced bits are in the FSR now.

http://cgi.ebay.ca/OS-MAX-40-FSR-Eng...742.m153.l1262

Both engines showed very little signs of wear when I got the plane, but there was no after run oil, (I use a 50/50 mix of air tool oil, basically turbine oil, and ATF. Best thing I've seen so far) and the bearings were pretty much pooched.

[Cougar429]

Just wanted to post an update on the running issues.

ALL MY FAULT!!!!!!!!!!!! Can anyone say, HOMER?

I guess 20 years out of nitro has let the brain fade a bit. Found I had the fuel curves all wrong, with the high and low-speed jets way out of whack. Finally figured out what I had so far off and was able to have the second and third motors set and running right within minutes.

On that note, the GMS47 seems to have gobs of power. Bolted on a 10-7.5 3-blade and could almost pull it out of my hand holding the nose vertical. Now it's time to decide which will end up on the tail of the Northstar, that one or the slightly lighter 40FSR.

[cassat]

The OS 40 FSR will be a collector model
Use the GMS if you trust the idle characteristics .

[Cougar429]

I replaced the O-Rings in the housing and at the base of the carb with slightly thicker bits, and it seems to seal well. I'd read about the air leak probs on some of them.

Oh, almost forgot to mention, I'd forgot how that FSR can wind up when set right! Running a 10-6 3-blade she would scream nicely. When I get someone to hold the beast I'll tach it to see what I get.

If anyone wonders why the 3-bladed props, the Northstar has the engine on the tail pod, with not a lot of clearance to the top of the wing.