OS GT33 Woes

During the last week I dug out Super Chipmunk Pennzoil as it had not used for since late last year.  Put the wing on  so I can run it up. Won't fire up.  Plug out dry. Check spark anyway, yep it's good.  Cowl off and take a peak into the regulator chamber. Dry. Pump membrane stuck.  Engine off, carb off and check membrane and replace with a new one.  Wet it with fuel and refit everything.  Fires on choke and that is about it. Um, got to be fuel. Carb off again and strip it out. Compressed air through orifices and re-assemble.  No change tries to run.  Check regulator chamber. Yep, got fuel.  Knackered from prop flipping.  Give up for now because I want tol oad up for Cashmoor on Saturday. 

First flight of the day was with Pepsi Super Chipmunk. No problems.  Later in the afternoon I wanted give Pepsi one more flight before going home. Now it is doing the same as Pennzoil. Fires on choke but flipping prop it tries to run but generally runs backwards and this undoes the prop nut. Three of us tried flipping as fast as we could but no joy.  Even an electric starter that was tried was not man enough to get it over compression.

Over the years I have always managed to hand start these two engines although you have to flip very quickly.  Why?  Well, according to many posts on many forums the OS ignition units will not fire until the threshold of 400 rpm is reached and the OS Manual does  state electric starter to be used.  So, I have suddenly been unable to flip fast enough?  And no you cannot use an alternative unit ie; DLE or Rxcel without a mod and re-timing.

Option I can see is the starter from Just Engines. 6.5 - 1 geared and runs on 12 to 24 volts. With the optional  lipo bracket and a spare cone just over £80 not including P&P 

In the meantime I have received some new plugs and have ordered an Ign Tester from MMMotors to cover those bases.

I think Peter Willis has one of the geared J/E starters -seems to work OK but might be worth his opinion

I have contacted Peter and he has both sizes although most of the time he uses the 4-1 stater for his four stokes and 30 -33 cc engines.  Going to try his first.

On Thursday 16th Feb I popped over to Peter's where he had left both sizes of starter out for me.  Early afternoon at home I got Pepsi out, did not bother with the choke and using the 6.5-1 stater on 24 volts spun the engine over it fired up after a few revolutions. The starter did not have any issues with overcoming the compression.  Next up is the Pennzoil fitted with similar engine.  This time I manually flipped with the choke on and then with the choke off spun it up on the starter. Fired up straight away.  Although the engine dies after a short period.  I have tested the ignition with a tester and the plug gives a nice spark.  Played with the low jet for a while but still no joy.  Annoying because I had re-kitted the carburettor last week. There is fuel in the regulator chamber so maybe there is crap in the idle/progression jets or an air leak somewhere.

Anyway, later I ordered a 6.5-1 starter from Just Engines.

Think you said the reeds have not been checked so suggest examine them for splits / distortion. You had a successful flight last week. Have you gone thru the fuel supply ?

Yes, reeds and block were checked on Pennzoil whilst the carb was off.  It is not a simple job to access the tank and lines but I will have to bite the bullet and take it all out I suppose to cover that base. Although saying that there is plenty of fuel in the chamber.  Maybe pull carburetor off again strip down and put it in the Ultrasonic cleaner although previously blowing the carb out at 120psi should have cleared any crap out.