Castor varnish
10-05-2006, 08:57 PM
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Castor varnish
My flying buddy and I were out flying F2D CL Combat planes and my engine got to acting like it was running lean and was slowing way down after a few laps. This was after running fine for a few moments. Check out, start it up and it was fine . . . for a few laps.
I could not figure out the problem and so switched engines and torn that one down after I got home.
What I found was a real bad case of varnish on the piston. F2D requires all castor lube in the fuel. Some guys run a blend in practice, but I have been using all castor. I suppose I will mix some 10% Klotz, 10% castor, 10% nitro and the remainder methanol.
The left two photos are what the piston looked like before I cleaned it with 0000 steel wool. The right photo is the cleaned piston. Before cleaning it was tight in the sleeve. Now the fit feels pretty good and is only tight at the top of the stroke.
This is the first time I can remember having varnish on other than a Cox .049 where it happened quite often and an good scrubbin' was often a good plan with my TeeDees if they acted lean when they were not.
I could not figure out the problem and so switched engines and torn that one down after I got home.
What I found was a real bad case of varnish on the piston. F2D requires all castor lube in the fuel. Some guys run a blend in practice, but I have been using all castor. I suppose I will mix some 10% Klotz, 10% castor, 10% nitro and the remainder methanol.
The left two photos are what the piston looked like before I cleaned it with 0000 steel wool. The right photo is the cleaned piston. Before cleaning it was tight in the sleeve. Now the fit feels pretty good and is only tight at the top of the stroke.
This is the first time I can remember having varnish on other than a Cox .049 where it happened quite often and an good scrubbin' was often a good plan with my TeeDees if they acted lean when they were not.
10-05-2006, 09:34 PM
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RE: Castor varnish
Just for fun:
Here is the sleeve and crank out of the same engine (an older Profi .15 I use for practice.).
Note the slot under the exhaust port. I'm thinking that is for sub piston induction. With the piston at TDC that slot allows air to enter the case. SPI is now illegal in F2D engines but probably was not when this engine was made.
And look at the opening in the crank. Nice and large and the opening duration is fairly long. No low reving stump puller here.
Here is the sleeve and crank out of the same engine (an older Profi .15 I use for practice.).
Note the slot under the exhaust port. I'm thinking that is for sub piston induction. With the piston at TDC that slot allows air to enter the case. SPI is now illegal in F2D engines but probably was not when this engine was made.
And look at the opening in the crank. Nice and large and the opening duration is fairly long. No low reving stump puller here.
10-07-2006, 07:13 PM
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RE: Castor varnish
ORIGINAL: Larry Driskill
Note the slot under the exhaust port. I'm thinking that is for sub piston induction. With the piston at TDC that slot allows air to enter the case. SPI is now illegal in F2D engines but probably was not when this engine was made.
Note the slot under the exhaust port. I'm thinking that is for sub piston induction. With the piston at TDC that slot allows air to enter the case. SPI is now illegal in F2D engines but probably was not when this engine was made.
My flying buddy thinks it is to trap a little oil on the hot side of the piston/sleeve and help keep things lubed.
