4 Stroke Engine With Air Leak

Here is a video illustrating how a 4 stroke engine operates with an air leak. I show how to determine if your engine has an air leak as well.
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[@stevebarr9604]

Great tips! I try to watch all your videos! Glad you got settled in in Wisconsin and making videos again!

[@JoshWeaverRC]

Much appreciated. Happy Thanksgiving!

[@bobgreen3116]

Thank you. That really helps a lot. Great job David.

[@mzgmajnb]

A very helpful vid. Thanks a lot ☺️

[@HondAttila]

Thank you for the video!

[@vulturedroid9804]

Always Helpful Videos !!!!!!!! Go for Glow!!!!!!!!!

[@ericrivest4423]

great vid!

[@miadulislam9469]

your videos are very very helpful I am requesting you to show how to add a clutch and flywheel with os fs-60. please....

[@dmrcflyr2]

Why would I do that?

[@miadulislam9469]

David McIntire sir, actually I want to use fs-60 to make an rc ship. for this I need some accessories with this engine but but that is not provided by the saler. so I need to add clutch and flywheel. so I need your help how can do this....

[@dmrcflyr2]

I'm sorry but I cannot help you with this.

[@miadulislam9469]

David McIntire ok

[@petermaidment1175]

Hi David i have recently found your videos and always find them beneficial. I have just purchased a Saito FA80 (my first 4 stroke) which i set according to the instructions, low speed flush with the barrel and hi speed 2 1/2 turns out. It started easily throttled well but would not run well above about 3/4 throttle, it didn't stall but was very lumpy and as i approached full throttle the revs drop off a bit and it got more lumpy. I eventually got it to run well with the hi speed set at 4 1/2 turns out which seems a lot and the tick over was steady but the transition was not so smooth. Could this be an air leak in the high speed needle, the o ring in the high speed needle seems pretty worn. I have ordered the carb and engine seal kits so will rebuild the engine and i have ordered a tacho for easier set up. Thanks in advance for your help andkeep up the great videos. Peter from Manchester England

[@dmrcflyr2]

Are you certain that you have the valve lash set properly? When you say 'lumpy' are you referring to it sounding richer? Does it go away if you attach the glow ignitor and then transition to full throttle. An air leak is possible but that usually manifests as going lean and dying.

[@petermaidment1175]

Hi David Thanks for your reply. I have not checked the bake lash, I will do this when I rebuild. The lumpiness at 2 1/2 turns is like it is rich however there was very little smoke and the engine ran hot as though it was lean. It ran well at full throttle. @ 4 1/2 turns. I let you know after I've done the rebuild.

[@T2garcia]

Hi David i have a problem with my 52 fs that i cant get a low enough idle to it i need to knkw what to do to get a good idle to it

[@T2garcia]

It holds an idle of about 3200 rpm lower than that the engine will just quittried moving thelow end needle but it still wont hold what can i do to make it run well

[@dmrcflyr2]

I do not know. It could have an air leak on the carb, maybe the low speed needle is set incorrectly. I have a video on how to setup a carb. kzbin.info/www/bejne/aH7Nh32ondh2a5I It is difficult to troubleshoot an engine issue without seeing it in person. I have done the best I can with this and the carb setup video. After that it is up to you.

[@davidhill5621]

Hi dave , got a question, would a front crank bearing on os fs 52 leak air?

[@Hans45]

Hi, i recently bought two OS fs 40 engines, and i got one of them running well, but the other one has a problem with the intake valve. I know that it is not the carburetor that is leaking, because it is blowing a little air out of the intake on the head, without the carburetor on. I thought the valve might be bent, but it seems straight enough when you spin it in a drill. I tried both to lap the valves and exchange the intake and exhaust valve with each other, but even after i lapped them again, it still doesn't seal properly. I know this is the problem, because the fuel going in to the engine is being blowed all the way back into the tank when the engine is being cranked and the intake is choked. To me it does not make sense that the intake valve wont seal even after being lapped several times, as the seat and the valves are shiny, and should be able to seal. The last thing i tried was to stretch the spring to make it seal better, but to no avail... Is there any way to fix this, or is it perhaps possible to use newer surpass parts to replace the valves and the valveseats? Thanks.

[@dmrcflyr2]

It sounds like the seat is damaged. A new head would fix it. BTW, I never have needed to lap valves on an engine to get them to seal properly. 9 times out of 10 lapping causes more issues than it solves on these small engines.

[@Hans45]

@@dmrcflyr2 Yes. however, i dont see any marks or any imperfections on the valves or valve seats. They are completely blank. Before i lapped them the previous owner somehow made some pretty deep scratches into the valve so i thought that might be the problem, but it was not apparently. The only problem with buying a new head is that it will be the new surpass type, and i dont know if everything will fit on the old pre-surpass engine i have. Also a new head would cost more than i gave for the engine

[@dmrcflyr2]

@@Hans45 Well a Surpass head will certainly not fit. This is the issue with buying older engines. Parts availability becomes a HUGE issue. Just because you can't see any issue on the valve seat does not mean it doesn't exist. Clearly if it isn't sealing then there is a problem. A new valve would be the only other thing to try. Otherwise the engine is a doorstop.

[@Hans45]

@@dmrcflyr2 If the surpass valves will fit, why cant the surpass valveseats be used also? I dont think it will work just to get the new valves, beacuse i tried to interchange the intake and exhaust valves, so it must be the seat which is causing the problem.

[@dmrcflyr2]

@@Hans45 How about you read for yourself and make that determination. There might be parts available if you search however. The valve seats are not, nor have they ever been, a part that can be replaced or sold. My research shows that the 40 and 48 Surpass share the same valves and they are not the same as the FS40 ones. sceptreflight.com/Model%20Engine%20Tests/OS%20FS-40.html sceptreflight.com/Model%20Engine%20Tests/OS%20FS-40%20Surpass.html sceptreflight.com/Model%20Engine%20Tests/OS%20FS-40%20Surpass%20%282%29.html sceptreflight.com/Model%20Engine%20Tests/OS%20FS-40%20Surpass%20%283%29.html