OS 91 FS backfired/kicked on start- now ill not restart
01-04-2015, 07:51 PM
#1
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OS 91 FS backfired/kicked on start- now ill not restart
Just purchased a slightly used OS 91 fs SURPASS. On first start attempt, I did a manual prime and the motor started as soon as I hit the spinner with the electric starter and it ran a few seconds. On the next restart it Kicked/backfired and would not restart. I found the prop nut was a little loose after the kickback. It now has a sight metal click when the prop is turned as if something broke but the valves and piston rotate up and down as you turn the prop. Compression seems fine but I have noticed on the attempts to start and on a second manual prime that the fuel doe snot seem to be pulled up to the carb as fast as the first prime.
01-05-2015, 05:26 AM
#2
Well,
I use a double nut system on all four strokes, seen too many props/spinners fly off 4 bangers.
I'd take it apart and find out whats up, might have damaged the con rod or cam gears, I sure wouldn't try to run it again while it's making a funny noise
good luck
I use a double nut system on all four strokes, seen too many props/spinners fly off 4 bangers.
I'd take it apart and find out whats up, might have damaged the con rod or cam gears, I sure wouldn't try to run it again while it's making a funny noise
good luck
01-05-2015, 08:56 AM
#3
A very common scenario with used four strokes (does not matter if only slightly used or not, its all about the fuel whether or not it was put away wet and if it was overheated when it was becoming slightly used) is stuck valves! Recommend removing the valve cover and confirm that both valves are fully operating with each two 360 degree rotations of the crankshaft.
Like 'scale' said if you over prime and hit a fourstroke hard its possible to cause damage. A very common so called technique I see often especially internet trained fellows on four strokes is to hit the starter button then slam the starters cone aginst the spinner/nut. This can be devastating to any engine but a delicate four stroke? man don,t do it if that's what you are doing.
John
Like 'scale' said if you over prime and hit a fourstroke hard its possible to cause damage. A very common so called technique I see often especially internet trained fellows on four strokes is to hit the starter button then slam the starters cone aginst the spinner/nut. This can be devastating to any engine but a delicate four stroke? man don,t do it if that's what you are doing.
John
01-05-2015, 04:35 PM
#5
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I still have a couple of the 91s and there is a slight little click at TDC, it's nothing new. A back fire is caused by over priming or having it too lean. My normal starting needle valve setting is about 2 out on the high and low end, sometimes 2.5 out on the high end. The engine should be run about 400 rpm fat to allow for the no load lean out in flight.
Questions on OS engines can be asked in the glow engine factory support forum, just ask Bax.
When you start leaning a FS and it gets too lean it will back fire and toss the prop, you don't ever want to be in front of the engine while tuning. If you have never had a FS then you may want to get with someone that really knows how to adjust and tune one, it's easy but things like a back fire will happen if you don't know what your doing.
Questions on OS engines can be asked in the glow engine factory support forum, just ask Bax.
When you start leaning a FS and it gets too lean it will back fire and toss the prop, you don't ever want to be in front of the engine while tuning. If you have never had a FS then you may want to get with someone that really knows how to adjust and tune one, it's easy but things like a back fire will happen if you don't know what your doing.
01-05-2015, 04:41 PM
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I have three other OS four strokes. I t cranked fine on the first attempt and ran a few seconds. Now it will not even try to start. I have sent an email to the OS company support. I will probably TAKE IT APART AND LOOK AT THE INTERNAL PARTS. Thanks.
01-06-2015, 07:55 AM
#7
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With four-stroke engines, it's normal to hear some clicking/clinking sounds when you turn it over. That's the cam follower moving up and down on the cam. With the steepness of the cam lobes, the follower will "fall" down to the main part after coming off the lobe, making the clink.
Starting by "popping" the starter on the engine is a common practice, and not detrimental to the engine if it's not flooded. We do it all the time. We energize the starter and then bump it onto the spinner or propeller center to spin the engine. That works better on tighter engines or those with high compression. We usually hand-prop four-stroke engines, though, with a "chicken stick". A backwards flip through compression usually does the job.
Starting by "popping" the starter on the engine is a common practice, and not detrimental to the engine if it's not flooded. We do it all the time. We energize the starter and then bump it onto the spinner or propeller center to spin the engine. That works better on tighter engines or those with high compression. We usually hand-prop four-stroke engines, though, with a "chicken stick". A backwards flip through compression usually does the job.
01-06-2015, 07:50 PM
#10
Member
Check the glow plug. I had a kick back on a brand new YS DZ 70 with a new
OS F plug. The engine would not fire again. Turned out the plug was blown. Changed plug and everything was okay. No problems since.
OS F plug. The engine would not fire again. Turned out the plug was blown. Changed plug and everything was okay. No problems since.
01-06-2015, 07:57 PM
#11
Hey pigs delighted you got the problem sorted out. I know you came back and said that you did not use the "popping" the starter thing but I was rather shocked to to hear above Hobby Services actually condone this practice and of course with the disclaimer "if its not flooded" .
Good grief there are a lot of things you can get away with if you know what you are doing but I thought this was a help board to try to help people with questions however this is no way to treat an engine, any engine or airplane. Its been more that once I have witnessed folks hit a loaded engine hard with a starter and the entire firewall and all fly out of the airplane. Now the starter slamming may not have damaged the engine but it sure was hard on the airplanes!
Its a bad idea kinda like a bad habit . I would urge anyone especially new folks to four strokes not to pick up this bad habit. If your starter is too wimpy then there are way to deal with that too and still operate it in a safe manner.
John
Good grief there are a lot of things you can get away with if you know what you are doing but I thought this was a help board to try to help people with questions however this is no way to treat an engine, any engine or airplane. Its been more that once I have witnessed folks hit a loaded engine hard with a starter and the entire firewall and all fly out of the airplane. Now the starter slamming may not have damaged the engine but it sure was hard on the airplanes!
Its a bad idea kinda like a bad habit . I would urge anyone especially new folks to four strokes not to pick up this bad habit. If your starter is too wimpy then there are way to deal with that too and still operate it in a safe manner.
John
01-07-2015, 03:40 AM
#12
I total agree John,
Sorry, Personally I think that's just bad advise Bax, especially for a newbie. maybe when you guys have a motor bolted to a work bench it's safer, but on a plane you're holding with one hand and the starter motor in the other,, I don't think so. I've seen everything from starter cones gone flying to broke props to broken skin caused by guys slamming a starter to the plane, And hand popping fourstrokes?? seen everything from broken props to chicken sticks flying through the pits.
No excuse for trying to start a flooded engine. Turning over by hand without the glow driver on tells you if you have resistance,, Lift the plane and make sure all the fuel is out of the engine before you try and start it.
A well tuned engine should not be hard to turn over/start with the correct equipment
good luck
Sorry, Personally I think that's just bad advise Bax, especially for a newbie. maybe when you guys have a motor bolted to a work bench it's safer, but on a plane you're holding with one hand and the starter motor in the other,, I don't think so. I've seen everything from starter cones gone flying to broke props to broken skin caused by guys slamming a starter to the plane, And hand popping fourstrokes?? seen everything from broken props to chicken sticks flying through the pits.
No excuse for trying to start a flooded engine. Turning over by hand without the glow driver on tells you if you have resistance,, Lift the plane and make sure all the fuel is out of the engine before you try and start it.
A well tuned engine should not be hard to turn over/start with the correct equipment
good luck
01-07-2015, 01:31 PM
#13
My Feedback: (-1)
I too have seen too many mishaps with slamming a starter on an engine but I have also seen it done more then once, mater of fact I have done it myself but I had a reason for doing it. I do however back snap my four strokes after they have been run and they fire right up. Once they are warm I don't often bother with the starter but I had an old pattern pilot teach me the method. Grabbing that spinner the first time and giving it a back flip did frighten me the first time or two.
I have never seen the running starter advocated by an experienced person though and I have never told anyone to do it. Kind of surprised me to see Bax OK it.
I have never seen the running starter advocated by an experienced person though and I have never told anyone to do it. Kind of surprised me to see Bax OK it.
