problems with my new os 70, 4 stroke
11-13-2002, 01:16 PM
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problems with my new os 70, 4 stroke
Need some help with my 4 stroke:
I just installed a new 70 surpass II in my great planes 40 size fokker D-VII.
The engine runs smooth at idle up to mid range. When you move up to full throttle the engine sputters and nocks violently, it has thrown the propeller and hub off on several occasions. I have run 5 tanks of 20% wiled cat 4 stroke fuel thru it.
The engine is setup with a 12x8 prop and a F type glow plug.
In general the low speed adjustment if fine.
What can I do about the full throttle issue?
( I have been told out at the field to use a #8 glow plug and 15% glow fuel, dose this sound rite? )
I have reset the low end setting, It did not help the top end to smooth-out.
I tried opening the high speed set valve from mid throttle to see if this would allow me to go up to full throttle, it did smooth out. As soon as the engine idles for a few minutes it starts the same problem when returned to full throttle.
I checked the head temp of the engine when it started detonating again, it was about 105deg. F.
I am at a total loss here, can you give me good starting point to fix this problem?
I have several O.S. engines and this one is the only one that I have ever had this kind of problem with,
please let me know if you can help with this
Thanks
Steve Molmer
at [email protected]
I just installed a new 70 surpass II in my great planes 40 size fokker D-VII.
The engine runs smooth at idle up to mid range. When you move up to full throttle the engine sputters and nocks violently, it has thrown the propeller and hub off on several occasions. I have run 5 tanks of 20% wiled cat 4 stroke fuel thru it.
The engine is setup with a 12x8 prop and a F type glow plug.
In general the low speed adjustment if fine.
What can I do about the full throttle issue?
( I have been told out at the field to use a #8 glow plug and 15% glow fuel, dose this sound rite? )
I have reset the low end setting, It did not help the top end to smooth-out.
I tried opening the high speed set valve from mid throttle to see if this would allow me to go up to full throttle, it did smooth out. As soon as the engine idles for a few minutes it starts the same problem when returned to full throttle.
I checked the head temp of the engine when it started detonating again, it was about 105deg. F.
I am at a total loss here, can you give me good starting point to fix this problem?
I have several O.S. engines and this one is the only one that I have ever had this kind of problem with,
please let me know if you can help with this
Thanks
Steve Molmer
at [email protected]
11-13-2002, 01:37 PM
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Engine
Your engine problem leads me to believe it is running to lean. Assuming no airleaks or plumbing problems, I'd recommend the following for this new engine:
1. Use a tach to tune your high end. Run her about 400 rpm shy of max lean rpm. Your engine's performance, bucking/spitting backfiring/prop throwing usually occurs when an engine is too lean or has too high compression or too high nitro. The OS .70 is not a high compression engine (at least the one I owned wasn't) and mine tolerated 20% nitro pretty well.
2. If this doesn't solve your problem, switch to a 15% nitro fuel, use OS F plug, and run her rich. See what happens. I normally use 20/20 type fuel in my engines but I prefer to run them at lower nitro when they are new and then move on up to higher nitros after I know the ring is properly seated.
3. Check for airleaks in fuel line or carb. Check fuel line for bubbles that may be caused by an out of balance carb.
4. I just reread your posting. It is possible that your low end may be a little lean and may cause problems transitioning to full throttle. If you can, richen her up about 1/8 of a turn and see if that helps before switching fuels and checking for airleaks.
Good luck and let me know if this helped.
1. Use a tach to tune your high end. Run her about 400 rpm shy of max lean rpm. Your engine's performance, bucking/spitting backfiring/prop throwing usually occurs when an engine is too lean or has too high compression or too high nitro. The OS .70 is not a high compression engine (at least the one I owned wasn't) and mine tolerated 20% nitro pretty well.
2. If this doesn't solve your problem, switch to a 15% nitro fuel, use OS F plug, and run her rich. See what happens. I normally use 20/20 type fuel in my engines but I prefer to run them at lower nitro when they are new and then move on up to higher nitros after I know the ring is properly seated.
3. Check for airleaks in fuel line or carb. Check fuel line for bubbles that may be caused by an out of balance carb.
4. I just reread your posting. It is possible that your low end may be a little lean and may cause problems transitioning to full throttle. If you can, richen her up about 1/8 of a turn and see if that helps before switching fuels and checking for airleaks.
Good luck and let me know if this helped.
04-02-2003, 12:14 AM
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on the os engin problem
The problem turned out to be the fuel.
I had been using a fuel with a very high nitro blend, I tryed a 10% mix the engine runs fine now.
thanks for your help.
sorry it to so-long for me to get back to you, I have been in volved in other projects.
I had been using a fuel with a very high nitro blend, I tryed a 10% mix the engine runs fine now.
thanks for your help.
sorry it to so-long for me to get back to you, I have been in volved in other projects.
