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Aug 29, 2016, 05:40 PM
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Help!

OS Max RG refuses to start Anyone familiar with a O.S Max RG nitro motor? Just picked


Anyone familiar with a O.S Max RG nitro motor? Just picked up a older Hyper 7 that's been built up pretty well and raced in its day but for the life of me I can't get this thing to even come close to starting let alone running..

So far I've done all the basic problem solving right down to pulling the motor and cleaning everything..

Has compression
Internals are clean and no damage visible
Can't find any leaks
Primed (flooded a few times even)
Using 25% Losi Nitro fuel (new bottle)
New plug (tested)
Multiple igniters used all tested to work

Attempted adding fuel directly to the cylinder with plug out.. And absolutely nothing! Not even a positive starting sound.

I see no reason why this thing shouldn't start! Won't even sputter like it wants to start!

Any advanced ideas or suggestions?

I run 2 HPI Savages so I half way know what I'm doing.

Attached is a video of said problem.. Honestly feels like I'm attempting to start it with no glow plug igniter.. But I am of course..
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Aug 29, 2016, 06:04 PM
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I have several OS rg with pull start and bump start. Is there a fuel filter? I don't see one. Crap can get stuck inside the carb needles preventing the engine to run.You can get engine instructions for tuning the engine @ osengines.com. When you say compression How do you measure it? It should be 35-30 PSI. if good. Poor is 20 PSI. with a 160 PSI. compression gauge. If you can see fuel getting into the carb while priming then it should run. OS engine require 18% oil lube and a #8 Os plug . . Another problem is if the engine isn't shimmed properly for high nitro it won't run. Use 20% nitro. I only run 15%nitro.
Last edited by txt killer; Aug 30, 2016 at 07:00 PM.
Aug 29, 2016, 07:57 PM
Registered User
Thread OP
Don't have actual tools required to fully test the compression.. But when I spin the motor with the plug out it I can feel a good suction on my finger over the hole.. I figure that this is at least acceptable enough to start and run a bit even if it's rough and stalls.. But it won't even do that..

Carb was disassembled along with the motor to look for gunk.. Needles and holes where also cleaned..

Could the fuel being 5-10% higher in octane cause it to not want to start at all?

And I don't mean sputter and die... I mean not start at all like there's no glow igniter on it..

Pretty sure my fuel flow is good.. Verified carb is getting fuel when it turns with my finger over the exhaust.

Verified needle stock settings at HS closed softly than opened 3-4 turns and LS set flush than back 1 turn..

Not 100% sure what plug I have in there as it came with the car. Seems to glow bright though.

So weird that it won't even attempt to start!! Just turn and turn and turn.

Thank goodness my starter bump box runs 12v
Aug 30, 2016, 07:14 AM
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The stock carb settings are wrong. The % of fuel is the other problem and changing from one brand is another. A said before get a engine manual and read it. Add a fuel filter.
Aug 30, 2016, 12:37 PM
Registered User
Thread OP
So one read the manual as suggested.. And the 2 needle settings listed in there are the same as I previously mentioned and are indeed not wrong..

I have also tried using 2 of the 3 plugs.. Going to buy the third today. Even though I really don't think this is the main issue.

So now I'm down to fuel % and adding a fuel filter? Seriously?

I really don't think either of those things will help me get running considering I don't even get a sputter now..

Any other suggestions? Txt killer I appreciate your help but is there any one else with some ideas?
Aug 30, 2016, 01:49 PM
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do you see fuel going into carb when trying to start?...
try another nitro fuel.. 25% is good..

fuel filter is no essential to start..pure bad info..
if your not getting a stutter then your compression should be checked..
Aug 30, 2016, 02:49 PM
Registered User
Thread OP
I do see fuel.. If I pop the complete air filter assembly off I'll get a very light nitro mist coming out..

As for compression.. I suppose the old finger over the plug hole to feel for suction when rotating the motor is not acceptable.. Fuel I'll need to invest in a proper gauge.. Can you find acceptable ones at hardware stores?
Aug 30, 2016, 03:09 PM
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Quote:
Originally Posted by rcdog69
do you see fuel going into carb when trying to start?...
try another nitro fuel.. 25% is good.

He already has fuel. % is not going to work if the engine is not correctly shimmed for it. Factor shim only allows 20% nitro with 18% oil lube. A fuel filter is not necessary to start but will prevent crap from getting into the carb and ruing the engine.

fuel filter is no essential to start..pure bad info..
if your not getting a stutter then your compression should be checked..
Quote:
Originally Posted by Camscam204
I do see fuel.. If I pop the complete air filter assembly off I'll get a very light nitro mist coming out..

As for compression.. I suppose the old finger over the plug hole to feel for suction when rotating the motor is not acceptable.. Fuel I'll need to invest in a proper gauge.. Can you find acceptable ones at hardware stores?
You should be getting more fuel than that when priming the engine. But the problem is the needle settings and the % of fuel if the engine is NOT shimmed correctly. 1 head shim is only for up to 20% nitro. You need 2 shims for +20% nitro. The high is 3 turn out from closed and the low is 1 turn in from flush outside. The idle should be 1-2 mm open. I suspect something else may be wrong if the engine refused to start. Check the fuel line and pick up tube in the tank. A compression gauge is $40 which you can't get at a hardware store. Online only. The only other way to check compression is to remove the piston and sleeve and see if the piston pushes all the way threw the sleeve. If it dose or is near the top the engine is finished.

http://www.dynamiterc.com/products/d...prodid=dyn2514
http://manuals.hobbico.com/osm/21rg-series-manual.pdf
Last edited by txt killer; Aug 30, 2016 at 03:20 PM.
Aug 30, 2016, 03:22 PM
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check carb setting,, byrons fuel is good and a compression guage can be found at a hobby store some might have one to test compression i know the 3 by me do its a $5 test have to pay fee,,http://www3.towerhobbies.com/cgi-bin...GcEaAorv8P8HAQ

no hardware store will have a compression guage..
Aug 30, 2016, 04:26 PM
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Quote:
Originally Posted by rcdog69
check carb setting,, byrons fuel is good and a compression guage can be found at a hobby store some might have one to test compression i know the 3 by me do its a $5 test have to pay fee,,http://www3.towerhobbies.com/cgi-bin...GcEaAorv8P8HAQ

no hardware store will have a compression guage..
READ THE ENGINE MANUAL! 18% oil lube minimum.
Aug 30, 2016, 04:34 PM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Unless the piston/liner fit is completely and utterly destroyed (zero compression with plug installed), the engine should at least start and run until it warms up. If the glow plug isn't wet when trying to start the engine, it likely isn't getting enough fuel to fire. Most glow engines like to be fairly "wet" to start. With the carb at factory settings (which are often way too rich to run a broken in engine), get the engine primed well - put 6-8 drops of fuel through the plug hole and prime the fuel line so fuel is to the carb. With a new glow plug and freshly charged glow driver, try starting the engine. If it doesn't fire with 3-4 attempts, try starting it with the throttle open to about 1/4 throttle. An engine even with weak compression will start and run. Ensure the head screws are tight and the backplate is sealed and tight. Those two parts being loose will not allow the fuel charge to transfer to the combustion chamber well or at all. If the carb isn't sealed well, it should still run albeit not well usually.

I'm not on the compression gauge bandwagon. I do not find them to be a useful tool on engines so small with tapered cylinder bores and ringless pistons due to the temperature changing the taper of the liner. You will get a different reading at 70 degrees from a reading at 200 degrees. The reading when warm is the reading that will mean something. Being that one doesn't have a reading from new will make the reading used moot and moreover there is no published standard by which to go by.
Aug 30, 2016, 04:35 PM
Registered User
Thread OP
It's been read.. And I'm using 20%..

5% over the "minimum"

Thanks anyway bud..
Aug 30, 2016, 04:41 PM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Quote:
Originally Posted by Camscam204
It's been read.. And I'm using 20%..

5% over the "minimum"

Thanks anyway bud..
That 18% oil crap that some guys spout off about is a way to keep the warranty valid. You will be hard pressed to find car fuel with 20% nitro and 18%+ oil content. What you will find is helicopter fuel and your engine manual will say to not use airplane or helicopter fuel. Unless you special order fuel - which is expensive and hardly needed. The fuel you have is more than adequate.

If you want bonafide advice that is real and true and no BS, post this over at RCTech. A lot of guys will refute every single thing I say, but if you want real advice from some of the most experienced nitro guys, go to RCtech. I learned what I learned on my own and some of what I found on RCtech.

And FWIW - if OS considers it a "racing engine", there's no warranty anyway regardless of fuel used.
Last edited by 1QwkSport2.5r; Aug 30, 2016 at 04:47 PM. Reason: Added info.
Aug 30, 2016, 04:54 PM
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you have no idea that the fuel you have is good.. do other nitro engines run on this fuel?... you can special mix oil in your nitro fuel to get whatever percentage of oil mix you want no special ordering needed,,unscrew glow plug put igniter on it see if you get a solid deep orange red glow ..
Aug 30, 2016, 05:24 PM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Unless the fuel is contaminated with enough water to make the oil settle out of solution (which is about 20% water by volume), the engine should fire on the fuel being used. Also - a glow plug can glow bright orange and still be contaminated enough that the engine won't run. Do not use the color of the glowing plug as an indicator of the glow plug being good. When in any doubt, use a brand new one to get the engine going. Check your glow driver on a new plug to verify the glow driver is working. If the engine will run on the new plug, try the old one right after.


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