Let me try and dispell some of the mystery surrounding this engine.
First, it is no secret that this engine doesnt have alot of low rpm power. It has been talked about alot in this thread how the engine has a high rpm power band and that changes in the way you set up your clutch, 2-speed and gearing is required to utilize the power that is produced by this engine.
If you try and use the same gearing and clutch settings that you previously used with your Nova based engines then you will definitely be dissapointed in the power delivery of the Orion engine.
When geared and clutched properly this engine has alot of power and is a potent racing engine. I have been using this engine for 6 weeks now almost every weekend and have found it to be very competitive on every track I have been to from the tiny Revelation raceway, to the medium Crystal Park, to the hugely enormous Rams track at Mission College in Santa Clara, CA.
I have found several great setups for this engine and I would like to share them with you guys, and hopefully you can share some of the same good results.
Orion CRF engine w/2601 novarossi pipe and med conical header
Good for long flowing tracks with lots of long straights (Rams for example)
This lets the engine really spin up and gives great power mostly on top end
The clutch was set up to engage around 28,000rpm and the gearing I used was (RRR) 17/61 1st and 22/55 2nd w/ tire dia. 61/59
The clutch I used was the orion weights with 2 set screws in each weight, and Orion spring set at 1.6mm preload. I used the Kyosho grey shoe with this set up. My clutch gap was set to .6mm
Orion CRF engine w/Skyline VR12 Plus pipe and header
Good for short tracks with tight corners
I had very good power off corners with this set up and still had alot of revs on top
The clutch was set to engage around 29,000 rpm and the gearing I used was (RRR) 16/60 1st and 22/56 2nd w/ tire dia. 59/57
I used the same clutch setting as before only I used the Orion spring set at 1.7mm preload. Clutch bell gap set to .6mm. I used the orion shoe at this track for a bit of more progressive clutch engagement out of the corners.
Orion CRF engine w/Orion CRF 2626 pipe and header
Good all around set up, good power off corners and decent top speed. But this setting would be better with -5mm header
Clutch setup was again set to 28,000 rpm and the gearing I used was (RRR) 16/59 1st and 22/55 2nd w/tire dia 60/58
I used the std Kyosho white weights and Evolva Red spring set to 2.2mm preload with grey shoe and also used the Orion clutch setup with Orion weights w/2 set screws in each weight, Orion spring set to 1.65mm and Orion shoe. Clutch gap set to .5-.6mm. Both clutch settings worked well, but I thought the Orion shoe had a little bit more slip initially than the Kyosho grey shoe which seemed to have a bit more initial grab.
The std settings I always start with for the carb of this engine are:
LSN 4 1/4
HSN 6
Nozzle turned in all the way tight then backed out 1/2 turn
These settings always seem to be pretty close, but I usually end up leaning the bottom a bit and also leaning the top to suit(slightly)
To set the low speed needle, you must set the HSN first on the track. The 4 1/4 LSN setting should be close enough to get you going pretty good, definitely good enough to set the HSN. For the HSN setting, run the car for 3-4 min before attempting to set the needle, because this engine takes a while to heat soak (due to all the crankcase fins I imagine) Afterthe engine is up to full operating temp, set the HSN progressively leaner to achieve good top speed. (make small adjustments at a time and sneak up on a good setting) Once top speed is achieved, I recommend richening 1-2 hrs for safety. You will know you are too lean if the engine seems to get a bit slower after 3-4 min of running at high speed (this will be an indicator that the engine is overheating a bit and the engine should be richened 1-2 hrs at a time until the high speed running stays consistant.
I also use the spit test to determine engine temp, as I never have great luck with temp guns. Spit always boils at the same temp so I know this is reliable. It the spit doesn't sizzle slowly, then the temp is to low or cold, it the spit dances off the head and won't stay at all then the engine is too hot. The temp is just right when the spit will stick to the head but will sizzle for 1/2 to 1 second. This should be around 230-250 deg. F.
To set the LSN I used two methods at the same time. First set the idle to a good steady speed, then listen to the engine and try and find the smoothest LSN adjustment. Then do the pinch test to the fuel line, as far away from the carb as you can (depending on the length of your fuel line-some fuel lines are rediculously long, so try to pinch the fuel line 2-3 inched from the carb. If the idle increases that indicates that the LSN is to rich (engine is getting to much fuel and is idling slower than if it was correct setting), if the idle speed imediately decreases and the engine stalls then the LSN is to lean (engine is starving for fuel), if the engine idles for 1-2 sec without changing idle speed then starts to stall that is very close to perfect LSN setting. Next check for throttle response. The engine should pick up rpm with no lag whatsoever, and return back to steady idle immediately, with out hanging at high idle. If the engine idle is unsteady, then I would suspect a leaky backplate, carb fuel fitting, carb body o-ring, crankcase o-ring, or front bearing. If the engine hold high idle when returning from high speed running then I suspect that the HSN needle is too lean or the engine has an air leak somewhere in the above mentioned places.
It is also a good practice to look at the combustion chamber regularly to see the condition of the engines combustion process. The combustion chamber should be light tan to brown as well as the top of the piston should be the same light brown, but also should appear a bit wet with oil residue. This will indicate a good tune. Also the glow plug should appear light tan arround the base of the plug outer ring, but the element should show no distortion and should appear slightly white to shiny silver. If the element is very dusty white looking or shows very small cracks or lines (use magnafying glass) then the plug has been overheated and should be replaced as it will fail soon. If the temps are good and the combustion chamber looks good but the plug is dust white then the next colder plug should be used.
I have also found that the optional Orion carb venturi that is more gently tapered helps to lean out the Mid speed slightly, offering better throttle response.
So in conclusion, with the proper approach to set up and settings this engine is definitely capable of running with the best engines out there. I hope this bit of info helps you with your own set up. If you continue to have trouble with this engine, please feel free to PM me and I will help in any way I can to make sure you are getting the best out of your CRF engine.
BK