Need help in tuning a new gas engine - RCCanada - Canada Radio Controlled Hobby Forum
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Old 04-28-2010, 10:06 PM   #1
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Need help in tuning a new gas engine

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Could anyone give me some ideas? I am having problems with my brand new RCGF 45cc rear carb engine. The total run time on this engine to date is about 35 – 40 minutes.

** It is prone to flooding especially when cold.
** Once started and warmed-up I cannot set the low-end mixture to idle smoothly
** When at idle the RPM is erratic. The RPM only starts to smooth out at about 3,000rpm.
** At idle (1,700 – 2,500rpm) the engine 4-strokes no matter how lean I set the low-end mixture.
** Seems to have adequate fuel flow with no air bubbles present in the fuel line.
** With the low-end set lean it’s then impossible to start. My arm is still sore!!!!
** With an 18’’ inch prop I can get a max RPM of 7,400 and there is no hesitation going from idle (1,600/1,700rpm) to full power.

Not sure if my NGF CM-6 sparkplug gap is at optimum setting. I believe I could open up the gap substantially and still get a spark because without the plug cap being connected to a sparkplug I get a BIG ark from the center pin in the plug cap to the metal ground of the cap. So there is plenty of voltage. According to the RCGF manual the voltage is around 15 kV – 17 kV.
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Old 04-29-2010, 04:34 AM   #2
michel gravelle
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Re: Need help in tuning a new gas engine

Hi Robert

The answer is very simple :
Youre timeing must be 28Degrees
The diaphram ( in the carb ) must be set properly

IMHO ,........... it is the diaphram , this give you real headachs when not set properly

Hope this helps

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Old 04-29-2010, 07:07 AM   #3
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Re: Need help in tuning a new gas engine

Hi Michel Gravelle thanks for the feedback and those three web sites. Looks like I have a lot of things to check. WOW! who thought there was that much to a 2-stroke engine! Never had these problems with my trusty old lawn mower that has been abused over the years. It just keeps running and if difficult to start a bit of “Easy Start” does the trick. Admittedly we only run lawnmower engines at minimum or full power and do not listen critically to its tuning refinements. Unlike RC engines that are put through their full repertoire of performance criteria and at the same time critically listening to every beat.
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Old 04-29-2010, 03:28 PM   #4
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Re: Need help in tuning a new gas engine

It's not the engines that give you the problems - it's the carbs.

How long until the experts chime in that the problem is that you didn't originally get "brand XX" engine??
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Old 04-29-2010, 04:09 PM   #5
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Re: Need help in tuning a new gas engine

Since this is a new engine I would think the carb is the same on many others that are running fine. If you have tried to adjust it you may have them set different than what the manufacture had them set at. Try and find out what they recommend as a start point and return them to that setting.

Long years of playing with two strokes there is not much to go wrong. If you have fuel and ignition they usually run just like your dependable old weed whacker that gets unceremoniously dumped in the corner of the shed each end of the season.

Hard starting and trouble with the low end lack of adjustment can be an air leak start by making sure that all the screws are tight and there is no apparent leakage of air into the crankcase.

They must have included adjusting instructions just take your time let the engine warm up and when you adjust make minor changes and let the engine run a bit to see the difference. A two stroke at lower rpm may have an access of fuel in the crankcase so a small adjustment may not be apparent until the engine has run through some of that excess fuel. Take your time. The links others have mentioned are good information.

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