DAVESDAD

Hi All

I've been running a CRRC 50i for about 18 months with no real problems after initially getting it set up. Ran it in using a mineral oil and then on to a synthetic oil used for Ryobi 2 strokes and it ran fine. This week changed over to a castrol synthetic 2 stroke oil at the same ratio of 50:1 and a world of problems. Basically the engine won't run, but keeps backfiring and throwing the prop. Number one son has the bruised fingers to prove the need for good gloves when starting these engines!
Anyway can a change of oil make such a difference or am I looking for another problem, plug, igition? The plug is not sooty but it is black but looks the same as it did when last removed. Any pointers please ?

Neo gold

Just to clarify....i'm sure the manual states a max of a 40:1 fuel mix yes?..( I could be wrong!!).....anyways, replace the dci & plug.
On both my crrc pro 26's i started as manual states.....25:1 for a nice rich mix for run-in...one gallon...on cheap synthetic comma oil,...steady air flying..& occasional high speed etc..
Then second gallon i ran fully synthetic putoline oil & a mix of 40:1..as manual....using a 4.8v 2700mah sanyo batt pack...& jumped to a 17"6 prop as opposed to a 16"8 for run in.
Dci's & plugs are a consumable item...they wear out/degrade & break down over prolonged usage.

DAVESDAD

Hi Neo Gold. You're right about the recommended ratio but we ran for over a year at 50:1 without problems. I'm really surprised just changing to a different make of oil could make such a difference which makes me wonder if something else is wrong. By the way the run in ratio was at 25:1. I'll try the original oil again and see if it solves the problem.

mpascual

My Feedback: (1)

Buy a contact cleaner spray can or NURAL 5000 carb cleaner. Dismantle the carb and remove the two covers. Remove the gaskets, pump and regulator membranes, and CLEAN all holes and passages with the contact cleaner or NURAL. Mount the carb again and DO NOT CHANGE the brand of syntethic oil.

Regards

thevirginian

DAVESDAD,
I have the same motor but it's still not broken in, yet. Sometimes it backfires big time. Even with a leather glove it hurts like hell. Check you hall sensor. It may have shifted. I don't believe it's the change to synthetic oil that makes it back fire all of a sudden.

apalsson

My Feedback: (1)

I agree, the most common reason for backfiring is incorrect timing.
Make sure it is set at or around 28 degrees

DAVESDAD

Thanks for the replies. Tried the engine again today with the original oil and the results are just the same, really vicious backfire, throws the prop every time, with no sign of running. Looks like something has either broken or slipped so I'll check the timing tomorrow.

mpascual

My Feedback: (1)

Of course , the hall sensor must be set around 28 degrees before TDC when the ignition fires.
I'm not talking about to change TO synthetic from mineral oil.
I've seen some times, engines and carbs clogged by change of syntethic oil of different brands . Before synthetic oil brand change is a good idea to clean the carburetor.

Check the woodroof key also ....

Regards

DAVESDAD

Ok I'm totally confused now. Checked the timing, 28 degrees. Checked the diaphragm in the carb, fine. Cleaned the plug, sparks fine. Filled up with fuel with the new synthetic oil mixture. Choked on until it popped. Then choke off, three flicks and perfect run with no backfiring. I don't get it! Completely back to normal with good idle and throttling. Holds max revs no problem. The only thing different is I ran it without the spinner and backplate and I wonder if we weren't getting the prop nut tight enough before. Because number one son had already suffered one injury from a backfire (bad bruising only fortunately despite wearing a heavy duty leather glove) maybe we weren't giving it enough of a flick (more worried about getting the hand out the way than anything else) and this was why it was tending to backfire. Definitely much more oomph with the flicks this time.

Anyway seems sorted now but I still don't get why it started backfiring?

jedijody

My Feedback: (1)

When the engine RPM is below about 300 the ignition fires at full advance, (28*). RPM is sensed by the module by how much time the magnet spends under the sensor. From about 300 to about 2000 RPM the module goes into full retard (28* - 22* = 6* BTDC). This allows the engine to start easier without biting you and also helps the engine idle slower and smoother. From about 2000 to about 4500 RPM the module advances the timing in predetermined steps for a total advance of 28*.

When starting a gasser always flip the prop briskly and expect it to start every time you flip it. That's the simplified explanation.

spaceworm

About how many RPM is a fast flip? If full advance is below 300 RPM is it very conceivable that retard is not then being seen, and thus the engine is hard to start?

This may seem like a frivolous question, but I think it is relavent and may encourage a more vigorous flip by hand starters. getting the fingers out of harms way is most important, but the objective is to get the engine started. TIA

jedijody

My Feedback: (1)

With a good smart flip it's very easy to exceed 300 RPM, I routinely see 500-600 on my Rcexl digital mini tach thatI use on my test bench when I hand start engines, I never use a starter for gassers.

apalsson

My Feedback: (1)

Fastest Flipper in the West

thevirginian

I think some engines back fire more than others. My Brison 104 twin back fires if I am not flipping fast enough. My DL-50 or my G-38 never back fired on me.

SRimer

I strongly agree with thevirginian, my crrc 40 may bit some times, even with new the rcexl ignition, i always use chicken stick ,
but Zenoah for example never do that. DLs appear to have soft start as well, (pop once then twice and then it start, more or less).

DAVESDAD

Excellent reply Jody, makes a lot of sense now. Just need to be positive when flicking, we were being chicken because of the backfire and made it worse. We've just run the engine again and retuned the carb while the cowl was off. Running sweet as a nut. Definitely a lot of engine for the money. Thanks for your help guys.

kirilos

Is the сompaction of an engine make it back fire?
I mean if the engine is in breakin and all the componets are not seated properly makes that hapen.
My crrc 40 back fire some times if I am not fliping the prop briskly.
This getting worse if the engine spins 18 or 19 inch props.

Daveb572

Hi folks! Got a great big issue here with a CRRC 50i. It's brand spankin' new and I can't seem to get it to run at all. All I'm getting is a pop or two or a backfire, but that's better than yesterday when all it did was to cause me to make up new cuss words. I'm using 93 octane fuel with a 28 to 1 ratio of Klotz synthetic oil. Maxford USA said they break theirs in at 25 to 1 ratio. The ignition power is a 4 cell 2000 mAh sub-c nicad pack supplying 4.8 volts. Unloaded voltage is 5.8 VDC, so it's fully charged. I'm getting fuel, air, and spark, although the original plug had a very weak spark. I tried a new plug today and started getting it to fire intermittently. I even tried a few shots of starting fluid. It only popped a little more frequently. I know I'm getting fuel because the plug is wet when I remove it. I know I'm getting air because I can see the butterfly valve open. I reset the low and hi speed needles to the factory settings. With the new plug, I have a much brighter spark, yet I can't get it to sustain anything beyond a pop or two. Any ideas, Guys? Thanks! Dave Bryer

ec121

My Feedback: (2)

You mentioned everything except the timing. If it is a brand new engine, don't trust the factory to set the timing correctly. Check it yourself. There are all sorts of explanations on how to do it on the web. 28deg BTDC. Ask me how I know!! ;-)

Tired Old Man

My Feedback: (1)

The Brison 6.4 will viciously backfire if the timing is way off. At least mine did until it was adjusted.

stephensackro

My Feedback: (6)

Jodi in your post you said that the engine spark doesn't retard until you have a RPM of over 300. I presume this feature is built into the ignition so you can time an engine by moving the prop very slowly since at the very slow prop speed the engine is at full advance?

Correct timing seem to be an issue with CRRC engines. I have two and both were timed with WAY too much advance, 44 degrees, and 40 degrees.