Dolo

Hey all,

I've been having a LOTof problems getting the (stock) engine to run properly. I managed to get through the full first tank after many, many restarts of the engine, and I'm working through the second. My hands are now bruised and battered beyond belief :P

Things I did wrong to begin with:
- Did not use a heat gun / hair dryer before starting. I'm doing that now, it makes a MASSIVEdifference, and the engine will usually start after 1-2 pulls on the rip-cord.
- Flooded the living hell out of the engine. I'm wondering if this is still the issue (although I'm not sure how to fully un-flood it, now). Initially, I got fuel to the carby, then kept going a lot longer. Ithink proceeded to try to start it for about 20 minutes (no pre-heating!!), during which time it would have been further flooded.
- Didn't check the factory tune. The manual suggests the high needle should be 4-4.5 turns out. Ididn't count how many turns out it was from factory, but after adjusting it to 4.5 turns out it is probably sunk 1mm deeper than it was before. Was maybe 7.5+turns, from factory? This probably contributed to the flooding problem.

What's happening now (high needle nominally tuned to 4.5 turns out):
I've just been trying to run it in some more for about 30 mins. Here's a brief run-down:
- Pre-heat engine
- (did NOT put my finger over the exhaust and prime the engine)
- 1-2 pulls and it starts. Last thing Idid yesterday was "unflood" the engine, so god knows where the fuel came from.
- Sounds pretty rough for 30 seconds, then it starts to sound ok - I would have though the pre-heating would make it run smoother from start.
- Usually when Istart to open up the throttle a bit, the engine stalls straight away.

The engine then runs for about 1-2 minutes, constantly "strobing" - RPM drops down almost to the point where it sounds like it will stall, then climbs back up almost to the point where the car starts to move, then back down... after this happens a few times, it simply stalls as the RPMs bottom out.

I've pulled the head off, held it upside down, disconnected fuel tube (both tubes, so the engine + exhaust are completely isolated from the fuel tank) and cranked it over many times. Ialso removed a THICKsheen of oil (ahh, dried nitro fuel Ithink) from everywhere inside the engine, further proof that Iflooded the crap out of it.

So what does everyone think - Is the "strobing" RPMissue just because there is still excess fuel lurking somewhere in the engine / exhaust? Do Ineed to rip the whole thing apart? Could this alternatively be an issue with the engine not being sealed properly (Iread a lot of posts saying CEN engines are rarely sealed properly from factory - I don't know how to check / fix this, yet).

It's depressing, having such an awesome beast of a car, with such a difficult engine. Imust admit, this is only my second nitro car, the first being an HSPWarhead. Maybe Ineed to start avoiding the cheapo chinese brands?

controlliner

It's too rich, try turning the HSN in 1.5 turns.

Dolo

I'm coming to that conclusion too.

Ijust pulled it all apart - the exhaust ports were basically covered with thickened nitro fuel, along with most of the rest of the engine internals. Cleaned it all up so everything just has a fine sheen of oil on it and put everything back together.

There was pretty much a pool of nitro fuel in the exhaust, as well!

Anyway, Ijust started it up - easy to start, ran a fair bit better (HSNwas at 4 turns), but it ended up stalling after ~2-3 minutes again. Then when Itried to start it again, the pull-cord was VERYhard to pull (i.e. hydrolock)!!!! So maybe 1.5 turns for HSNis the way to go.. seems extremely lean compared with 4-4.5 turns that CENrecommend.

I sure hope nitro's get easier as time goes on - 10 minutes of work for 2 minutes of run time is going to get old pretty soon..

subbass

My Feedback: (13)

To check the engine for air leaks start the the engine and plug the carb with your finger(stay clear of moving parts)the engine should stop instantly.If not there is a airleak check area were the carb meets the engine the o ring there should be compressed and check the backplate screws.When the engine floods disconnect the fuel line and loosen the glowplug 1 or 2 turns and energize the plug and start the engine,That should clear the engine and also make sure the plug is good because breakin can be hard on plugs even more when you flood it.

Dolo

Ok, I just got through about half a tank of fuel before stalling. The only real change was to the HSN - 3 turns in instead of 4.5. This engine still seems very temperamental - Ihope that improves as I continue to break it in.

subbass

My Feedback: (13)

Remember breakin should be done close to normal operating temps(180F min)But at lower RPMs.It is not good to run it cold(under 180F).

Dolo

Ijust got through a full tank, no stalling!

After running, Ipulled the plug out and the element is gray, almost white - completely dry. I guess I'm running it too lean for breaking in? Oh well During the run, Itipped the car forward several times, usually getting a puddle of pinkish oil coming from the exhaust - To me it just looks like thick nitro fuel. Idon't know if this is normal, and Icannot figure out how Ican be running it too lean but still getting puddles of fuel coming out?!?

SLAYERDUDE

That engine doesent use pinch anyways so it don't mater lol.
(That's what CEN told my friend anyways)
Welcome to the world of large displacement MT engines!
My MGT 8.0 (Thunder tiger heli engine) was 3 turns lean for break in, as far as AE was concerned..

I broke it in to their specs, they warrantied it, then I got it back and had to go a full 3 turns richer to make it run right...

http://www.rcuniverse.com/forum/m_10274385/tm.htm

subbass

My Feedback: (13)

As long as you have smoke coming out of the engine at all RPMs you will be ok,If the glow plug is gray in color that is good but not if the coil is distorted.If you ran the engine a little lean it will be ok as long as you did not over speed it.You should be fine don't worry just have fun.Like I said breakin should be done close to normal operating temps at lower RPMs so your ok.

Dolo

I'm in no way worried, just got frustrated at the stalling. If it happens to blow up in 6 months, so much the better - Sounds like there are much better engines out there that will put the NX7.7 to shame (despite having significantly lower displacement).

1QwkSport2.5r

There's a lot of misconceptions on break-in regimens of Glow engines. Some engines can be more unforgiving for the first tank or two but after that they should be loosening up some. If it isnt, then you're probably not getting it hot enough. Your fuel mixture should be richer than it would be for normal running but lean enough to have the engine temps high enough for the sleeve to expand - JUST rich enough so its slower to spool up but cleans out good and has a good slightly rich sound. I am unsure if this engine is ringed, but I would doubt it. I assume its ABC constructed, so the temp rule should apply. Get it up to 200°F minimum and run it for 5-10 minutes and cool it off for 5-10 minutes. run it for 5-10 cool it off 5-10. Do this on and off 5-6 times and you should be good to go. Listen to the engine - the noise it makes will tell you if its "right" or not. If its stalling at idle after sitting a few seconds, lean your idle mixture just a touch until it quits stalling. (This is roughly how I break-in ABC engines though I am a little more in-depth with specific needle settings and such but this is just a general guideline. All ABC engines need a nominal amount of heat for the metals to properly expand and sufficient time to cool off and contract between runs.)