DirtTorpedo

OK... So i set up my H9 spit with a 100FZ (not the s model)

Twoo weekends ago, i took the airframe out to the field, strapped it to the test stand and fired it up....

Using 14X9 3-blad prop, YS 20/20 fuel and an OS-f plug, Keleo scale exhaust..

Got 9300 max RPM and richend it back to 9050.. Set idle at 2K and with a slight adjustment of the idle screw, it held it perfectly.... It ran at 4k perfectly and transitioned good with no hicups... I let it cool, started it again and it ran great, would go from max RM to idle and hold it and run at 4k flawlessly.


Flash forward to this weekend...

Started right up and ran good until i tried to idle it....

Won't hold idle.. hard to start after first fire up.. Top end is still good and so is midrange, but there a lumpy idle, bad transition and nothing seems to fix it..

Flew the plane anyway... plane performs great as long as you don't try and idle it... it loads up and shuts off... two deadsticks.... (no problem on this plane, really)

NOW THEN....

CHANGES since last week...

1) sullivan glow driver installed
2) A few dremel modifications to cowling to allow keleo exhuast to fit without vibrating on the cowel.

THIS IS WHAT I SUSPECT..... I got some dirt in the regulator that i didn;t get cleaned out after dremeling the cowl.... I'm going to clean the regulator today and try again

I don't think its the glow driver (but i'm open to suggestions!!)... cause i left the external driver on last time while it was idling for a while, and then took it off and nothing changed.

If i idon;t find any dirt in the regulator, anything else that i should be looking for???

petec

My Feedback: (58)

If I am reading this right, the engine ran flawlessly on the test stand and then the idle problems happened once you had it in the airframe. Is that correct?

Did it idle dfine in the airframe? If so and it was before you did the grinding on the cowl did you try changing the plug in the event any dust from the cowl was ingested and may have poisoned the plug although a glow driver should mitigate that issue. The other thing that might be happening is the airflow in the cowl at idle may be turbulent enough to cause you an issue. If you try a new plug and still no joy try pulling the cowl and see if that makes a difference.

Again this is assuming the only change was poutting the engine in the plane.

Iflyglow

My Feedback: (79)

Get rid of the Glow driver and fix the problem. I have never ever heard of on board glow on a YS. Where is your idle RPM set? The low speed needle is an airbleed screw not a needle. The low speed can only be set at 2000 rpm where it is not under fuel injection. Any Rpm higher than that and it is transitioning to pressureized fuel injection. So if you do not have it ideling at the correct Rpm your low speed adjustments are doing nothing but confusing you more.
Like I said before, get rid of the onboard glow and learn to tune it. You will never get it tuned correctly when useing it.

DirtTorpedo

OK...... Thanks for the replys

1st.... didn't find anything in the regulator

2nd... Engine was never in a test stand... It was in the airplane when i took it to the field to test fire it two weeks ago when it ran great .. so nothing changed with the plumbing nor orientation of the motor...

3rd.. two weeks ago idle was 2050 RPM and it held it perfect. This weekend it would go to 2050 and then start acting like an idiot after a few seconds...

4th ... Glow driver.. Hmmmmmm.. being that i didn't find anything in the regulator AND this is the only change since when it was running right....... maybe Motorman is right and this is the culprit... its set to come on under 1/8th throttle, and it wasn't there when it was running right.... [:@]

I always put a glow driver / ignitor OF SOME SORT in my planes with inverted engines... the reason is that i HATE trying to find the glow plug under the nose of the plane.. On my other 4 strokers, they are just switches connected to a Sub C cell to light the glow plug for starting, and then i turn them off for flight. These are mostly warbirds, and i use the sub-c cell to balance the airplane along with the RX pack so i don;t need to add external weight.


HOWEVER....in this case, i had the sullivan unit availalbe, so i used it and had it set to come on below 1/8th throttle, figured i might as well use the "auto on" function of the thing.... Never used a sullivan unit on a four stroke before, only on inverted two strokes..... go figure



SOOOOOOOOO

I'll turn the glow driver completely off while the engine is runnin and use it for starting only and see if that fixes the problem..... maybe having the glow plug heated all the time at idle aint a good thing on the YS.... []

I'll let you know if taking the glow driver out of the loop fixes the problem!

Again.. thanks for the help!

DirtTorpedo

OK... Found two issues when i went to start the girl up at the field today...

1) Exhaust leak... acutally... the bolt that secures the exhaust to the engine was loose and rattling around on the pipe (keleo scale exhaust bolts to engine mount, else it would have fell off!!!!!!)

So... there was a MAJOR exhaust leak..... and i know that is gonna screw stuff up BIG TIME....

2) the O ring between the carb and the air chamber was bubbling where ther was fuel laying on it... that means its leaking right???

BUT... the engine was not running when i noticed it........... should htere be pressure in the air chamber when the engine is not running...


Fixed the exhaust leak, used the glow driver to start the plane and then shut the driver off and made adjustments...and she ran much better... MUCH better... its almost there!

Now.... that leaky O-ring between the air chamber and carb.... That needs fixed right??? (i know it needs fixed...... )

Got a whole set of O-rings..... but from eyeballing it, looks like i'll need to order a gaskett kit as well when i remove the parts to install a new o-ring.. correct?

what material for o-ring""

FINALLY... top end was a bit... weird.. it would hit 9000 and climb a hundred RPM after a couple seconds....... O-ring causing this???

petec

My Feedback: (58)

That o-ring needs fixed or you will drive yourself nuts chasing a lean surge. I'm not sure what the YS o-rings are made from since I just buy theirs and the gaskets when I need to do repairs. Central Hobbies should have them in stock though.

DirtTorpedo

Thanks... thats exactly what going on on the top end too... slight lean surge... it reaches the point i dialed it in at and then drifts up a couple hundred rpm and back down... etc..

Ordered a gasket and O-ring kit.. give her a "freshening" and check the lifter clearance as well before flying again...