Strange motor issue; only after heat up...

[d-rudie]

Hey all,

I'm having a strange issue with my Hanson 26 3D Max and Spectra G. After approximately a third of a tank, when the motor is nice and warm, I start getting some strange issues. For example:

RPM will be steady in hover, then the motor will start to race, then start to slow, over a period of about 20 seconds. This will happen for a couple of minutes until the motor starts to slowly lose power all together; over a period of about 30seconds from surging hover to the motor starting to kick and finally cutting out.

Now I have no idea where to start looking. I'm still breaking the motor in, so I'm running 25:1 full synthetic oil mix ratio. So far I've put just about 4 litres through it, approximately 1 gallon. I've only been hovering throughout this time; certainly hasn't been under much load.

Any ideas??? Too lean? Too rich? Too much oil?

[Peter]

Prob a tad too much oil, and just hovering doesn't let the motors temp vary , also an occasional circuit and short, full power climbs lets it blow excess oil out of the muffler , and also cleans the plug a bit too ...

What pitch is it hovering at , and how far open is the carb butterfly at hover throttle position ?/ and what's the hover head speed ?

[d-rudie]

Peter, I thought that might be too much oil, but I kinda figured that too much is too little when in break in...
I'll keep in mind what you said; I've give it a few circuits and see if that makes a difference.

I'm not sure of the head speed, but I'll post my pitch and throttle normal curves that I'm currently using.
(0% throttle is carby fully closed, and 100% fully open)

Throttle: 14 20 22 23.5 36.5 INH 65
Pitch: 38 50 100

Forgot to mention in the original post: after the motor cuts out completely, it will not start again (save a couple of 1 - 2 second runs) until it cools down...

[Peter]

Have you looked at the plug when it stops ? that can tell you a lot!!

the figures really mean nothing ; but it seems the throttle isnt fully opening in your " normal " mode ? ie 65% , when 100 % is open .. that will mean the jets will have no idea where they are !! Sorta!!

And can you measure the pitch at hover and full power too ?

[d-rudie]

Hmmmm I changed the throttle to 100% at full stick. I took a look at the plug; the electrode in the middle is a light brown colour, and the outer ring is a dark brown.

As terrible as it is for setup, but i don't have a pitch guage :P It rungs 0 degrees at mid stick I know, but other than that, it's just the pretty well the most I can mechanically get on the Spectra headup (extreme head) with out binding. hmmmm do you think it's something to do with the loading?

[Peter]

Maybe!!! If it's trying to hover with , say, 7 degrees of pitch , the head speed will be too slow for the motor to be running on the High needle, especially with that oil ratio ; it'll prob overheat ....... ideal hover pitch is 5 - 5.5 degrees... If it's trying to hover at 4 degrees , it'll run too hard and prob overheat as well !!!

I'd suggest getting onto someone locally with a pitch gauge ; Glenn ?/ ; to check it for you , or, BEST PLAN ,, get one yourself !!!

And , probably equally as important as the pitch , the carb butterfly should be approx 1/3 open at the hover throttle position ... if the butterfly is wrong , it's impossible to get the needles set right so the mixture is correct over the whole throttle range...

[rbort]

Sounds like your ring might be stuck (the won't start bit after shutting down)
And also you may have a fuel flow problem or some airleak. If you are using the stock stents clunk with the one way valve for vent check that neither is plugged and that fuel flow is good.
Add 2oz of Yamalube Ring Free cleaner to your gallon of gas and fly some more. The no-start problem should fade away after a gallon of gas or so.

-=>Raja.

[d-rudie]

Peter: I changed throttle to 100% at top stick and it seemed to (other than having higher head speed of course) be more stable and smoother in the air. So that's excellent!

rbort: Thank you very much for the info! I think you nailed the problem right on the head; an air leak! I took the carby off to find that the factory install rubber section (sorry can't for the life of me think of its name) was quite loose! I took it all off to find oil/fuel covering gaskets on both sides of the carby. I cleaned them up and reinstalled, being sure to threadlock the bolts and tighten them nice and snug.

Just went for a test fly. ALL previous issues have disappeared! Very smooth throttle in hover now! I've finally finished up my first gallon of fuel, so I'll be leaning the oil back to 33:1 on the next one. Will there be much adjustment on the needles required with this change?

Thanks for all the help guys! Second to none :D :)

[Peter]

It's amazing how often the " air leak " thing pops up !! I was sure you had the Z-R/c insulator on your heli; it's worth getting if you haven't... http://www.z-rc.com/?action=displayProductsPage&viewItemID=6 .. it replaces the plastic piece between the carb and motor.. I assume this is what you mean by the " rubber bit " ??

It'll take a while for the motor to get used to the different fuel, a tank or so , so don't get too carried away with needle adjusting .. it'll prob be able to go a tad leaner on both needles , but go very gently!!! the petrol is where the power comes from ....... too lean = rather expensive......

Now you'll find out why we all enjoy the gassers so much!!!

[d-rudie]

Hey again Guys,

Peter: I'll certainly be getting one of the Z-RC Insulators, however they're currently out of stock :( Any where else I can track one down?

Finally, I'm having a different issue now. I think it's started from using an air-line filter rather than a fuel line filter by mistake... this resulted in the lines becoming very restrictive when even the smallest amounts of grit were captured.

On my last flight, the heli started losing power (over a period of about 20-30 seconds) to the extent that it could barely stay in the air. Pushing the priming bulb would not suck any more fuel through; it would not fill the bulb regardless of how many times I pressed it. Deciding that the heli had been starved of fuel resulting in the loss of power, I ended up packing it up and taking it home concluding that simply removing the filter would fix my problem.

I have since removed the filter and bulb fills within a couple of pushes. However, I cannot get the motor to restart! I've tried a couple of plugs and verified that they are sparking. I pulled the carby off, took out both low and high speed needles and cleaned it out with compressed air. I found some shavings of plastic to be covering the two inlet holes either side of the main intake to the piston (carby side). I cleaned them up with a razor to allow clear passage, but it hasn't helped!

I'm not sure what else to look for! Nothing but the filter being removed was changed since the previous flight. What am I doing wrong??

I'm runing 33:1 synthetic oil mixture, and 1 3/8 out on both needles.

Thank you in advance :)

[Peter]

Glenn may have the insulators , or know where to get em in Aus ....

Have you checked the carb filters under the plate on the opposite side to the primer ? I assume the filter you had just decomposed ? the remnants may be blocking the inlet filters ?
or the diaphram ruptured ?

[d-rudie]

Hey Peter,

Thanks for the info. I took the Carby apart the most I could see how to (priming bulb with plate underneath, with spring-loaded rocker needle.. and on the other side seemingly just a filtration gasket of sorts). Now I couldn't see anything much wrong until I realised that when covering the fuel intake nozzle and pushing the primer, the bulb still popped back up with no hesitation; so there was an air leak. I took out everything that I could find and gave it a wipe and a blow then reinstalled everything. The bulb now stays stuck in while covering the intake :D

I had another go at starting it. At first it didn't run, but after changing the spark plug and giving it (substantial) more throttle than usual, it continued on and idled well. I increased revs for spool up and all seemed fine. At approximately 30% throttle (where the high speed kicks in?) the revs started the drop A LOT. As soon as I put the head under any load with some pitch the motor would shake terribly and die all together!

Now I figure there's still something blocking an intake somewhere, but I don't know where else to look; it seems that I've pulled the carby apart as much as I can!

EDIT: And by the way, who's Glenn, in regards to the Z-RC Insulators? :)

[cbergen]

These carbs are fairly cheap, try a new one and avoid all this frustration....:))

[d-rudie]

These carbs are fairly cheap, try a new one and avoid all this frustration....:))

Which one would you suggest as a replacement? I'd like one that's going to perform very well and that has a priming bulb if possible...

[cbergen]

Replace it with the same one you have now, probably a 645. If you can't find one in Oz, let us know, we'll get one coming in your direction. We have the insulators also. :)

[Peter]

Standard carb appears to be the 643 , I have them on mine , and 644's , which is the same but with a choke added,, Chris , what's a 645 ? I see you have carbs at great prices, compared to what they sell for here anyway ......

Glenn is Glenn Asquith at www.rcheliworld.com.au , the MA distributer in Aus......


Sounds like the carb is still blocked somewhere , there's a filter screen under that " filtration gasket of sorts " , which I take it to be the diaphram , which tends to block up , and diaphrams have been known to split with high air pressure too ......Chris's suggestion of a new carb , they have an inlet trumpet too !! , sounds like a plan !!!!

[d-rudie]

Excellent, thanks for your suggestions!

I notice quite a few people stock the 813 Carby, stating it is a high performance upgrade... Have you had any experience with it? Or should I just stick with the 643/644?

I'll open mine up again and be a little more rough when cleaning it; if it looks like I have to replace it it doesn't hurt :P I'll certainly check out the filtration screen as your mentioned Peter.

EDIT: While I've got the motor out of the heli and I'm trouble shooting, I thought I should take a look at the electrical side of things too. Do you know where I could find some info regarding the resistance of the coil? Also, what sort of spark should I be getting across the plug? At the moment, the sparks look quite small, they certainly don't crack across the gap, instead simply look very blue and subtle. Is this how they are meant to be?