Rotax 503 DCDI Dual Carb Questions

[Hardy]

I've got 250 hrs. on my 503 DCDI without a hickup of any kind, I would not trade my oil injection for anything. Well their is a red head down the street that's really hot looking.

 

[DennisFetters]

I've got 250 hrs. on my 503 DCDI without a hickup of any kind, I would not trade my oil injection for anything. Well their is a red head down the street that's really hot looking.

I thought Rotax only had blue heads.....

:suspicious:

 

[CLS447]

Phantom, where is the shaft failing ? Gear end or otherwise ? 3 times on different engines ? Did you learn why & try to correct it or not ? Which way did your carbs tilt ?

Hardy, which way do your carbs tilt....Air filter high or low ? From your avatar it looks like an Air Command with an inverted engine. I would love to see some pics of your installation. Did you do it or buy it that way ? What prop are you using? C box ? Prerotator ?

I would also be interested to see how you routed your cables.

Edy....air filter high or low ?

Here is my old "red head" 447 . I can't say for sure how many hrs it had but it still runs great.

Always premixed with AV2 oil. Never decarboned or dismantled. Only problem was when I decided to mess with the timing. I put in new points & finally got her right again.

That little engine is AMAZING !!

 

[Edypaul]

I have blown 3 rotax 503 engines due to plastic shaft failing.

I would like to here some specifics on this. What were you flying, where, type of oil,climate conditions,same engine or different engines,or is this B.S. from some guy with just one post that I never herd of before?

 

[CLS447]

Edy, are you air filters up or down ?

 

[Edypaul]

My filters are down.

 

[Hardy]

Hardy, which way do your carbs tilt....Air filter high or low ? From your avatar it looks like an Air Command with an inverted engine. I would love to see some pics of your installation. Did you do it or buy it that way ? What prop are you using? C box ? Prerotator ?

I would also be interested to see how you routed your cables.


Chris I built it myself, carbs are tilted down, eng. is mounted plugs up, Warp Drive 60 inch with a B box and prerotator. I'll try to get some pictures of the cables routing for you.

 

[CLS447]

Hardy, do you have the CLT machine or just the upright engine version?

I fired mine up yesterday & set the prop pitch, now I need to do the break-in run.

Sounds like a Rotax ! I can definitely hear a difference when I do the mag check. She starts very easy. The chokes work great when cold.

I have 100/1 premix in the tank. These guys have me so paranoid about the oil injection. How do you know for sure that it is pumping oil ? I am keeping an eye on the EGTs!

Until the injection lines were full, I was really worried about my new engine!

LEAF said that below 3000rpm she only needs about 125/1 ratio. She really only needs 50/1 under full load.

I will just have to learn to trust the injection. Watch my temps & hopefully the oil level in the tank will always be dropping.

I will just have to keep the oil tank topped up & the gas tank full.

LEAF also said ....always premium gas. I used Sunoco 93 Ultra.

 

[Hardy]

Chris, I have the CLT machine, belive me after the second take of fuel you'll forget all about the injection system. I keep the EGT's around 1100 degs. and never think about it.

 

[CLS447]

Thanks, My EGTs held around 1000 for the whole break-in. But that was with the premix.

The highest my CHT got was 350, That was the 3 minute full power segment at the end.

I think I am going to LOVE this engine !!!!!!!!!

Resasi, Read this again but don't believe the part about hand cranking the engine to get the oil through the injection lines ! You gotta start her !


http://www.ultralightnews.ca/articles/enginesetup.htm

Uh oh....I NOW read the break-in section. I broke mine in with a max of 6200. It says the max is 6800 so I should have been more like 6500 static......Oh well ...I babied it !

Any thoughts on the max rpm for the 503 ??????

 

[Resasi]

Still a ways off from getting her started Chris but got the run in chart and will try to follow that.

No harm in babying, that's your ass in the seat and a coddled and well cared for engine stands a better chance of looking after it.

Thought 6800 was max.

 

[CLS447]

Yeah , I think you're right 6800 rpm.

My old westberg tach only goes to 7000. The new ones got to 8000.

If I bury the needle , it's time for more pitch !

 

[scottessex]

Chris, the Rotax book states for the 503 and 582, that 6450 max sustained RPM, and 6800 for a max of 5 minutes.

So you should set the pitch for around 6200-6300 on the ground.

 

[Resasi]

Scott thank you for clearing that point up for us.

I had not taken on board the 68 was a five minute only.

The break in chart I see calls for a properly loaded engine, prop set to a correct pitch for running in, ie around 10-11 degrees for the 62' Warp on the B box DCDI 503, and for the chart to be adhered to and the engine not 'babied'.

 

[CLS447]

Thanks Scott, I broke her in with a max of 6200 rpm. Do you think that was high enough rpms to break her in ?

LEAF said not to loosen the headbolts after run-in. But when I retorqued them , after the initial budge, they moved more till they reached 18 ft lbs.

The exhaust was definitely in need of retorque !

After she has been started, it takes about 1/2 a pull to start, I love it.

 

[scottessex]

Chris that should be fine, The engine will continue to break in for a short time.
Just watch your temps, keep them within limits and you will be fine.

That is why you retorque! Yes they will move some during the retorque.

Another technique you can use during retorque is to make a small witnes mark with a sharpie pen, slightly loosen the bolt, then retorque, and you can tell from your mark that it has moved.
The reason for this is because the bolts/nuts can stick, so it you break them loose
you will get a better torque reading when you retighten. But do them one at a time.

 

[nickjaxe]

CLS447 I know this is an old topic and I am hoping to bring it back to life,

Hi all by the way my 1st post on your forum looks very interesting,

Hope you guys don't think I an being cheeky but I don't fly a rotary craft but an ultralight trike in the UK....but I was looking for an answer to my problem on Google and came across my problem on your post,

I have just fitted a new 503 DC Ducati ignition to my trike, my old engine was a single carb 503 so I have had a bit of work to do with throtle cables ect,

But my problem is that the carbs point down with the angled inlet manifold like yours CLS....did you ever find an reason why this should be and does the motor run ok like this....I was worried about the float sticking in the float chamber being on an angle....hopefully there is an answer.

Nick.

 

[CLS447]

Welcome Nick !

My engine is running great ! No Problems.

The only answer that I could get from the Rotax people is that the oil injection lines should enter from the bottom of the intake manifolds.

So whether the engine is plugs up or plugs down(inverted) the manifolds must be installed with the oil lines into the bottom of the intakes.

This will always have the carbs tilted away from the engine( air filter down).

I never got a solid answer as to WHY !

Are you using the oil injection ? How about some pics of you trike ?

 

[nickjaxe]

Hi Chris many thanks for getting back to me, today I rang the one and only Rotax importer here in the UK where I got the motor from last week, only 2 or 3 new 503s left in the UK now.....I got the same as you.....Mmmmmmm not sure....I can send you the old style sockets if you like they said, no I just want to know why there like this....I will see if I can find out the guy said, if he gets back to me I will let you know Chris,

NO using pre-mix, somebody did tell me they thought it was to stop oil and fuel or water running into the cylinders when the engine is stopped....it will then drain into the filter???? not sure on that one but makes sense,

How many hour have you got on the 503 now Chris....and yes I will attach some pics when I get a moment.....not as exciting looking as your machine though Chris.

Nick.

 

[nickjaxe]

Hi Chris, went through the break in procedure Sunday just gone....scary,

My EGT was 1110f-600c WOT 6300rpm with a hot spot around the 4500rpm mark of 1110f...at 4000rpm it was 1040f and 5000rpm also 1040f...I wonder what causes the hot spot at 4500rpm,

What MAX egt do you get on WOT Chris and what fuel burn at what RPM,

I have mounted my carbs the same as yours ie downwards.

Nick.