Microlighters

Hi All,

I need some advice on a 503 dcdi. I brought the trike up from the coast a while ago. I have been battleling with getting the engine to respond quick when reving it . It had 158 jets which I changed to 148's just to test The engine reved much better, but I had to do a forced landing yesterday when the engine suddenly lost power.The landing was fine but when I tried to rev the motor whilst on the ground I could only manage 3000 rpm.

I striped it today and found that the one piston had a hole in it, hence the fact that it didn,t want to rev.

Anny coments
Regards to all

Hi Cutman

At Higveld ALT we fly with 150 main jets,11k2 needles ,2nd clip setting on needle (from top O ring then cerclip on needle-inshort 2nd clip) and then your carb setting must be between 1/2 a turn to 3/4 turn from 0.

Sounds like your 503 was to lean.Thus the hole in piston.

Maybe Morph could help out with advice as well,his the technical bof.

Cheers

Hi.

Yup, you definately heat seized the motor, and put a hole through the piston.

Where did you get the information to fit 148 jets.

regards.

You can only play around with jets IF youv'e got EGT's - Otherwise you need to stick to the recommended jets and needles.

This doesn't help you much now though Look at it as a valuable lesson learnt... (although expensive too!)

Hole in piston, way too lean. What do your plugs look like, I suspect burning very light brown to white.

I agree, messing around with jets without having EGT's to check the results is dangerous. The EGT will give you an indication of how rich/lean the motor is burning. Low egt =lean, high egt = rich. A 2 stroke should rather be too rich than too lean. Too lean the motor runs briliantly but there is insufficient oil to lube and cool the motor and viola burned holes and seized engines.

A 148 jet is for 6000feet, average temps of around 20deg C. Is this the altitude and temps you are flying in?


It could also be that the jet needle settings were not standard as per the settings CHARLIE WHISKEY gives above.

Glad you guys are OK and managed to land safely. Sorry about the engine.

I would recommend that everyone get something like the MGL EMS 503. It's a full engine management system for the 503 in one gauge, 2 CHT's, 2 EGT's, RPM, Hobbs all in one. You can link it to an external alarm light that will glow when any of the parameters are exceeded. I think they are about R1700 for gauge, and 2 X CHT and 2 X EGT senders

http://www.mglavionics.co.za/Docs/503.pdf

Check in the classifieds, PMarshall is selling a 503 engine, no gearbox for a really good price.

Here's a thread on a 503 rebuild viewtopic.php?t=2057

Hi everybody,

Thanks for all the input from you all. I gues I should have made sure prior to fitting the 148 jets, even just for a test. It's a R3000.00 plus mistake, but that's what yiou call the school off learning.

Regards and fly safe
cutman

Morph wrote:.... The EGT will give you an indication of how rich/lean the motor is burning. Low egt =lean, high egt = rich.........

Huh? Who wired that EGT gauge

Duck Rogers wrote:

Morph wrote:.... The EGT will give you an indication of how rich/lean the motor is burning. Low egt =lean, high egt = rich.........

Huh? Who wired that EGT gauge

= or <> that r the q.

Give Morph a break - He was thinking faster than he can type!

Low EGT = rich
High EGT = lean

Revs and prop/load also play a part in EGT's but that is getting too technical...

sorry, I did have it wrong .

the richer the mixture the cooler the motor, therefore lower egt

nice catch Duck

Morph wrote: nice catch Duck

One handed..... :D

So what was the "OTHER" hand doing at the time ??