Grettings all

[Guest schrammy]

Hello all,Brad here signing in from Tassie.I,ve been a bit quiet on the flying scene of late as i have been busy renovating and a few other bits and pieces on the go at once.I own an Xair of which has been quite in the shed for some time .I have had a couple of problems with the old girl particulary the 618 rotax,so guys expect a few questions to follow.!!!!!! I ,d like to get her up and running spot on for Summer,,,,,,,,,,,,Cheers,Brad,Pleased to be aboard.......

 

 

[dazza 38]

Hi mate, i cant help you with your rotax 618, but i would like, i hope you have a good time flying your X-air, cheers

 

 

[Guest Decca]

Hello Brad, and welcome to the forums.

 

There's help waiting here, a few with valuable experience in engines - ask away.

 

Regards, Decca.

 

 

[Tomo]

Welcome Brad! good to have you...:thumb_up:

 

Ask away... we're all listening!

 

 

 

[farri]

G`Day Brad and .

 

I`ve flown the 582 powered XAir several times as there`s one housed here on our property,good AC and flies well.

 

Cheers,

 

Frank.

 

 

[icebob]

Hi Brad,

 

Welcome to the forum, I have an X-air still in its containers ready to build, like you other issues have got in the way.

 

I'm an ex Ulverstone boy now in Sydney for a while.

 

Bob.

 

 

[Guest schrammy]

thanks guys for the warm welcome!!!!!,Sorry about the delay as i work shift work,so things get a bit on again off again if you can understand!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

 

[Tomo]

No worrys Brad! you gotta keep the money flowing one way or another! :big_grin:

 

 

[Guest schrammy]

well heres the problem,the engine seems to miss or start to shake under 4000rpm,and gradually gets worst back to idle.I did read an article from one of the other guys with a similar problem,it seemed his problem was the gearbox,differentto mine though,i have an e type box which i inspected but seemed ok to me! Engine done about 260 hrs,and just o/hauled with the original prob still existing!, Carbie wise i replaced the needle and seats .THe engine starts really easily but runs rough and a little better when she gets warm.Checked all electrics,coils ok,replaced,plugs,leads,stator plate.Gut feeling I,m thinking,carbs or prop out of balance.......:hittinghead: Any ideas,or am i just missing something too dam simple...........Brad

 

 

[Tomo]

Have you checked to see if the Carby's are balanced? (Ie, each giving the same amount of fuel)

 

That would cause rough running, because each piston is giving a different sized "Bang" and it would even out at higher rev's resulting in smoother running, or it just isn't as noticeable...

 

Has your engine got EGT sensor for each cylinder? on a ground run it may show up on them if the carby's are out of balance...?

 

Ps. I'm not an aircraft mechanic so don't rely on my speculation as being correct, but If it was me, I'd check that.

 

 

[Guest schrammy]

Tomo,I,m not quite how to check if each carb is delivering the same amount of fuel but i did check that the slide openings were the sameon each carbie at idle and at various open throttle settings! However come to think of it there was some difference in the 2 egt,s,I,m only guessing maybe up to 100F

 

 

[Tomo]

You have to consider the prop flow also cooling which ever cylinder more than the other... more noticeable on tractor types though.

 

If the slide openings are correct it could be the air fuel mixture screw's... if one cylinder is noticeably hotter than the other, (taking into consideration air flow etc...) one cylinder is running leaner than the other, the hottest being lean.

 

Another way to find out if each pot is operating differently to each other is to pull the spark plug out of each one (don't mix them up!) and look at the bottom of them... if one is whiter than the other, you've got a lean fuel mixture problem, if it's terribly black and carbonated its rich. Technically speaking, both plugs on both pots (cylinders) should all look the same if everything is right.

 

 

[Guest schrammy]

tomo,I,ve adjusted the mixture screws to correspond with the leaner cylinder, the problem being then the engine runs even rougher at idle.I read an article not long ago on tuning 2 stroke engines ,it basically said you must get the engine to run super smooth at idle buy adjusting the mixture screws before changing any other settings!!!! when i find that "sweet spot" the engine in my opinion is still shaking too much! All the plugs are very similar in appearance,I didnt know you should not mix them up though,thanks for the advice......

 

 

[Tomo]

All the plugs are very similar in appearance,I didnt know you should not mix them up though,thanks for the advice......

It really isn't an issue to the running at all, just for diagnoses. The spark plugs can be a very useful thing in telling what is happening in the engine... so if you just pull them out an chuck them down on the bench without taking note which is which, and then discover later on that one plug looks whiter than the other etc... you'd be kicking yourself about knowing which ones which!

 

Also the 503 I fly does vibrate a bit on the idle stopper... but you bring the rev's up just a tad and it smoothes out.

 

 

[Guest schrammy]

tomo,thanks for all your help,just one last thing,do u know is there a rotax manual u can buy that shows u how to check,measure,and adjust most stuff on the 582/618 for an overhaul,

 

 

[Guest Crezzi]

tomo,thanks for all your help,just one last thing,do u know is there a rotax manual u can buy that shows u how to check,measure,and adjust most stuff on the 582/618 for an overhaul,

All the Rotax documentation is available for free here Rotax-owner.comX Information Training Support .

 

Cheers

 

John