Microlighters

Hi need some expert advice please

Long story short I had my 582's sleeves rebored and fitted brand spanking new 1'st oversize pistons

We did the run-in and she's running beautifully and not leaking a single drop of oil or water anywhere (and the rotary valve oil reservoir is now maintaining its level 100% )

So generally I'm very happy but the problem is its not getting the expected revs

We have another aerie (A) with standard size pistons which gets max 6200rpm with its own NC prop on the ground

My aerie (B) currently only gets about max 5900rpm with its own NC prop on the ground

Now if we put aerie A's prop on my aerie B, my aerie only gets max 5800rpm on the ground

Shouldn't my brand new oversized pistons and sleeves be getting at least the same or better revs/performance as aerie A's engine?

We also put in new spark plugs and measured the clearance between sleeves and pistons (0.05mm)

What could be causing this?

Could it be the that the exhaust is faulty/dirty or must the engine still get 'loose' (400rpm difference is a lot though)?

Or what else can we try please?

Many thanks in advance
Ant

Would it be necessary to change the jets in the carb ?

Alkemac wrote:Would it be necessary to change the jets in the carb ?

Hi we thought about that thanks I'll ask Ian to give it a try

You think the jets can make such a big difference? (400rpm)

Not too sure, but try to remove the possibles.

Would doing a compression test help ?

Ant, did you maybe changed the pitch on your prop? Had the same problem but over-revving. After correcting the pitch, problem was gone and she climbed like "'n poep uit 'n bad"

Bulletjie wrote:Ant, did you maybe changed the pitch on your prop? Had the same problem but over-revving. After correcting the pitch, problem was gone and she climbed like "'n poep uit 'n bad"

Hello, I can adjust the pitch of the prop but that's not the problem

We're trying to compare "apples with apples"

My trike with the same prop is giving less rpm than another trike (also 582)

Alkemac wrote:Not too sure, but try to remove the possibles.

Would doing a compression test help ?

Hi I'll ask Ian to check

When they re-bored the sleeves I notices they're quite rough (honed)

Perhaps the rings must still grind smooth and create a better seal? (We only did the standard Rotex 1 hour run-in)

Hi Ant

Assuming that your fuel and air are within the parameters then I believe Bulletjie is correct, check out your Propeller. It is the only other thing that will effect the RPM. Sounds like it is over loading and causing a reduction in the RPM. Just my 2c worth. Let us know what the cause was once you have established it. Good luck.

Regards

Station Kariba wrote:Hi Ant

Assuming that your fuel and air are within the parameters then I believe Bulletjie is correct, check out your Propeller. It is the only other thing that will effect the RPM. Sounds like it is over loading and causing a reduction in the RPM. Just my 2c worth. Let us know what the cause was once you have established it. Good luck.

Regards

If you read the post, you can see they tried swapping props. The same prop makes 6200 on another engine but only 5800 on this engine.

I am not sure how long a Rotax takes to break in - but it does add a couple of RPM when it is fully broken in. I would suspect some sort of assembly issue. Rotary valve indexing, leaking induction boot, etc...

Justin

I read the post . You cannot assume that if you try a propeller off one Trike onto another that the pitch will be the same. This is not true, as the angle of the hub may differ on both planes, thus altering the pitch angle on the Prop, when you swap them over. The ONLY thing that will effect the RPM on the engine, is the Propeller. I wait with interest to see the results of the findings. Let us know.

Regards

Im also no expert but i think what they did with the swopping of the props (apples against apples) is correct and will give a fairly accurate "reading".

What was your RPM's before thet whole engine re-boring process? What was else was changed.
Swopping the props between trikes IMHO i dont think will change the pitch of the props even if its 2 diff trikes. Maybe the angle of the whole prop but the "roughness" of the blades stay the same so the amount of drag caused by the angle of hte blades with the air. So my verdict is that maybe the engine must still seat in or smooth out the rough edges and extra friction.


Maybe the prop manufacturers can elaborate on this.
Keep us posted.

Thanks, we never compared the engine's performance with the other aerie before the new pistons

And we changed the pitch of the blades (to be more or less the same as the other aerie since we assumed the new pistons should be as good if not better as the other aerie's) - now we can't really say if it's better or worse than it was before (bummer)

How you Measuring the RPM, maybe the gauges are not accurate enough?

L:

Karman wrote:How you Measuring the RPM, maybe the gauges are not accurate enough?

L:

Hi I'm using an analogue tach on my instrument pod but I don't think it matters since we tried the same prop on 2 different trikes?

The same prop on another trike gets 6200rpm and when we put that prop on my trike it only gets 5800rpm

Other things to check:

Ignition Timing (even 0.5 degree will give you big rpm changes)

Carb/s actually opening fully.
Same Air cleaners (some air cleaners allow more air than others)
Same carb jetting (not so easy to check)

Spark plug same type/gap correct
plug leads good order
Resistors on plug caps still fine ( dunno if applicable)

Then of course. ... Same fuel, same oil, same fuel/oil ratio .. etc etc etc