Nightmare
 

Morning.
I have a little knowledge with nitro so know the basics but I have a friends hyper 21 engine and standard carb that will not lean down on the HSN.
I have had the thing apart and nothing obvious. There doesn't seem to be any major air leaks but it still runs rich.
Just at th point it is running out of fuel for that last 10 seconds it absolutely sings but prior to that premenopausal bog down at high end.
I have even marked the mid range and leaned that in which helps a little but still no scream. Other than from me!
Any ideas, other than throwing in the pond, would be appreciated.
Thanks
James

Little knowledge, yet you stripped it down?
Air leak would make it lean...
Have you tried a new plug?
Is it fresh fuel
Is the clutch OK
By screaming do you mean you want it to blow up??

Are you trying to help?
 

The fuel is fresh!
Plug is good
Why would I want it to blow up. You understand what I mean

I mentioned air leaks as this can be a problem.

I stripped down as I could not think of anything else.

The clutch comment is interesting. How would this effect the engine tune?

Thanks

James

Mark was saying that an air leak would make it run lean, whereas you say it runs rich, therefore the problem can't be an air leak.

asuming your not "screaming " it on the starter box, a faulty clutch can bog down or over load the engine.
ho old is the engine?
how new is the air filter?
is it getting full throttle from the servo? (ie carb fully open)

A 3port engine will sound boggy compaired to a 7port,
is the bottom end to lean,
if you richen up the bottom end soem so it boggs down as you pull off,the start to lean out the top untill you get the crisp rasp rather than the scream,assuming like i say that its not the 3 port,then if you get that ok,lean out the bottom,

Thanks
 

The engine is about 3 years old but only run in plus about 6 tanks fuel.
Screaming is probably the wrong word but it isn't clearing its throat top end.
I think it is the 3 port. Can you tell from the outside.
I washed dried and reoiled air filter which seems ok.
The bottom end started at factory setting of 2.5 turns from flush but this seemed much to rich. Read another article that says 5 out from closed.
It is currently 3 out from closed. If I richen any further it struggles to pick up at all.

set the lsn back to factory setting and then lean the lsn in half a turn.

fire engine up and get it warm by blipping the throttle for a couple of minutes.

let the engine idle for about 5 seconds then pinch the fuel line hard with finger and thumb,the revs should rise after 2-3 seconds very slightly then cut,that is what your aiming for.

if it takes a long time to rise then lean the lsn in 1/8th of a turn and try again,it may take you half a dozen tries or more but this is a very simple way of getting your needles in the ballpark

the idle will probably increase as you lean the lsn so you may have to back the idle screw out a little as you go on.


once the lsn is set go drive it in an open space and do some full throttle runs.
adjust the hsn 1/8th at a time until it starts to clear up on the top end.

once happy richen the lsn 1/8th and you should be good to go.

It could be the seals have gone hard over the years then split when you have put fuel through it,
If you take the head off,move the piston down,this will show you the ports,i carnt remember if the exhaust is classed as a port though,but you get the idea:thumbsup:

Thanks
 

Reg

Thanks. I became fed up so bought a new carb and it now works perfectly.
I think one of he needles may be damaged, bent, broke at the end as it was just permanently getting too much fuel.

Thanks to everyone for heir help

James