wkloppen

Gents,

I'm running an .21 XRD 5 ports Cup motor in my Serpent GT. It's completely off tune. It has run 10 litres of runnertime 16%. Im running an OS RP6 plug with moderate ambient temperatures between 19 en 25 degrees celsius.

The symptons

Preps: I heat up the engine a little with an engine heat socket
* After the first start it seems to run idle normally and when I hit the throttle it produces an awfull lot of smoke and accelerates as a 4 stroke engine.
* Then on the track after run idle for let see 30 seconds it still accelerates with a lot of smoke and running like a 4 stroke.
* After a lap of 3 the 4 stroke sound is gone and when I come in the pits the idle stay abnormally high with clutch almost engaging.

Now I've read the various bibles on the net including the one on this forum several times.
Could it be the needle balance with a way too rich LSN smothering the engine with fuel in the crankcase compensated with a too high idle screw setting?
When I come into the pits with more or less an empty crankcase the idle is high due to the wrong idle setting. Then the crankcase starts slowly flooding due to the too rich lsn to finally slow down the engine a bit.

Im still a noob on nitro engines but 2 stroke plug engines I understand quite well..

any advise would be nice...for instance how do I get a very basic setting at first. There is no manual which tells me how the needles should be set initially



willem

nitrodude

iTrader: (8)

It seems like a you LSN is set too lean.

Roelof

Why not going to 2brothers in your village, they can help you as a supplyer for the GT cup.

wkloppen

Ok...and whats the theoratical explanation for it? would help me if I understood why the lsn is too lean based on the symptons...

thx in advance

w.

dan_vector

iTrader: (27)

Coming in the pits and having a very high idle which eventually drops down and possibly stops is a classic symptom of lean HSN too.

First step is reset the carb to factory settings which should provide a stable yet rich setting and so from there. Usually the LSN is pretty much within the ball park at factory setting on a Novarossi but I don't know about the XRD.

Also run a new plug. Chasing tune with an old plug or a plug that has been run lean is a hike into nothing too.

Roelof

And that is also a classic error. The same behavour excist with a too rich LSN

With a rich LSN the idle is set higher to keep it running. The amount of smoke when driving out of the pits tells that.
Leaner on the LSN results that the idle can be screwed down also with the result less smoke when driving away, quicker on speed and a better return to idle.

But keep the HSN in sight! When the LSN is set leaner you probably need to set it richer.

wkloppen

Thx Roelof...my feeling is you are spot on....

W

wkloppen

Sorry...pressen the wrong quote. @dan and roelof...will let you know what the outcome is. Im running a new manifold as well. The nova 41032.

W.

dan_vector

iTrader: (27)

Changing the manifold will of course affect the tune.

In my experience the phenomenon that you are suffering could be either HSN and LSN causing that effect. Roelof is right but don't discount the HSN being the issue as well.

So as I recommended it is best to return the needles to factory setting and go from there.

wkloppen

I like this forum and the helpfull attitude...thx guys....

W.

Foodie

I would change the glowplug to rp7. I would start from scratch and screw out hsn until it 4 strokes a little bit at full throttle. Then adjust lsn and idle afterwards. If it smokes alot during acceleration lean the lsn and turn out the idle screw. When you have adjusted then adjust hsn.

wkloppen

thx....will give it a serious go on saturday

thommi

First step, verify and adjust the Idle Gap. Take the venturi out and set the idle gap to around 0,5 to 0,7mm. If the idle gap is not in this range, you will have strange behaviour of the engine and tuning will be dificult based on symptoms.

After that, tune HSN and then LSN.

M7H

Exaclty this Willem. Both Roelof and Dan say the same actually.

A too rich LSN, compensated with a too lean HSN, will result in a very high idle rpm, because of a too high idle set point.

Richen the HSN half a turn, and lean the LSN bit by bit, toghether with lowering the idle rpm. Slowly you will notice the engine pick up better out of the corners, and returns to a nice and steady idle rpm (for about 10 seconds, after that it is ok if it will stall)

Please note, that if you can not tune your engine anymore, the piston/sleeve might be worn and you can keep hunting for a good tune.

I told you this a some time ago, but I understand you were not ready for that amount of information yet....

Also this is exactly why the car of Alexander was so much faster then others, because the engine was set correctly.

wkloppen

Who told me?...As I don't have a db in my head which allows me to query on matching forum usernames with people who advised me a while ago

BTW: The engine with the new GT manifold is now running as it should...a nice low idle with good overall performance

greetz

w.