Cut out after a run issue

[Jury1]

Hi guys, so I recently changed my clutch on my wr8 hpi g3.0. I have it tuned nice it starts up and will idle for ages it drive good so I'm happy with the tune. But, when I bring it back from a run and it drops to idle again it then cuts out every Time so I'm abit confused why it's doing it as its spot on everywhere else? T.i.a

 

[WickedFog]

Hi guys, so I recently changed my clutch on my wr8 hpi g3.0. I have it tuned nice it starts up and will idle for ages it drive good so I'm happy with the tune. But, when I bring it back from a run and it drops to idle again it then cuts out every Time so I'm abit confused why it's doing it as its spot on everywhere else? T.i.a

Is it running too hot?

 

[Greywolf74]

This tuning flowchart should help

https://www.rctalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/

 

[Jury1]

Is it running too hot?

I havnt got a temp gun but I shall order one. If its too hot would that e the cause? Also would that mean uts running too lean?

 

[WickedFog]

I havnt got a temp gun but I shall order one. If its too hot would that e the cause? Also would that mean uts running too lean?

I am not a nitro guru, but if it runs good when you first start it then runs bad after it is ran for a bit, that would be my guess. In any engine, running lean will cause it to run hotter, causing the tune to be off because of the change in temp.

@cbaker65 and @StonerRC365 can help ya figure it out.

 

[Jury1]

I agree but when I rev it and let the rpm come down slowly it stays running? It's really odd

 

[cbaker65]

I agree but when I rev it and let the rpm come down slowly it stays running? It's really odd

Very hard to diagnose the problem ,could be as simple as your idle is a tad too low ,for the ratio
of the Lsn needle is set at ,after a run an you bring in an your idle drops ,then drops again even
lower ,then that is called a two stage idle!

A two stage idle can happen 2 ways ,one way is a false reading because your model may not
have a throttle return spring that keeps constant tension on the throttle rod in the closed
position an causing a false idle setting tune ,if you tune the engine with out it ,you can be tuning
with the throttle slightly opened up than normal ,so make sure that you have some kind of return
spring that puts a little tension on the throttle rod linkage!

Second ,your Lsn tune is not properly set or in sync with your idle gap ,at this point ,you are not
far off of the tune ,you are just having a flame out ,so your LSN could be either too lean or could
be too rich ,how to determine which!

If your engine puts out heavy smoke an is sluggish on take off ,then it is too rich ,lean the Lsn
needle in a little ,dont turn needle too much ,only a 1/16 of a turn at a time an make another
pass an check to see if it cured the problem ,the RPM's may raise slightly if it does ,lower your
idle setting!

If its too lean for idle your ,you wont have harley no smoke or residue coming out of the exhaust .
simply richen up the Lsn. until you have a good take off with some smoke ,but may have to bump up
the idle set screw to raise the idle up or match the air ratio with more fuel coming in for a good idle!

So ,you have to determine what the engine is doing ,is it flooding out & choking itself out or is it
starving of fuel?
If it is flooding a little too much ,sometimes all you need is to bump the idle up a little ,it is not
really good to have the idle set as low as it can ,because the engine can load up with fuel if
it sits too long at idle an flames out when you pull the trigger to take off ,that is also a good indication
that the Lsn is a little too rich!..

 

[WickedFog]

Very hard to diagnose the problem ,could be as simple as your idle is a tad too low ,for the ratio
of the Lsn needle is set at ,after a run an you bring in an your idle drops ,then drops again even
lower ,then that is called a two stage idle!

A two stage idle can happen 2 ways ,one way is a false reading because your model may not
have a throttle return spring that keeps constant tension on the throttle rod in the closed
position an causing a false idle setting tune ,if you tune the engine with out it ,you can be tuning
with the throttle slightly opened up than normal ,so make sure that you have some kind of return
spring that puts a little tension on the throttle rod linkage!

Second ,your Lsn tune is not properly set or in sync with your idle gap ,at this point ,you are not
far off of the tune ,you are just having a flame out ,so your LSN could be either too lean or could
be too rich ,how to determine which!

If your engine puts out heavy smoke an is sluggish on take off ,then it is too rich ,lean the Lsn
needle in a little ,dont turn needle too much ,only a 1/16 of a turn at a time an make another
pass an check to see if it cured the problem ,the RPM's may raise slightly if it does ,lower your
idle setting!

If its too lean for idle your ,you wont have harley no smoke or residue coming out of the exhaust .
simply richen up the Lsn. until you have a good take off with some smoke ,but may have to bump up
the idle set screw to raise the idle up or match the air ratio with more fuel coming in for a good idle!

So ,you have to determine what the engine is doing ,is it flooding out & choking itself out or is it
starving of fuel?
If it is flooding a little too much ,sometimes all you need is to bump the idle up a little ,it is not
really good to have the idle set as low as it can ,because the engine can load up with fuel if
it sits too long at idle an flames out when you pull the trigger to take off ,that is also a good indication
that the Lsn is a little too rich!..

Boy, I learned a lot. Thanks!

 

[Jury1]

Cheers mate I will try the spring. I got the lsn to cut off on pinch test at 4 seconds so I'm happy with that and the idle gap. I will give it a go with some of thos tips and see how it goes thankyou.

 

[cbaker65]

Cheers mate I will try the spring. I got the lsn to cut off on pinch test at 4 seconds so I'm happy with that and the idle gap. I will give it a go with some of thos tips and see how it goes thankyou.

I noticed a few people that had annoying issues ,they didnt have a throttle return spring on or it was loose
an didnt have no tension on it!
What happens when there is no tension on that spring or not having one at all ,the carb barrel will float
open slightly giving you a unstable idle gap!
Then what happens ,people tune their LSN & idle set screw to that false reading ,an when that carb does
close all the way ,like in braking mode ,your engine will die or flame out!

Not sure if that would be your case ,but it is little things like that ,that is over looked that makes people
pull their hair out!..

 

[Jury1]

Yeh I'm with ya dude it dont cut out on breaking it dont cut out until after a run it seems like if the rpm drops to fast it shuts off. Its really odd but I'm sure I will get there with it I will definitely put a spring on as this would be a nice fail safe also.

 

[WickedFog]

Yeh I'm with ya dude it dont cut out on breaking it dont cut out until after a run it seems like if the rpm drops to fast it shuts off. Its really odd but I'm sure I will get there with it I will definitely put a spring on as this would be a nice fail safe also.

The linkage from the servo will have enough play in it to cause your tune to be all over the place like baker said. You definitely need a spring on there.