Rc engine low speed needle tuning

[Daniel J]

Well ,I'm in warm sunny California an always ran 30% ,I've tried a 20% 0ne time an my stuff just wouldnt
run worth a hoot ,some of the engines I run are size Os 18 ,Ofna hyper 21 , an 2 Hpi 5.9's!

An I also try to run my engines a little on the rich side to acomidate any type of heat or an accidental
lean out!...
I would like to try 25% nitro myself ,but ,30% should be ok if you reset to factory an retune with a new
glo-plug!....

Thanks man!! Need my hobby shop to get 25% nitro in stock. It's so annoying. I Will give you future updates

 

[olds97_lss]

Usually, engines are shimmed to run 15-25%, if you deviate beyond that, then reshimming may be necessary. I run 25% in everything with a medium temp plug and it works well for me.

While the SH28's I've had in the past weren't super powerful, they did hold a tune pretty well and were pretty reliable. They just didn't hold a pinch for very long. 5-6 gallons and they would start getting very fussy to tune/run/start.

I'm wondering if you have your idle set too high. A LSN will only screw in until it bottoms out in the carb slide, usually. If your idle screw has the carb too far open, then the LSN won't be able to do it's job properly.

With the throttle at neutral, and the idle screw set properly, there should be a 1mm or so gap down the throat of the carb:

The gap on this is overly wide, but it's because there's no pressure from the throttle wire pushing it shut so it's resting on the idle screw.

 

[cbaker65]

Usually, engines are shimmed to run 15-25%, if you deviate beyond that, then reshimming may be necessary. I run 25% in everything with a medium temp plug and it works well for me.

While the SH28's I've had in the past weren't super powerful, they did hold a tune pretty well and were pretty reliable. They just didn't hold a pinch for very long. 5-6 gallons and they would start getting very fussy to tune/run/start.

I'm wondering if you have your idle set too high. A LSN will only screw in until it bottoms out in the carb slide, usually. If your idle screw has the carb too far open, then the LSN won't be able to do it's job properly.

With the throttle at neutral, and the idle screw set properly, there should be a 1mm or so gap down the throat of the carb:

The gap on this is overly wide, but it's because there's no pressure from the throttle wire pushing it shut so it's resting on the idle screw.

That's a very good tip Olds!.............

I've been out of the game too long to remember ,I'm glad your here!....

 

[sv250]

Shim is fine. Higger nitro content can require more shims. I've never added. 30% runs cooler than 20 and has a bit more punch win win.

That looks like the same 8.5 sh carb we see on everything.

Grease and factory settings. Qell start 1/2 turn leaner than stock. Every sh, lrp, mach engine comes set extremely rich. I've always had to lean just to get them running. I have owned 5 of em.

 

[Daniel J]

Usually, engines are shimmed to run 15-25%, if you deviate beyond that, then reshimming may be necessary. I run 25% in everything with a medium temp plug and it works well for me.

While the SH28's I've had in the past weren't super powerful, they did hold a tune pretty well and were pretty reliable. They just didn't hold a pinch for very long. 5-6 gallons and they would start getting very fussy to tune/run/start.

I'm wondering if you have your idle set too high. A LSN will only screw in until it bottoms out in the carb slide, usually. If your idle screw has the carb too far open, then the LSN won't be able to do it's job properly.

With the throttle at neutral, and the idle screw set properly, there should be a 1mm or so gap down the throat of the carb:

The gap on this is overly wide, but it's because there's no pressure from the throttle wire pushing it shut so it's resting on the idle screw.

Thanks I will try that!! Could someone send me a picture of a 1mm opening gap so I can get an idea of what it looks like

 

[cbaker65]

Thanks I will try that!! Could someone send me a picture of a 1mm opening gap so I can get an idea of what it looks like

Its about the thickness of a paper clip wire!

 

[olds97_lss]

Thanks I will try that!! Could someone send me a picture of a 1mm opening gap so I can get an idea of what it looks like

Couple images to hopefully help:

 

[Daniel J]

Couple images to hopefully help:

Thanks a ton!!

 

[Daniel J]

Well ,I'm in warm sunny California an always ran 30% ,I've tried a 20% 0ne time an my stuff just wouldnt
run worth a hoot ,some of the engines I run are size Os 18 ,Ofna hyper 21 , an 2 Hpi 5.9's!

An I also try to run my engines a little on the rich side to acomidate any type of heat or an accidental
lean out!...
I would like to try 25% nitro myself ,but ,30% should be ok if you reset to factory an retune with a new
glo-plug!....

tried it again today. no changes. clueless now

 

[Daniel J]

Couple images to hopefully help:

tried it again today. no changes. clueless now

 

[cbaker65]

tried it again today. no changes. clueless now

If the things & tips that me & Olds suggested don't work ,then your engine could be wore out ,
maybe check for compression!

 

[Daniel J]

If the things & tips that me & Olds suggested don't work ,then your engine could be wore out ,
maybe check for compression!

There's a ton of compression. Can lift the whole buggy up

 

[cbaker65]

There's a ton of compression. Can lift the whole buggy up

Can you list all the things that you've tried?

The engine should start an run fine if the tune makes a difference in engine performance ,
the only thing that I can think of ,is to get a whole new carb. ,I've had
to do that on my Ofna hyper engine ,I used the Ae. 28 carb. ,they are reliable & easy to tune!

 

[Daniel J]

Can you list all the things that you've tried?

The engine should start an run fine if the tune makes a difference in engine performance ,
the only thing that I can think of ,is to get a whole new carb. ,I've had
to do that on my Ofna hyper engine ,I used the Ae. 28 carb. ,they are reliable & easy to tune!

Ok.
Put some grease on the o rings on the needles.
Compression test (Good compression)
Took of the carb gave it a clean
Lowered idle screw
New fuel
Checked for airleak. (Non)
That's it

 

[cbaker65]

Ok.
Put some grease on the o rings on the needles.
Compression test (Good compression)
Took of the carb gave it a clean
Lowered idle screw
New fuel
Checked for airleak. (Non)
That's it

Ok ,other than a new carb. ,the thing that I would try ,is the higher nitro count & different plug,
I also see that its not too cold where your at ,unless you live on the side of a mountain!

The carb. that I had to swap out was made of a composite material in which they start leaking
where the metal parts are pressed on to the composite part of carb..
Your carb. ,if not a composite one ,could still have a leak ,but ,needles could also be damaged
to the point of causing it to flood out!

But ,I would still change to higher nitro % even if its a carb. issue!..

Whats your elevation where your at?

 

[Daniel J]

Ok ,other than a new carb. ,the thing that I would try ,is the higher nitro count & different plug,
I also see that its not too cold where your at ,unless you live on the side of a mountain!

The carb. that I had to swap out was made of a composite material in which they start leaking
where the metal parts are pressed on to the composite part of carb..
Your carb. ,if not a composite one ,could still have a leak ,but ,needles could also be damaged
to the point of causing it to flood out!

But ,I would still change to higher nitro % even if its a carb. issue!..

Whats your elevation where your at?

Sea level. Live very very near the coast. Thanks for the reply!! I will try that

 

[cbaker65]

Sea level. Live very very near the coast. Thanks for the reply!! I will try that

Is the tip of your muffler very wet with un-burned fuel?" if so ,that could be
a sign of not a hotter glow plug or fuel isn't burning do to % ,or fuel is bad!

 

[Daniel J]

Is the tip of your muffler very wet with un-burned fuel?" if so ,that could be
a sign of not a hotter glow plug or fuel isn't burning do to % ,or fuel is bad!

Hmm I will check that tommorow. It's like a little wet

 

[Hristo Al]

Hmm I will check that tommorow. It's like a little wet

The fact we have the same model and the same problem worries me, kind of points towards a faulty something that comes with the NRB-5...

 

[Daniel J]

The fact we have the same model and the same problem worries me, kind of points towards a faulty something that comes with the NRB-5...

Yeah. Hmm I might try a longer needle and see if it helps. Or might install a modified novarossi in it