Notices
RCV Engines Support Ask RCV Technical Support all your RCV engine questions!

120sp surging

Old 06-06-2008, 07:43 PM
  #1  
speedaholic
Thread Starter
My Feedback: (4)
 
Join Date: Apr 2002
Location: fresno, CA
Posts: 304
Likes: 0
Received 2 Likes on 2 Posts
Default 120sp surging

have a sp 120 in my new skyraider, ran great on the stand, using coolpower 10% fuel, i have run about 2.5 gallons through the engine and now mounted it in the plane and first problem i had was the muffler too hot and burning the cowl. the exhaust from this engine is very hot, but another problem that i havent fixed yet is the motor surges at full throttle, I am pretty sure the problem is fuel foaming from the vibration of the engine, any sugestions? i dont think i can rap in foam. i hate to get rid of this engine as it fits the plane nicely, please help. thanks
Old 06-07-2008, 06:43 AM
  #2  
andi3142001
Member
 
Join Date: Aug 2007
Location: , AUSTRIA
Posts: 71
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 120sp surging

Hello,

the exhaust of every 4stroke is hot. You need a few mm and cooling between muffler and cowling.
The engine does reach max rpm before the throttle is max. open, something I learned here in rcuniverse. See the post "Carburator" below.
If that is not the problem and you see bubbles in the fuel line, use a Bubbless or Tettra tank. It has a bladder inside and do not allow air enter the fuel.

regards
Andi
Old 06-07-2008, 11:33 PM
  #3  
speedaholic
Thread Starter
My Feedback: (4)
 
Join Date: Apr 2002
Location: fresno, CA
Posts: 304
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 120sp surging

so what is this carb problem, if it reaches full throttle before its all the way open, do i set it up to not open all the way, it ran perfect on the stand, will the tetra tank keep it from foaming?? also i mean the exhaust is so hot that i almost caught wood on fire on the test stand, that is a bit hotter than my ys i think, but i think i have that issue fixed, i mainly need to fix the surging. I think the foaming fuel is the problem, it idles great. i will run it with the cowl off next to see if bubbles are entering the tank.
Old 06-08-2008, 07:45 AM
  #4  
andi3142001
Member
 
Join Date: Aug 2007
Location: , AUSTRIA
Posts: 71
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 120sp surging

Hi,
well I dont consider it a problem. When you set the main needle on your RCV with the throttle on the mechanical max. open point and you throttle back, you will see that there is a increase in rpms when the throttle is a few millimeters in direction "closed".
Take this point as max open on your linkage. And readjust the main needle, it might be too lean. (It was on mine thats how I found out )

Bubbles are also a reason for a too lean run.
One of these things (or both) might be the reason for your hot exhaust.

The tettra tank will solve the bubble problem.

regards
Andi
Old 06-09-2008, 12:37 AM
  #5  
speedaholic
Thread Starter
My Feedback: (4)
 
Join Date: Apr 2002
Location: fresno, CA
Posts: 304
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 120sp surging

i would think if you richen the motor for full open and then close it a bit it would richen up as you are bringing in less air, i could be wrong, i see they are making a tettra tank in the 20 oz size, i may go for that. does that mean that i have to fill it with that syringe thing, that sucks.
Old 06-09-2008, 04:46 PM
  #6  
andi3142001
Member
 
Join Date: Aug 2007
Location: , AUSTRIA
Posts: 71
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 120sp surging

Yea you are right. Just a guess. The thing is, I was tempted to lean the engine out too much since rpms where low with fully open throttle.
You can fill the bubbles tank without a syringe, if set the tubing as shown on the instructions.
But you have to make shure that there is no air in the bladder.
If you want to avoid this tank - sometimes an unbalanced prop is responsible for vibrations and bubbles.
Maybe it also helps to make a somewhat "loose" installation of the tank. Let it move for 2mm and avoid direct touch with the fuselage, and try some foam inbetween, no matter how thin.

regards
Andi
Old 06-10-2008, 12:07 AM
  #7  
speedaholic
Thread Starter
My Feedback: (4)
 
Join Date: Apr 2002
Location: fresno, CA
Posts: 304
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 120sp surging

i will try, not sure when, pretty busy here. i am gona try some armoral in the fuel to prevent the foaming. thanks.
Old 06-19-2008, 09:15 PM
  #8  
speedaholic
Thread Starter
My Feedback: (4)
 
Join Date: Apr 2002
Location: fresno, CA
Posts: 304
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 120sp surging

well i tried the armoural and it is still foaming in the tank a bit, I did see some airbubbles in the line to the carb, next i will be tring a tettra tank. thanks for the help.
Old 06-20-2008, 02:09 PM
  #9  
andi3142001
Member
 
Join Date: Aug 2007
Location: , AUSTRIA
Posts: 71
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 120sp surging

If your tank is fully enclosed I would suggest to remove air with the syringe and bring in the fuel thereafter.
If your tank is visible its easy to fuel it normally, til the fuel reaches the overflow on top. Then remove the small remaining airbubble with the syringe through the overflow.
Its essential to remove ALL the air.
When you run your engine, and stop it again, some air might enter the bladder through the fuel line from tank to carburator - just to make you aware of this.

On the good side you get rid of airbubbles in fuel line.
Fuel pressure is more constant throughout the flight.
Whatever maneuvres you wil fly - the fuel will reach the carburator.

regards
Andi

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2022 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.