Notices
Speed - RC Gas Boats Discuss gas RC boats right here!

Fuel Blowby

Old 06-09-2008, 11:21 AM
  #1  
fuelman8
Senior Member
Thread Starter
 
fuelman8's Avatar
 
Join Date: Oct 2007
Location: Sanford, FL
Posts: 201
Likes: 0
Received 0 Likes on 0 Posts
Default Fuel Blowby

I've got a walbro 771 and when I have it open full throttle fuel is blowing back out of the carb.

Do I have the end point on my radio set to high or is there another problem?
Old 06-09-2008, 08:11 PM
  #2  
lildude2599
Senior Member
 
lildude2599's Avatar
 
Join Date: Dec 2007
Location: Norco, LA
Posts: 500
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

That carb is a 12.7 mm venturi. You may have it too rich try to lean it and see if it doses it again.


http://wem.walbro.com/walbro/product...m=WT%2D771%2D1
Old 06-09-2008, 08:17 PM
  #3  
juicr
Senior Member
 
Join Date: Dec 2006
Location: Toledo, OH
Posts: 137
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

Some spit back is normal.
Old 06-10-2008, 03:57 AM
  #4  
fuelman8
Senior Member
Thread Starter
 
fuelman8's Avatar
 
Join Date: Oct 2007
Location: Sanford, FL
Posts: 201
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

Thanks for the info guys
Old 06-10-2008, 04:43 AM
  #5  
martno1fan
Senior Member
 
martno1fan's Avatar
 
Join Date: Jan 2005
Location: blackpool, UNITED KINGDOM
Posts: 11,390
Likes: 0
Received 1 Like on 1 Post
Default RE: Fuel Blowby

stick the spit tube back on and problem solved
Old 06-10-2008, 04:47 AM
  #6  
fuelman8
Senior Member
Thread Starter
 
fuelman8's Avatar
 
Join Date: Oct 2007
Location: Sanford, FL
Posts: 201
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

Mart

I haven't taken anything off the carb and i'm still not sure where to even look for the spit tube.
Old 06-10-2008, 04:54 AM
  #7  
martno1fan
Senior Member
 
martno1fan's Avatar
 
Join Date: Jan 2005
Location: blackpool, UNITED KINGDOM
Posts: 11,390
Likes: 0
Received 1 Like on 1 Post
Default RE: Fuel Blowby

the black plastic thing sometimes called a velocity stack
Attached Thumbnails Click image for larger version

Name:	Qo40583.jpg
Views:	7
Size:	21.5 KB
ID:	967807  
Old 06-10-2008, 07:37 AM
  #8  
OLD_SLOW and in the WAY
Senior Member
 
OLD_SLOW and in the WAY's Avatar
 
Join Date: Aug 2002
Location: , OR
Posts: 1,428
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

tuning your intake length will stop the blow back, i wont go into the math here but its approximately 3 7/8" from the piston face to the end of the spit tube. basically you are overcoming the mass of the blow back with the inertia of the air entering the intake tract. if you run a can muffler then a Hemholz resonator will give you a 15% boost which is about what a tuned pipe gives an engine. ive done extensive testing with these devices and they come on like a shot of NOS. plus they will prevent you from hydro'ing the engine in a roll over.
Old 06-10-2008, 09:54 AM
  #9  
fuelman8
Senior Member
Thread Starter
 
fuelman8's Avatar
 
Join Date: Oct 2007
Location: Sanford, FL
Posts: 201
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Fuel Blowby

Thanks Mart & Old and Slow good info

I have a velocity stack I ordered seperate from the motor, but I didn't put it on because the fuel tank is in the way. I think i'll check into going with a gas bag I can locate elsewhere.

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 or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.