Polaris Discussions about Polaris ATVs.
Sponsored by:
Sponsored by:

Needle valve won't stop gas flow

  #1  
Old 01-09-2019, 09:21 PM
Weekend Warrior
Thread Starter
Join Date: Jan 2019
Location: Cleveland, OH
Posts: 4
Default Needle valve won't stop gas flow

Mikuni VM carb on my 87 Trail Boss keeps pouring fuel out of the overflow. Within 10 seconds of opening the petcock, gas pours out of the overflow, not just drips. Even with the engine idling, it's not enough to keep up, only around 1/2 throttle. I rebuilt the carb with a kit. Included the needle and seat. I thought it was the floats, but they float fine in the bowl when it is off. I hooked up the gas line with the bowl off still, and I have to really squeeze the valve shut in order to stop the gas flow. Definitely more force than any float could provide. Rubber tip on the needle seems fine, and I don't notice any issues with the seat surface. What am I missing here?
 
  #2  
Old 01-10-2019, 09:03 AM
Kymco 450i's Avatar
Pro Rider
Join Date: Jan 2016
Location: Perrysburg Ohio
Posts: 1,495
Default

I have had bad ones in a new kit before, not common but it happens. Also check for a small piece of crud stuck there to keep seal from closing. Sometimes cleaning them loosens crud and allows it to get trapped. Most seats have a gasket under them, are you sure your has one?
 
  #3  
Old 01-10-2019, 04:27 PM
Weekend Warrior
Thread Starter
Join Date: Jan 2019
Location: Cleveland, OH
Posts: 4
Default

There is a gasket that seals the seat to the body of the carb. I noticed that the new seat was about 1/16" longer than the old seat. The wire connecting the needle to the float arm would hit the face of the seat before it completely sealed against the seat. I took a 5/16" drill bit and drilled a hole in the face of the seat about 1/16" deep. The needle then had plenty of clearance. Put it all back together and there's no more leaking,
 
  #4  
Old 01-12-2019, 10:10 PM
Trailblazer
Join Date: Mar 2018
Posts: 68
Default

Originally Posted by jake317 View Post
Mikuni VM carb on my 87 Trail Boss keeps pouring fuel out of the overflow. Within 10 seconds of opening the petcock, gas pours out of the overflow, not just drips. Even with the engine idling, it's not enough to keep up, only around 1/2 throttle. I rebuilt the carb with a kit. Included the needle and seat. I thought it was the floats, but they float fine in the bowl when it is off. I hooked up the gas line with the bowl off still, and I have to really squeeze the valve shut in order to stop the gas flow. Definitely more force than any float could provide. Rubber tip on the needle seems fine, and I don't notice any issues with the seat surface. What am I missing here?
Did you replace the o-ring UNDER the needle valve seat? With todays alcohol fuels they harden and commonly fail.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
LTAHABINAZ
Honda
5
05-26-2006 10:13 PM
Warrior02man
Yamaha
13
02-02-2005 10:00 PM
roosthrower
Yamaha
6
08-11-2003 03:13 AM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Quick Reply: Needle valve won't stop gas flow


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: