Notices
YS Engines Support Direct support from YS Performance Engines by Dave Shadel

YS 120F Won't hold valve setting

Old 04-20-2002, 04:55 PM
  #1  
GAK
Junior Member
Thread Starter
 
Join Date: Apr 2002
Location: Bedford, NH
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default YS 120F Won't hold valve setting

Wondering if someone can help me with my YS 120F.

It runs fine, but one of the valve adusters is nearly bottomed out. Also, after 4 flights or so, I find I need to reset the valve clearance. Anyone have any ideas. I thought it was a short pushrod, but replaced it and no change.

Thanks in advance.
Old 04-20-2002, 05:20 PM
  #2  
peso
Senior Member
 
Join Date: Dec 2001
Location: Stockholm, SWEDEN
Posts: 123
Likes: 0
Received 0 Likes on 0 Posts
Default YS 120F Won't hold valve setting

I had this trouble when I run my YS on fuel with castor oil. After I switched to fuel with synthetic oil the problem disappeared
Old 04-20-2002, 06:00 PM
  #3  
GAK
Junior Member
Thread Starter
 
Join Date: Apr 2002
Location: Bedford, NH
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default YS 120F Won't hold valve setting

Thanks. That's a good point. I think I was using Castor. Wonder why that would cause the problem?
Old 04-20-2002, 07:09 PM
  #4  
peso
Senior Member
 
Join Date: Dec 2001
Location: Stockholm, SWEDEN
Posts: 123
Likes: 0
Received 0 Likes on 0 Posts
Default YS 120F Won't hold valve setting

Well I thought it was due to carbon build up on the valves. Anyway try another oil before you look for mechanical errors.
Generally castor oil more than 2 % should be avoided in fourstroke engines. Use a good synthetic oil instead. I have an YS 120 engine that is 10 years old now and it still runs as it was new. A very reliable engine if set up correctly.
Old 04-21-2002, 03:01 PM
  #5  
w8ye
My Feedback: (16)
 
w8ye's Avatar
 
Join Date: Dec 2001
Location: Shelby, OH
Posts: 37,576
Received 9 Likes on 9 Posts
Default YS 120F Won't hold valve setting

I agree that the carbon under the valves could be a problem but this will only be on the exhaust side. If a valve is being held off it's seat, it will look lower cmpared with the other one when at top dead center on the compression stroke.

Also you should look at the offending push rod.

If your push rod is even a slight amount bent. It will bend even more as you use it. Valve float from running the engine too fast will further bend a slightly kinked pushrod. It will cause problems with even a good push rod.

Pull out the push rod and roll it on a nice flat smooth table. A slight bend and the rod will flip when it rolls. You will have a difficult time trying to straighten it. Maybe in a small lathe with a dial indicator. Anything less and it will just bend again. I would suggest a new push rod in case you find it is bent.

Good luck,

Jim
Old 04-21-2002, 03:33 PM
  #6  
GAK
Junior Member
Thread Starter
 
Join Date: Apr 2002
Location: Bedford, NH
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default YS 120F Won't hold valve setting

Also, a good idea. I'll pull the pushrod and check. As you face the engine from the front it is the right tappet that has the adjustment nearly bottomed out. I have several pushrods, so I'll replace if necessary.

I am using an APC 16 x 8 prop. It has been a while since I ran it, but thinking it was turning around 8500. Wouldn't think this would be an overspeed situation.

This is good stuff thanks.
Old 04-22-2002, 01:02 AM
  #7  
Dave Shadel
Senior Member
 
Join Date: Apr 2002
Location: Gardnerville, NV
Posts: 5,385
Likes: 0
Received 1 Like on 1 Post
Default YS 120F Won't hold valve setting

Good advise. Could also be that the pushrod was not heat treated properly and is getting shorter as it runs, we've seen this before. Also look to see that the rocker arm shaft is tight in the head.

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 -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.