The Jack's Small Engines Forum - Join Our Online Community
Jacks Small Engines Lawn Mower & Power Equipment Forums
Community Stats
1 day 7 days 30 days Max. View More
Top Posters
  1. SRTsFZ6
    (100 Recent Posts)
  2. doug2500
    (15 Recent Posts)
  3. stony69jason
    (12 Recent Posts)
Most Active Threads
  1. Briggs 21 HP Single Cylinder. Bad rings?
    (27 Replies)
  2. Compression Release on FS111R Trimmer not working
    (17 Replies)
  3. 19hp Intek won’t start
    (16 Replies)
Top Rated Posts
    There is no record available at this moment
Birthdays
There is no record available at this moment
2025/07/14 23:32:03
just4fn

What should the compression be?

I have a toro 7.25 HP mower.  I think is has a decompression cam.  What should the measured compression be?  I'm getting 40lbs.  I think that is ok with a decompression valve but not sure. 
4 comments Leave a comment
SRTsFZ6
40 is super low...
 
Can you post an engine model #????
 
.
2025/07/15 06:28:44
just4fn
model # 128M02-0017-F1
2025/07/16 07:28:31
SRTsFZ6
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/100000-19z999-series/128m00-to-128m99/128m02-0017-f1
 
That model # is showing a "flat head" engine-NO overhead rockers. 
I don't believe they had a flat head engine that large..
 
IF it is a FLAT HEAD engine, check  / tighten the THREE HEAD bolts CLOSEST
to the exhaust valve.  They loosen up (very, very common) and will cause
no start issues...   
 
About 15' lbs on the head bolts.  
 
If you have an overhead valve engine, advise.  I own a 7 HP Briggs OHV
engine and can get you a pressure #...   Advise..
 
.
2025/07/16 15:25:58
just4fn
Thanks for the info.  I will look at it this weekend and report back. 
2025/07/16 19:16:11

Comments are closed.

Copyright © 1994 - 2016 Jacks Small Engine & Generator Service, LLC
© 2025 APG vNext Trial Version 5.5