Notices
Gas Engines Questions or comments about gas engines can be posted here

Compression issue

Old 06-23-2013, 03:31 PM
  #1  
jaubone
Junior Member
Thread Starter
 
Join Date: Jan 2005
Location: Buenos Aires, ARGENTINA
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default Compression issue

Hi, from down south!
Would like to know if any one has ever found out why some gassers will exhibit more compression while hand rotating the prop clockwise instead of the normal operating mode, counter-clockwise??
It occurs with or without the crankcase back plate bolted on, so I have discarded crankcase pressure.
Thanks for any enlightening comments.
Juan
Old 06-23-2013, 05:31 PM
  #2  
w8ye
My Feedback: (16)
 
w8ye's Avatar
 
Join Date: Dec 2001
Location: Shelby, OH
Posts: 37,576
Received 7 Likes on 7 Posts
Default RE: Compression issue

It depends on which side the ring gap(s) is on
Old 06-24-2013, 03:46 AM
  #3  
pe reivers
Senior Member
 
Join Date: Jan 2002
Location: Arcen, , NETHERLANDS
Posts: 6,571
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Compression issue

+1 on ring gap
Old 06-24-2013, 04:40 AM
  #4  
TimBle
Senior Member
 
Join Date: Apr 2010
Location: Cape Town, SOUTH AFRICA
Posts: 2,744
Likes: 0
Received 1 Like on 1 Post
Default RE: Compression issue



+2

Old 06-26-2013, 03:10 PM
  #5  
rexbirk
 
Join Date: Dec 2001
Location: Gahanna, OH
Posts: 529
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Compression issue

As long as we are on a discussion about compression why do the Chinese Engines have so little while my 3W Engines have so much when cranked by hand?
Old 06-26-2013, 04:19 PM
  #6  
closetguy
My Feedback: (13)
 
Join Date: Jul 2004
Location: berlin hts, OH
Posts: 1,462
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Compression issue

your kidding rite.
Old 06-26-2013, 04:36 PM
  #7  
captinjohn
 
Join Date: Jan 2002
Location: Hesperia Michigan, MI
Posts: 12,957
Received 4 Likes on 4 Posts
Default RE: Compression issue


ORIGINAL: rexbirk

As long as we are on a discussion about compression why do the Chinese Engines have so little while my 3W Engines have so much when cranked by hand?
China made engines lack precise fitted parts.Sometimes too large of a ring end-gap. Cylinders can be out of round ...rings cannot seal good. Cylinders can have a taper...again rings cannot seal good. Ring material can be to hard...rings do not seat good. Ring could lack good machining...poor fit.
Old 06-26-2013, 05:10 PM
  #8  
rexbirk
 
Join Date: Dec 2001
Location: Gahanna, OH
Posts: 529
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Compression issue

Im kidding a little. It's funny though that I have weed eaters and chain saws that are not top of the line but they have good compression.

I have numerous Chinese Engines that run well but have little compression when hand cranked. My two 3W Engines on the other hand really get your attention when you hand crank them. I'm sure they have much better tolerances and fit. I'm sure thats some of what the extra cost gets you.


ORIGINAL: closetguy

your kidding rite.
Old 06-26-2013, 05:39 PM
  #9  
closetguy
My Feedback: (13)
 
Join Date: Jul 2004
Location: berlin hts, OH
Posts: 1,462
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Compression issue

you have a point that I have made in the past.you can go out and buy a 79.00 weed eater feed it the cheapest oil you can find.it has great compression and never a problem with bearings and it just keeps running.
Old 06-26-2013, 09:04 PM
  #10  
bcchi
Senior Member
 
Join Date: Jan 2006
Location: riverton., WY
Posts: 975
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Compression issue


ORIGINAL: captinjohn


ORIGINAL: rexbirk

As long as we are on a discussion about compression why do the Chinese Engines have so little while my 3W Engines have so much when cranked by hand?
China made engines lack precise fitted parts.Sometimes too large of a ring end-gap. Cylinders can be out of round ...rings cannot seal good. Cylinders can have a taper...again rings cannot seal good. Ring material can be to hard...rings do not seat good. Ring could lack good machining...poor fit.
Maybe all of the above. Notice my new DLE 35&55 RA have much better compression feel than the older ones. Bowman rings in both.
BCCHI
Old 06-28-2013, 08:08 AM
  #11  
captinjohn
 
Join Date: Jan 2002
Location: Hesperia Michigan, MI
Posts: 12,957
Received 4 Likes on 4 Posts
Default RE: Compression issue

The more I read about all the problems with a lot of all these engines of various brands, I think it would be better to get a good conversion RC engine from one of the guys that know this stuff in the first place. They know by experience what goes wrong & rebuild/convert them to be more trouble free................
Old 06-28-2013, 09:11 PM
  #12  
MetallicaJunkie
 
MetallicaJunkie's Avatar
 
Join Date: Sep 2006
Location: Donna, TX
Posts: 5,464
Received 1 Like on 1 Post
Default RE: Compression issue


ORIGINAL: rexbirk

As long as we are on a discussion about compression why do the Chinese Engines have so little while my 3W Engines have so much when cranked by hand?
3Ws have dual piston rings.....that might contribute also
Old 06-29-2013, 02:40 AM
  #13  
Lifer
My Feedback: (1)
 
Lifer's Avatar
 
Join Date: Aug 2008
Location: Kansas City, MO
Posts: 4,441
Likes: 0
Received 17 Likes on 17 Posts
Default RE: Compression issue

I don't think ring gap has anything to do with it as ABC-type engines have the same characteristic. Perhaps it has something to do with intake and exhaust timing.
Old 06-29-2013, 04:56 AM
  #14  
jaubone
Junior Member
Thread Starter
 
Join Date: Jan 2005
Location: Buenos Aires, ARGENTINA
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Compression issue

Thanks for returning to the original thread subject, ie: CW and CCW compression!!!
The subject still baffles me.
Juan

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 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.