opinions on whether i should buy new engine or not - Page 2 - Honda Rebel Forum
 2Likes
Reply
 
Thread Tools Display Modes
post #11 of 25 Old 08-06-2019, 12:46 PM
 
Join Date: Nov 2014
Location: NYC
Posts: 176
My manual says compression should be 159 PSI for CMX250C.

Honda Rebel 2005; Yamaha TX500 (prior)
reb2005 is offline  
Sponsored Links
Advertisement
 
post #12 of 25 Old 08-06-2019, 12:57 PM
Moderator
 
Join Date: Aug 2008
Location: Monroe, Louisiana
Posts: 28,459
The compression test is supposed to be done when the engine is warm, and his doesn't run. You would expect them to be lower on a cold engine, just not sure how his cold readings correlate to what he'd find if the engine was warm.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
flitecontrol is offline  
post #13 of 25 Old 08-06-2019, 01:16 PM
 
Join Date: Nov 2014
Location: NYC
Posts: 176
Perhaps a 20 SAE oil (in the summer) would simulate a warm engine?

Honda Rebel 2005; Yamaha TX500 (prior)
reb2005 is offline  
 
post #14 of 25 Old 08-06-2019, 01:52 PM
Moderator
 
Join Date: Aug 2008
Location: Monroe, Louisiana
Posts: 28,459
At the minimum, the rings, pistons and cylinders would need to be heated to operating temps.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
flitecontrol is offline  
post #15 of 25 Old 08-06-2019, 02:45 PM
 
Join Date: Nov 2014
Location: NYC
Posts: 176
I did a cold test with 50 SAE oil. Left cylinder is 122 PSI, Right is 112 PSI. Ambient temperature is just over 80F.

Previously, with a warm engine and 40 SAE oil, the test result was 161 PSI and 155 PSI.

I think there is some generous allowable tolerance but the manual just has a line in the tolerance column.

Can this be extrapolated to OP's measurements?

I just realized I did this without WOT. Will send that data soon.

Honda Rebel 2005; Yamaha TX500 (prior)
reb2005 is offline  
post #16 of 25 Old 08-06-2019, 03:33 PM
Moderator
 
Join Date: Aug 2008
Location: Monroe, Louisiana
Posts: 28,459
I would think it should! Thanks for posting that info.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
flitecontrol is offline  
post #17 of 25 Old 08-06-2019, 04:02 PM
 
Join Date: Nov 2014
Location: NYC
Posts: 176
200 PSI, is that Honda manual? Does that makes sense?

I have CMX250C (2005 year) and the manual says 159 PSI.

Quote:
Originally Posted by milmat View Post
So I tested the compression in the engine. 90 psi in both cylinders when wet. it was much lower when dry. I read in the manual it needs to be 200psi +/- 28 psi. When I tested the compression, the engine was cold. Would it test higher when the engine is hot? Is 90 psi a good reading for a cold engine?

Honda Rebel 2005; Yamaha TX500 (prior)
reb2005 is offline  
post #18 of 25 Old 08-06-2019, 07:18 PM
 
Join Date: Nov 2014
Location: NYC
Posts: 176
I rode and so waited 2 hours for engine to cool down. It felt skin temperature, perhaps 90F.

Compression test with carburetor off the engine (I'm fiddling with it, other stuff). Could this be considered "WOT" in effect?

Results: 158 (left cyl) and 148 (right cyl).

By the way, is this difference between the two cylinders, indicative of a problem for me?

OK now I see in an earlier post, Buickguy wrote:

"One of the major things to look for is difference between the cylinders. Ideally, you want 10 percent difference or less."

Honda Rebel 2005; Yamaha TX500 (prior)
reb2005 is offline  
post #19 of 25 Old 08-07-2019, 08:21 PM
Moderator
 
01-7700's Avatar
 
Join Date: Oct 2011
Location: Maine
Posts: 3,446
Garage
here's a good video on extracting exhaust studs - it's on a truck but same idea - there are plenty of other videos like this

ironbadge likes this.

1985 CMX250 ... 1986 CMX450 ... 2005 Ruckus 50
Keith from Maine USA - Banning Spammers since 2016
01-7700 is offline  
post #20 of 25 Old 08-07-2019, 08:27 PM
Moderator
 
Join Date: Aug 2008
Location: Monroe, Louisiana
Posts: 28,459
Those short extractors look to be ideal for DIY exhaust stud extraction. Don't have to drill into the stud very far, or drill perfectly on center. Link to the extractors: https://www.thegrabitstore.com/

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
flitecontrol is offline  
Reply

Tags
cold/hot comp test, stud extractors best

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda Rebel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome