ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-07-2013, 09:18 PM   #1
GiantFrog OP
Uh.
 
GiantFrog's Avatar
 
Joined: Feb 2006
Location: Seattle, WA
Oddometer: 76
Hot, smokin r75/5 motor - need some help interpreting test results

Howdy all
I have a sidecar rig built around a R75/5 motor. When it gets hot it will start blowing smoke out the left exhaust. Not all the time, but occasionally when stopped at a light. Might happen once in a 20 mile ride.

The motor has been mostly rebuilt: hot tanked, new bearings and seals, new timing chain, R90s cylinders and pistons with new rings, R75 heads with re-ground seats, one new valve, new springs. New dual output coil and wires. Rebuilt carbs. Currently has about 200 miles on the rebuild.

Tests performed:
The plugs: right side is a nice tan, left side is black and oily.

Compression cold: right side is 120, left side is 125.

Compression warm: right side is 105, left side is 125.

Thinking the carb sync was off I messed with them. Originally I set them by ear and plug color. The right side was popping at idle and the plug was dark. Leaned it out until the color was tan. the popping stopped. Left side was close enough color wise. That was 190 miles ago. (I pulled the plug before i messed with the sync, the plug was black and sooty. )

This time I tried the shorting method. Shorting the left told me that the right idle was too low, brought the right side up to a close match. When shorting the right the motor dies immediately. I assume that this is a current direction thing, but I thought I should mention it. I did adjust the left mixture by ear. Ending up about a 1/8 turn in from where I started. I only spent a few minutes at it but the left started really smoking so I called it a night. Tonight for the compression testing I started it up. It ran poorly and smoky from the get-go. Residual oil in the exhaust?

I took on this project as a learning experience as I've never owned an airhead. I've done some basic wrenching before but have never really torn into a motor before. The opposing results from the compression testing and the plug colors is throwing me. The big book of airhead knowledge is falling short and my Google fu is failing me.

Where should I go from here?

Thanks!
__________________
Hacked 2000 R1150GS
GiantFrog is offline   Reply With Quote
Old 05-07-2013, 09:34 PM   #2
Airhead Wrangler
Adios Mexico
 
Airhead Wrangler's Avatar
 
Joined: Mar 2008
Location: Back in Seattle, FINALLY
Oddometer: 6,281
Your compression numbers are LOW. Did you take the carbs off or at least open the throttle all the way when you checked compression? A healthy R90S top end should be making 140 or 150 psi. Make sure you did your compression check right and follow it up with a leak down test to see where you're losing compression. Then attack.
__________________
R80ST Gets The HPN Treatment
Seattle to TDF on an airhead

Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
Airhead Wrangler is offline   Reply With Quote
Old 05-07-2013, 11:17 PM   #3
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,544
Quote:
Originally Posted by GiantFrog View Post
Howdy all
I have a sidecar rig built around a R75/5 motor. When it gets hot it will start blowing smoke out the left exhaust. Not all the time, but occasionally when stopped at a light. Might happen once in a 20 mile ride.

The motor has been mostly rebuilt: hot tanked, new bearings and seals, new timing chain, R90s cylinders and pistons with new rings, R75 heads with re-ground seats, one new valve, new springs. New dual output coil and wires. Rebuilt carbs. Currently has about 200 miles on the rebuild.

Tests performed:
The plugs: right side is a nice tan, left side is black and oily.

Compression cold: right side is 120, left side is 125.

Compression warm: right side is 105, left side is 125.

Thinking the carb sync was off I messed with them. Originally I set them by ear and plug color. The right side was popping at idle and the plug was dark. Leaned it out until the color was tan. the popping stopped. Left side was close enough color wise. That was 190 miles ago. (I pulled the plug before i messed with the sync, the plug was black and sooty. )

This time I tried the shorting method. Shorting the left told me that the right idle was too low, brought the right side up to a close match. When shorting the right the motor dies immediately. I assume that this is a current direction thing, but I thought I should mention it. I did adjust the left mixture by ear. Ending up about a 1/8 turn in from where I started. I only spent a few minutes at it but the left started really smoking so I called it a night. Tonight for the compression testing I started it up. It ran poorly and smoky from the get-go. Residual oil in the exhaust?



I took on this project as a learning experience as I've never owned an airhead. I've done some basic wrenching before but have never really torn into a motor before. The opposing results from the compression testing and the plug colors is throwing me. The big book of airhead knowledge is falling short and my Google fu is failing me.

Where should I go from here?

Thanks!
First, clean the plugs, set the valves and tune the carbs properly.

Here's some nfo on the shorting method:

http://www.eskimo.com/~newowl/setting_airhead_CV_carbs.html




With it tuned, see where you are on smoke. Beware overfilling the oil. You can rig a hose to dump the windage down the right instead of the left and see what that does.

Check compression wet and dry, throttles WFO, all plugs out and battery fully charged. Not likely to be an issue but put the results in your log.

When you are setting the valves, look for a lot of brown deposits on the rocker side of the head, exhaust side.

Eyeball the piston crown and valve lips through the spark plug holes. (Streamlight Reach or similar for light)
Plaka is offline   Reply With Quote
Old 05-07-2013, 11:24 PM   #4
disston
ShadeTreeExpert
 
disston's Avatar
 
Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 7,970
It sounds like you put one new valve in the heads, which valve? And lapped the valves in. One of the valve guides is probably loose. Oil in the combustion chamber comes from the rings or the valve guides.
__________________
.
Never memorize something you can look up.
---Albert Einstein

Pay your debt, piratejohn.http://www.advrider.com/forums/showthread.php?t=949341
disston is online now   Reply With Quote
Old 05-08-2013, 07:25 AM   #5
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,544
Quote:
Originally Posted by disston View Post
It sounds like you put one new valve in the heads, which valve? And lapped the valves in. One of the valve guides is probably loose. Oil in the combustion chamber comes from the rings or the valve guides.
Or the breather.
Plaka is offline   Reply With Quote
Old 05-08-2013, 12:09 PM   #6
Kai Ju
Beastly Adventurer
 
Kai Ju's Avatar
 
Joined: Jul 2009
Location: So Cal
Oddometer: 1,657
Quote:
Originally Posted by Plaka View Post
Or the breather.

But on a /5 that would be the right side, not the left, IIRC.
My clamshell /7 dumps the breather into the right side intake.
Kai Ju is offline   Reply With Quote
Old 05-08-2013, 01:19 PM   #7
Stan_R80/7
Beastly Gnarly
 
Stan_R80/7's Avatar
 
Joined: May 2012
Location: VA
Oddometer: 1,009
The problem stated is that the left cylinder smokes only when hot and idling. Based on this information, it is possible the left cylinder intake valve guide has some wear and is allowing oil into the cylinder when hot. Cooling off the cylinder by enriching the mixture along with cleaning the aluminum head and cylinder for better transfer heat should help reduce or eliminate the smoke.

This is fairly simple to validate or void by getting the engine hot while stationary, then check if the smoke starts on the left cylinder. If so, let the engine cool (I use a box fan), enrich the mixture slightly, and repeat the test. Good luck!
Stan_R80/7 is offline   Reply With Quote
Old 05-08-2013, 01:28 PM   #8
disston
ShadeTreeExpert
 
disston's Avatar
 
Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 7,970
Or get a proper valve job done.
__________________
.
Never memorize something you can look up.
---Albert Einstein

Pay your debt, piratejohn.http://www.advrider.com/forums/showthread.php?t=949341
disston is online now   Reply With Quote
Old 05-08-2013, 03:06 PM   #9
halflive
Gnarly Adventurer
 
halflive's Avatar
 
Joined: Apr 2009
Oddometer: 317
Quote:
Originally Posted by disston View Post
Or get a proper valve job done.
And guides
halflive is offline   Reply With Quote
Old 05-08-2013, 05:49 PM   #10
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,544
Quote:
Originally Posted by Kai Ju View Post
But on a /5 that would be the right side, not the left, IIRC.
My clamshell /7 dumps the breather into the right side intake.
right. M'i dyslexic.
Plaka is offline   Reply With Quote
Old 05-08-2013, 08:40 PM   #11
GiantFrog OP
Uh.
 
GiantFrog's Avatar
 
Joined: Feb 2006
Location: Seattle, WA
Oddometer: 76
Wow, some great advice. The compression check was done with the carbs off. Am I wrong to assume the numbers are low because the rings only have ~200 miles on them? I'm also thinking that my break-in has been less than ideal, too much time at idle trying to dial the carbs in.

Regarding the breather, in my case it isn't dumped in into either side... Ends at a crankcase filter.

Before I do anything else I will do a leak down test and report back.

For those that might be interested here's a link to the build: http://www.anotherhappyidea.blogspot.com/
__________________
Hacked 2000 R1150GS

GiantFrog screwed with this post 05-08-2013 at 08:53 PM
GiantFrog is offline   Reply With Quote
Old 05-09-2013, 07:39 AM   #12
Airhead Wrangler
Adios Mexico
 
Airhead Wrangler's Avatar
 
Joined: Mar 2008
Location: Back in Seattle, FINALLY
Oddometer: 6,281
Quote:
Originally Posted by GiantFrog View Post
Wow, some great advice. The compression check was done with the carbs off. Am I wrong to assume the numbers are low because the rings only have ~200 miles on them? I'm also thinking that my break-in has been less than ideal, too much time at idle trying to dial the carbs in.
By 200 miles your new rings are MOSTLY broken in. Even brand new rings with 0 miles should get at least 90% of their final compression. Any compression you gain from here on won't be much if any. I'd say that some disassembly is going to be necessary. Let us know what happens with the leak down test. As for idling new rings, don't worry about getting your carbs perfect or even close. Just get the bike running and immediately go for a ride and load the engine hard. Don't rev it too high, but don't be shy with the throttle. Also be sure to do plenty of engine braking. Accelerate and brake over and over again. Maybe after 50 miles come home and get your carbs happy. As for source of your oil smoke, add upside-down oil ring to your list of possibilities.
__________________
R80ST Gets The HPN Treatment
Seattle to TDF on an airhead

Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.

Airhead Wrangler screwed with this post 05-09-2013 at 10:44 AM
Airhead Wrangler is offline   Reply With Quote
Old 05-09-2013, 10:34 AM   #13
disston
ShadeTreeExpert
 
disston's Avatar
 
Joined: Mar 2011
Location: Silver Spring, Md
Oddometer: 7,970
Quote:
Originally Posted by Plaka View Post
right. M'i dyslexic.
Too say the least.

I have Autism.
__________________
.
Never memorize something you can look up.
---Albert Einstein

Pay your debt, piratejohn.http://www.advrider.com/forums/showthread.php?t=949341
disston is online now   Reply With Quote
Old 06-02-2013, 08:38 PM   #14
GiantFrog OP
Uh.
 
GiantFrog's Avatar
 
Joined: Feb 2006
Location: Seattle, WA
Oddometer: 76
Leakdown test

Reporting on the leakdown test.

Zero. Nothing. I set the cold motor to OT. 0% loss. Spun it 360 deg, did the other side. Same. 0%

Now let me back-up a sec. I actually did the test twice because I didn't realize that I needed to spin the motor 360 deg. The first time I had 18% loss on one side and 0% on the other. I removed the valve covers to check clearances and found my error. Why were the valves loose on one side and not the other? Duh.

So, yeah, checked it twice and checked the valve clearances. The valve clearance is spot on.

Moving on. Curiosity got the best of me so I pulled the left side cylinder apart. There is a lot of baked on oil on the top of the piston. The piston side of valve head is black with residue.

Of note, the rings (six of em) have all rotated to end up between the 10 and 2 o'clock positions. The oil ring is a three piece and the whatever-it-is-named middle ring is a two piece.

Otherwise, to my untrained eye, everything looks fine.

My thoughts on an initial plan: 1) The problem with the motor dying when the right side was shorted during the sync process is a factor. Not so much that it was dying but that I was causing more load on the left side because I wasnt setting the sync properly. I was causing the left to run way hotter because it was carrying the load. So first, eyeball reset the idle then enrichen the left slightly. 2) Replace the rings with proper on-piece ones from Huckys BMW and do a better job breaking them in. Less idle more riding.

Can anyone tell me why the motor was dying when the right side was shorted?? I am using a single Dyna dual output coil.
__________________
Hacked 2000 R1150GS

GiantFrog screwed with this post 06-02-2013 at 10:01 PM
GiantFrog is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

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 On

Forum Jump


Times are GMT -7.   It's 08:49 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014