Strange engine issue
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Outstanding HDF Member
Joined: Dec 2012
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From: Texas
I doubt valve train is the problem unless a pushrod adjustor has backed off; if pushrods are adjustable I would check. Symptoms are not typical of a failing CPS but symptoms can be different. Pull it out and take a look, clean it up and try again. If there is improvement, replace it; if not, leave it alone.
Have you grounded plugs and checked the spark? Electrical is not my long suit but if the bike starts easily but won't run unless the enrichener is open, still leaning toward a fuel issue
You mentioned a "bottom up rebuild" on the carb but did you check the emulsion tube. The last bike I worked on had the exact symptoms yours is presenting. Pulled the carb, very clean inside. Looked through the slow jet and couldn't see any light on the other end. Ran a piece of copper wire through, put the carb back on, problem solved; just sayin.
Have you grounded plugs and checked the spark? Electrical is not my long suit but if the bike starts easily but won't run unless the enrichener is open, still leaning toward a fuel issue
You mentioned a "bottom up rebuild" on the carb but did you check the emulsion tube. The last bike I worked on had the exact symptoms yours is presenting. Pulled the carb, very clean inside. Looked through the slow jet and couldn't see any light on the other end. Ran a piece of copper wire through, put the carb back on, problem solved; just sayin.
Like you, I hit on the fuel issue first and pulled the carb and intake off, disassembled and soaked every piece in Seafoam, blew everything out with carb cleaner and shop air and looked over each part thoroughly before putting it back together. I have been through this carb dozens of times since getting this bike and I just didn't see anything wrong...
But since I don't seem to be getting anywhere with this problem, it would not hurt to go back and check again before I tear into the top end.
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From: Texas
LOL, I did that the first time I rebuilt this carb...and I make sure to check that every since.
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From: Texas
it is not running "good" with the enricher out, it cranks easily, but runs rough and will not respond to the throttle like it should. That is why I started with the carb/intake first...
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From: Texas
I wish I could! I do have another carb and intake, a SE CV44 that goes with the big-bore kit but it is too much carb for a stock 88 which presents a whole new set of problems. BTDT. Also, the SE intake is not a match for the stock heads so it cannot be used with the SE carb on this stock 88.
You said you rebuilt the carb. Did you remove the cap over the idle mixture screw, make sure the o-ring hadn't disintegrated, verify you didn't damage the tip of the needle and replace the spring/washer/o-ring?
And you are 100% you have the main needle jet installed correctly with the curved side facing the needle?
Also - does the bike have a tach? If you are thinking ignition, if the tach is flaking out that's indicative of a crank sensor breaking down - but they usually just outright fail.
And you are 100% you have the main needle jet installed correctly with the curved side facing the needle?
Also - does the bike have a tach? If you are thinking ignition, if the tach is flaking out that's indicative of a crank sensor breaking down - but they usually just outright fail.
Last edited by Ed Ramberger; Feb 3, 2018 at 09:20 AM.
Thread Starter
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Outstanding HDF Member
Joined: Dec 2012
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From: Texas
You said you rebuilt the carb. Did you remove the cap over the idle mixture screw, make sure the o-ring hadn't disintegrated, verify you didn't damage the tip of the needle and replace the spring/washer/o-ring?
And you are 100% you have the main needle jet installed correctly with the curved side facing the needle?
Also - does the bike have a tach? If you are thinking ignition, if the tach is flaking out that's indicative of a crank sensor breaking down - but they usually just outright fail.
And you are 100% you have the main needle jet installed correctly with the curved side facing the needle?
Also - does the bike have a tach? If you are thinking ignition, if the tach is flaking out that's indicative of a crank sensor breaking down - but they usually just outright fail.
I am not sure I understand what you were saying about the main needle jet but those three components were checked and I made sure I can see the needle jet holder was in right side up.
The tach is working normal. Everything I look at and check looks and acts normal. Aggravating.
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From: Texas
What I found today:
Rear cylinder compression = 120
Front cylinder compression = 90
I checked several times and each time it was the same; the rear is a solid 120 every time and the front hits 60 on the first stroke and 90 on the second. The new front plug shows a more lean burn than the rear although it has been running with the enricher out and I expected them to look pretty much the same.
After I finish my coffee, I'm headed out to start pulling it down. This may pretty much seal the deal with where that Screaming Eagle big bore upgrade is going.
Rear cylinder compression = 120
Front cylinder compression = 90
I checked several times and each time it was the same; the rear is a solid 120 every time and the front hits 60 on the first stroke and 90 on the second. The new front plug shows a more lean burn than the rear although it has been running with the enricher out and I expected them to look pretty much the same.
After I finish my coffee, I'm headed out to start pulling it down. This may pretty much seal the deal with where that Screaming Eagle big bore upgrade is going.
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Joined: Jun 2006
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From: san antonio
What I found today:
Rear cylinder compression = 120
Front cylinder compression = 90
I checked several times and each time it was the same; the rear is a solid 120 every time and the front hits 60 on the first stroke and 90 on the second. The new front plug shows a more lean burn than the rear although it has been running with the enricher out and I expected them to look pretty much the same.
After I finish my coffee, I'm headed out to start pulling it down. This may pretty much seal the deal with where that Screaming Eagle big bore upgrade is going.
Rear cylinder compression = 120
Front cylinder compression = 90
I checked several times and each time it was the same; the rear is a solid 120 every time and the front hits 60 on the first stroke and 90 on the second. The new front plug shows a more lean burn than the rear although it has been running with the enricher out and I expected them to look pretty much the same.
After I finish my coffee, I'm headed out to start pulling it down. This may pretty much seal the deal with where that Screaming Eagle big bore upgrade is going.
The 30psi difference between cylinders may still exist with a proper test which would give me cause to follow the the compression test with a leak down test.