Cold vs. Hot compression numbers.
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Cold vs. Hot compression numbers.
1997 FLHR, screaming eagle airbox, slip on mufflers, EV13 cam.
Cold compression: 150 front, 160 rear
Warm: 135 front, 150 rear
I was expecting to see these results reversed... higher compression with the warm engine.
The carb was recently rebuilt and Ive been waiting since Tuesday 9/11/18 for a new slide needle. (USPS slowed due to Hurricane Florence.)
The spark plug on the rear cylinder is loading up, very black and a bit oily. The plug on the front cylinder has one spot near the electrode thats a bit black, the rest of the plug is a nice dry cream color. WTF?
Cold compression: 150 front, 160 rear
Warm: 135 front, 150 rear
I was expecting to see these results reversed... higher compression with the warm engine.
The carb was recently rebuilt and Ive been waiting since Tuesday 9/11/18 for a new slide needle. (USPS slowed due to Hurricane Florence.)
The spark plug on the rear cylinder is loading up, very black and a bit oily. The plug on the front cylinder has one spot near the electrode thats a bit black, the rest of the plug is a nice dry cream color. WTF?
Club Member
Joined: Aug 2008
Posts: 22,841
Likes: 17,870
From: Lafayette, Louisiana
Originally Posted by Kingglide549
When you talk about carbs here and AFR ratios we all have to stop guessing, or continue dwn the same path.
People as devoted as they are top helping you will be just guessing too.
People as devoted as they are top helping you will be just guessing too.
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
I was really looking for some input on the odd compression numbers.
The dramatic difference in the color of the plugs can be explained by an intake leak on the front cylinder. I replaced the manifold seals last week, but I could still have a leak.
I checked for leaks using a propane torch and didnt find any. Ive never used a torch to check for leaks before, but thought it would be a bit less messy... Ill check again using starting fluid.
Im fairly sure I have an issue with the slide needle, so Im waiting on a new one from CVP and Ill be changing the main jet to a 180 when the new needle arrives. Im not too concerned with the carb being rich or lean at this time, Ill get this right soon enough.
Im planning on taking off for a few days of riding on Tuesday, surprisingly shes running okay.
Im concerned with the compression going down when the engine warms up. I just dont know if I could have something going on that could cause damage, beyond a fouled plug, and hopeful someone could explain this condition.
Sorry for muddying the water by including the carb issue with the compression question... but Im not sure they couldnt be related.
The dramatic difference in the color of the plugs can be explained by an intake leak on the front cylinder. I replaced the manifold seals last week, but I could still have a leak.
I checked for leaks using a propane torch and didnt find any. Ive never used a torch to check for leaks before, but thought it would be a bit less messy... Ill check again using starting fluid.
Im fairly sure I have an issue with the slide needle, so Im waiting on a new one from CVP and Ill be changing the main jet to a 180 when the new needle arrives. Im not too concerned with the carb being rich or lean at this time, Ill get this right soon enough.
Im planning on taking off for a few days of riding on Tuesday, surprisingly shes running okay.
Im concerned with the compression going down when the engine warms up. I just dont know if I could have something going on that could cause damage, beyond a fouled plug, and hopeful someone could explain this condition.
Sorry for muddying the water by including the carb issue with the compression question... but Im not sure they couldnt be related.
Last edited by GOGOBECK; Sep 22, 2018 at 03:41 AM.
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Im highly caffeinated and nicotined up this early morning and my brains racing along!
I recently replaced the cutch cable. I had to loosen the exhaust headers for clearance to remove the transmission side cover. Could an exhaust leak at the head explain any of this?
I recently replaced the cutch cable. I had to loosen the exhaust headers for clearance to remove the transmission side cover. Could an exhaust leak at the head explain any of this?
Trending Topics
Banned
Joined: May 2018
Posts: 4,576
Likes: 978
From: Viet Vet, crossroads
What is the problem?
If the AFR is being suspected one has to start somewhere with real facts.
Use a meter with two inputs and it becomes a process of elimination.if suspected.
That is my natural inclination, as I hate guessing carburation when it is not necessary anymore.
It is just caveman!
.For this case I would start with an leak dwn test.
Last edited by Kingglide549; Sep 22, 2018 at 05:12 AM.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Thread Starter
|
Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Im at 98k miles and never been into the motor, just the cam change 21 years back.
The two plugs showing different things is totally new... Just happened after installing a carb kit. Prior to this both plugs were a bit black and sooty, but not overly so and no wetness.
I dont have the equipment to do a leak down test. But Im not opposed to purchasing one... any recommendations for an economical and effective tool for this?
The two plugs showing different things is totally new... Just happened after installing a carb kit. Prior to this both plugs were a bit black and sooty, but not overly so and no wetness.
I dont have the equipment to do a leak down test. But Im not opposed to purchasing one... any recommendations for an economical and effective tool for this?