No Start/ No Compression

[rkrcpa]

Put the bike (stock '07 FLHT) in the shop trying to diagnose an intermittent no start issue. It's been in the shop before for this issue but the problem never occurs when it's in the shop, until today. Basically, it appears that there is no compression on the rear cylinder hence it doesn't fire. The question now is what do I want them to do to diagnose why there is no compression.

For that I turn to the HTT brain trust. I am at a loss as to what would cause an intermittent loss of compression in the rear cylinder. When it runs it runs strong and quiet so it doesn't seem like something is broken. This happens at random times, sometimes the first start of the day sometimes the last gas stop on a 1000 mile day. Literally no rhyme or reason to it.

I'd rather not have them start pulling "Potty mouth" apart just in the hope that they find something.

Thoughts?

[smoserx1]

Sticking valve?  Easy start cam malfunctioning intermittently?  Can't imagine pistons/rings behaving this way.

[Hossamania]

Any modifications to the bike, motor?

[rkrcpa]

Any modifications to the bike, motor?

Factory original (I know, shame on me)

[Ohio HD]

Agree, probbaly a sticky valve.

[Hossamania]

Any modifications to the bike, motor?

Factory original (I know, shame on me)

The rarest of all Harleys.

Good luck in getting to the bottom of the problem.

[838]

I'd rather not have them start pulling "Potty mouth"
apart just in the hope that they find something.

Thoughts?

Could some sea foam help if it's a sticky valve?  some in the tank, some through the manifold???

[rigidthumper]

Bad cams- had it happen on more than one 2007- the lobes are a light press fit, and they have come loose- cam lobe will indeed spin on the shaft...

[rkrcpa]

What gets me is the fact that it runs great when it finally starts.

Hard to understand how there could be a catastrophic failure that goes away once the engine starts.

[Coyote]

Well it's not too hard to pull the CAM plate and you probably need too look at the tensioners anyway on an 07. Course it's hard to say since you gave so few details. Like mods, mileage etc.

[fleetmechanic]

That was the first year with ACRs. Could one be staying open?

[Ohio HD]

In 2007 only CVO bikes had compression releases.

[rkrcpa]

The bike has 45,000 miles on it with no mods at all. It still has the stock intake and exhaust. No compression releases, no cam upgrades, nothing.

Looks like the plan is to work our way down the cylinder until something is found. Once the cam plate is removed it's going to mean cam upgrade. I've got a set of SE 255's sitting on the shelf waiting.

[rigidthumper]

I'd start with the cam plate (since you have replacements awaiting).

[HogMike]

Put the bike (stock '07 FLHT) in the shop trying to diagnose an intermittent no start issue. It's been in the shop before for this issue but the problem never occurs when it's in the shop, until today. Basically, it appears that there is no compression on the rear cylinder hence it doesn't fire. The question now is what do I want them to do to diagnose why there is no compression.

For that I turn to the HTT brain trust. I am at a loss as to what would cause an intermittent loss of compression in the rear cylinder. When it runs it runs strong and quiet so it doesn't seem like something is broken. This happens at random times, sometimes the first start of the day sometimes the last gas stop on a 1000 mile day. Literally no rhyme or reason to it.

I'd rather not have them start pulling "Potty mouth"
apart just in the hope that they find something.

Thoughts?

I had an '09 with a similar issue years ago. We found the rear exhaust guide had stuck intermittently on the stem until it finally pulled loose from the head. Replaced the guide, valve and serviced the others to make sure everything was good.
Suspect was either poor clearance from the factory and/or excessive heat.

Just a thought.

[Sycho01]

Just do a leak down test and find the problem. Why guess? Ion sensing ignition, no compression, no ignition.

[PoorUB]

Pretty hard to do a leak down with zero compression. Although the air coming out of the intake, exhaust or oil pan would give a good idea what is wrong, but it really doesn't matter. Stuck intake, exhaust, or blown piston and the head still has to come off so why bother?

[smoserx1]

Hard to understand how there could be a catastrophic failure that goes away once the engine starts.

My thoughts exactly.  Did the shop actually do a test for compression or a leak down test?  I sure hope they didn't just assume since there was no fire there was no compression.  Something like a spun cam lobe or a hole in a piston seems like it would be permanent, not intermittent.  Is the problem just when starting or does the cylinder actually drop out while riding (or both).  It looks to me like if the valve was stuck open very much the piston might hit it.  Regardless, try and rule out an intermittent electrical issue before tearing the engine apart.

[Chief0299]

Hang on a sec... why are you saying no compression? Have you done a compression check, or is that what the DTC code comes up saying?

[rkrcpa]

Hang on a sec... why are you saying no compression? Have you done a compression check, or is that what the DTC code comes up saying?

Hold your thumb on the spark plug hole and there is no compression. Zero, zilch, nada. Yet when it does eventually fire it runs just fine.

That is why I am at a loss for an explanation. It is a very unusual intermittent symptom. It could very well start with no problem on the next try.

[HogMike]

Hang on a sec... why are you saying no compression? Have you done a compression check, or is that what the DTC code comes up saying?

Hold your thumb on the spark plug hole and there is no compression. Zero, zilch, nada. Yet when it does eventually fire it runs just fine.

That is why I am at a loss for an explanation. It is a very unusual intermittent symptom. It could very well start with no problem on the next try.

No ACR?

valve sticking in guide?
Seen it more than once.

When it DOES run, how does it sound?
Stock bike with stock muffler and intake?

[Appowner]

Bad cams- had it happen on more than one 2007- the lobes are a light press fit, and they have come loose- cam lobe will indeed spin on the shaft...

But if it does that wouldn't there be a noticeable change in engine performance as the lobe that moved would effectively have changed the timing for that cylinder?

I see what you mean with the lobe slipping but I would think there would be some more obvious symptoms.

[rkrcpa]

Hang on a sec... why are you saying no compression? Have you done a compression check, or is that what the DTC code comes up saying?

Hold your thumb on the spark plug hole and there is no compression. Zero, zilch, nada. Yet when it does eventually fire it runs just fine.

That is why I am at a loss for an explanation. It is a very unusual intermittent symptom. It could very well start with no problem on the next try.

No ACR?

valve sticking in guide?
Seen it more than once.

When it DOES run, how does it sound?
Stock bike with stock muffler and intake?

Once it starts it runs and sounds normal, as if nothing had happened. The only thing I can think is a valve sticking, but the intermittent nature is what is baffling.

[rigidthumper]

Bad cams- had it happen on more than one 2007- the lobes are a light press fit, and they have come loose- cam lobe will indeed spin on the shaft...

But if it does that wouldn't there be a noticeable change in engine performance as the lobe that moved would effectively have changed the timing for that cylinder?

I see what you mean with the lobe slipping but I would think there would be some more obvious symptoms.

These went from running to not running, with no compression on one cylinder. No start/no run until repaired, so different from your scenario.

[PoorUB]

Could have dropped a valve seat too. Not sure on a Harley if there is piston clearance, but on other engines I have had similar running problems and one of the valve seats was more than loose. Sometimes it would fall in place and run, other times get cocked over a bit and hold the valve open.

[Sycho01]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

[HogMike]

Hang on a sec... why are you saying no compression? Have you done a compression check, or is that what the DTC code comes up saying?

Hold your thumb on the spark plug hole and there is no compression. Zero, zilch, nada. Yet when it does eventually fire it runs just fine.

That is why I am at a loss for an explanation. It is a very unusual intermittent symptom. It could very well start with no problem on the next try.

No ACR?

valve sticking in guide?
Seen it more than once.

When it DOES run, how does it sound?
Stock bike with stock muffler and intake?

Once it starts it runs and sounds normal, as if nothing had happened. The only thing I can think is a valve sticking, but the intermittent nature is what is baffling.

The intermittent nature is how mine started also, until the guide finally came loose in the head. Probably due to the heat of the engine.
It was the rear exhaust guide.

[Ohio HD]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

A lifter won't extend unless there is no pressure on the pushrod. For that to happened a pushrod would be bent, or the valve sticking open. A collapsed lifter wouldn't cause lack of compression in a cylinder.

[kd]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

A lifter won't extend unless there is no pressure on the pushrod. For that to happened a pushrod would be bent, or the valve sticking open. A collapsed lifter wouldn't cause lack of compression in a cylinder.

  A collapsed intake lifter will actually raise the compression when cranking due to the change in valve closing timing.  Hot start bleed down is an example of that.

[motorhogman]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

A lifter won't extend unless there is no pressure on the pushrod. For that to happened a pushrod would be bent, or the valve sticking open. A collapsed lifter wouldn't cause lack of compression in a cylinder.

  A collapsed intake lifter will actually raise the compression when cranking due to the change in valve closing timing.  Hot start bleed down is an example of that.

For my continuing education.. and off topic a bit.. If a lifter bleeds down so much that it won't open a valve on an engine at normal operating temp and you experience the "hot soak" thing wouldn't that lifter make a lot of noise when the engine does start until it's pumped up again ?

[kd]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

A lifter won't extend unless there is no pressure on the pushrod. For that to happened a pushrod would be bent, or the valve sticking open. A collapsed lifter wouldn't cause lack of compression in a cylinder.

  A collapsed intake lifter will actually raise the compression when cranking due to the change in valve closing timing.  Hot start bleed down is an example of that.

For my continuing education.. and off topic a bit.. If a lifter bleeds down so much that it won't open a valve on an engine at normal operating temp and you experience the "hot soak" thing wouldn't that lifter make a lot of noise when the engine does start until it's pumped up again ?

For the sake of your question and discussion, a typically set lifter is .100 deep (whether one piece or adjustable pushrods set to usual instructions). That isn't enough to prevent a valve from opening.  Remember even OEM cams have about .500 lift available.  What it does do is change the timing of the valve opening (later) and closing (earlier).  Early closing intake valves do cause higher compression with the cranking speed and makes the engine stall it's rotation (due to higher compression) or kick back (starter grinding or similar symptoms).  For example, if after fueling at the pumps with a hot engine it cranks hard and one or more valves clack a few times before pumping up, it usually indicates bleed down from hot thin oil escaping the lifter(s). Even if the lifters are set full depth at .200 deep, it will still open the valve(s) but you will hear the tell tale clicking of the valves for the first seconds of start-up. This can be exaggerated with stronger valve springs causing the leak down to occur more often. The main point is the valve will never fail to open due to bleed down.  It just opens at a different time in the slow cranking speed and can cause the symptoms I described for the reasons I mentioned.  Hope that helps.

[motorhogman]

Put air into the cylinder with no compression and see which valve is not sealing.
I would also consider a dirty or clogged lifter on that cylinder before removing the head for further inspection.

A lifter won't extend unless there is no pressure on the pushrod. For that to happened a pushrod would be bent, or the valve sticking open. A collapsed lifter wouldn't cause lack of compression in a cylinder.

  A collapsed intake lifter will actually raise the compression when cranking due to the change in valve closing timing.  Hot start bleed down is an example of that.

For my continuing education.. and off topic a bit.. If a lifter bleeds down so much that it won't open a valve on an engine at normal operating temp and you experience the "hot soak" thing wouldn't that lifter make a lot of noise when the engine does start until it's pumped up again ?

For the sake of your question and discussion, a typically set lifter is .100 deep (whether one piece or adjustable pushrods set to usual instructions). That isn't enough to prevent a valve from opening.  Remember even OEM cams have about .500 lift available.  What it does do is change the timing of the valve opening (later) and closing (earlier).  Early closing intake valves do cause higher compression with the cranking speed and makes the engine stall it's rotation (due to higher compression) or kick back (starter grinding or similar symptoms).  For example, if after fueling at the pumps with a hot engine it cranks hard and one or more valves clack a few times before pumping up, it usually indicates bleed down from hot thin oil escaping the lifter(s). Even if the lifters are set full depth at .200 deep, it will still open the valve(s) but you will hear the tell tale clicking of the valves for the first seconds of start-up. This can be exaggerated with stronger valve springs causing the leak down to occur more often. The main point is the valve will never fail to open due to bleed down.  It just opens at a different time in the slow cranking speed and can cause the symptoms I described for the reasons I mentioned.  Hope that helps.

Thanks KD. Appreciate that explanation.

[smoserx1]

If a lifter bleeds down so much that it won't open a valve on an engine at normal operating temp and you experience the "hot soak" thing wouldn't that lifter make a lot of noise when the engine does start until it's pumped up again ?

IMO not necessarily if you are using good lifters.  The thing KD was explaining pretty much happens every time you shut down your engine.  It comes to stop at a random place and chances are at least one valve will be partially open.  For any valve(s) that are open the respective lifters will bleed down until either the valve closes or the lifter runs out of travel, whichever happens first.  You would think this would cause noise but a good lifter will pump up so fast you won't perceive any noise.  My engine is a very early twin cam and the lifters that originally came in the bike would clatter very loudly for a second or so almost every first start of the day (actually it is not the lifter making noise rather the resulting slop in the rest of the valve train caused by the "up-pumped-up lifter".) "B" lifters virtually eliminated this for me.  The slower a lifter pumps up the more likely is is to cause a racket and the longer the noise might persist. Travel limiters can help here as well as making starting easier since they greatly reduce the timing shift that KD explained above.  Hope I didn't hijack anything...just wanted to clarify.

[JDhog211]

I'd try and take a look inside both cylinders. Use a bore scope for this, mine has
2 cameras , one which is side mounted and gets a good look at my valves, while the straight tip lens can take a look at piston top.

[Don D]

When the valves, rear exhaust usually, has oil coming down the guide they carbon up and will stick. It can be intermittent as valve spring pressure can usually get them closed. Next step is they stick so bad they get stuck so bad they bend from hitting the piston and/or the other valve.

[kd]

If at this point the engine still has no compression in the one cylinder, IMO the quickest and easiest way to check for a stuck valve would be to open up the pushrod covers and slowly rotate the engine through TDC compression while spinning (or trying to spin) the pushrods. It may even show up approaching TDC.  A stuck valve will have a pushrod with considerable loose wobble or up and down play.  Removing the rocker cover will also confirm the same but with considerably more effort. . 

[rkrcpa]

A stuck valve will have a pushrod with considerable loose wobble or up and down play.  Removing the rocker cover will also confirm the same but with considerably more effort. .

This was my thought as well.

[OldBogie]

The simple way to get an idea of where which has already be mentioned is when this is happening get a spark plug to air hose adapters and run some compressed air in there, you will hear where the leak is.

Given it comes and goes it most likely is a sticky valve. This is pretty common on air cooled engines. Lifters don't have a lot of internal movement. Even a fully collapsed lifter has enough lift left to get the engine running, and they don't recover all that quickly that you wouldn't hear it tick for a couple, three seconds or more. Generally a cam lobe or lifter going away will still pass a compression test. If it's gone so much that no compression is read it's not likely to be an intermittent cause.

On the list of strange it could be a valve spring is giving up and no longer exerts enough pressure to get a valve closed without the dynamic of actually running.

Valve face and valve seat failures tend to be permanent rather intermittent. If you ran leaded fuel the deposits that collect on the back side and lower stem of the valve can do this it persists till they break or burn off.

A slipping cam lobe is unlikely to slip to somewhere then find its way home again. In any event such a happening would let piston and valve meet somewhere along this path.

As far as sticking valves go and running out of piston to valve clearance winding the motor out to where the valve train looses control of the valve could result in pistons smacking valve thus bending it a bit which could be a source of the problem. So consider if this started after winding it out.

Since you don't have compression relief cams that at least you don't know of I haven't put that on the table.

I go back to a simple air pressure test when this happens that will let you hear where it's getting out be that one of the valves or around the piston.

Bogie

[jsachs1]

The simple way to get an idea of where which has already be mentioned is when this is happening get a spark plug to air hose adapters and run some compressed air in there, you will hear where the leak is.

Given it comes and goes it most likely is a sticky valve. This is pretty common on air cooled engines. Lifters don't have a lot of internal movement. Even a fully collapsed lifter has enough lift left to get the engine running, and they don't recover all that quickly that you wouldn't hear it tick for a couple, three seconds or more. Generally a cam lobe or lifter going away will still pass a compression test. If it's gone so much that no compression is read it's not likely to be an intermittent cause.

On the list of strange it could be a valve spring is giving up and no longer exerts enough pressure to get a valve closed without the dynamic of actually running.

Valve face and valve seat failures tend to be permanent rather intermittent. If you ran leaded fuel the deposits that collect on the back side and lower stem of the valve can do this it persists till they break or burn off.

A slipping cam lobe is unlikely to slip to somewhere then find its way home again. In any event such a happening would let piston and valve meet somewhere along this path.

As far as sticking valves go and running out of piston to valve clearance winding the motor out to where the valve train looses control of the valve could result in pistons smacking valve thus bending it a bit which could be a source of the problem. So consider if this started after winding it out.

Since you don't have compression relief cams that at least you don't know of I haven't put that on the table.

I go back to a simple air pressure test when this happens that will let you hear where it's getting out be that one of the valves or around the piston.

Bogie

Not as simple as just putting air in the cylinder with the engine completely together. You need to be sure you're on the COMPRESSION STROKE of the cylinder you're checking.
John

[kd]

  And you have to prevent it from rolling over when you add the air.

[OldBogie]

It doesn't matter if the piston is TDC or preferable at BDC we're not doing  leak down test we're only looking to hear if these is a significant leakage past either valves or rings by expectation is rings. If air rushes out the intake you can figure it's an intake if exhaust then  it's exhaust. At this point we're not solving the problem, just trying to get some confidence as to where it might be. I not totally convinced other than it might be interesting to know as it sounds like the engine needs to come out no matter and your not going to have a complete idea of the damage till it's apart.

All we're trying to here is confirm our suspicions.

Bogie

[kd]

I am sorry but I don't agree.  You are in fact doing a leak down test of sorts only wild and not with gauges.  If you put air to a cylinder that is anywhere but on TDC compression you will get "natural" bypass.  On the intake stroke the air will rush out the intake "because the cam is holding the intake valve open".  Not because it is sticking.  Same for exhaust if on the exhaust stroke.  You MUST have the engine at TDC compression (both valves closed) to do a test listening for air bypass.  If it passes a valve on TDC compression it "could" mean it is stuck or otherwise damaged.

[rkrcpa]

And the answer is......... the exhaust valve guide came loose.

Looks like I need to look for a rear head.

[kd]

One of the head porters here can probably help you out with an oversized guide. 

[chaos901]

And you have to prevent it from rolling over when you add the air.

I have a roll in chock on my lift table, and the first time I ever did a leak down I was focused on the gauges and almost missed that the bike was rolling backwards.  I grabbed the clutch my son grabbed the front brake the front brake and disaster was averted.  Strap it in now, and hold the rear brake.   

[kd]

You can but a tool that fits in the crank sensor hole and locks the flywheel.  I don't have one (yet) but do intend to one day.  I never think of it until I feel like doing a leak down test.

[chaos901]

You can but a tool that fits in the crank sensor hole and locks the flywheel.  I don't have one (yet) but do inte3nd to one day.  I never think of it until I feel like doing a leak down test.

I do have one of those since you mentioned it, likely got it after that episode.  But, being older, I forgot about it when I did some leak down tests before rebuilding one of my engines a couple of years ago.

[hattitude]

You can but a tool that fits in the crank sensor hole and locks the flywheel.  I don't have one (yet) but do inte3nd to one day.  I never think of it until I feel like doing a leak down test.

I do have one of those since you mentioned it, likely got it after that episode.  But, being older, I forgot about it when I did some leak down tests before rebuilding one of my engines a couple of years ago.

I hate it when that happens...!!!

I just upgraded the spring tensioners on an older softail I bought a couple years ago. This time I decided to just change the tensioner pads, instead of the '07+ cam plate/hydraulic tensioner upgrade I did on my other bike...

I decided to order the new Cyco pads and the pad installation tool...

I ordered the tool, then checked for gaskets, and other parts for the job.

I found out I had bought the new Cyco tensioner pads/pad tool for my other bike, before I decided to go with the cam plate/hydraulic tensioner upgrade...   

Luckily I was able to cancel the order, so I don't now have two of them...!

[barny7655]

are there any noises when no compression ,any top end noise when running nice , one would assume  a bent valve , if guide was loose causing valve to be open , piston hitting it ,, one needs three things for , Air,fuel , ign ,its so easy , take exuast off on that pot , take  throttle body off , get your scope camera and have a look while some one spins the rear wheel , you will see the guide , valve movement etc , , then one would think if cam was at fault ,,no valve movement , im thinking exaust valve ,or a faulty lifter   cheers

[Hossamania]

are there any noises when no compression ,any top end noise when running nice , one would assume  a bent valve , if guide was loose causing valve to be open , piston hitting it ,, one needs three things for , Air,fuel , ign ,its so easy , take exuast off on that pot , take  throttle body off , get your scope camera and have a look while some one spins the rear wheel , you will see the guide , valve movement etc , , then one would think if cam was at fault ,,no valve movement , im thinking exaust valve ,or a faulty lifter   cheers

See post #42.

[OldBogie]

And the answer is......... the exhaust valve guide came loose.

Looks like I need to look for a rear head.

Among the mechanical sins I intentionally commit is to nick the exhaust stem seal. The reason is unlike the intake the exhaust sees a lot of heat and pressure that burns and blows what little lube there is out. So I tend to feed it a little more oil.  Air cooled engines run hotter in this area than liquid cooled engines so like I said some posts back this is a fairly common problem which having a pressed in guide come loose was probably helped by a sticking valve. Once in it you might find this was initiated by piston kissing valve, so carefully check the piston for dings and the valve for bent. Also check the valve spring for meeting pressure, if you don't over rev the valve train which leads to adventures like this it still can be the result of a spring loosing tension and allowing the valve to float off the seat to where it gets hit.

So take the time to cover the contingencies.

Bogie