Valves sneezing? Need help diagnosing.

[Oklahoma_Valk]

Every time I ride my 97 standard, either the valves or exhaust on the right side of the bike intermittently "sneeze"

It's a loud PSSSST sound, and it only happens once or twice during my whole ride, but it ALWAYS happens. After it happens, I can always smell something like burnt fuel (if my speed is low enough, and wind is light)

When it "sneezes" it feels like the bike temporarily loses power, But regains it before the blink of an eyelid.

It only tends to happen at low speed (0-40mph)

My bike is completely stock, engine, exhaust, and intake wise.

I've adjusted the valves to spec, but am still having the problem. Bike has 75k miles, and I have not replaced the vacuum hoses, or intake runners. Im not sure if that could be the problem. The exhaust headers are snug and tight against the cylinders. If I had to guess...Id say it's the valve making the noise. But why would that cause me to smell a weird fuel smell? The valves are sealed tightly under the valve covers! I just cant figure this out. Its been bugging me since day one with the bike.

Anybody have any ideas?  ??? ??? ???

[Chrisj CMA]

Every time I ride my 97 standard, either the valves or exhaust on the right side of the bike intermittently "sneeze"

It's a loud PSSSST sound, and it only happens once or twice during my whole ride, but it ALWAYS happens. After it happens, I can always smell something like burnt fuel (if my speed is low enough, and wind is light)

When it "sneezes" it feels like the bike temporarily loses power, But regains it before the blink of an eyelid.

It only tends to happen at low speed (0-40mph)

My bike is completely stock, engine, exhaust, and intake wise.

I've adjusted the valves to spec, but am still having the problem. Bike has 75k miles, and I have not replaced the vacuum hoses, or intake runners. Im not sure if that could be the problem. The exhaust headers are snug and tight against the cylinders. If I had to guess...Id say it's the valve making the noise. But why would that cause me to smell a weird fuel smell? The valves are sealed tightly under the valve covers! I just cant figure this out. Its been bugging me since day one with the bike.

Anybody have any ideas?  ??? ??? ???

Well the intake runners never need replacing, but they have O-rings at the base of each one.  You will know when the O-rings need replacing because there will be a brownish fluid leaking out around the base of the intakes.

CHANGE YOUR VACUUM LINES.  At 75K I guarantee the lines are cracked and the plugs on the unused nipples are dry rotten, change them too, then tighten all the intake connection screws (18 in all) then check tightness on the exhaust header nuts, just be careful, they break!

[Rio Wil]

Long shot,,,,,,but maybe a loose plug????

[Oklahoma_Valk]

A loose plug sounds very plausible. Very very. Thanks rio

[Patrick]

I agree with the vacuum line/cap replacement.. These monsters have very little engine trouble,, but,, quite a bit of vacuum line problems.. They do need to be replaced with quality line every so often.. Once this is done let us know if there is still a problem..

[Ricky-D]

Never heard that!

Valve sneeze.

To me they either work or don't work, no real middle ground except for a sticking valve.

A desmog would be a good thing to do. It would eliminate a lot of confusion and wrong diagnosis.

***

[Patrick]

If your monster has not been de-smogged and has vacuum lines on #3 and #4 then these are prone to split along the bottom of the tube which is hard to see.. But,, like said before,, just install good material on all intakes..

[Oklahoma_Valk]

Ok. It sounds like a desmog and vacuum line replacement would be to my advantage.

As soon as we have a weekend that it's too wet to ride, I'll have to do those things.

I should note: yesterday I removed the chrome covers (I hate covers) which cover the plug wire-tops and the lower half of the intake runners. I removed each spark plug. The plugs were very difficult to turn, and were nearly frozen. I got them all out though, and cleaned the threads. I lubed and re-seated the plugs. Tightened to spec. I have not had the odd sneezing happen again since.

Fingers are crossed though! Updates to come.

-Okie

[YoungPUP]

Just my thoughts, but if the plugs were "nearly frozen." I'd replace them. 

[Farther]

I wonder if you had a loose plug wire which caused an intermittant loss of spark and the "sneeze".

[Oklahoma_Valk]

I wonder if you had a loose plug wire which caused an intermittant loss of spark and the "sneeze".

I think that could have been. The weirdest part still has me puzzled though....the fact that I could SMELL an odd fuel smell each time this happened. While moving down the road at low speeds.

[salty1]

A lot of good thoughts above. As youngpup has suggested get those plugs changed and use anti seize compound on the threads. These are two dissimilar metal surfaces that mate and you need to prevent a seizure. Sounds like you were close. All the suggestions on vacuum lines and desmog sure sound like the thing to do. Rich at redeye tech has the intake runner Orings and several desmog kits to choose from. I like the shiny desmog kit myself. You might want to consider an electronic fuel shutoff valve while your at it from Dan Marc. FWIW. 

[custom1]

I have two thoughts.

Were the chrome covers you removed aftermarket covers? Could they have been rubbing on the plug wires at any point? I had a car one time that had the insulation off of the bottom of the hood and one plug wire was rubbing on the metal and it would cause an intermittent miss.  The PSSST sound might be the spark jumping to ground? How did the plugs look when you had them out?

Or, you might have one float needle sticking open from time to time and flooding one cylinder.

[HayHauler]

Could it be a small backfire? 

Hay 
Jimmyt

[Oklahoma_Valk]

Well, She sneezed again tonight. Several times while riding around the block.

I believe that I have ruled out the spark plugs. They are all brand new, and snug in the cylinders.

I am starting to think that it's coming from one of the exhaust headers. I have not replaced the header gaskets, and I doubt any owner before me ever replaced them. (Because no owner before me serviced hardly anything.)

It is not a backfire, no pop at all. Its more of a PSST. Coming from the engine area, always on the right side.

So my rainy day list is:

1) Desmog
2) Vacuum line replacement
3) Header gasket replacement



For kicks, here's a pic of one of my old spark plugs. This one was in the worst condition.

You can see the weird corrosion.





thanks to all who reply,

-Okie

[salty1]

Rusty suckers! Good luck with the other tasks.   

[97Valk_CT_Euless]

Wondering if the noise could be a reed in the PAIR valve.  I did a PAIR-ectomy when I desmogged/de-vacuum leaked her.  If you want to keep them in I'd be happy to part with mine.  It's just 5lbs of garbage as far as I'm concerned.

[Patrick]

Those plugs look fine,, they just look as though water has gotten past the boots and set in the 'hole' for awhile.. Maybe the drain holes should be checked just to make sure they are clear..  Did this bike sit outside or the previous owner use a lot of water when cleaning it ??

I was going to start another thread rather than kinda hi-jack this one.. Whenever you find a sparkler that does not want to come and turns hard.. Just stop if it has been turned out 1/8 or 1/4 turn and if you think its going to be stubborn.. Spray it with carburetor cleaner or dump some brake fluid on it and just let it sit for awhile.. Thats time well spent rather than have to possibly heli-coil that hole..

[Brian]

Those plugs look fine,, they just look as though water has gotten past the boots and set in the 'hole' for awhile.. Maybe the drain holes should be checked just to make sure they are clear..  Did this bike sit outside or the previous owner use a lot of water when cleaning it ??

I was going to start another thread rather than kinda hi-jack this one.. Whenever you find a sparkler that does not want to come and turns hard.. Just stop if it has been turned out 1/8 or 1/4 turn and if you think its going to be stubborn.. Spray it with carburetor cleaner or dump some brake fluid on it and just let it sit for awhile.. Thats time well spent rather than have to possibly heli-coil that hole..

There are drain holes in the spark ports? I need to go look for them.