Knock upon cold startup

[Mike M in ohio]

     A quick question to those "in the know." I bought a 2003 Valk back in late May, and she's been performing awesomely throughout the Summer. Of late, with colder air here in the Adirondacks, I've noticed a new concern, when I fire her up in the colder air. (30's-40's) Upon startup, there's a noticeable "knock" in the lower front area of the engine. It's also noticeable because I can actually FEEL the knocking through the frame. The knock calms down in about a minute and is never there again throughout the subsequent warm start ups.
     Any ideas about the source? Is this something that I should be concerned about?
     By the way, when I first heard it, I put in fresh synthetic oil and filter, but it made no difference. Thanks for any help or direction you can offer.               Mike in New York

[BonS]

Just a WAG but have you checkled your valve adjustments?

[Patrick]

What kind and weight oil ?  More importantly, what filter ?
Can you determine if its a crankcase or a valve noise ?  Maybe even an exhaust leak ?

[Mike M in ohio]

     Used the Mobil 1, 10-40 motorcycle oil, with the M-1 filter. Definitely not exhaust related. Seems low enough to be crankcase. Tho' I'm not 100 percent on that. But, definitely a metal on metal rap that repeats with the revolutions of the engime.                   Mike

[Patrick]

Hmmmm, kind of an odd one. These things are pretty bulletproof. Haven't heard of such a thing before. It isn't in the timing case is it ?
I asked about the filter, maybe thinking it was draining back.

[Earl43P]

My 99 IS did that very thing on really cold starts. I'm talking below 30, frost-covered from a rainy ride the night before. First time it did that I was very concerned, but like yours, mine quit as soon as it ran for about 15 seconds or so. I was in Rayville, La on my way to Az and it got really cold that night.

I attribute it to a fuel delivery "issue", because I have to use full enrichment when it's that cold soaked.

My bikes are typically garaged at night and each of these instances have occurred while traveling. Bike sits out overnight in a parking lot and if it is down in the teens - 20's, it'll rattle and knock for 5-10 seconds until the idle stabilizes. As soon as it is hitting on all 6 cylinders, it's solid and I ride away. I rarely if ever let it idle for more than a minute before I ride away. I typically remove the enrichment completely in the first 1/8 mile, but if I have any stops after that I do have to prop up the idle using my throttle lock.

It no longer concerns me, but I will say that my 93 does nothing like that (knock/rattle). And that thing is a cold-blooded beast; I can't really ride off on it until I pull the enrichment back to less than 1/2 stroke (~1500 rpm idle) when it's cold-soaked. I realize it's a completely different animal with two carbs vs. 6.

I'd recommend a heavy dose of Berrymans B12 in the next two tanks, see if that helps. I do a heavy dose (1/2 bottle) in a 1/4 tank every other month or so. Other than when I left Robbinsville last month, it hasn't been cold enough for it to recur on mine. That morning it rattled and cleared up about 5 seconds after starting. No clue what the temp was that morning, but I saw 26 on a bank sign about an hour later, close to I40.

[Pete]

Earl43p is on the right track.
Fuel issue on cold start.
Probably 1 pr 2 cylinders that are not getting enough or to much fuel.
As soon as it starts, check the exhaust at the head for heat to help determine which cylinder.
Also start it and let it run for 30 seconds and stop it and check the plugs for overly rich cylinder(s).

[Ricky-D]

     A quick question to those "in the know." I bought a 2003 Valk back in late May, and she's been performing awesomely throughout the Summer. Of late, with colder air here in the Adirondacks, I've noticed a new concern, when I fire her up in the colder air. (30's-40's) Upon startup, there's a noticeable "knock" in the lower front area of the engine. It's also noticeable because I can actually FEEL the knocking through the frame. The knock calms down in about a minute and is never there again throughout the subsequent warm start ups.
     Any ideas about the source? Is this something that I should be concerned about?
     By the way, when I first heard it, I put in fresh synthetic oil and filter, but it made no difference. Thanks for any help or direction you can offer.               Mike in New York

That's just not supposed to happen and I think fuel supply has nothing to do with it. My first inclination would be to consider that the engine is idling too slowly.

Then I would look to the trigger wheel and see if it has been replaced with and advance wheel or if the stock wheel has been altered. Maybe a cam is out of time.

Because of the fact you say you can feel it in the frame, would make me feel you have a serious problem and 30°F to 40°F is not cold for the Valkyrie engine.

There's something going on and a thorough investigation is warranted to avoid a catastrophe.

***

[Bagger John - #3785]

Because of the fact you say you can feel it in the frame, would make me feel you have a serious problem and 30°F to 40°F is not cold for the Valkyrie engine.

There's something going on and a thorough investigation is warranted to avoid a catastrophe.

***

Per Ricky's comments, I've fired mine up in weather as cold as 10 degrees F. No knocking.

It would be interesting to see the oil pressure reading on that bike from a completely cold startup, along with an engine oil analysis. Methinks you may have a slightly worn con-rod bearing and these two tests could help confirm that theory.

[Pete]

I fixed an IS for a guy that had a cold weather start knock.
The number 2 carb low speed adjustment screw was opened 2 turns more than the other carbs.

So yes fuel (mal) adjustments can induce a cold weather knock as well as a mis fire, which is sometimes taken as a knock.

[flash2002]

Maybe a wild guess but, is it possible that one or two carbs are sticking because of the cold causing the motor to knock.

[Steel cowboy]

have you tried turning the engine over when its cold with all the spark plus removed to listen for the knock. just voicing my thoughts

[stoked]

I too have had that knock on cold start up in the morning on my 98 tourer. It goes away with in a couple seconds, I've onley heard it a couple times.

[Challenger]

My 2000 STD had set a while when I got her, always had a cold start knock and would rattle for the first mile without full choke, Once warmed up, it ran great. Removed the slow jets a year ago and they were plugged solid. Cleaned jets and Has not knocked or rattled since. Also starts with out choke now which was impossible before. So yes it could be fuel related.

[sandy]

Just a thought: Could it be cold stiff cam belts. They warm up and smooth out.

[Patrick]

Just a thought: Could it be cold stiff cam belts. They warm up and smooth out.

Thats kinda what I was wondering too in #4.

Learn and hear some thing new every day I guess.

[DK]

While it could conceivably be something terrible such as a big end insert, wrist pin, slapping piston, loose flywheel, broken crankshaft, or bad main bearing, I seriously doubt it. Those sort of things seem to be unheard of in Valk engines based on all I have read about them. Also, problems like this don't go away after the engine runs a minute or less and are more pronounced in a warm engine under load - they remain noticeable and don't go away.

I've noticed the same in some other cold natured multi cylinder gasoline engines during cold weather. I think may be caused by only one or two cylinders beginning to ignite & provide power before the others for a few revolutions which puts a higher load on the ignited cylinder pistons and rods and also has the same effect as the engine being badly out of balance.  

This is my best guess and only a guess.

Pull a bunch of plug wires and start it. I think you will get pretty much the same sound and vibration.

Dan