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TOPIC: Re:Low RPM engine knock
#412973
B1gRed (User)
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Low RPM engine knock 6 Years, 6 Months ago  
Hi All.

First off I'd like to say that I know low rpm engine knock is considered normal. I'd just like to see if I can reduce it some.

I have an 04 road star with 3500 miles. It had cobra pipes when I bought it a couple months ago. I've since replaced them with the stock pipes. I'm not sure if the carb had been jetted for the cobra pipes. I believe the rest is stock. I live in Denver, CO so the altitude is about 5,000 ft above sea level.

The engine mostly knocks under load when I start from a stop or shift gears. However, it also knocks slightly when I crack the thottle quickly in neutral.

For some reason I have it in my head that if I retard the timing just a little it may help. Just to satisfy that notion, I'd like to test that theory. However, I read in the manual that timing is not adjustable.

Does anyone know if it's possible to test that theory or is it not even worth the trouble. Is there other issues that could causing the timing to advance abnormally? Is there anything else that could be causing excessive low rpm knock in my situation?

As always, any advice is greatly appreciated.

dave
 
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#412977
Curt (Moderator)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
The timing advance is handled by the ignition module and there is nothing you can do with it. You can change it to a Dyna 3000 but with stock pipes and motor it isn't worth the cost. I would say make sure you have enough oil in it by doing a full oil and filter change and go to synthetic oil. If you still have it the take the carb off and see how it is set up.
 
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#412980
B1gRed (User)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
Thanks Curt. I just had the oil changed at the dealer. They didn't use synthetic though. Is it worth dumping it and adding sythetic? Does it make any noticable difference?

Also, outside of the cost would the dyna 3000 make a difference?
 
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Last Edit: 2011/08/25 10:25 By B1gRed.
 

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#412987
Curt (Moderator)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
Go ahead and run it for 3000 miles then change it and the filter. These bike are noisy to start with when you do go to synthetic make sure it is V-Twin motorcycle oil and has no friction modifiers. I run Amsoil 20W/50 other user Mobil1 V-Twin in the same weight.
 
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#413070
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Re:Low RPM engine knock 6 Years, 6 Months ago  
Wow, sorry to here you have a knock. Mine does not knock. If it did I would be very unhappy, it is not normal. If it's not the timing I would guess connecting rod or wrist pin.

If I had the dealer change my oil and they put anything other than a 20w50 synthetic something in it. I would ask them WTF were you thinking.

Don't ask the dealer anything. You'll get all you need right here. Good luck, hope it doesn't cost to much to fix.
 
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#413081
MikelJay (User)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
You know, that is something I never really noticed. I figured a large displacement, air cooled V-twin would make some noise, especially since I was sitting on top of it. Does it do it when it's cold? Or hot?

I've got an `06 with 40,000 plus miles on it. I've heard everything to rattles at part throttle to valve train noise when it gets REALLY hot, but nothing I would worry about. All I have ever run in mine is Yamalube.

 
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Mike
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#413088
About_Time (User)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
It sounds to me like the cause of your engine knock may simply be the fact that you are lugging the motor.

Last year, when I first got my RoadStar, I thought that, since this is a large displacement V-Twin, the last thing it wants me to do is over-rev it. As a result it would knock from time to time down in the really low rev range especially if I put in under load.

After joining this forum I came to learn that these engines are actually happier if you keep the revs up. I have a tach on mine and routinely run it anywhere from 2500 - 3000 rpm just cruising. I won't even touch 5th gear until just about 70mph. They also suggest bumping the rev limiter every now and again, although I don't do that too often.

Anyway, keep the rpm's up a bit from where you have been would be my suggestion...your engine will thank you

Good luck
 
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#413091
ultrastar (Moderator)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
the PO could have put in HP pistons mine will knock if I don't use 91 oct.
 
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#413093
Curt (Moderator)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
That very well could be.
 
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#413114
ultrastar (Moderator)
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Re:Low RPM engine knock 6 Years, 6 Months ago  
dschock if he did put in HP pistons he would of had to put in a Dyna 3000 check and see if he did and if so try a tank of 91 oct
 
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