Rocks in my engine????
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Intermediate
Joined: Feb 2007
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Rocks in my engine????
I have a 2008 street bob. I have about 1700 miles on it so far. My question to you is this—when I put the bike in 5th or 6th gear and give it the gas, sometimes it sounds like there are rocks in the engine banging around. This only happens when I pull the throttle back fast. Does anyone have an idea what this may be and if so should I have it looked at?
Road Captain
Joined: Jul 2007
Posts: 674
Likes: 1
From: FLORIDA
RE: Rocks in my engine????
Its been my experience over the years, that harley vee twin engines are made to ROLL the throttle to accellerate, not to snap it quickly.....[ especially in 5th or 6th gears } I have had excellent service outta my bikes over the years doing this....Back when i owned a few jap bikes with inline 4 cylinder engines with short strokes etc.....I would snap the throttle quickly on them with no problems....Harleys are a differnt animal in my opinion.....Of course when starting from a stop in 1st gear, i occasionally NAIL it through the gears up till about 3rdgear, then i just kinda ROLL the power to it....It just seems to me that the vee twin engine, and its stroke etc....like it that way, and i know the transmission and clutch prefer it that way as well......
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Road Captain
Joined: Jun 2007
Posts: 644
Likes: 5
RE: Rocks in my engine????
Mine sounds like metal being stressedto a breaking point. Hard to described but like a high pitched piiiiiiing piiiiing piiing piing ping. I like sgt. joseph's answerso will roll with his suggestions.
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Cruiser
Joined: Aug 2006
Posts: 190
Likes: 1
From: Warwickshire
RE: Rocks in my engine????
Gentlemen, this is called pinking. It happens when your ignition (spark) timing is not quite in synchronisation with your engine load and fuel (gas) uptake. It represents detonation of the gas air mixture rather thanthe smooth (but fast) burn you should have. It will damage your engine, burn out valves and pistons and is overall a very bad thing.
In the good old days (pre CDI/EFI) you had to set your ignition timing to the correct crankshaft angle before the piston reached top dead centre on the firing stroke. Once you got this base setting correct the advance/retard mechanism in the ignition changed the setting continually depending on the accelerationyou asked of the engine. You may remember the little weights and springs that use to tear round underneath the points/condenser that allowed the cam to turn slightly independently of the engine drive shaft. This is what allowed the timing to adjust automatically dependent on acceleration.
Even so, setting the timing was always a fine balance between getting an engine to run and getting it to start (and sometimes neither!!).
Nowadays the control over the fuelling and the spark timing with CDI and EFI is much much better but even so you should not give it the berries in too low a gear. If you make a habit of doing this - you will, as sure as eggs is eggs, damage your engine.
The Octane rating of the fuel (RON) has a heavy bearing on this. The lower the value the more the possibility of pinking. In jolly old England our 2 star fuel is around 92 Octane and is not too much of a problem. I understand in the colonies it can be as low as 87 Octane which certainly doesn't help.
So the upshot is - lugging an engine is bad for the bearings etc. but lugging it and trying to compensate with the gas is much worse.
This is a test, I'll be asking questions later on
All the best
Walt
In the good old days (pre CDI/EFI) you had to set your ignition timing to the correct crankshaft angle before the piston reached top dead centre on the firing stroke. Once you got this base setting correct the advance/retard mechanism in the ignition changed the setting continually depending on the accelerationyou asked of the engine. You may remember the little weights and springs that use to tear round underneath the points/condenser that allowed the cam to turn slightly independently of the engine drive shaft. This is what allowed the timing to adjust automatically dependent on acceleration.
Even so, setting the timing was always a fine balance between getting an engine to run and getting it to start (and sometimes neither!!).
Nowadays the control over the fuelling and the spark timing with CDI and EFI is much much better but even so you should not give it the berries in too low a gear. If you make a habit of doing this - you will, as sure as eggs is eggs, damage your engine.
The Octane rating of the fuel (RON) has a heavy bearing on this. The lower the value the more the possibility of pinking. In jolly old England our 2 star fuel is around 92 Octane and is not too much of a problem. I understand in the colonies it can be as low as 87 Octane which certainly doesn't help.
So the upshot is - lugging an engine is bad for the bearings etc. but lugging it and trying to compensate with the gas is much worse.
This is a test, I'll be asking questions later on
All the best
Walt