So, after the engine is well warmed up, say 10-15 miles my trouble starts. From cold there is no problem. Under acceleration and on overrun there is no noise and engine sounds sweet but if you hold her at constant speed (ie: very little load) at high revs (over 7000) in low gears she sounds like she's knocking at the crank. The bike is a uk model P reg and has covered only 16000 miles. Recently did an oil filter and oil change (made no difference).
Any ideas?
Sounds like Pre-ignition, aka Detonation, aka Engine knock. Carbon deposits build up on the head, valves and piston. They can get hot enough to ignite the fuel before the spark plug has a chance to. This is the Pre-ignition noted above. This is VERY hard on the engine. Take the head off the cylinder then beat the valve area with with a hammer followed by aggressively beating the top of the piston. Pre-ignition does the same thing. Not good for the top end, and not good for the crankshaft. Use only good quality premium gas. Change to a spark plug one heat range colder than the stock plug. Seal up any air leaks on the intake system. Running a lean fuel mix means running hot.
A “very helpful” rating for this answer? Thanks!
If the bike is running hot and the fuel is lean, detonation from hot carbon is possible even at 16K. Only the dealer should check the ICU, and yes, most anything electrical can go sour. I am not suggesting removing the head. I was describing the damage detonation can do. A bad head gasket is a possible air leak location. I would not remove the cylinder head unless a bad head gasket is certain. Sounds like your cooling system is operating properly. Living in the UK I would stick with the 10w40 oil. My only other suggestions would be checking the carb balance and the obvious > don't run the engine at constant high revs in low gears with no load. I would do that before putting any money in fixing an avoidable concern. :) Best wishes from Dallas, Texas USA
I don't know why the type was so largs and bold. I could not get it to be normal size. Sorry.
Are you burning premium gas?
Did you change to colder spark plugs?
Do the above two things first.
I am fearful that you will wind up tinkering with the engine needlessly. "If it ain't broke, don't fix it". Another phrase that comes to mind is "Fix it until it is broken". Just one time I am going to be your conscience speaking to you > >
"Am I creating the problem myself by forcing the engine to run high speed, low gear, and with no load? Didn't the designers of the engine know I would do something like this? I wonder what would actually happen If I changed to colder plugs, used premium gas, and didn't do the high rev-no load thing? I would probably have more time for pretty girls instead of mess'in with the bike."
Okay, that's all I am gonna say. tombones49.
You are a better mechanic than most other guys I run into. Why you asking me questions? :) It sounds like you have the skills needed already!. Let me know what you find.
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Carbon build up at 16K miles? I'm not so sure about that. It does sound like an ignition problem though. Could there be anything electronic giving a wrong signal to the ecu?
In the mean time I'll check all the intake connections for an air leak as this is considerably easier than taking the head off. The bike runs perfect and ticks over perfect.
One other thing I've noticed is the bike runs really cold according to the temp gauge (needle hardly moves even when engine is at normal operating temps) until you sit in traffic on a hot day then it goes up high and the fan cuts in as normal, could this be connected?
I was tempted to put some 20/50 oil in her as it seems that the problem is only when the oil is really hot. But I thought that was probably not the cure, just a work around (that might not work anyway).
Any ideas?
Last weekend I checked for leaks around the inlets and air filter, no leaks found. I also decided to take a look at the plugs, all were the same colour and in good condition, no probs there. I cleaned an earth up for the temp guage and took it for a 50 ride. At first I noticed no difference but by the time I got home the engine that used to knock at 7000rpm no nocks at 4000rpm.
I decided to check the exup valve just in case but that is perfect apart from the two bolts I snapped getting it apart!
Next job is to get the engine out and strip it till I find something. Watch this space.
I tried putting super unleaded petrol in the bike and it didn't help.
I've stripped bike engines, car engines and gearboxes before, don't worry, it'll go back together just fine. I want to find this noise before it really does some damage. I reckon it's going to be gasket sealant in an oil way (had that problem with a VT500) or loose oil pump bolts or something like that. One thing is for sure, I'm going to strip this engine from the top end downwards until I find something that isn't right. I've ordered a Haynes manual for technical stuff. I should have it stripped this weekend and I'll keep you posted.
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