What Does a Normal, Healthy Engine Sound Like?

I just bought a used 1983 VF750 Interceptor yesterday and am wondering how I can tell if the engine is healthy. The noise that the engine makes when it starts up is a bit loud, like a rattle, which sometimes goes away after warming up and at others, it stays there but at a lower volume.

I am wondering what a healthy Honda VF750 motor would sound like. The guy who sold me the bike says that this sound is normal.

Can anyone please chime in and give some guidance and feedback?

 

Sounds normal to me. You might want to check valve clearances through.

-Jake

 

Cam chain rattle possibly. There are others here far more qualified than me though...

 

The basic health of ANY engine is a compression test. It is the bottom line. It is the gold standard.

IF the compression test is satisfactory it means the important internal parts of the
engine like the piston rings and valves are working properly.
The total milage must also be taken into account and the care that the engine has been given.
Cam chain slack must be taken up BEFORE any valve adjustment and will significantly reduce the engine noise.
Check your manual.

The sound of the engine can is determined by the type of intake and exhaust system and the fine adjustment of the other parts.
A straight tube exhaust will be raspy and sharp and if you try to muffle those you will run into tuning problems and jetting problems.

If you have larger mufflers they will have a full sound and be a little more forgiving as far as jetting.

There are many other fine points about tuning., Like throttle response etc.,.

 

Cam chain rattle goes away if you rev the motor as the slack will be taken up. You then get a real nice slap when you let up and the slack whips around in there. There's no mistaking this noise if you've ever heard it before. I stripped out the cam chain tensioner on my CX, which caused this, and it makes a god awful racket. On the older VF's it's normal for the valve train to make noise and then get quieter as the motor warms up.

-Jake

 

Hear the motor.
Find a beat.
When a motor is good, the music of the machine plays with out effort.
What I say'n' is that if it don't sound right, it ain't right.
I an not a mechanic.

 

If the noise comes and goes very abruptly, and it's a loud rattle...it's probably the automatic cam chain tensioner backing off (it's not supposed to).

If it's a tick that tends to quiet a bit when the engine get's warmed up, it's probably a valve clearance adjustment.

If it's more of a loud tick...or knock...could be valve clearance adjustment...or worse.

Make sure the noise isn't coming from an exhaust leak...or if applicable the exhaust collector underneath the engine.

It's really hard to describe the sound a healthy engine makes.

 

Would it help identify the noise if I somehow was able to post up a link to an audio file of the engine noise for you al to hear?

Sometimes, when I rev the motor, the noise gets dampened (gets less noisy) and when I let go of the accelrator, it comes back. And at others, after letting go of the gas, it stays less noisy. And then it would come back after a few seconds on its own.

I think I should start off with checking the compression in each cylinder and go from there. Since I have never worked on a bike engine before, would i use the same/similar gauge as the one used on cars and do it through the spark plug hole?

On another note, would someone happen to know if a later model engine from another VF750 drop right in, into a 1983 VF750? I know I may have to go for a 700 or 500, but its fine.

 

A persistent knocking sound that sometimes goes away at higher revs may be big end wear.