I have a 87 600f with 40k on it. At the end of last season it started making a loud rattling noise and started losing power when engine speed came up. It was an internal noise, i suspected the timing chain. I pulled the chain tensioner, it moved freely. All the info I could find about the tensioner was that it had to move freely. I pulled the cylinder head cover off to check the chain and guides. With the tensioner installed the chain at any given point had about 1/2 an inch of slack.

My first question:
Is the tensioner have oil pressure to it for more tension or is it just spring loaded? It seemed to me that at the rpm's this motor is capable of it would need more tension.

My second question:
How tight should this timing chain be? I am a automotive mechanic and every timing chain i have ever put on is much tighter then this. I have very little experience with motorcycle engines but I figured the timing set up would be similar.


If anyone has any advice or information it would be very much appreciated.

Thank You

 

Welcome to the CBR's CCT foibles - the OEM tensioner seems to be unreliable, possibly because the non-return valve inside the tensioner may malfunction (there's no info about it in the manuals). Answers to your Qs:

1. The tensioner uses oil pressure to augment the spring pressure - typically around 5 times the spring pressure, according to my calcs. (Metric forces: spring = 20N at about mid travel, oil = 100N at 500kPa oil pressure. Plunger travel is about 25mm total.)

2. No idea how tight the chain should be. I did see somewhere that in general for transmission chains (including this type) the slack should be about 3% of longest span. You could Google it. Chain pitch 7mm, silent chain (ie inverted tooth type), 4 plates wide incl. side plates. Longest span is about 250mm, runs over 38mm and 76mm sprockets.

Many people fit a manual tensioner and adjust it up until offensive noises stop, but I don't know long term effect of this approach.

Actually, if you did that and found the answer you could post the info to the CCT sticky for this bike (top of this forum), and any future questions about CCT there.

I've also converted a standard OEM tensioner to manual - see recent post - which fixed the noise mostly, but I didn't try to get rid of it entirely.

G

 

Thanks a lot. I will look into a manual tensioner and see what I can find on the chain slack. Do you know of a place that sells a manual tensioner? If you dont off the top of you head don;t worry I can do some research. Thanks again