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BF75A timing belt tensioner setting?

Cretster

Contributing Member
I'm about to put out to sea for the first time in my rebuilt boat (as soon as the weather permits), but the timing belt tension is one thing I haven't checked properly yet on the engine, and I'd rather ensure this is correct first since I haven't used this engine before other than running it in a barrel.

Basically it appears to purely have a spring to set the tension, but when I look in the (genuine!) workshop manual that I've got, I'm not seeing a procedure for correctly setting the timing belt tension.

Given that it's just a spring, is it the case that I simply 'crack' the bolt untight for the idler pulley, then the spring will set the correct tension by itself, then torque up the bolt again? Or is there more do it than that?

I'm used to hydraulic tensioners on car engines, which obviously add a heck of a lot more tension than a little spring!

Secondly, if it purely is down to the spring to dictate this tension, how often should it be replaced? Springs lose elasticity/tension over time, and I'd hate to think the one on my engine (which looks a bit rusty) isn't doing its job properly any more. Cambelt slip is not the sort of thing I want to happen obviously!!

Thanks
Jim
 
The procedure is in section 6 (at least of the manual that I have). It is on p 111. I do have the most current manual so, the procedure in your manual should be close.

You have assumed pretty much correctly.

The procedure involves rotating the crank pulley twice, then a little farther. The loosening the adjustment bolt, letting the idler pulley spring set the tension, then torque the bolt to 33 ft lb.

I think the procedure is mostly used for installing a new belt.

Your point about spring tension seems valid, but I have not had to replace one yet. Just serviced two of the first 75's Honda made that have at least 2000 hours on them, and they are still doing fine.

If it is rusty, then that might be another matter. It may tend to break if very rusty. Might be good to replace it if it is more than just surface rust.

Mike
 
Sorry for the delay replying Mike, and many thanks for confirming this - much appreciated.

For some reason my manual has no page numbers to get to page 111 as you mention. Pages 6-2 and 6-3 both have a diagram that shows the spring and gives the bolt torque etc but no info relating to the spring other than this from what I can tell in that whole section. Not a worry since you've clarified it now.

Just need to find a suitable UK supplier for parts to order a spring and a few other bits & pieces.

Thanks for confirming anyway. :)

Jim
 
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