Author Topic: CB650 primary tensioner fitted into CB550  (Read 1060 times)

Offline philgresty

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CB650 primary tensioner fitted into CB550
« on: December 30, 2016, 09:54:49 PM »
Some of you may remember i was after a 650 primary tensioner a while ago, well iv finally fitted one in my 550. It's a fairly popular mod in the US but as far as I know noone on here has done it yet, so I thought I'd share some of the things Iv had to overcome fitting it on mine.
Heres a pic from the US SOHC forum



I contacted a local machinist I know to make the required bracket to mount it, using measurements off the US forum, it came out real nice and the price was super cheap too.



Engine obviously has to come out. I wanted to keep the engine in one piece to fit the tensioner which presented a few problems.
The first hole is relatively easy to drill and tap with an m6 tap.
In order to drill the second hole that runs through the front of the engine case, the starter clutch had to be removed, or at least moved out of the way to fit the drill in. It was a pain but not completely terrible.
Procedure for this is.
Oil pan off, clutch cover off, clutch basket off, primary shaft bearing retainer off. Then you can pull the primary shaft out using the bottom engine bolt ( it threads into primary shaft and can be used as a slide hammer)
Now, there is a bolt holding a pin running through the starter gear, with that pin removed the starter gear can be moved out of the way, and the starter clutch can be moved to the side with a bit of wiggling.
Now the coast is clear to drill a straight line through the front of the case to bolt the tensioner in.
A copper washer on the outside seals to stop oil leaking out.


not the best photo but you get the idea

Reassemble everything, with the tensioner bolted in and your ready to go.
The arm of the tensioner that is contacting the oil pan can be bent up slightly so that the 550 pan and oil pickup can be used.

A few months on and no sign of trouble, hasnt leaked and runs smooth as, definitely a worthwhile mod if your primary chain is a bit stretched and you dont want to split cases to replace.


It could do with more of an exhaust though (there is a baffle in there)
« Last Edit: December 30, 2016, 10:04:00 PM by philgresty »

Offline Oddjob

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Re: CB650 primary tensioner fitted into CB550
« Reply #1 on: January 04, 2017, 03:48:16 PM »
Any chance your machinist could knock up another Phil?

Really fancy doing this mod as the primary chain is really one of the few weaknesses in the 500/550 engine design.

When you say the arm of the tensioner which is contacting the oil pan can be bent up how hard is that to do as the metal it is made of looks fairly substantial, doesn't look that easy at all and does the bent detract from it's ability to tension the blade correctly?
Don't play stupid with me, I'm better at it

Offline philgresty

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Re: CB650 primary tensioner fitted into CB550
« Reply #2 on: January 04, 2017, 05:09:16 PM »
Yeah sure, ill get in touch with him, i think he charged me around £40 so a bit of a bargain really.
it is pretty easy to bend in a vice. it only requires a very small bend, in theory it would take a little bit of tension off the spring, you could always install a shorter spring, although the tensioner still has a good amount of spring in it regardless
ill call in to see him tomorrow and let you know when he can get one done
Phil

Offline Oddjob

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Re: CB650 primary tensioner fitted into CB550
« Reply #3 on: January 04, 2017, 05:23:22 PM »
That's fine Phil, cheers.

I'm sure I'll be able to help you out as some point in the future as payment for your trouble.
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