Pee Dubs Posted May 15, 2021 Share Posted May 15, 2021 Ok so I have my CT125 engine (70s/80s SOHC design, same as CB125 and others) somewhat apart after timing advancer failed. I suspect lack of cam chain replacement and excessive slop caused this, so intent is to replace the cam chain + tensioner before timing her up and sending it. The tensioner came with the cam chain guide that sits on the opposite side of the chain. I thought it would be a simple case of flicking the either the top or bottom end out from where it seats to remove the old one, and reverse procedure to replace with the new, but the bottom end is out and the guide won’t budge. The new guide has moulded pins part way up it that (I think) sit between the barrel and the head and hold it in the middle, so looks like I can’t replace it without taking the head off - who’s done this before and can confirm this is how these work? Next question: how important is it to replace the guide as well as the tensioner? I don’t really want to take the head off as if I do then I might as well take the barrel off, piston out, and nek minut I’m rebuilding the whole top end, which wasn’t the plan! So, should I just replace the chain and tensioner and she’ll be right? Quote Link to comment Share on other sites More sharing options...
tortron Posted May 15, 2021 Share Posted May 15, 2021 Yeah same as the gn125 I reckon. One side sits in the grooves under the head gasket and the other is held in place between the barrel and head It's honestly a 10 minute job so you may as well replace the guide as well. If the chain was worn out the guide probably is Quote Link to comment Share on other sites More sharing options...
Pee Dubs Posted May 15, 2021 Author Share Posted May 15, 2021 11 minutes ago, tortron said: Yeah same as the gn125 I reckon. One side sits in the grooves under the head gasket and the other is held in place between the barrel and head It's honestly a 10 minute job so you may as well replace the guide as well. If the chain was worn out the guide probably is That's kinda what it looks like to me. But obviously then need to order a new head gasket, which could make a 10min job another week or more... And while the head is off I might as well chuck in new rings yeah? Quote Link to comment Share on other sites More sharing options...
tortron Posted May 15, 2021 Share Posted May 15, 2021 Nah reuse the gasket and rings itl be fine on one of these Quote Link to comment Share on other sites More sharing options...
Pee Dubs Posted May 15, 2021 Author Share Posted May 15, 2021 Yep, lugs sit in notches in the barrel, under the gasket. Quote Link to comment Share on other sites More sharing options...
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