Tuckermoto Posted May 16, 2019 Share Posted May 16, 2019 Hi all Update on my little Honda cbf 125 engine rebuild ...Barrel/ rings / piston replaced the engine is all back together and started on the button straight away ..after leaving the bike on tick over for 15 minutes to run the new piston rings and barrel in I’ve noticed that the rocker cover had a slight oil leak all the way round the gasket ...I’ve retorqued the cover down and it’s still weeping oil ..the gasket is new I’ve retook of the cover and redone up the cover bolts but still the same weep of oil ..I’m used to working on car engines and normally the rubber gaskets hold good on them ..is it advisable to add some instant gasket ( high temperature resistant) to back the rubber gasket up and ideas Quote Link to comment Share on other sites More sharing options...
Guest Richzx6r Posted May 16, 2019 Share Posted May 16, 2019 Yea I'd give it a sparing tickle with some gasket sealant Quote Link to comment Share on other sites More sharing options...
Tuckermoto Posted May 16, 2019 Author Share Posted May 16, 2019 Thank you for responding I’ve got some clear instant gasket that I use for when I replace water pumps on cars RTV silicone rubber sealant it goes up to temperature 250 Celsius do you think that’s ok to use Quote Link to comment Share on other sites More sharing options...
Guest Richzx6r Posted May 16, 2019 Share Posted May 16, 2019 Thank you for responding I’ve got some clear instant gasket that I use for when I replace water pumps on cars RTV silicone rubber sealant it goes up to temperature 250 Celsius do you think that’s ok to use Yea I'm sure it is fine, just go sparingly with it Quote Link to comment Share on other sites More sharing options...
Westbeef Posted May 16, 2019 Share Posted May 16, 2019 Did you clean the old gasket off the faces? Quote Link to comment Share on other sites More sharing options...
Tuckermoto Posted May 16, 2019 Author Share Posted May 16, 2019 Yes I did with gunk Quote Link to comment Share on other sites More sharing options...
fastbob Posted May 16, 2019 Share Posted May 16, 2019 I'd have another look at both surfaces because reusable rocker box gaskets don't usually leak . There shouldn't be any oil under pressure behind them so I'm puzzled as to what's causing seepage . Quote Link to comment Share on other sites More sharing options...
Guest Richzx6r Posted May 16, 2019 Share Posted May 16, 2019 I'd have another look at both surfaces because reusable rocker box gaskets don't usually leak . There shouldn't be any oil under pressure behind them so I'm puzzled as to what's causing seepage . Could be a breather pipe blocked or something? Quote Link to comment Share on other sites More sharing options...
Tuckermoto Posted May 17, 2019 Author Share Posted May 17, 2019 I’ve taken cover back of and going to check for blocked breather pipes and then put instant gasket on and put rubber gasket back on and try ..there’s no pressure it’s just weeping ...I’ve looked on you tube and it seems many people fitting cam gaskets ( my one is rubber ) also back up the gasket with instant gasket it seems Honda gaskets instant gasket is used Quote Link to comment Share on other sites More sharing options...
Fozzie Posted May 21, 2019 Share Posted May 21, 2019 I've rebuilt one of these engines, the gasket was an absolute pain to get on right as it sort of slots into the cover, but it twists and moves around and kept slipping out of place as I tried to refit it. Took about half an hour of fiddling about to get it on perfect. Put up some pictures of it so I can have a look. Hopefully all you need is a smear of instant gasket to get it to seal fully, but I didn't need it which is why I'm probing a bit further. Quote Link to comment Share on other sites More sharing options...
fastbob Posted May 21, 2019 Share Posted May 21, 2019 What you do is " Glue " the gasket to the cover with silicone sealant, put the cover on a flat surface with a weight on top somewhere warm to set . When it's dry , just bolt on the cover . Easy . No need to over do the silicone , just use enough to stick the gasket . Quote Link to comment Share on other sites More sharing options...
fastbob Posted May 21, 2019 Share Posted May 21, 2019 I've rebuilt one of these engines, the gasket was an absolute pain to get on right as it sort of slots into the cover, but it twists and moves around and kept slipping out of place as I tried to refit it. Took about half an hour of fiddling about to get it on perfect. Put up some pictures of it so I can have a look. Hopefully all you need is a smear of instant gasket to get it to seal fully, but I didn't need it which is why I'm probing a bit further. It was hard to re fit because this type of gasket tends to swell slightly upon exposure to chemicals . One way to shrink it is to put it in a moderately hot oven for a little while but don't blame me it you bugger it up . This also works with brake caliper dust seals that won't go back in . Quote Link to comment Share on other sites More sharing options...
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