Joda76 Posted February 11 Report Share Posted February 11 (edited) Hello good people. I bought my self a cheep defective Ossa. It is in a rather good shape, only inner head gasket is blown. After cranking it pops like a champagne when opening a radiator cap. Coolant that I have drained smells on gassoline. As I can see 4 side bolts will be the problem to torque with my Nm torque wrench because of a frame interference . Should I use some special tool , or release engine in front and pivot it a bit to make some clearance? One more thing. I read that inner oring is better to be silicone than NBR one, any oppinion on that? Many thanks ! Edited February 15 by Joda76 Quote Link to comment Share on other sites More sharing options...
kurtas Posted February 11 Report Share Posted February 11 Silicone has a higher heat tolerance than NBR, so if you can that would be better. Both will tolerate the Glycol. 1 Quote Link to comment Share on other sites More sharing options...
pauls320 Posted February 16 Report Share Posted February 16 Be a good idea to inspect the o-ring grooves in the back side of the head for cracks. The exhaust mount bolts to the head stay and if the suspension is bottomed out it tags the header pipe and levers against the cylinder head , have seen it fracture the head in the mentioned location ..hopefully yours is okay 1 Quote Link to comment Share on other sites More sharing options...
Joda76 Posted February 18 Author Report Share Posted February 18 (edited) On 2/16/2026 at 2:26 AM, pauls320 said: Be a good idea to inspect the o-ring grooves in the back side of the head for cracks. The exhaust mount bolts to the head stay and if the suspension is bottomed out it tags the header pipe and levers against the cylinder head , have seen it fracture the head in the mentioned location ..hopefully yours is okay Great point! Thank you for advice. I will inspect. I was just checking if the head is flat, while waiting on o ring shipment. Managed to take a head off no problem. Accept Ossa manual says that the bolts are T20 and they are T25. Also wanted to comment about a muffler. I mean, even though I really respect Ossa's designe team work in many ways, making muffler into a prying tool for an engine head is such a bad idea. I am seriously considering doing some mod to dissconect muffler fron an engine. Edited February 19 by Joda76 Quote Link to comment Share on other sites More sharing options...
Joda76 Posted February 18 Author Report Share Posted February 18 (edited) I have found two, next to a muffler mount (photo1),it was almost invisible util I started digging into it.... next one in line further away from muffler mount (photo2). Edited February 21 by Joda76 Quote Link to comment Share on other sites More sharing options...
Joda76 Posted February 19 Author Report Share Posted February 19 (edited) Pauls320 thank you so much for your comment. If I did not inspect head grooves I would of slammed it back with a new o-rings and afterwards would be like🤔 I was suspicious though, because when disassembling I figured by the head bolts that the head was done before, and when I inspected o-rings they were flexible an in like new condition. Previous owner must of bin frustrated for not fixing it and sold it Edited February 19 by Joda76 Quote Link to comment Share on other sites More sharing options...
pauls320 Posted 1 hour ago Report Share Posted 1 hour ago Sorry to hear that this was indeed the problem. If I remember correctly, the later ones had a larger bottom out bumper on the shock shaft...? Depending on your ride weight you may want to adjust the spring a littler stiffer and/or possibly modify the header pipe,where it tags the swing arm, before trying out a new head. Hope you get her sorted out Quote Link to comment Share on other sites More sharing options...
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