I wanted to make a post about the valve train in the 660cc (JB-DET) Copen. In short: If your engine has over 55k miles or so on it, I would advise checking the valve clearances and monitor as necessary. The exhaust side should be 0.30mm (Allowed tolerance 0.27-0.35) and 0.20mm (Allowed tolerance 0.17-0.25) on the intake side. Part numbers: Exhaust Valve: 13715-87210 Valve Lifter: 13751-87201-xx (xx to be replaced by the size required, e.g, 21) (Sizes range from 01-29) The big long bit: These valve lifters have 2 jobs. To open the valve when the cam pushes on them, and to set the clearance between the cam and the valve. Over time valve train parts can wear out, resulting in incorrect clearances. Incorrect clearances can result in either, a rattly engine (typically caused by too large clearance) or a sudden failure of the whole engine, aka a burnt valve (too small clearance) Not too long ago my engine with 67k miles suffered a blown exhaust valve on cylinder number 3. It is typical for the exhaust side to be the first to fail. This resulted in only 3/4 cylinders making power. I have since replaced my engine (after discovering another major and uneconomical to repair fault) with a used engine that had 59k miles based off a video of its "last running" and that one had a couple valves right on the edge of the allowed tolerance. It seems the debris from this also created a small scratch on the cylinder walls perhaps. The valve clearance is important because as these parts heat up (and the exhaust side will heat up more) they also expand. Too small of a clearance can prevent the valve from fully closing once up to temperature as the cam will be in constant contact with the lifter, keeping the valve open slightly. The exhaust that then leaks past it weakens the valve over time until one day, at random, pop. Instant 0 compression in that cylinder. How to do it -When adjusting clearances, rotate the engine so the cylinder you want to check is at TDC all valves closed. -The cam lobe should be pointing straight up on the cylinder you wish to check. -Insert a feeler gauge in-between the cam lobe and lifter. Gradually increase the size of feeler gauge until you cant get it in anymore. -Take note of the gap. -Check all cylinders. -Remove camshaft (see section B in service manual NO.9845) -Take note of all lifters, the stamped number (i.e 13) and location (i.e cylinder 1, exhaust 2). -A magnet on a stick makes removing the lifters very easy. The lifter sizes go up in increments of 0.02mm -If clearance is too small, You need a smaller size lifter to open the gap. -If clearance is too big, you need a larger size lifter to close the gap. The exhaust side should be 0.30mm (Allowed tolerance 0.27-0.35) The intake side should be 0.20mm (Allowed tolerance 0.17-0.25) As a guide, if your exhaust clearance is 0.26mm with a size 15 lifter (gap too small), to make it 0.30 you will need a size 13. (0.26 is 0.04 smaller than 0.30 resulting in a size difference of 2) Extra notes: -I hope this post can help prevent more JB-DET failures in the future. -I am not sure if the same applies to the 1.3L model. -I was able to purchase the parts from Hepworth Motor Co. Be aware that the parts will come from Japan as there's none left in the UK. You may have to wait a couple months for them to arrive. -I know I made a similar post before, but I wanted to compile all the information and part numbers etc. in a nice neat package. -As always, if you have any more useful info in regards to this post, please share!
