Tech Tuesday: Engine cleaning

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This week we’re going through the process of cleaning and checking your X30 engine after a race meeting.

Remove the chain guard, the earth cable and the carb and plug up the holes so degreaser doesn’t get inside the engine.



Remove the clutch, using a tool to hold the ring gear so you can undo the nut that holds the clutch on. It’s better to use that than a piston stop tool which will put the crank out of balance costing valuable power!


Check the clutch for wear on the teeth – the one taken off our engine was good, but the 10-tooth shown here for comparison has some “shark-fin” wear on it which will get worse.


The old style clutch drum shown here on the right has holes which can let grease and track crud in which can make your clutch illegal if checked by the scrutineer, so check your clutch for grease (you should do this throughout the weekend anyway).



The washer and the o-ring that sits inside the clutch helps prevent ingress of grease from the needle roller bearing that the clutch drum rotates on. Make a note of the order – bearing, o ring then washer – as you take them off the clutch.


The clutches shoes are very robust, but you need to watch closely for wear and cracks on them in the area indicated by the screw driver and for wear and possible corrosion on all the parts you took off.


Finally take the cover off the Bendix to clean it


Spray the engine with elbow grease and give it a good scrub with a paint brush, leave the elbow grease on for a few minutes and keep brushing. You can get parts cleaners from Machine Mart which use kerosene or even old mixed petrol as a cleaning agent but we prefer to use Elbow Grease which is a cheap and gentle degreaser. Engines can be filthy after a wet weekend, covered in oil and mud. The aluminium cases and barrel are naturally porous which holds on to dirt so when you give them a good clean you have the chance to get a close look at everything. The engine looks much better after a good scrub too!


Once you’ve given it a good wash and scrub with degreaser then rinse it off with brake cleaner and to dry it blow it off with a compressor.


The Bendix cover and the chain guard are damaged from a chain which snapped at the last race so we’re going to replace them.


Next take the reed block out and check the reeds for chips and cracks, it will usually be at the corners and edges.



Check the condition of the two reed block gaskets.


Check the big end of the con rod for discolouration which will indicate a serious problem, although it’s rare.


Check the oil level – this needs to be done when the engine is level and due to the engine mount it isn’t. You can either take the engine mount off or prop it up with something.

Take the 14mm gold bolt out. The oil is just starting to drop out here so the level is OK. The amount of oil required in the gear case is specified in the owners manual. Although the owners manual specifies a relatively thick SAE30 engine oil it’s best to use a thin oil like light gear oil or Automatic transmission fluid. Thin oil in the gear case saps the least amount of power. If you need to put more oil in take the cap for the breather out and use a syringe to fill it up again.



Take the head off to check the general condition of the piston and the o-rings inside the head.


If you’re going to take the barrel off make sure the o-rings don’t fall down inside the engine! It’s easily done and a pain to get them out again. Worst case scenario is you would have to split the cases to find the O ring although washing the bottom end out using petrol and turning the engine upside down would probably get the lost O ring out.
In good light, have a look at the condition of the barrel, looking for scoring of the bore and any unusual wear marks. Check for carbon deposits around the exhaust port and scrape off the carbon if there is any.


Check the general condition of the piston, looking for bad score or wear marks and check that the ring is free around the piston. The piston has ‘rings’ present on the skirt from the manufacturing process. These rings help retain oil on the piston. If there are any polished areas on the piston where you cannot see the rings then this is a likely place where a seizure could occur. The older a piston gets the larger the polished areas get and the less oil being retained on the piston. The coating on the IAME pistons is very good and the engine is not prone to seizure unless by human error on the carburation but the longer a piston is left in the engine, the higher the chance of damage to the bore by normal wear or by a seizure!


Check the crankshaft for cracks.


Reassemble, paying special attention to the o-rings and the gaskets and when you go to put the nuts back on the head you need to do them up to the torque specified in the owner’s manual.


Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Carbs

Tech Tuesday – Axles