The Ultimate Guide to Assembling & Installing the Howin L6-210 Inline Engine | Stirlingkit

The Ultimate Guide to Assembling & Installing the Howin L6-210 Inline Engine | Stirlingkit

The Ultimate Guide to Assembling & Installing the Howin L6-210 Inline Engine | Stirlingkit
=The following procedure is enhanced in conjunction with the original factory assembly steps. Each step confirms that the components, after installation, are still working smoothly.


Put the crankshaft (66) onto the cylinder block (79) with the power output end's flat surface facing you, and the camshaft bearing bore located on your right-hand side.



Assemble the split-type bronze bearing (51 and 52), starting from the center of the crankshaft. The split-type bronze bushing is located by the bearing cap (60), steel pin (03), and cap bolt (04). Due to possible machine tolerance among the split-type bronze bearings, first use hand effort to screw in the two cap bolts (04) so that the bearing cap (06) is just seated in the crankcase. Then, use a small rubber mallet to slightly tap the crankshaft ends, ensuring the bearing is correctly centered within the bearing cap. Finally, tighten the two cap bolts (04). If done properly, the crankshaft should turn freely.



Install the split-type bronze bearings in a diverging manner from the center, as in step (2). Each time a bearing is installed properly, the crankshaft should still turn freely.



After installing five sets of split-type bronze bearings, add a few drops of normal engine oil (e.g., 30W-40) to the five bearings' sliding surfaces. You should immediately feel the smoothness but with some viscous feeling.



Insert the camshaft (49) into the cylinder block. The cross-pin hole should be located on the same side as the crankshaft cross pin hole.



Place a dab of engine oil onto both shaft ends' surfaces, then install the oil seal (26), flange bearing (57), and e-locking ring (19). Repeat the process for both ends.



Install the crankshaft rear ball bearing (56), oil seal (63), flywheel housing (64), gasket (44), drain nipple (01), nipple gasket (02), screw plug (05), and fix the flywheel housing with cap bolts (07).



Place the steel pin (15) onto the crankshaft slot, preferably with some grease to adhere to it. Check the starter gear (62) one-way bearing setting: when facing the starter gear and manually rotating in the counterclockwise direction, it should drive the crankshaft in that direction. Turning the starter gear in the clockwise direction should be free, and the crankshaft should not turn.



Align the starter gear (62) with the one-way bearing slot, just touching the steel pin, and press in the starter gear with even hand effort all the way.



Install the flywheel (75), secured by the serrated washer (18) and lock nut (20).



Install the crankshaft front bearing (56).



The timing gear housing (74) needs to machine two countersinks cutting on the two bolts close to the camshaft location and fixing (07). Two of them need to be changed to M3×8 countersink bolts.



Place the cross-pin (03) onto the camshaft and seal (11) onto the timing gear housing, followed by gasket (47). Fix the timing gear housing with two countersink bolts and one cap bolt.



First, tighten the two countersink bolts inside the timing gear housing, making sure it is flat with the gear housing internal surface. Then, carefully tighten the outside cap bolts with slight effort, as the gasket (47) does not extend down to this bolt position. Over-tightening on that cap bolt may result in the mounting lug bending.



Install the timing gear (53) onto the camshaft, aligned properly with the cross-pin. With the assistance of a small rubber mallet, slowly tap the gear to fully engage with the cross pin, and put in the e-ring (19) to lock it in place.



Install the key (16) onto the crankshaft key slot, slowly rotate the flywheel to match with the key with timing gear (50), and at the same time locate the timing marks with both gears (50) and (53) so that three points come together. Then, push in the timing gear (50). With a small rubber mallet and tube-shaped tooling, tap the gear all the way in and lock the gear in place with e-ring (17).



Install the screw plug (06) into the engine block.



Now, the flywheel can still be easily turned. Every two turns of the flywheel, all three timing marks should point meet again.



Put several drops of engine oil onto the timing gears, install the timing gear housing cover (65) with locating steel pin (03) and gasket (46), then fix it in place with cap bolts (13).



Install the front oil seal (09), seal retaining ring (59), and fix it with countersink bolts (10).



Install the crank pulley (69) with cross pin (15). When tapping the pin into the pulley, exercise great precaution not to accidentally hit the pulley surface and jeopardize its surface finish.



Up to now, the flywheel can still turn quite freely, only with some resistance feeling on it. This resistance mostly comes from the two crankshaft oil seals and two camshaft oil seals.



Now, install the piston (77). It is a straightforward job but has to be done one-by-one. The piston rings are pre-installed onto the cylinder bore, so don't mix them up. Push them out one-by-one, setting the piston ring gap at approximately 45 degrees to the crankshaft center line. Then, align the connecting rod split-bearing alignment mark facing the pulley end. Use the piston ring insertion tool (38) to facilitate installing the piston with the ring. After tightening the con-rod split bearing bolts, use a small screwdriver to gently pry the con-rod in the direction of the crankshaft center line. It should have very slight movement, indicating it is not jammed. Add a few drops of engine oil on the con-rod bearing and cylinder wall. The flywheel can be turned but with a bit of heaviness; this is normal due to piston ring tension.



Repeat on the rest of the cylinders. Finally, the flywheel turned a bit hard but with uniform effort.



Put the engine block upside down, add a few drops of engine oil on all the main bearings and connecting rod bearings. Then, install the oil pan (83) with gasket (43) and fix it with bolts (07). Tighten the bolts evenly to prevent oil leakage.



Install the valve tappet (78) into the cylinder block. This needs to be cleaned and have a drop of oil added onto the working surface. If any tappet is not working smoothly, don't force it in place. Try the mix-and-match method. Ultimately, if 1 or 2 cannot work smoothly, use #1,500 emery paper to polish the tappet surface and the brass tube inner surface to make it smooth. Then clean it with industrial petrol. After all tappets are in place, put a drop of engine oil on every tappet top. With the aid of a toothpick, slightly press downward and slowly rotate the flywheel in the normal running direction (counter-clockwise facing the flywheel). The tappet should move up and down freely without any great effort felt on the toothpick.



Ensure the cylinder block surface is clean and free from oil. Place the cylinder head gasket (40) and the locating steel pins (03) onto the cylinder block surface.



Install the screw plug (05), bore reducer (27), and coolant nipple (25) into the cylinder head (82).



Check the valves on the cylinder head (82) to ensure they are working smoothly without binding. Press each valve with a steel pin, then place the valve bucket (55) onto the recess. Check again for smoothness, followed by the push rods (21). If everything is satisfactory, place the cylinder head assembly onto the engine block (79) with the spark plug side aligned with side cover (02). Use cylinder head bolts (29) and slowly tighten from the center in a cross pattern, securing the cylinder head evenly on the cylinder block.



Install the adjusting bolts (22) by screwing them all the way down until they are jammed.



Mix-and-match the valve rocker arm (54) with shaft (61), ensuring each set of rocker arms can work smoothly with the shaft before putting them onto the adjusting bolts. Follow this by adjusting collar (23), and the locking nut (24) should be hand-tightened at this moment.



If the rocker arm cannot work smoothly on the shaft, again use #1500 emery paper to correct any rough surface, burr, and shaft surface until it can work smoothly.



Repeat steps (29) and (30) until all rocker arms are installed.



Install the two intake pipes (48) and one exhaust pipe (81) with high-temperature O rings (32) and fixing bolts (30).



Then, those valves aligned with the intake manifold are intake valves, and those aligned with the exhaust manifold are exhaust valves.



Each cylinder has one intake valve and one exhaust valve.



Valve adjustment is a bit tough but not difficult. On this inline 6-cylinder engine, cylinders 1-6 are complimentary cylinders, followed by 2-5 cylinders, then 3-4 cylinders are complimentary cylinders. Complimentary cylinders have pistons with the same movement but with different working strokes. For example, if the 1st piston is going upward, then the 6th piston also goes upward. If the 1st piston (pulley end) is on compression, then the 6th piston (flywheel end) is on exhaust. The valves must be adjusted when both valves are fully closed, corresponding to the end of compression. No obvious valve movement can be observed when the 1st piston is at the end of compression. On the 6th piston, it just changed from exhaust to suction (intake), and the rocker arm movement is very clear. This engine's firing order is 1st-4th-2nd-6th-3rd-5th, then adjust the valves according to the following table:



Cylinder number


1st 4th 2nd 6th 3rd 5th


6th 3rd 5th 1st 4th 2nd

By observing the complimentary cylinder valve movement, the valves can be correctly adjusted, and the engine should have maximum smoothness and performance. Manually turning the flywheel, observe the 6th cylinder exhaust valve is about fully closed (rocker arm pressing on the valve stem nearly moves up), and the intake valve is just open (rocker arm pressing on the valve stem just presses down). Then, the 1st cylinder both valves can be adjusted. Use an aluminum sheet of about 0.2mm (2 folds with a Coca-Cola can) between the rocker arm (54) and the valve bucket (55). Carefully turn the adjusting collar (23) until just tight, then tighten the lock nut (24). If adjusted and locked properly, the aluminum sheet can be pulled out with some resistance. Also, you can use a small screwdriver to pry up the rocker arm on the valve side, exhibiting a small gap equivalent to the thickness of the aluminum sheet; then, this is perfect.


Repeat on the other cylinders, making sure the correct complimentary cylinder valve movement has been observed.



Now, each valve bucket (55), rocker arm (54), rocker arm shaft (61), and push rod (21) can have drops of engine oil to lubricate it.



Manually rotate the flywheel in the normal direction of running until 1 cylinder is on top with the combustion stroke (looking at the 6 cylinder exhaust valve just close and intake valve just open).



Place the seal (12) inside the timing gear housing recess, affixed with a dab of grease for help.



Remove the distributor cap, align the distributor (84) shaft driving tang onto the camshaft slot, with the rotor copper plate pointing at about the 8 o'clock position. Also, the distributor body's silver color side should face the drive belt side. Then, temporarily tighten the bolts (13).



Install the valve cover (70) with bolts (28).



Install the starter motor (73) fixed with bolts (14).



Use a small grindstone to grind smooth the crankshaft output end sharp edge. This is to prevent damage to the oil seal in the flywheel bell housing.



Install the flywheel bell housing (68) completed with gasket (41) and locating steel pins (03), then fix it with bolts (13).



Install side cover (72), oil nipple (01), nipple gasket (02), gasket (42), and fix it with bolts (36).



Install the two carburetors (71) fixed by bolts (31), then the throttle synchronized link bar (76) with countersink bolts (35).



Install the water pump (67) with gasket (85), then temporarily fix it with cap bolts (34).



Install the oil pump mounting bracket (58) with fixing bolts (07).



Install the oil pump (80) together with the mini-cog belt (45). Then, adjust and fix it with the through bolt (36), flange nut (37), and cap bolt (08).



Spark plug wire connection sequence follows the instruction on page (27).



Coolant piping and oil piping from Stirlingkit can be provided.



Starting, running, and maintenance procedures can be referred to in the factory instruction.


Prepared by CHAN Jacky


1 comment

  • javier alan: March 01, 2024

    please your help. i bought this engine, ensambled it but no work.
    there is a spark in plugs but nothing happen.
    i tried to adjunt the valves with 0.2 mm of gap but no work

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