Good Day All,
Im new to this forum, but not to these "wonderful" 48cc bicycle engine kits. Ive done 3 conversions, and I have found the following overhaul points to be very helpful.
1-Tear the engine down to every last nut and bolt
2-De-burr all edges on the case
3-lap mating surfaces on surface plate
4-Machine the case to accept "normal" 30mm OD crank seals, and use decent Corteco seals from CR seal.
5-Replace the crank bearings with SKF units
6-Replace the jackshaft bearings with SKF sealed ( not shielded ) units
7-Actually align , redrill, and helicoil most of the holes in the case
8-Replace the cylinder studs with stainless (english threaded units)
9-Re-true and polish the crankshaft journals, especially where the seals ride
10-Deburr and chamfer everything slightly, these engines are full of burrs and sharp edges.
11-chamfer and polish the edges of the ports in the cylinder
12-lap the cylinder and cylinder head to make sure they are flat
13-lightly hone all the edges of the piston rings, and check the fit in the piston.
14-De-burr the primary reduction gears, glass beading works well for this
15-Clean and relube the clutch idler bearings with high temp nlgi-3 grease
16-Bush the clutch shaft in the sprocket cover with a bronze bushing
17-Ultrasonicly clean every part (if you can) and assemble with a decent lube one the engine parts, high temp grease on everything else, and a removeable sealer on the gaskets.
18-Assemble using allen head good quality fasteners
19-Seal the excitation coil in the engine with epoxy
20-I have run blendzall 455 at a 32:1 ratio in all of mine with great results.
This probably seems like overkill, and it does take a bit of time. But boy are they reliable after that! All of the kits I bought, from various suppliers, had quite a lot of grit, dirt, metal chips, bad bearings, and all had torn crank seals. Just a good cleaning, de-burring, and hand fitting, and sealing up would make a world of difference. Anyone else gone this far to save a buck?
Im new to this forum, but not to these "wonderful" 48cc bicycle engine kits. Ive done 3 conversions, and I have found the following overhaul points to be very helpful.
1-Tear the engine down to every last nut and bolt
2-De-burr all edges on the case
3-lap mating surfaces on surface plate
4-Machine the case to accept "normal" 30mm OD crank seals, and use decent Corteco seals from CR seal.
5-Replace the crank bearings with SKF units
6-Replace the jackshaft bearings with SKF sealed ( not shielded ) units
7-Actually align , redrill, and helicoil most of the holes in the case
8-Replace the cylinder studs with stainless (english threaded units)
9-Re-true and polish the crankshaft journals, especially where the seals ride
10-Deburr and chamfer everything slightly, these engines are full of burrs and sharp edges.
11-chamfer and polish the edges of the ports in the cylinder
12-lap the cylinder and cylinder head to make sure they are flat
13-lightly hone all the edges of the piston rings, and check the fit in the piston.
14-De-burr the primary reduction gears, glass beading works well for this
15-Clean and relube the clutch idler bearings with high temp nlgi-3 grease
16-Bush the clutch shaft in the sprocket cover with a bronze bushing
17-Ultrasonicly clean every part (if you can) and assemble with a decent lube one the engine parts, high temp grease on everything else, and a removeable sealer on the gaskets.
18-Assemble using allen head good quality fasteners
19-Seal the excitation coil in the engine with epoxy
20-I have run blendzall 455 at a 32:1 ratio in all of mine with great results.
This probably seems like overkill, and it does take a bit of time. But boy are they reliable after that! All of the kits I bought, from various suppliers, had quite a lot of grit, dirt, metal chips, bad bearings, and all had torn crank seals. Just a good cleaning, de-burring, and hand fitting, and sealing up would make a world of difference. Anyone else gone this far to save a buck?
