So the box engine is basically finished. Overall Im impressed with the quality. After much discussion with Map, Dave z and others I have concluded it is a GT5 engine. Basically means its a 38mm stroke long rod(114mm as measured) engine. Here is the thread, lot of good informative discussion on engine type.
http://motorbicycling.com/showthread.php?t=57810
Heres the basic build. I built this engine to be basically stock only machining was to match the transfers and clean ridges/flashing from all the ports. Bearings are SKF both crank and clutch shaft. All fasteners replaced with 1/4 20 hex heads. Head and cylinder trued, no raise in compression. Intake manifold matched to the port, slight trimming top and bottom, both trued, run with no gasket but yamabond 5. This crank had some side play, set clearance to .002 using shims. Replaced wrist pin caged roller with high quality unit, and lighter moped wrist pin. Cylinder stud/nuts replaced with hex bolts tightened on double hardened gr8 washers. No/never use lock washers! Chinese use them for some reason, I believe spacers to keep dumb acorn nuts from bottoming-doesn't work all the time. Installed bent/long clutch arm. The cases run no gasket but are sealed with Yamabond. Since they are so well sealed and the SKF bearings have such good seals I added ATF to the clutch shaft case to smooth clutch action. Replaced drive sprocket to run BMX chain, I really like those chains compared to the bigger ones.
I guess that's about it. As discussed this engine does have the bigger nicer drive gears, which has a taller gear cover. If you wind up with one of these, DONT buy an after market CNC cover it wont fit!
Doesn't look much different than normal in the pics. Notice the bigger gears. The bag is all the stuff I didn't use. For you Noobs DONT think your new engines head is loose because you see daylight around the gasket its usually normal on a stock head. Also unless it just wont fit the proper position for the plug on a slant head is to the rear, it adds less heat to the pistons already hot exhaust side. I didn't know this until recent reading on tuning.
http://motorbicycling.com/showthread.php?t=57810
Heres the basic build. I built this engine to be basically stock only machining was to match the transfers and clean ridges/flashing from all the ports. Bearings are SKF both crank and clutch shaft. All fasteners replaced with 1/4 20 hex heads. Head and cylinder trued, no raise in compression. Intake manifold matched to the port, slight trimming top and bottom, both trued, run with no gasket but yamabond 5. This crank had some side play, set clearance to .002 using shims. Replaced wrist pin caged roller with high quality unit, and lighter moped wrist pin. Cylinder stud/nuts replaced with hex bolts tightened on double hardened gr8 washers. No/never use lock washers! Chinese use them for some reason, I believe spacers to keep dumb acorn nuts from bottoming-doesn't work all the time. Installed bent/long clutch arm. The cases run no gasket but are sealed with Yamabond. Since they are so well sealed and the SKF bearings have such good seals I added ATF to the clutch shaft case to smooth clutch action. Replaced drive sprocket to run BMX chain, I really like those chains compared to the bigger ones.
I guess that's about it. As discussed this engine does have the bigger nicer drive gears, which has a taller gear cover. If you wind up with one of these, DONT buy an after market CNC cover it wont fit!
Doesn't look much different than normal in the pics. Notice the bigger gears. The bag is all the stuff I didn't use. For you Noobs DONT think your new engines head is loose because you see daylight around the gasket its usually normal on a stock head. Also unless it just wont fit the proper position for the plug on a slant head is to the rear, it adds less heat to the pistons already hot exhaust side. I didn't know this until recent reading on tuning.
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