ok.... big bore work By sweets (Read 1,143 times)

[sweets]

If i took a 50 cc engine and got a big bore kit (72cc) how long would it take to complete the modifications on a 139 qmb style engine? Its a 4 stroke type. What else would i need to make the engine work at its peak while climbing a semi steep hill where i currently go 20 mph and below while climbing it? This is a full stock from the factory bashan scooter with a hondaclone brand engine. Could anyone give me a list of things to do to my scooter to unrestrict its power? Please and thankyou 

[jct842]

Time depends on how familiar you are with working on the engine. Aircleaner and exhaust mods help too. Honda never made an engine like a 139qmb regardless what brand they say it is.

[Bashan]

How about some sliders and a different main spring BEFORE you try the BBK? You might say "wow, I'm there" and skip the expense. If you did just the top end without splitting the case I'm guessing 4 hours max. Take off carb and intake, valve over, take off the cam, take off the dowel bolts, take off the head, take off the cylinder, replace the rings, new gaskets, cylinder, head, cam, get timing right, cam retainer, tensioner, you must have a torque wrench, take pix as you go along for reference.

[tvnacman]

It will take twice the time to do with the engine in the scooter . Better to pull the engine out of the scooter and put it on the bench .

John

[sweets]

Whoa.... alrighty. :-) thanks!

[sweets]

With a new bore, do i need to break it in? If so for how many miles?

[Bashan]

Yes! First, I crank mine with the valve cover off until oil has made it to the top and dribbles down a little. This insures you have oil in the crank journals etc. And don't crank it endlessly, hit it with short bursts until it comes up. It doesn't hurt to squirt some oil on the parts as you assemble. Then I run an easy 100 miles and swap the oil. Then run easy to 500 and swap the oil. After the first 100 give it some RPMs once in a while, start pushing a little. I DO NOT agree with the "break 'em like you stole them" doctrine and I challenge anybody to make a logical case for that.

[sweets]

Ah, ok. That sounds easy enough. Should i wear latex gloves and clean off the engine first beforeworking  on it and wearing  latex gloves while switching over to the new bore?  Also s a recomendation, would you suggest thread lock and any gasket silicone for any part?

[Guitarman]

Wear the gloves just because it makes washing your hands afterward so much easier.

[cyborg]

i use assembly lube when i build a mill,but first get a manual and study the procedure, line up all the tools you'll need,,

[Bashan]

Jul 26, 2014 22:06:56 GMT -6 Guitarman said:

Wear the gloves just because it makes washing your hands afterward so much easier.

ha.......ha. Hilarious.... I do get dirty smart aleck....and then go scrub the horrible horrible dirt off OF ME!