New member with a Jonway 250 By boksie (Read 457 times)

[boksie]

hi all, I'll be hanging around here every so often. Bought the thing secondhand for R7000 which should be devided by 10.36 to get the dollar value of about $675. Stuff is stupid expensive here.

Anyway bought it with a noise emanating from the engine and thought it should be only the variator. Turns out the crank is shot. Stripped the motor and will be repairing it soon. 

I custom fabricate most parts for stuff I do, build cars and manifolds and stuff and just wanted the scooter as a daily commute to my day job, which happens to be software developer, go figure. I'll be building it a nice exhaust, intake pipe and what not and also giving the panels a make over of sorts.

Will post up some picture at some stage.

[fflintstone]

Welcome )we would like to see some pics--other members will probably want to know where you are--and will be glad to have other good techs and wrenchers --keep us updated on your progress

[JR]

Yes by all means tell us more about yourself and we love Pics!

JR

[alleyoop]

Welcome Boksie , good to have you on the forum. Bummer on having to find out the motor was shot and having to tear the motor apart. But I see your handy and will not be a problem. And by all means pop up pictures of your build.
Alleyoop

[boksie]

Hi all, thanks for the welcome. I'm from sunny(not so much now) Cape Town, South Africa, which is at the bottom tip of Africa. Much of my knowledge comes from working with my dad on cars, he's been doing it as a profession for 47 years.

Ok so the motor has been completely stripped and it seems the big-end of the rod is still fine, but the wrist pin of the piston has worn down. I'm sure the small end has also worn out, but not sure how much until we mic it up. Anyway, I also happen to have a soft spot in my heart for early Datsuns and happen to know that the A12 engine, which is a 1158cc engine found in the 1200 Datsun has a 73mm piston with a 17.45mm wrist pin.

Not sure about compression height just jet, but if it's close and it requires minor machine work on the piston top and skirts to fit properly you can bet your backside this scooter will soon be running with a Datsun piston.

I'll take some pictures and post them up soon.

[boksie]

Ok turns out the Datsun piston might not work as it's compression height is much bigger than the OE piston. The OE piston has compression height of 22mm or so and the Datsun piston 30mm or so. Not sure if there's ehough meat on top of the piston to machine it down to still fit or if it will cut into or weaken the top ring landing to much, will see.

Dad took the crank, barrel and piston to work today. He'll be checking around all the 100's of junk pistons they have there for a possible suitable replacement. Will also look into other bike pistons as they have bunches of those lying there as well.

I'll let you guys know which fits if we find one. I know I can just buy a new one, but I get the machining for free and most probably the donor piston as well if we can find one, plus the barrel has to be bored as it has score marks al the way from the top to the bottom. Not sure if they even sell oversize pistons for these engines. If I end up having to buy a new barrel and piston I might as well get the big bore 300cc kit then.

[boksie]

Been searching high and low, there seems to be some Opel/Vauxhall/Chev 1.0/1.2 engine that has a piston which can work. But finding no luck getting specs on it.

However I have thought a bit more about the Datsun pistons and think it can still work. If I make a spacer for between the block and barrel to move the barrel upwards, I can still make up some distance to fit the top of the piston in.

Next thing someone might say is your cam timing is going to change, well seeing as I have about 8mm to make up , I'm going to measure the lengh of a chain link on the cam chain. If I make the spacer exactly the thickness of one chain link, it means the cam will just move backwards one tooth on the chain and be precisely where it should be.

Wil do some measurements tonight and see what we can do.