hi jus wondering if any1 can help.my speedfight2 100cc.the threaded end of the crankshaft that connects to the varitor has wore away the thread and the thread on the nut jus wondering if there is away to re-thread it or do i need a whole new crankshaft. please help thank u

gary white, June 2009

hi gary the best thing you can do is just buy a complete new or second hand engine because i have the same problem but my crankshaft berings have gone and it has jammed up because the crankshafts are only ment to last for about 4000-5000 miles.
and to change the crankshaft you have to take the engine out and it is a 5hour job to remove old one and replace with new one but you will also need to buy crankshaft berings aswell and you will be looking at near enough £130- £180 to replace it all. That is only because they are near enough impossible to find

adam smith speedfight 1 owner, June 2010

yep also a common problem with them the end of the variator nibbles the splines of the crank if it comes loose.you may be able to put a thinnish washer in behind he variator half to repostition it to a place where the spline is ok.

adam bike doctor, June 2009

thanks for ur help. got it re threaded but turns out the splines the varitor sits in to is woren away to.

gary white, June 2009

the best thing to do is get an 8mmx1.25 mm die and try to file or gring the end of the crank down evenly to about 9mm and then run the die down it,then you can use a 8x1.25mm nut instead of the 10mm one it has normally.i would add a washer too though pref an 8mm one on top of a 10mm .p.s i am a bike mechanic and have had to do this a few times over the years so i know it works its whether you can do it or not?good luck.

adam bike doctor, June 2009

Hi Gary, before I get slaughtered by the purists on this forum for giving duff advice I am not recommending that you weld your crank or re-thread it. i have advised you to go to an engineering shop as they would have the expertise to tell you what your best option is....hope this helps & safe driving.

steo, June 2009

Hiya Gary that is not good news coz i think it's a new crankshaft but you maybe able to re-thread the old one by using a tool called a dye which cuts a new thread into the shaft & depending how bad it is you could get away with just using a slightly smaller nut.
I've seen a few cowboys putting on a spot weld to hold on the variator but it would only be a short term fix to get you outta a jam. Every time you had to change the rollers you would have to grind off the weld to get the variator off.
Best bet is to bring your ped to an engineering shop & ask them if they can cut you a new thread, if not then it's a new crankshaft.....

steo, June 2009