Flywheel center boss swap question???

[Robi D]

Fair enough. Thanks guys.

[scoothappy]

yes i had problems with it. it happed because it originally domed allen bolts screwed into a threaded ring and flywheel was sandwiched in-between. it worked great for about 500 miles then it came loose. cause all kinds of problems. but good bolts with nyloc nuts should work great. just make sure everything is really tight!

[shocky]

Great. I will order one up then. I have full intentions of welding a new boss in place, cause that's what i do! so I'll only have to get it in line and then check to make sure it is in the right space, bolt it up, and then weld it up.
Thanks very much.

if your gonna weld it id use a nickle rich rod (18/8,304,347) and TIG weld it all the ones ive MIG/ARC welded with standard wire have cracked through the weld indicating carbo being drawn into the center of the weld pool i did arc weld one with a stainless electrode and that has so far held up but all of these were riveted or bolted as well and all were lightened to 2.0-2.1 kgs

[dirtyhandslopez]

On this issue, I have always thought that it would be a good idea to throw everthing on a lathe or something to make sure everything is running true, ie the the boss being central to everything else.
Any thoughts on this any one?

[oldbiker]

On this issue, I have always thought that it would be a good idea to throw everthing on a lathe or something to make sure everything is running true, ie the the boss being central to everything else.
Any thoughts on this any one?

That sounds like a damned good idea (if you have all the tooling etc).

I don`t know what type of steel is used for the flywheel boss, but at a guess it is an alloy steel containing a fair amount of carbon. This will make the steel harden as it cools,
this hard steel is brittle and will then snap sooner or later.

That is also why it is a waste of time welding HT bolts for other jobs(it`s all down to carbon\chrome content).

[shocky]

On this issue, I have always thought that it would be a good idea to throw everthing on a lathe or something to make sure everything is running true, ie the the boss being central to everything else.
Any thoughts on this any one?

your not wrong there; sadly scooter engine builders dont ballance and blueprint from the start in my experiance(altho some prob do) there are big gains to be had in this area if not power then reliability , same as for wheels/tyres/hubs when did anyone on a 80mph last get theres done if ever(ok the DAC boys have this area under development ) i wouldnt dream of riding one of my autos without balanced wheels , id rather dealer X developed a rim/hub that was strong and balanced than yet another £500 kit or an air fitration package that works and doesnt rob power or a cooling system that works using the latest airflow/fan designs and not something of a flymo or washing machine couse it looks like it fits

[davidblythe]

On this issue, I have always thought that it would be a good idea to throw everthing on a lathe or something to make sure everything is running true, ie the the boss being central to everything else.
Any thoughts on this any one?

made an extended shaft without the crank web but with a keyway to hold a flywheel for lightening, still working on how to balance a flywheel thou

[RICSPEED]

i guess you'd have to make up a plate/adaptor to fit lammy or vespa rims to a balancer

[dirtyhandslopez]

On this issue, I have always thought that it would be a good idea to throw everthing on a lathe or something to make sure everything is running true, ie the the boss being central to everything else.
Any thoughts on this any one?

made an extended shaft without the crank web but with a keyway to hold a flywheel for lightening, still working on how to balance a flywheel thou

That what I was going to do, if I ever got a round to it. All I ever get is square to its
Just cut the flyhweel side taper off a crank, have centered, bolt the boss to it, make sure it is centered as well and bolt/weld away.
The only crank I ever had balanced, the machinist wanted everything that attaches to the crank:piston, gudgeon pin, gp circlips,dust cover, dust cover clip, sprocket, sprocket bolt, the lot. He then worked his magic and said I had to either lighten it by 2oz or increase the weight by 2oz. It was for a touring bike, so in went two titanium plugs. Absolutly amazing. No vibrations what so ever and the motor just wanted to keep pulling(wiseco jetski piston, yammy rod 215).It was a shame the mag flange bearing took a dump, locking the trans up tight the twisting the crank all to hell. Still, not all is lost, I have two lovely pieces of titanium to do something with, one day.

[Robi D]

FYI, SR have said the bosses are a straight swap.