Dong Fang DF 250 RTB Bobber Information

[bowtiewagon]

Wow, guess these are not "harden" studs.. jimmyhen has some info and a pic. Just use a tap and die to thread the hub and use at least grade 8 bolts is SAE or grade 10.9 in metric.

http://www.mychinamoto.com/forums/sh...ll=1#post42442

Thats the paln...still not sure why the snapped like they did?




My only question is do i leave the sleeves that are in the hub in and just run the bolt to the back of the hub? I think that is the best bet. Plus a spacer on each bolt to fill the gap that the original studs had on them.

[alleykat]

Thats the paln...still not sure why the snapped like they did?



My only question is do i leave the sleeves that are in the hub in and just run the bolt to the back of the hub? I think that is the best bet. Plus a spacer on each bolt to fill the gap that the original studs had on them.

Just tap the sleeve thats in the rubber bushings, try not the "break" the sleeve from the rubber if you can. Work slow.
Make sure your new harden bolts don't bottom out in the hub, watch your length. Use blue Loc-tite. Spacer sounds like a good idea. If you don't have a metric tap & die set, Harbor Freight is your friend. Besides, you may need it in the future. LOL Use oil on the tap.

What size hole is in that sleeve in the bushing in metric?
In some of the smaller tap sets the largest tap is 12mm.

[ghost1133]

Those studs are meant to shear off. If you replace them with a stronger stud then something else will be damaged at the next weakest point. Transmission on up into the motor. You do not want that. The studs are meant to shear off to prevent more extensive damage elsewhere. Everyone thinks when a bolt breaks, I'll just put in a stronger one. Bolts come in varying degrees of hardness for a reason. You want the bolt that snaps to be the one that will cause the least amount of damage. I'm just saying.

[DanDaMan]

my bet is snap ring failed , sprocket backed out enough to spin and thats what sheared them , but who knows

they have Insets , like a compressed spring , slide it right into the existing unthreaded hole , when run bolt in it "expands" that insert to grab the hole and keep it securely in place , without any tap/die

[alleykat]

Those studs are meant to shear off. If you replace them with a stronger stud then something else will be damaged at the next weakest point. Transmission on up into the motor. You do not want that. The studs are meant to shear off to prevent more extensive damage elsewhere. Everyone thinks when a bolt breaks, I'll just put in a stronger one. Bolts come in varying degrees of hardness for a reason. You want the bolt that snaps to be the one that will cause the least amount of damage. I'm just saying.

Good point Ghost. I'm still trying to understand the reason for the design in the first place. I would go back with the original "studs" but the problem is getting replacement could take a month or so...

[alleykat]

my bet is snap ring failed , sprocket backed out enough to spin and thats what sheared them , but who knows

they have Insets , like a compressed spring , slide it right into the existing unthreaded hole , when run bolt in it "expands" that insert to grab the hole and keep it securely in place , without any tap/die

Maybe the snap ring wasn't fully seated? Bow, what is the condition of your ring?

Dan, I haven't seen the insert that your describing. Where would we find those?

[bowtiewagon]

my bet is snap ring failed , sprocket backed out enough to spin and thats what sheared them , but who knows

they have Insets , like a compressed spring , slide it right into the existing unthreaded hole , when run bolt in it "expands" that insert to grab the hole and keep it securely in place , without any tap/die

Snap ring was in just fine.It was where it should have been.The sprocket was not detatched in any manor.I am not sure the purpose of this design..the sprocket should be attached to the hub some way,and to me this was just a design for a quick release of the sprocket to be changed out..I see no reason why the fix could not be to run studs all the ay through the hub itself,and attach it that way.But I will look into more before i do anything else to it.

Plus what has me scratching my head is why did it happen.There was no sign of anything wrong at all.The trans shifts smooth, the wheels are straight, the chain is not tight..in fact maybe a little loose. what would cause this malfunction to happen. Could the road conditions and the hard tail combo be the issue...doubt it. The snap ring was correctly seated as far as I could tell when i removed it. any thought on that?

[DanDaMan]

http://www.emhart.com/brands/heli-coil , http://www.toolbank.com/p/C3546/RCL27103 , http://www.newmantools.com/recoil1.htm , I get mine from http://www.fastenal.com/web/products...0160262&ucst=t , Ive used em on stripped holes and holes without threads at all (center valve cover bolts on 81 Jeep limited rebuild - unthreaded)l


if the snap ring was seated then i havnt a clue , perhaps just a bad "batch" of bolts got sent out

ive no issues with mine and i treat it pretty hard , matter of fact out of the 3 super bikes ive owned , this 1 is the only that will burn out

81 Honda CB 750F super sport 65 in 1st bury speedo @95 in middl of third , 77 Kawi KZ 1,000 (turd unless only goin straight line) , 77 suzuki 750 GS (meh and at 23 mpg ....really - time to order something small ---->) , 2010 DF 250 smoke them tires at will (not that I do (tire be expensive) just that it can)


so what kinda milage everyone else getting , I'm running about 70-75 mpg with about 90% my riding being highway travel at 70mph (on $3 I top off ride to my momma'a 35 highway miles away do yard work and ride home (yes 70 miles on 3-3.50)) , and I just slapped new sprocket on to drop RPM's at standard cruise speed to try to further increase it

[ghost1133]

[URL]I just slapped new sprocket on to drop RPM's at standard cruise speed to try to further increase it

So Dan, what tooth sproket did you slap on and how much difference is there in the ride?

I went to a 38 tooth. Feels pretty good at 60.

[DanDaMan]

I put a 36 on and 4th hits what 5th used to

5th used to top out max revs at 70 , 4th now pushes to 65-70

so instead of a screaming engine on highway , it almost a growl / heavy purr