gear box problems

hi! i needs some advice on my gear box if i set everthing up in one side of the crank case everthing turns and i can select all gears, when i bolt the cases together i can select 1 and 2nd gear easily and they turn freely but the third gear selects and will turn stiffly then the box locks up if any body can advse me on the problem i would be grateful. i have put new bearing in but hav,nt changed the bushes,tried my spare shaft no difference,overhauled the selector mechanism thats as far as i have got thanks

Hi there gear box is an all too common problem, in my opinion always down to how its set up in the first place, or the condition of the gears.
so your issue will be the selector is pushing on the middle slider gear, as it pushes the slider gear across the main shaft into connection with the sleeve gear(top/output gear that takes sprocket).
when in top, I always make/adjust to stop this by shimming or and machine the top sleve gear inner bearing face, to get it set all st up so that its in the corrct position and then have approx 0.002 though floaton the shafts, a little more on the layshaft, you of course must be able to spin the shafts in all gears after the cases are fully locked up with all screws. ( its not uncommon for me to grind the V notches either but never by much.

regards Derek

thanks for your help i will get weaving on your points this week end regards ted

Ted, have you got a 3speed standard box or a close ratio version?
Its just std ratio boxes have just as many problems if not more than
C/r boxes with reference to torque loading and unable to get out of
a gear. If you are doing a test set up with road gears and may be
back at square when you put another box in?? All good experience
mind :-)

Mike

Hi ted I omitted lots of detail, but I found out many years ago no matter what the gearbox (3speed only), the most important detail is to set the gear box positions of shafts and gear off the gear overlaps, when in second gear, this can be adjusted but difficult as the parts that need to be machined are hard, I actually machine the main shaft - I will continue latter need to do somthing with my kids
derek

hi! thanks for your help, i am using a standard road box never encountered a brain teaser like this one ive built a few engines up in my time on a closer inspection tonight i found a burr on the selector ball holder which i carefully filed off,the selector plate itself is not clicking over to the 1sr gear postion.have tried a different plate and changed the ball i have changed the return spring for good measure i will keep you posted on my finding regards ted

ok 1st gear, hmm usually method for this is a size Nine boot, !!

or a Birminhma spanner, !
or Mark Carkeek approaching mansfield lifting his nee to his chest with then a downward movement of such force/momentum, that it lifts him clean off bike, or Bike off track!!!! resulst are Ist gear is well and trully connected, or f@kd - the third option is a Birminham spanner (Hammer abreviated usually does the trick).

Seriously the Bantam box is one of the most simple boxes and selector mechanisums I have come accross, set up correctly, it give no problems. Problems usually occure due to poor assembly fit, or modification to improve it often the latter. some real specialist knowledge is required for a racing 3 speed set up to run relaibly/consistently.

where are you based Ted we have a meeting every now and then your welcome to come and join in many bring engines stripped or ready to strip.
we even had the club champion and his latest creation turn up at the last meeting. so all are welcome.

Regards Derek

hi! i,m based in biggleswade in beds would be interested in one of your metings always willing to learn regards ted. enjoyed the test day at mallory my 85 year old dad did take a shine to the new imperial which was there

hi! after everones help i have made further investigations today(i did manage a couple of hours in the workshop after senior management told me i had to clean the van out and my day off as well) anyway , after taking the gearbox apart it was noted that one of the bushes had a ridge worn on it anyway to prove a point i took it out and faced it off in the lathe and shimed it out approx. bingo a changing gearbox again obviously alot of end float there ,so new bushes have been ordered, the other thing i found the top slider gear was waggling around too much, so i found a replacment in my box of spares and we have a non looking gear box as well,the one thing that baffles me about the gear i can't see any thing obviouse as to why it appeared to be riding the other gear, if any one has an idea i would be grateful so i can put this in the memory banks regards ted