750 SF gearbox rebuild
- Thread starter ludiluka
- Start date
G
Grant
Guest
Send it to an expert.
It's pretty simple. Assuming cogs, shafts and selector forks are ok, there's not very much to set up.
Most important is very likely the selector drum, the one in the bottom of the crankcase whose shimming is critical since it determines the setup of the whole box.
Paul
Most important is very likely the selector drum, the one in the bottom of the crankcase whose shimming is critical since it determines the setup of the whole box.
Paul
I know some basics to check thickness of selector forks, fork pins, selector drum, i want to know more about shimming. What do you have to check, how, what gaps (tolerances) should be in properly shimmed gearbox?.
Are there some tolerances, thicknes of forks,... i found something on laverdamania
Are there some tolerances, thicknes of forks,... i found something on laverdamania
http://www.laverdamania.net/clearance.htm look on bottom of the page
Things that i don't know:
- min fork thickness (at the ring that changes gears)
- How much play must have selector drum in axial direction? I know that i have to shim left and right side of selector drum so that forks don't rub against the ring (ring on sprocket don't know the name this part ?) when gear is selected.
- and the part that i really don't understand is how to shim gearbox sprockets ?? There are some axial tolerances on the link above but dont know how to measure them ?? between each sprocket where shims are now ? and i set them to lower subscribe number ? how to you measure this with feeler gauges? or do i have to pay attention to anything else?
Things that i don't know:
- min fork thickness (at the ring that changes gears)
- How much play must have selector drum in axial direction? I know that i have to shim left and right side of selector drum so that forks don't rub against the ring (ring on sprocket don't know the name this part ?) when gear is selected.
- and the part that i really don't understand is how to shim gearbox sprockets ?? There are some axial tolerances on the link above but dont know how to measure them ?? between each sprocket where shims are now ? and i set them to lower subscribe number ? how to you measure this with feeler gauges? or do i have to pay attention to anything else?
Ok Luka, I've picked these up in the Green Book which I have to hand. Diametral clearance as given in Laverdamania shouldn't be much of a problem. Check cogs running bronze bushes.
Side play is critical for gear box function and there isn't much to play with.
2nd gear to mainshaft end float: maximum, 0.5mm
4th gear to main shaft end float: max 0.5mm
3rd gear to layshaft endfloat: max 0.5mm
I didn't find specs for the selector drum, it's shimmed at either end but that is critical. 0.5mm difference is enough for the gearbox to be sweet cold, but for gears to clash in neutral when hot.
I found out when I bought my SFC with a dodgy gearbox. All was well cold, but when hot, gears were touching. Took it aoart 3 times in a week!
I'd recommend drilling that selector drum to lighten it. It's weight and inertia is for a lot in the slowness of 750 gear boxes.
Paul
Side play is critical for gear box function and there isn't much to play with.
2nd gear to mainshaft end float: maximum, 0.5mm
4th gear to main shaft end float: max 0.5mm
3rd gear to layshaft endfloat: max 0.5mm
I didn't find specs for the selector drum, it's shimmed at either end but that is critical. 0.5mm difference is enough for the gearbox to be sweet cold, but for gears to clash in neutral when hot.
I found out when I bought my SFC with a dodgy gearbox. All was well cold, but when hot, gears were touching. Took it aoart 3 times in a week!
I'd recommend drilling that selector drum to lighten it. It's weight and inertia is for a lot in the slowness of 750 gear boxes.
Paul
Great thanks for help and advice about drilling selector drum do you have some photos of drilled drum or some advice where to drill?.
How did you solve your problem with selector drum? the only missing information is end play of selector drum and i know that this is the most important. I rebuild couple of ducati engines but i have workshop manual and all infos were inside + all needed pictures so it was like walk in the park.
How did you solve your problem with selector drum? the only missing information is end play of selector drum and i know that this is the most important. I rebuild couple of ducati engines but i have workshop manual and all infos were inside + all needed pictures so it was like walk in the park.
Get hold of 750sf manual tolerances are in back. But as Piet said its not straight forward if you do it right you will need to press on and off the end bearing at least a couple of times and I've done it 1/2 doz to shim and remeasure to get every change perfect. Each time you change it has an effect on the gears down stream. So while not hard a lot of patients and knowing where your fixed point are on each shaft are, there at opposite ends so you have a x over movement. You also have to remember that the dogs have a slight taper on the faces so pull into each other when loaded so you have to check the fork clearance on the engauged dogs with them held hard together. They will look ok at rest but when held hard can load the fork. I have also see the fork have casting lumps on them straight out of the factory that were wearing on the wrong spot on the shank of the fork, look for wear arks in the wrong spot. ( I have some pic will put them up when I find them. )
Will
Will
Yogi
Hero member
- Location
- Bellingen NSW Australia
...and I like to add that Will did a fantastic job of shimming the gearbox on my SF1 when rebuilding the engine. I know he spent a good deal of time getting it the way he wanted, and it shows - made such a difference.... Thanks Will!!
Yogi
Yogi
There you go Luca for the selector drum. It's the one on my electronica which has the sweetest gearbox of any 750 I've riden.
When I bought the bike, a first start up revealed not only a noise in the gearbox in neutral due to that selector drum being badly shimmed but also plenty of aluminium particles due to the cogs having been shimed with home made aluminium shims!
Paul
When I bought the bike, a first start up revealed not only a noise in the gearbox in neutral due to that selector drum being badly shimmed but also plenty of aluminium particles due to the cogs having been shimed with home made aluminium shims!
Paul
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Simonr501
Hero member
- Location
- Lympne, Kent. UK
Paul Marx said:
Coca Cola cans do have their uses you know!!!!
