aprilia rs 125 crankcases will not go back together

[merky69]

aprilia rs 125 rotax 122

hi all, thanks for looking at my thread. any help will be greatly appreciated.

ok so to start with the problem.
simply the crankcase wont go back together they go as close as about 3-5 mm gap which i know is excessive any further seems like its being forced

the job that's been done was main bearings replaced, the crank is all the way in Rh side case.

it seems to come together over the crank if you force it but the gap over the gearbox side is still there.

i immediately thought it has something to do with the gear box so i removed and replaced and its still the same.

maybe i'm doing something wrong i do not know?

but they wont go back together

please help

[Kickstart]

Hi

I would suspect a locating dowel is catching.

However, note that you are meant to pull the crank into the crankcase half, not press the crankcase halves together over the crank. Pulling the crank into the crankcase half avoids pre loading the main bearings.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[merky69]

[merky69]

Checked the dowels are goin in fine from what I can see I've got a pic here that shows me puttin just hand pressure on crank side to show it go down but it jus won't go down gear box side any more suggestions please

[andy_uk]

[bladerunner]

Something is stopping it going together so fair does for not just bolting it up and hoping that worked! Sometimes it can be gears not meshing....so try turning gear shafts,crank,water pump.....balancer shafts etc to see if that helps it drop in......failing that take it apart and strip the cases....if they go together....fit the crank and try again....then the gearbox etc etc....at least that way you find out what the problem is. Slow but you'll know for next time! Try the fit each time! Also worth checking your crank is central on the mains as if the bearings don't slide fully home your in for short engine life. Also worth setting the piston to TDC and your balancer shaft with the weight at BDC as the marks on the 122 motor are known to be miles out giving you dumper truck levels of vibration if you take them as correct!
____________________
Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[merky69]

thanks for the help guys ill get the tools out soon and investigate further , thankyou for the help

the funny thing is i know ive got to be doing something wrong ive got 3 engines in bits that are doing exactly the same thing lol.

ive rebiult loads of these engine doing main bearings jobs and gear box jobs and never had this problem before so to baffle me with 3 engines having the same problem at the same time is a bit too coincidental.

thanks for the suggestions anyway guys

[merky69]

OK SO I TOOK ON THE SUGGESTIONS PLACED HERE.

i stripped the cases of nothing they come together flush very easily

put the crank in they come together flush easily

put the balance shaft they come together flush easily

put the input shaft in they come together flush easily

so i have found that what is stopping them coming together easy is the output shaft bearing (LH side of case) is struggling to go over the out put shaft it seems to be gettin jammed and not lettin the case come together. i dont quite understand as the case did come apart easily .

[Pete.]

Inspect the shaft for burrs and make sure there's no old bearing fit on the surface where it's been assembled before. If you can get the bearing out of the case you can try pressing it onto the shaft by pressing on the inner race, then assembling the lot into the cases afterwards.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[merky69]

still a no go

ok so to try narrow the problem further it seems to be when the full gearbox is in place it just will not go.

if i take one shaft out it goes on with ease

(remove input shaft leaving output shaft in there goes in with ease , do opposite leaving the input shaft in there goes on with ease(

both in there together and the case gets stuck

any more suggestions please been trying ll sorts for hours today and had no success

please help

[Pete.]

Are you sure you have assembled the clusters properly?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[andy_uk]

[andys675]

are you sure the main bearings are correct?

IME

on DT125R and honda visions, one or both of the main bearings are thinner than ordinary bearings, if you use off the shelf bearings the cases won't go back together because of this and you have to use OE bearings
____________________
Some people feel the rain, others just get wet.

[merky69]