Maybe it is as simple as enlarging the holes on the front mounts .... install the engine with correctly sized washers external to the drilled out holes .... then simple weld the new washers in place.
Could be that simple.
Alastair.
Broken Cota frame
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Re: Broken Cota frame
petenz wrote:FM350 wrote: The best way might be to remove the mounts which are out of line, and reweld them in the right place?
WHAT ?..
the frames is what has moved , twisted..e...
I agree it is stupid to try and cut then reweld the mounts - maybe if I had access to a machinists workshop and skills - but I don't.
However the frame has not twisted - the mounts all line up longitudinally through the frame - the forward mount is simply closer to the middle mount than it should be. Frame may be bent but not twisted
Re: Broken Cota frame
As you now have a bent frame, unless you are able to get it straight again, cutting off and re-welding the pair of mounts which are out, is by far the easiest way to do the job properly. Although its a bodge, drilling the holes bigger on the mount thats out and fitting the bolt using thick washers that are then welded on will work, but looks a bit of a mess.
To most easily sort the frame out, cut off the set of mounts which dont line up, fit the motor into the frame and put in the bolts that do fit and tighten, bolt those that have been cut off to the motor, align them side to side, and MIG weld back onto the frame.
The only other likely problem is that if the front down tube has pulled due to being TIG welded without using a jig, is that the headstock might not now be at 90 degrees to the swinging arm spindle, and if so this will need to be aligned properly.
To most easily sort the frame out, cut off the set of mounts which dont line up, fit the motor into the frame and put in the bolts that do fit and tighten, bolt those that have been cut off to the motor, align them side to side, and MIG weld back onto the frame.
The only other likely problem is that if the front down tube has pulled due to being TIG welded without using a jig, is that the headstock might not now be at 90 degrees to the swinging arm spindle, and if so this will need to be aligned properly.
Re: Broken Cota frame
i would drill out the engine mounts and stick the engine and backwheel on, make sure it is alligned perfectly[rear sprocket to front sprocket] then weld on the washers. But you have to make sure that the steering head is straight first, eg put the forks/shocks/wheels back on . you may then have the only straight cota on the planet 
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Takhli44
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Re: Broken Cota frame
pop wrote:i would drill out the engine mounts and stick the engine and backwheel on, make sure it is alligned perfectly[rear sprocket to front sprocket] then weld on the washers. But you have to make sure that the steering head is straight first, eg put the forks/shocks/wheels back on . you may then have the only straight cota on the planet
I had a Bull with a broken/welded frame and the front wheel sat about an inch right of center line and leaned left a bit. Rode pretty well though or I didn't ride well enough to tell the diffrence. Bottom line, you might want to try it before you twist it into shape as a twist can put stress on parts that may break later unless stress releived with heat. The washers can be made to the shape of the mount and look OK.
Don't let competition get in the way of having fun.
Re: Broken Cota frame
Sorry to repeat myself but there is nothing to suggest the frame is twisted - it looks straight and the engine mounts line up - the hole centres are not correct. I have an idea and will run with it - I will let you know how I go.
Re: Broken Cota frame
If your frame is bent enough to mean the motor wont fit, if you are unlucky it might also be twisted (unlikely though). Easy enough to check this, as you simply fit the swinging arm spindle, and check the steering head is at exactly 90 degrees to this using a cheap Ebay digital angle gauge. If you choose to do nothing and it is twisted though, as Tak44 says its not going to make any awful lot of difference on something like a 247 Mont.
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Takhli44
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Re: Broken Cota frame
My inclination is to insert a hydraulic jack into the middle of the frame and try to push the forward mount away - but will I break the frame in doing so?[/quote]
This is what I was refering to about putting stress on the frame.
This is what I was refering to about putting stress on the frame.
Don't let competition get in the way of having fun.
Re: Broken Cota frame
Takhli44 wrote:My inclination is to insert a hydraulic jack into the middle of the frame and try to push the forward mount away - but will I break the frame in doing so?
This is what I was refering to about putting stress on the frame.[/quote]
Takhli, it must be friday night overthere, perhaps one too many Kentucky vintage's?
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petenz
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- Bike: 77 montesa Cota 348
- Location: NZ
Re: Broken Cota frame
pop wrote:Takhli44 wrote:My inclination is to insert a hydraulic jack into the middle of the frame and try to push the forward mount away - but will I break the frame in doing so?
This is what I was refering to about putting stress on the frame.
Takhli, it must be friday night overthere, perhaps one too many Kentucky vintage's?
[/quote]I wouldn't be to concerned about puting stess on it... it was stressed any way or it wouldn't
have moved when the tube broke... you weld that meany tubes togeather its going to
be under stress because of weld pull... don't think they were put though a normalizeing
process after welding..
you will just be putting the stress back to where it was.. after all you are not moveing that far...
it may require heating to get it back.... the only thing to keep in mined is that a less stressed
part of the frame may move first.. where heating will go along way to stop that..