Jota frame front tubes

ngiles

ngiles

Senior member
Location
Sydney, Australia
I'm in the process of getting the frame sprayed on the Jota. The painter wondered whether the shape of the front tubes of the frame is as intended. I have assumed that the slight kink on the right one (looking from the front) is intended not to be totally straight as it fits the engine mounting comfortably. Just to be sure I attach a photo and seek confirmation or alternative view.

Cheers Nick
 

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Is that good engineering practice?? Remember having a heart attack seeing that on my Jota for the first time...
 
Here's one I prepared earlier. You can also use the sheen of the original silver paint as a reference

 

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I had one owner who had straightened that tube before he brought the bike to me for restoration. 
 
I remember frantically looking for pictures of Jotas...recall it was shown and pointed out in Andy Wagner's Laverdaparadies catalogue.. a very useful thing to have btw
 
the 1000 prototypes had a "cut and shut" on the LHS front exhaust pipe, right on the exit of the port, to clear the prototype (straight) frame tube.

In production they all had square on exhaust pipes and a kink in the left front frame tube, it must have been cheaper, and since the frames are stick welded from gas barrel, the kink does not produce any  ill effects. It would probably take 400 tonnes in tension to straighten the tube, (much less to push it sideways with a risk of flattening) so not likely to happen when under normal running

CLEM
 
CLEMTOG said:
the 1000 prototypes had a "cut and shut" on the LHS front exhaust pipe, right on the exit of the port, to clear the prototype (straight) frame tube.

In production they all had square on exhaust pipes and a kink in the left front frame tube, it must have been cheaper, and since the frames are stick welded from gas barrel, the kink does not produce any  ill effects. It would probably take 400 tonnes in tension to straighten the tube, (much less to push it sideways with a risk of flattening) so not likely to happen when under normal running

CLEM
Click to expand...
Hmm so when did they change to round headers then ? (bolt)
 
No! No! You're all wrong! They're BOTH supposed to be bent take it to a reputable frame builder and have him kink the offending straight arrow to match.

8) 8) 8) 8) 8) (goodjob)
 
Piranha Brother 2 said:
No! No! You're all wrong! They're BOTH supposed to be bent take it to a reputable frame builder and have him kink the offending straight arrow to match.

8) 8) 8) 8) 8) (goodjob)
Click to expand...

That?s a statement to confuse everyone Q. Right side straight left side bent.
 
It's not really a bend so much as the down tubes being completely asymmetric above the engine mount.  The left downtube comes out of the headstock at a shallower angle and goes vertically down just like the right tube, but closer to the centre line of the bike.  Below the header it then kicks back out to be symmetrical at the engine mount.  Pretty impressive tube bending to make the whole thing, would have loved to see the production process.  Davo's photo above shows it really well.  You'd have a hell of a time getting it 'straight' ie symmetrical!!

On an RGS I think the down tubes are symmetric down as far as the outer upper tubes and also at the engine mount.  On the left tube there is a proper kink in between for the header, I can well imagine this being able to be straightened out and have heard anecdotes of it being done.  :)
 
I still remember my first triple restoration, when I sandblasted the bare frame and saw the bend in the downtube I thought I had a real problem to deal with. Still bugs me when I notice it...?.

sort of like the "red line" on the triple tach, way too low because of the tach from the 750 twin also being used on the triple, one of these days I am going to have my tach rebuilt with a proper redline...?

Paul LeClair
 
The redline on a twin bears no relationship to the redline on the tacho either. I have heard that the red zone simply means 'don't  stay in there for extended periods of time'!! Not sure I believe the story. But I have always treated 8,000 as max revs on my twin. I ended up using a Honda tacho and 10,500 or 11,000 became the new redline. It's all relative. Later I had a new face printed up so that 11 became 8 ... with no redline.

The reason triple tachos have the same redline has nothing to do with it being based on the twin.

My Marshall goes up to 11  :D
 
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