Ppuxley
Full member
- Location
- Sulham, Berkshire, UK
MY JOTA 120 REBUILD : THE FINAL CHAPTER
Been away from here for some time, so this isn?t ?what I did today? but at least brings me up to date on my 120 rebuild from my last post back in December 2015.
The refurbished rolling chassis finally went up to Keith in May 2016, I think it was, and the motor came to the front of the queue around November.
The work included
? New Liners
? New 80.6mm Forged Omega pistons to take it to 1133cc
? New KN special Arrow Con rods
? Dynamic rebalanced crank with new bearings throughout
? Camchain
? New valves, support bearings, but retained the 4C cams
? Indexed cam wheels
? Flowing of the head for the Mikuni RS36 carb conversion
? Quite a lot in the gearbox to account for a knackered mainshaft
? Witt DMC2 ignition, TEC coils
? Fork conversion
In Keith's workshop in Linwood
image by Patrick Puxley, on Flickr
Arrow Conrod to Keith's own spec; .....at the heart of the worlds most powerful engines!
KN Arrow Conrod by Patrick Puxley, on Flickr
Although the bill was eye watering indeed, and the overall time it took was long, all the work needed doing and the hours of care spent were more than fair.
This was all wrapped up in early 2017 and March was spent waiting for the weather to improve enough for Keith to put about 400miles on it to shake it down,
finishing up with a dyno run, in which he managed to get 101 out of it.
I think the only issue that came to light was what Keith called my ?booby trap?, of him not finding the breather ball that I had put up the breather tube for safe keeping when I sent everything up to him, so it had two for a while till he discovered it following some head scratching over the odd oil leak. Ooops!
First ride out with Keith Nairn, more than a little nervous after at least 10 years off the bike.
image by Patrick Puxley, on Flickr
So in early April the date was set for me to collect it and at Keith?s insistence- ride her back to Berkshire. We stayed an enjoyable night with him and Eileen in Kilbarchan before setting off on Friday morning for the ride home, which I did over a couple of glorious days on the weekend before Easter, having prised it from his grip, it being pronounced one of the ones he really didn?t want to give back. It was definitely right to undertake the long ride home, I got to know the bike again after such a long lay off and saw some great countryside on the way back as I tried to keep off the motorways.
Kirkstone Pass
image by Patrick Puxley, on Flickr
On the way home, overnight in the Dales, at The Traddock, Austwick
image by Patrick Puxley, on Flickr
We stayed a night in the Dales on the Friday night and completed the journey on Saturday. I was considerably younger the last time I rode a decent distance on it, so was quite surprised to be suffering no ill effects by the time I got back on Saturday afternoon, so on Sunday I went across to Blackwell for the ILOC AGM.
The oil was then changed again, on Keith?s advice. It now had getting on for 1000 miles on it and this was the 3rd change.
Now its home I have been making the most of the decent weather to get out and about on it, and get reacquainted.
It pulls like a train, with a really smooth delivery and has far more power than I know what to do with.
I couldn?t be more pleased with it.
ILOC Challenge 2017 180417 by Patrick Puxley, on Flickr
Ppuxley said:Last Post December 2015
Got the long awaited call from Mr Nairn, this evening!![]()
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My 120 motor is in bits and has the had the expert eye over it. The cause of the smoke is apparently down to a set of pistons, bores and rings that bear no fit to each other or anything that Mr Laverda ever intended.
Thats good news really- for there not to have been an obvious problem would have been more of a concern.
The proposal is to do Keiths bored out to just under 1200 version, with a realigned and balanced crank and new Carrillos.
The head will be undone of some previous poorly executed work and some more tractable camshafts installed
Not doing the Mikuni conversion at the moment and sticking with the Dellortos for now.
The other thing uncovered was a worn gearbox mainshaft at the sprocket end- a not unusual problem apparently caused by a lack of lubrication to the needle roller bearing and never sorted till very late on in the production run. A replacement will need to be sourced, so if anyone has something to offer please get in touch.
Great to know this is moving now, but under no illusion that I'll be getting the next call for a bit yet.
Been away from here for some time, so this isn?t ?what I did today? but at least brings me up to date on my 120 rebuild from my last post back in December 2015.
The refurbished rolling chassis finally went up to Keith in May 2016, I think it was, and the motor came to the front of the queue around November.
The work included
? New Liners
? New 80.6mm Forged Omega pistons to take it to 1133cc
? New KN special Arrow Con rods
? Dynamic rebalanced crank with new bearings throughout
? Camchain
? New valves, support bearings, but retained the 4C cams
? Indexed cam wheels
? Flowing of the head for the Mikuni RS36 carb conversion
? Quite a lot in the gearbox to account for a knackered mainshaft
? Witt DMC2 ignition, TEC coils
? Fork conversion
In Keith's workshop in Linwood
image by Patrick Puxley, on FlickrArrow Conrod to Keith's own spec; .....at the heart of the worlds most powerful engines!
KN Arrow Conrod by Patrick Puxley, on FlickrAlthough the bill was eye watering indeed, and the overall time it took was long, all the work needed doing and the hours of care spent were more than fair.
This was all wrapped up in early 2017 and March was spent waiting for the weather to improve enough for Keith to put about 400miles on it to shake it down,
finishing up with a dyno run, in which he managed to get 101 out of it.
I think the only issue that came to light was what Keith called my ?booby trap?, of him not finding the breather ball that I had put up the breather tube for safe keeping when I sent everything up to him, so it had two for a while till he discovered it following some head scratching over the odd oil leak. Ooops!
First ride out with Keith Nairn, more than a little nervous after at least 10 years off the bike.
image by Patrick Puxley, on FlickrSo in early April the date was set for me to collect it and at Keith?s insistence- ride her back to Berkshire. We stayed an enjoyable night with him and Eileen in Kilbarchan before setting off on Friday morning for the ride home, which I did over a couple of glorious days on the weekend before Easter, having prised it from his grip, it being pronounced one of the ones he really didn?t want to give back. It was definitely right to undertake the long ride home, I got to know the bike again after such a long lay off and saw some great countryside on the way back as I tried to keep off the motorways.
Kirkstone Pass
image by Patrick Puxley, on FlickrOn the way home, overnight in the Dales, at The Traddock, Austwick
image by Patrick Puxley, on FlickrWe stayed a night in the Dales on the Friday night and completed the journey on Saturday. I was considerably younger the last time I rode a decent distance on it, so was quite surprised to be suffering no ill effects by the time I got back on Saturday afternoon, so on Sunday I went across to Blackwell for the ILOC AGM.
The oil was then changed again, on Keith?s advice. It now had getting on for 1000 miles on it and this was the 3rd change.
Now its home I have been making the most of the decent weather to get out and about on it, and get reacquainted.
It pulls like a train, with a really smooth delivery and has far more power than I know what to do with.
I couldn?t be more pleased with it.
ILOC Challenge 2017 180417 by Patrick Puxley, on Flickr




