May 2023
The latest of Allan's bikes in the form of this tidy Thunderbolt aka A65T. I have never ridden or even heard this bike run, so it will be a case of checking everything and recording compressions and oil pressures.
I had better swat up on what are good figures and what are not.
Sweet looker...
There is not enough room in my shed to begin work on this bike in earnest, so it will wait until the soon to be complete Norton leaves. However, while awaiting parts for the latter, I spent some time rebuilding the broken indicator assemblies with parts from Allan's copious collection of indicator bits.
Very happy with the result.
As can be seen in that photo, the bike has Koni rear shocks, which were pretty upmarket fitments in the day. No doubt they will have improved the ride.
It seemed that the carb was gummed up as the throttle would not operate, so the carb came off for first attention.
When the carb is off is the best time to do compression tests, as it saves one from having to hold the throttle wide open while kicking repeatedly and supporting a gauge etc. Right side was first and without any oil down the bore, so as to get a worst case scenario. Must have been years since this last ran.
That - is very impressive, even disregarding the layup period. I understand that the Thunderbolt has less compression than the Lightning, so this bodes well.
Not that it means the other pot will be as good...
Ok. Its better.!
I doubt that Allan put many miles on this bike, so perhaps it had received engine work before he bought it. Not sure when that was, but it gives the impression that the head and cylinders, rings and valves, are all in good condition indeed.
All the oils got dumped and replaced, with straight 30 in the primary, 20W50 engine and synthetic 75W90 in the gearbox.
The carb was stripped, cleaned, alloy float needle fitted in place of brass, needle lowered to correct position and float height adjusted. The fuel lines were way past best-by, so a new set was made up and fitted. That completed the fuel system, and it proved free of leaks.
Cleaning everything as it went back on was getting us looking better all the time..
The sidecovers came off to rectify some nasty wiring issues which I felt needed sorting before putting a battery in it. The fuseholder needed new wires attached to it, and there were a number of connections under the seat that must have been causing a few misfires.
The left side switch paddle on the bars was broken, so the indicators were really hard to work. I found a good used one from a later model which worked successfully so that was a fortunate fix.
There were disconnected earth wires in the headlight, and fixing those got the indicators suddenly working, after which I was game to test everything else and all was well. That resulted in a test run and carb tune, after which I connected an oil pressure gauge in place of the oil light switch and did another start.
Cold idle gave us a sniff under 400KPa, or 56psi in English. I think that sounds respectable.
A short ride around the local perimeter was enough to get things properly warmed up, and when I returned we had about 43psi hot idle. That all looks good to me.
Reassured that we have a sound engine, it was time to do the dirty stuff - removing the wheels to measure everything brake related, make sure bearings and tyres are ok, and of course - cleaning the brake assemblies and adjusting them to optimum operating clearances.
Rear first then..
Pleasingly the rear brake linings and drum were all above board, as were tyre and bearings.
Lets try the front then..
Same again, which is a real blessing. It takes an inordinate amount of time to do all this, which we forget when we only ever seem to remove one wheel for a tyre change every 5 years. Drum brakes also have a lot more grubby bits to clean and adjust.
Never mind, it gets us past the compliance test, and I include these photos with the paperwork so it can be seen to have been done.
A test run proved the bike to be a delight to ride, and apart from a quick tune of the carb when it was hot there was nothing left to do but arrange the compliance test.
It took 2 weeks to organise that, and another 6 days while the bike was left in their care before I got the call that it was done. No comments from their end at all, so it would seem they were as happy with it as I am. The price for compliance/plate/rego has now risen to $400. Figures.
Today the new plate went on, and the gearlever got repositioned as my large boot was having trouble fitting between it and the footpeg. A little play removed from the throttle cable and it is as good as it may ever be.
I know a man who wants to test ride it.
A couple of interested chaps showed up so we all went for a ride to see how impressed they might be. Unfortunately, I was not too impressed from the start.
Now that I could ride behind it I could smell oil burning although not see it until we got to the open road, whereupon it gave off a moderate amount of smoke on the left side. Of course I had been totally unaware of that while I was riding it, and the performance and the compressions gave no hint of either cylinder being other than happy.
I watched closely to see when it actually exhibited the smoke, and it was under acceleration. This would tend to eliminate worn valve stems or guides as the culprit, but suggest rings in trouble. There is a slight chance that the rings are just a bit gummed up from long storage, so it may be worth trying a remedy for that by the way of oil additives, but failing results it becomes a decision of what to do next. If the head comes off it becomes a matter of having to remedy everything that one finds in need, although at a mere 18,000 miles I think the first diagnosis may be the right one.
I shall ride it a few more times to see if things loosen up at all, but currently the plugs look like this.
While the smoking gun is indeed the plug on the right, the left one looks to have been running rather rich too.
Another thing occurred. I rode the bike across town to collect some parts. This involved a slow crawl through city traffic on what had developed into a long overdue hot day. The bike performed beautifully, but when I was about to park it in the shop carpark I noticed the oil light had come on. I gave it a rev and the oil light went off, but at the roughly 500rpm setting it came on again. I rode it home keeping the idle speed up to avoid the light and once home let it cool down. I then started it again and everything was back to normal.
This behaviour had not occurred on any of the previous rides, but they had been open road events and the weather was a fair bit cooler. So - what do we now know.
The smoking problem indicates that the rings are not doing their job properly. This may respond to a hone and a set of rings, but could amount to a rebore and new pistons. In either case, the engine will then likely develop more compression which would put a greater strain on the bottom end, so you would not leave that to chance.
If we allow for a full engine recondition it is hardly likely that we would recover anything extra in resale above normal market price, so it would make more sense to offer the bike as-is for a fitting price. The bike starts and runs perfectly, does not oil plugs or otherwise misbehave, but to avoid any possibility of causing it harm I would consider it necessary to overhaul the engine to some extent, depending on what was found.
I figure I could do a pretty comprehensive job for well less than 2K, but I would not be paying for someone else's labour. We are going to offer the bike for 7K initially and see what happens.
It has recent wof and 12 months rego with its new plate. I will notify my people by email and see if anyone wants to run with it. Give me a yell if you would like to check it out.
Meanwhile I will put an oil pressure gauge back on to see that we do not have a faulty oil pressure light switch. It can happen.!
No - the low pressure is for real, so either not pumping enough oil, or too much pressure escaping which would mean worn bush/bearings. On the other hand the smoke seems to have tailed off with increasing use, so it would be feasibly possible to just use the bike as-is for the time being.
Have drained the oil and filled with Penrite 20W60 to keep things safe.
Cheers all