should I or shouldn't i ?

[DAVE BRADY]

Hi,

My '68 Thunderbolt has covered a possible 130,000 miles without a full rebuild.  I bought it with perhaps 25,000 already covered and I have done the rest along side my wife's 51' Flash which shows about 115,000 miles so corroborating my mileage.  Even allowing for some inaccuracy in the mileage recorded by the speedos it is still quite a bit.  Both have needle roller timing side conversions and have been run on 20/50 oil with inline filter.
So the dilemma is, do I strip it down and overhaul the bottom end or wait a bit longer?
Until recently even when the engine was very hot the oil light would stay off at tick over so indicating enough oil pressure.  During our return from Belgium whilst enduring up to 42ºC the oil light had started to flicker and a tad of throttle was needed to turn it off.  Similarly, after a very spirited run locally on a hot day, the oil pressure light behaved the same way.  I will have to do a sedate run as a comparison but I suspect that the time has come for a bottom end overhaul.

Dave.

[Spaceman]

If it was me, I think I would try to measure the oil pressure to quantify whether there is a problem with it or not. That said, you've probably had your money's worth out of the current set of big-end bearings and it may well be time for a new set?

[ducati2242]

if in doubt .

[DAVE BRADY]

Hi,

I think I will strip it down.  It would be a shame to push my luck and end up with damage rather than wear. 
It will be interesting to see if there is any wear in the main bearings and if the it is just new shells needed or a regrind as well. With having been run a full detergent 20/50 with a filter it will be interesting to see how much sludge, if any, has built up in the crank.

Dave.

[Mike Farmer]

 

Dave. This is an interesting dilemma. Your decision to do it has to be the right one. As stated "if in doubt, theres no doubt".  I would be very interested in the amount of crankshaft wear so would appreciate it if you could keep us in the loop.

Mike

[chaz]

Dave, a dilemma Im looking into, The A10, I rode a few weeks ago for 3 miles. thats the first time Ive ridden it for 11 years! Ive started it a few times over the years but it wet sumps. As you know, this means a total strip of the motor.
Do I want to do it??? The T100 was running, I thought a tidy up, so £2500 later its rebuilt.
Didnt need it but hey ho.
The recent import A50 has been stripped, the cases are still away 20 months later along with crank so if I take A10 apart how long will that be off the road AND with finances being hit by energy prices etc, will I be able to afford it?
The B40 has just been finished but has to be sold to recoup the £2500 spent on it and son needs his money out of it for his investment in it.

I suppose, as you ride it a lot, its worth it to you to check and rebuild, once the A50 is finished, Im not doing any more. Availability and quality of parts being the main hang up, machining services the next. In the past I would have machined myself, had works contacts for paint and chrome. As previous discussion quality of parts has been talked about, I liked to do my own but you just have to put up with what you can get and put that right.

[DAVE BRADY]

Hi Chaz,

As your A10 stands for long periods some wet sumping is almost inevitable.  There is a trick to avoid stripping the engine to replace the spring and ball. 
Remove the pump and carefully drill out the hole that contains the ball and spring to release them outwards.  Ensure that all bits of aluminium are removed and the drilling is smooth.  Use some suction if possible.  Seat the new ball on the back of the pump ensuring good contact all around and refit.

Dave.

[chaz]

thanks Dave, will look into it, but as mentioned... 3 miles in 11 years, probably needs a decoke at the least, the Triumph started that way!!

[Mike Farmer]

 

The expensive words--"while I'm at it I'll just check"

Mike

[paulm]

My Question is the loss of oil pressure, i have never had a Engine end fed (Genuine bushes are fine) so how would rebuilding cure that as on the old engine worn bush loss of pressure on a end fed what controls the pressure

[JulianS]

Wear or other damage to the end feed oil seal will reduce pressure.

[DAVE BRADY]

Hi Paul,

Yes, with the bush the oil flow to the big ends is dependant on a good fit on the bush.  This obviously helps to keep the oil pressure up.  The big end shells also contribute to the oil pressure.  Shells within tolerance offer resistance to the oil hence pressure is created.  Worn shells offer less resistance so oil pressure drops.
No matter how good your pump is, it is the resistance to the oil flow that causes the pressure, so lower resistance results in lower pressure the pressure.  A good pump will certainly ensure a good flow which is as important as pressure.  At tick over the pump is proving very little pressure and very little flow so this is the danger zone.  Less oil is also bad for cylinders and at tick over there almost no 'splash' up the bores.
Although it is nice to have slow and steady tick over it is probably not good idea to leave and engine ticking over for any longer than necessary. 
As part of my pre strip down I will see what rpm I have at tick over and what increase is needed to keep the oil light off when the engine is very hot. 
Just to throw another variable in, is the oil pressure switch working at the right pressure and, as Julian said, is the seal in good order?

Dave.

[DAVE BRADY]

Hi,

A bit of an update.  After good ride to warm things up I had a reliable tick over at 700rpm and the oil light was on. Increased the rpm to 1000 and light went out.  Previously the light would not come on at all with the engine running at 700 rpm.  So I have a base line to work from so next I will try a different oil switch.  Although that one may not be perfect either.  Is there a way of testing them?

Dave.

[Bess]

Hi Dave,
             The switch could be tested by connecting it to a tyre inflator and calibrated gauge.

Best wishes...

[DAVE BRADY]

Hi,

I decided that I should as even if the oil pressure switch was iffy I have put a doubt in my mind.  Also, considering the mileage the bottom end has done I thought better to do it now than wait until a disaster.
So with the with the primary and timing sides stripped it was time to start having a look.
The crank pinion was quite happy to stay where it had been last 30+ years and well over 100,000 miles but with persistence and a much modified two leg puller I managed to get it off.  I suspect a bit of a Loctite product had been used.  I had to be very careful as the quill of the end feed had to be protected at all costs.
So once the pinion was off the inspection could begin with the outer race of the ball race being first.  For those of you not familiar with the bearing used in the end feed conversion there is a radial ball race that locates the crank to the timing side.  A couple of photos show what I have found so far.
You can see that the bearing surface is visibly rough but is not that rough as to be very noticeable to the touch but never the less, as I now know about it, replacement is necessary.  The other image is perhaps a bit dark but look closely and the wear (arrow) to the cage for the balls can be seen.  Again, once known about it has to be replaced.
I will post a few more images as I progress with the strip down.

Dave.