B44 has seized!

[jossbatey]

 I bought a BSA with a B44 newly rebuilt engine. The engine started life as a B25.

Well after less than 100 miles the piston nipped up. It is on its second rebore which is a bummer.
Took it apart and piston and barrel were bone dry
The oil pump must have been doing something as the oil was returning to the tank with the usual air gaps.

How do I check the oil is making it to the big end?

Thanks.

[chaz]

I wonder if a new bush was fitted but the cross holes not drilled.
if I was to strip the engine to check I would use an oil can to check,  as it will with a small force pump oil out of various holes.
Air lines could be used but wont show flow that an oil can would , if there is a small or blocked hole air will get through, oil pressure will back up.

[cdsdorset]

Quick question. Was the mixture correct. I have done a few snipped up engines now where people err other side of caution and run a bit rich. This usually ends up with "bore wash" taking the oil off the barrel wall.

[Spaceman]

Both the B25 and B44 engines used an end fed crankshaft - this meant that the oil from the pump passed through passages in the inner timing cover into the end of the crankshaft. The oil was prevented from leaking past the end of the crankshaft via an oil seal in the cover retained by a circlip.

If this seal fails or the seal pops out because the circlip has not been inserted, the oil will leak past the crankshaft back into the sump resulting in no oil to the big-end and none to the cylinder walls. Also, it is no unknown for the seal to be inserted the wrong way round. Also, according to Rupert Ratio, if you use a B44 crankshaft with a B25 inner timing cover, the crankshaft may not project far enough to engage with the seal resulting in no oil flow to the big-end.

It sounds as though the inner timing cover will need to come off to check what is happening with the crankshaft and oil seal. Unfortunately, I'm not sure there is any easy way of testing that oil is getting to the big-end without taking off the inner timing cover first.

[Spaceman]

It is also worth checking that the oil passageway from the crankcase into the inner timing cover is not blocked. The oil from the pump enters the cover through a hole on both sides just underneath where the end of the crankshaft engages with the small oil seal. On later unit singles, there was a small O-ring between the cover and the crankcase to seal the passageway but this is not there on earlier models. If this passageway is blocked then oil will not get to the crankshaft.

Problems could be caused if the O-ring is missing or someone has blocked one of the holes inadvertently with sealant.

[jossbatey]

I wonder if a new bush was fitted but the cross holes not drilled.
if I was to strip the engine to check I would use an oil can to check,  as it will with a small force pump oil out of various holes.
Air lines could be used but wont show flow that an oil can would , if there is a small or blocked hole air will get through, oil pressure will back up.

No bushes on mine, all roller or ball bearings I believe...

[jossbatey]

Quick question. Was the mixture correct. I have done a few snipped up engines now where people err other side of caution and run a bit rich. This usually ends up with "bore wash" taking the oil off the barrel wall.

I did wonder. The plug looked good. The bottom of the piston was dry of oil as was the crank and con-rod. There was no burnt oil under the piston...

[JulianS]

Piston seizure may becaused by being bored with insufficient piston to cylinder clearance - not unkown for an engineer used to boring liquid cooled engines to use too tight a clearance when boring an air cooled engine.

If using the B25 oil pump then it has a greater feed capacity than the B44 type, which uses a narrower gear with a thrust washer in the oil chamber on the feed side.

[cdsdorset]

Looking at that picture the gudgeon pins has got damn hot. The small end is probably scrap as well.

[Spaceman]

If there is no oil around the big-end bearing area (as well as the piston) then it looks as though the oil feed to the big-end is not working, possibly for one of the reasons mentioned above. However, before you pull the timing side of the engine apart, it might be a good idea to check the oil pressure release valve is ok. Although highly unlikely, if the valve internals were missing or stuck in the open position, this would divert the oil from the pump straight back into the sump with none going to the big-end.

[jossbatey]

Both the B25 and B44 engines used an end fed crankshaft - this meant that the oil from the pump passed through passages in the inner timing cover into the end of the crankshaft. The oil was prevented from leaking past the end of the crankshaft via an oil seal in the cover retained by a circlip.

If this seal fails or the seal pops out because the circlip has not been inserted, the oil will leak past the crankshaft back into the sump resulting in no oil to the big-end and none to the cylinder walls. Also, it is no unknown for the seal to be inserted the wrong way round. Also, according to Rupert Ratio, if you use a B44 crankshaft with a B25 inner timing cover, the crankshaft may not project far enough to engage with the seal resulting in no oil flow to the big-end.

It sounds as though the inner timing cover will need to come off to check what is happening with the crankshaft and oil seal. Unfortunately, I'm not sure there is any easy way of testing that oil is getting to the big-end without taking off the inner timing cover first.

Thanks for the information.

Distance from end of crank to crankcase face is 22.4mm (please see pictures)
Distance from lip of oil seal to face is 21,6. Not a lot spare...

Two other things I have noticed:
1)The inner timing cover has been machined away to fit over oil pump. Please see picture. Why did this need to be done?
2) The boss where the oil feed O-ring fits on is rather small. Barely bigger than the O-ring. Is this mismatch because the wrong parts are used?

Thanks...

[JulianS]

The machined rib to avoid cover pressing on the pump?

See below service bulletin.

[Spaceman]

Here's a pic of the timing end of a B25 crankshaft - you can see where the oil seal contacted it. If your crankshaft is only just contacting the seal then that looks to be a problem?

[jossbatey]

The machined rib to avoid cover pressing on the pump?

See below service bulletin.

Thanks 

[jossbatey]

Here's a pic of the timing end of a B25 crankshaft - you can see where the oil seal contacted it. If your crankshaft is only just contacting the seal then that looks to be a problem?

Thanks 

B25 crank does look longer. I measured mine and used toolmakers blue. The lip of the seal is 1mm in from end of crank shaft. I could remove circlip and pull oil seal out a bit like earlier models?