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gunnag

I once fitted a WD B40 engine into an OIF B25 frame, my thoughts are as follows:- - the rear engine mount needs spacers fitting as already mentioned - the frame cross member will foul the oil manifold as Kommando mentions, easiest solution is to cut out the cross member, it doesn't affect the frame ...

gunnag

Fantastic work MM and thanks for sharing this info which may be of some use on my B44 which currently uses a JRC 28 (Kehin PWK replica). I've often wondered about getting more performance from my B44 including gas flowing, bigger valves & carb etc. and why the unit single BSA's couldn't quite get th...

gunnag

Regarding the plug on the outer gearbox/timing cover, its definitely meant to be an oil filler/level plug for a B40WD. Have a look at the B40WD workshop manual on the BSA unit Singles website Here plate A10. There's also a handy B40WD parts list Here which shows the plug on plate A11 part 20 which i...

gunnag

IMHO the best way to ensure the springs and screws don't come undone is to use lock wire, don't rely on the pip or the springs being wound the right way, they invariably come loose unless lock wired in place.

gunnag

Well done Beat, great to see you have finally got it working :)

gunnag

I had exactly the same problem when I rebuilt my B44 several years ago using a JCC piston and iron rings. The bike would smoke loads on startup and when warmed up despite a hard run-in process and a coarse hone. I swapped the rings for Hepolite versions and a fresh hone but the problem persisted. Ev...

gunnag

If you cant get the Esso ethanol free unleaded in your area then one possibility is to use Briggs and Stratton fuel stabiliser which claims to keep fuel fresh for up to 3 years. Admitedley its meant for lawnmowers but I cant see it doing much harm in our old nails, see This Link.

gunnag

Dont know if this helps but looking on eBay there is a B40WD enclosed chainguard and a B40/B44 chainguard available:-- - the first one is for a B40WD its the fully enclosed version, it seems original enough, maybe you could just loose the lower section if you dont want fully a enclosed chaincase, se...

gunnag

This does not apply to Scotland or the South West where there are no reliably ethanol free petrol of any description. I can't imagine why Esso would have different formulations for Scotland and the South West, but perhaps its related to the capabilities of refineries in these areas? I guess you wil...

gunnag

The problem is that it does not have that big a demand so it can get old

Thanks for that info, luckily I have at least 6 Esso stations nearby which stock super unleaded and they all seem to be busy with customers. My guess is that the super unleaded is used alot so should be fresh in the tanks.

gunnag

From my research only Esso super unleaded (97RON) has no ethanol That's a top tip and the lack of ethanol is confirmed on the Esso UK website, see This Link , they also have a UK petrol station locator so you can find your local outlet. I'm going to fill my bikes with Esso super unleaded and see ho...

gunnag

Some worthwhile fixes I have tried on unit singles to cure rocker box and cylinder stud leaks are as follows:- - countersink the rocker box stud holes on the cylinder head to remove any 'pulled up' metal, this will help ensure the rocker box flange on the head is reasonably flat and help prevent lea...

gunnag

I'm using Cords rings on my B44 and can recommend them, see This Link for the original post.

gunnag

Good question B44Claus and as an owner many years ago of a Ducati Darmah 900cc Bevel drive which used Dellorto PHF carbs with accelerator pumps, I often wondered whether these carbs would be useful on other bikes. If I remember correctly, the purpose of accelerator pumps is to enrich the mixture whe...

gunnag

Some thoughts which might be of use:- - have you checked the gearbox oil level? Its common for the gear box oil to slowly leak out as well as emulsify into a brown sludge, hindering lubrication - the engine and chain-case share the same oil so although there are traces of silver in the oil, if youre...

gunnag

I have never tried the K-Line guide insert system but it looks like a good idea and I agree that its best to keep valve guides in place since removing them causes wear in the head. One of the motorcycle head specialists who offers this service in the UK is the Cylinder Head Shop, see This Link , so ...

gunnag

Try using a tank of fresh petrol, cleaning out the carb bowl and idle circuit, which is notorious for becoming clogged.

Additionally try a fresh plug and make sure the battery is showing at least 12.5v which is essential if using electronic ignition.

gunnag

There was a post on this site years ago titled "High RPM B40", see This Link , some of the authors recommendations included:- - b44 crankcases, late b40 crank lightened and balanced to 66 percent, late b40 rod and bigend bearing, rod polished, bsa b44 slipper piston, b44 cylinder shortened because o...

gunnag

I'm rather doubtful that these are actually B44 cases (though I'm willing to be proved wrong), some of the issues I see are as follows:- - the oil pump mounting on the inner timing case appears to use three studs, as far as I know B44's only used two studs. I believe 1971 onwards B25 and B50 models ...

gunnag

I had the exactly the same problem with my B44 and the problem was eventually traced to the fact that I was unwittingly using a high output 3 phase alternator. This type of alternator requires 2 zenor diodes to cope with the wattage generated and a single zenor wont cope by itself and will blow. Che...

gunnag

B44's usually rev quite freely so I imagine your problem is related to ignition, carb, charging or exhaust, so lets tackle them one by one. Ignition, according to the Rupert Ration unit single manual, the timing for a 69 B44VS is 29-31 degrees btdc, so almost what you have but not quite. When timing...

gunnag

First thing I would check is the oil pump, if you have an OIF B25 then you should have the three stud iron bodied oil pump. This pump should use the larger feed gears to generate pressure for the plain bearing big end, note that it was only the B25 which needed high oil pressure, other models such a...

gunnag

Some random thoughts which may or may not help:- - check the tappet clearances, sometimes after a rebuild the clearances can increase or close up causing problems. I would also check the pushrod end caps, sometimes they can mushroom on the soft alloy pushrods - check the coil has the correct ohms an...

gunnag

Although the carb is new, the idle jet could have become blocked with debris after a few hundred miles, so I would try cleaning this out first and see if there's any improvement.

gunnag

On the B40WD I believe it was the 1st, 2nd and maybe 3rd gears which were especially low geared for off road use, I think 4th gear was unchanged and the same as normal unit singles. The other big change you can make is to swap the crank sprocket (23 teeth ?) to use the B44 28 teeth version. I did th...

gunnag

I think there is a reasonable amount of gearbox part interchangeability between a B40 WD and the pre OIF B25, your best source of information on the differences will be the Rupert Ratio Unit Singles Engine Manual, see This Link . I once built a pre OIF BSA B25 with a B40 WD engine. One of the first ...

gunnag

Just a thought, but perhaps the leak is actually on the timing side between the inner cover and gearbox gasket flanges. With the bike leaned over the oil could be leaking from the timing side area and running down the gearbox case bottom to the drive side and then dripping onto the floor. What happe...

gunnag

Is the raised lip of the commonly available gaskets a neccessity ? I don't think the raised lip on gaskets is essential, although it probably helps to ensure a good seal between the head and cylinder. Sometimes people reuse head gaskets and re anneal them by heating up to red hot, in these situatio...

gunnag

When I first built my B44, I had trouble getting a good seal around the head gasket and found the pattern copper gaskets were on the thin side. This caused all manner of problems including oil leaks around the oil drain and pushrod tunnel. In the end, I decided the fire lip on the barrel was protrud...

gunnag

Regarding the oil leaks, I have managed to seal the sump plate on my B44 by using a SRM type alloy sump plate together with changing the original 4 mounting studs with socket caps and using thread inserts in the crankcase holes (with loctite thread sealer) as the original threads invariably strip. I...

gunnag

I'm not sure whether an EP (extreme pressure) gearbox oil is actually needed in unit single gearboxes and as far as I know, this type of oil is intended for situations where there is sliding contact between gear teeth such as in differentials which use bevel gears. Some of the original early specs f...

gunnag

Could be several problems causing the engine not to rev past quarter throttle, here are some random things I would check:- - what happens to the battery voltage when you rev the engine? Maybe the battery is being under or over charged? Also check the battery earth connection and that the engine is e...

gunnag

Sounds like the tank is rubbing against the frame and causing it to resonate. Usually on BSA unit singles there are rubber buffers mounted between the frame and petrol tank to stop this kind of resonance so I suggest you have a look at the relevant parts list for your B40 model/year and check everyt...

gunnag

This is the same problem I had with my B44 when it was belching oil and I eventually discovered the fire lip was too high causing a poor seal with the head. On mine, with the head and barrel mated, I used feeler gauges to measure the gap that the gasket is supposed to fill. I worked out I had 0.5mm ...

gunnag

Ahh the old B44 belching smoke scenario, I've had this problem on my B44 which defied all efforts to solve it for several months. Eventually I cured the issue which involved several steps as follows:- - I sealed the head gasket/cylinder joint using a new copper gasket of the correct thickness togeth...

gunnag

Looking good

Check the oil return asap

gunnag

Check the Owners Manuals on This Link for unit singles including C15's, B40's, B44's, C25's, B25's and B50's (1962 to 1973). You will see that up to around 1967, the recommended oil for the gearbox was the same as the engine and from 1968 onwards, the recommended gearbox oil was EP90. I assume this ...

gunnag

I would clamp the ring gently in a vice with a tiny amount standing proud, then use a very fine file to carefully remove excess metal. Then refit and remeasure. By the way, make sure you run the rings in to ensure a good seal and compression. When the bike is first started, ride it straight away and...

gunnag

The part number stamped on the piston definetly identifies it as +40 oversize so you can go ahead and order +40 rings. The compression rings are 1/16 inch thick whilst the oil control ring is 1/8, this is fairly standard accross many BSA's of the era, however the ring gap needs checking to ensure a ...

gunnag

The 100mm actually means 1.00 mm oversize which is nearly the same as 40 thou (second oversize). The part number 71-2751 identifies the piston as BSA B50 +40 oversize slipper type, 10:1 compression. I would take your piston back to the machine shop and get them to measure the piston and bore. The co...

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