BSA B50 -500 APG Build

[Koncretekid]

Thanks,
I dunno.  BSA always has lots of mechanical noises!  I'm thinking small end of rod in piston.  I had an issue last year with this motor with the pin sticking in the piston.  Probably lack of oil to small end.  It didn't help that the oil pressure gauge blew off it's needle on day 2, and I couldn't read the air/fuel gauge in the bright sun.  Following is a picture of the bike as it ran in open class (APG).

[Nortonist 592]

We don't need no steenkin' gauges!   Hope thats all it is.  So long as thee were no foreign objects poking out of the crankcase.

[Old Scrambler]

Motor noises in a BSA are somewhat related to motor noises in a Triumph.............some are just more serious (expensive) than others. I hope your not trying to purchase the same fairing I am looking at for my T20!  Hope to see you next year.

[wobblywalrus]

As best as I can remember, those engines needed frequent tear downs and inspections under racing conditions and the rod bearings were weak areas.   Do not run it if makes new or loud noises like a loose rod bearing.  It is best to tear it down and to investigate.

One thing I did on all tear downs was to mount the cranks between centers, check the flywheel run out with dial indicators, and to true the flywheel with a lead hammer.  Usually I fussed with them till the runout was 0.002 inches or less on the flywheel periphery.  I always thought the bearings lasted longer and the engines ran smoother with true flywheels.

[bak189]

I did not get a chance to see your Bonneville BSA on the salt.....but did see it at the Miller track....very nice.....regarding the possible wrist pin problem......bean oil....bean oil.... Castor Racing Oil the only oil to use in OLD stuff..
Morris still makes and sells the stuff....classicoilsupply@aol.com...804-261-4140...they will ship to you...

[Koncretekid]

I did not get a chance to see your Bonneville BSA on the salt.....but did see it at the Miller track....very nice.....regarding the possible wrist pin problem......bean oil....bean oil.... Castor Racing Oil the only oil to use in OLD stuff..
Morris still makes and sells the stuff....classicoilsupply@aol.com...804-261-4140...they will ship to you...

So far, I have pulled the top end off, including the cylinder, and can find no problems.  Pin is free in the piston.  I'll continue the tear down this weekend.

As best as I can remember, those engines needed frequent tear downs and inspections under racing conditions and the rod bearings were weak areas.   Do not run it if makes new or loud noises like a loose rod bearing.  It is best to tear it down and to investigate.

One thing I did on all tear downs was to mount the cranks between centers, check the flywheel run out with dial indicators, and to true the flywheel with a lead hammer.  Usually I fussed with them till the runout was 0.002 inches or less on the flywheel periphery.  I always thought the bearings lasted longer and the engines ran smoother with true flywheels.

Bo,
Lead hammer won't work on this crank.  It is a one piece 250 cc crank with bolt on flywheels.  I have found a guy here in Longmont, Co. who is going to dynamically re-balance the crank, probably at a different balance factor, so I hopefully won't get blisters on my hands next year.

Motor noises in a BSA are somewhat related to motor noises in a Triumph.............some are just more serious (expensive) than others. I hope your not trying to purchase the same fairing I am looking at for my T20!  Hope to see you next year.

If I knew what fairing you were going to buy, I might!  I think mine will have to be custom made with a large clear plastic window in front of my headstock.  I go out and look at it every day trying to figure out how to start on such a project. As for the noises, maybe I should just insulate my chin rest, so I can't hear them!
Tom

[wobblywalrus]

Tom, both of your records are on the AMA list posted on the BUB website.  It is nice to see a BSA winning again.. Good job.

[Koncretekid]

Just a follow up.  Tore the rest of the motor down and found no significant damage.  The big end of the rod bearing inserts were starting to flake, but not enough to hurt the crank.  Piston pin was not seized in piston, light carmel color on underside of piston.  One issue was the pinion gear that drives the camshaft was loose on the shaft.  It seems as though it never got cinched up tight, as the nut must have bottomed out.  As a result, the key was worn as were the keyways and I could rotate it back and forth, perhaps a degree or two. I don't know if that's why I went as fast as I did, or maybe I would have gone faster if it had been steady!  I had the crank re-balanced, as it seemed to be out a little when on a dynamic balancer (18 grams one flywheel, 28, the other -- is that a lot?)  Hopefully it will be better so I won't get blisters  on my hands next year.

I'll be starting on bodywork over the winter.

Tom

[Koncretekid]

I took some photos of the rod bearing that were about to give up the ghost.  Also had to make a new keyway in the crankshaft that drives the pinion gear and worm gear that drive the cam gear and oil pump respectively. Here are a couple of photos of the bearing inserts after 14 runs (5 at Loring, and 9 at Bonneville.)  It is possible that I ruined the bearings when I started the motor up in the Spring without priming the oil pump, hence no oil pressure.  Also shown is crankshaft with new keyway (3/16") because the original 5/32" Woodruff keyway was worn about .020" at the top - - hard to make a new woodruff key that would be tight.  So we made a straight 3/16" keyway and then made some stepped keys.  Just for the hell of it, I made a couple of extra ones with the offset to the right and to the left for fine tuning the cam timing (mainly because I could do so in a few minutes after the Bridgeport Mill was already set up.) The one in the center is stepped .015" on each side, while the one on the left is stepped .030" on the left.  The one on the right is stepped .030" on the right, but you can't see it.  The top of the back of each key had to be relieved to make sure it didn't interfere with the oil pump drive worm gear that it drives. My luck in finding a guy like Doug Edwards (machinist in Longmont, Co.) is truly amazing.  I have the use of all the tools of a modern machine shop and a teacher as well.

[wlarryglick]

Beautiful and innovative solution(s). )

[Old Scrambler]

Great work..........so now you will be ready to run in a few weeks! 

I am looking at the HD XR Fairings from airtech..........To bad they have openings for the handgrips.  I will likely make my own by laying up glass over existing pieces gleaned from small bikes.  At my speed I am concentrating on the front and sides only.

Since you have a 250cc crank........you may want to investigate big and small end roller bearings...........I have a roller on my big end from Alpha Bearing.

[Koncretekid]

Great work..........so now you will be ready to run in a few weeks!  

I am looking at the HD XR Fairings from airtech..........To bad they have openings for the handgrips.  I will likely make my own by laying up glass over existing pieces gleaned from small bikes.  At my speed I am concentrating on the front and sides only.

Since you have a 250cc crank........you may want to investigate big and small end roller bearings...........I have a roller on my big end from Alpha Bearing.

I didn't realize you could use a roller bearing with a one piece crank. However, I am not disappointed with the plain bearing big end -- it is after all what all the modern 15,000 rpm rice burners use.  I'll try it again with the newly balanced crank.

As for a fairing and windscreen, I agree that there doesn't seem to be anything off the shelf for the small bikes for land speed racing.  Of course, if we lived next door to Airtech, we might be able to try some of theirs.  I'll follow Wobbly's lead and start with a bunch of curved metal or wood strips, cover them with hardware cloth or screen and sheet rock filler, then fiberglass.  It might not be as pretty as some of the factory builds, but then a golf ball ain't all that pretty, either!

Beautiful and innovative solution(s). )

Thanks for the complement!
Tom

[38flattie]

Real cool to see a BSA running and winning!

28 grams is all but an once- seems like a long way off to me. Add the 18 grams off on the other flywheel, and depending on their relationship to each other, it could be quite a bit!

[wobblywalrus]

Tom, I am not familiar with a 500cc single having a plain bearing rod big end.  I cannot give advice based on direct experience.  The twins had plain bearing big ends and most of my experience was with those.  Special care was used to check the oilway clearances throughout the rest of the engine.  A worn crank journal on the timing side, for example, would pass a lot of oil.  This would reduce the amount of oil reaching the rod bearings and problems would occur with them.

A few questions.  Is the oil hole for the rod bearing chamfered?  Are you using an original Lucas spark advance with bob weights?     

[Koncretekid]

Real cool to see a BSA running and winning!

28 grams is all but an once- seems like a long way off to me. Add the 18 grams off on the other flywheel, and depending on their relationship to each other, it could be quite a bit!

I re-questioned my balancer guy about the difference and he was not exactly clear.  Maybe 18 grams one side, 13 on the other.  Being 5 grams difference is a small amount, but then I noticed a bunch of new holes drilled in the flywheels, so I just have to trust him on this one.  I'll know as soon as I'm able to re-start it, as the handlebars visibly shake at high rpm.  And yes, great to make a slow bike fast -- sort of like making a slow car go fast.  To me, a lot more satisfying than buying speed right off the shelf.

Tom, I am not familiar with a 500cc single having a plain bearing rod big end.  I cannot give advice based on direct experience.  The twins had plain bearing big ends and most of my experience was with those.  Special care was used to check the oilway clearances throughout the rest of the engine.  A worn crank journal on the timing side, for example, would pass a lot of oil.  This would reduce the amount of oil reaching the rod bearings and problems would occur with them.

A few questions.  Is the oil hole for the rod bearing chamfered?  Are you using an original Lucas spark advance with bob weights?    

Bo,
The crank in this bike started life as a 250cc crank with a 70mm stroke.  It was welded up to use a larger BSA twin bearing, and the stroke was changed to 75mm (although tech at BUB measured it at less than 74?). It is using a carrillo steel rod, for a BSA twin I believe.  The oil holes in the bearings are for the BSA twin, which had a corresponding hole in the rod to spray oil on the ball bearing main, on one side only (the BSA twin had a bushing on the other side.)  The bottom end, including cases, was built by a renowned BSA guru, who also opened up some of the oil passages.  The crank itself rides on a ball bearing and a roller bearing on the drive side, and a roller on the timing side very stout for a single.  The oil pump end feeds the crank which oils the rod journal as well as the end of the camshaft, as far as I can see. Top end is oiled by a Tee fitting in the oil pressure gauge tapping.  Oil pressure seemed to be good, until the gauge self destructed.  I am using a Boyer electronic ignition for advance, but have not been happy with the advance curve, as it seems to vacillate at moderate rpms before settling out after 4000 or so rpm (hard to see with timing light.)  One of the things I would like to do is to find a programmable ignition that would work, could either be cam mounted like the Boyer, or perhaps mounted on end of crankshaft where the rotor used to be.
Tom