Gearing down

[RoyC]

I am gearing down for the sidecar and have two questions.
1.  How do I get the split pin out that is inside the recessed locknut (see picture)
2.  My existing engine sprocket is 19 teeth.
     I have got a 17 T and a 16T , which one would be best ?

Thanks, Roy.

[duTch]

1.  How do I get the split pin out that is inside the recessed locknut (see picture)

    ....(1)  straighten the legs and pull it out by its head, or (2) Cut the head off and pull each of the legs out...

 

2.  My existing engine sprocket is 19 teeth.
     I have got a 17 T and a 16T , which one would be best ?

 A. Depends on the terrain around where you plan to ride. If it's super hilly, the 16T would haul easier but rev more. Personally I think best to go bigger on the wheel sprocket, but the downside of that is a wheel sprocket may be hard to find, and it will affect the speedo/odometer reading, but that's easy to compensate for by don't look at it, just calculate the % of inaccuracy for mileage/fuel consumption/range

[Greybeard]

1.  How do I get the split pin out that is inside the recessed locknut (see picture)

I don't think you should have a problem with that split-pin. Bend the legs straight. Use long-nose pliers to pull the pin out. If that doesn't work, bend the head up and grip it with a mole wrench then tap the wrench with a hammer to pull the pin out.

[RoyC]

I will do what you both suggest and rip it out, problem will be getting the new one back in.

Pretty flat around here so will go with the 17T to retain a little top end speed and MPG.
Thanks for the replies.
Roy

[chaterlea25]

Hi Roy,
Have you tried the bike on the existing gearing?
Back when the bikes were built the traffic speeds were much lower,
To keep up with modern traffic with "low" gearing the engine will be revving its nuts off 
On the BSA twins that I have rebuilt for solo use I have geared up from standard and the results are
good for today's road speeds

John

[RichardL]

Roy,

My gearbox is a scrambler type, so, lower gearing for 1-3 to start with. Maybe this is why I found my existing 19T sprocket too.low. Changed to a 22T for solo and was much happier.  I don't really know about sidecars, but I would have thought the 19T was low enough. I think John hit it in suggesting trying it as is. If it's good you don't have to go through the sprocket change and potential chain modifications, twice.

Regarding replacing the cush nut pin, problem solved if you get an SRM cush nut. Use a regular socket on a torque wrench and tighten to 65 ft-lb. Locking up the clutch while tightening is another question. Some use a clutch-locking plate, some stand on the brake with the bike in gear. I use a piece of aircraft cable laced in the primary chain and anchored to the frame. I'm sure there are more methods.

Richard L.

[Greybeard]

I have geared up from standard and the results are good for today's road speeds

Me too. I agree.

[JulianS]

It is easy to overgear an outfit so that it is faster in third than in top. And flexibiity suffers.

[RichardL]

Julian,

For my understanding, are you saying that a lower drive ratio, say 19T instead of 17T can cause the condition you mention, and why is this?

Richard L.

[JulianS]

19 tooth on either engine or gearbox will give higher overall gearing than 17 tooth sprockets.

Factory recommended sprockets for A7 sidecar were 18 (solo 18) engine and 17 (solo 19) gearbox.

 overall ratios with STD box;

 1st =13.62 (solo) 15.2 (sidecar)

2nd= 9,28 (solo) 10.35 (sidecar)

3rd=6.38 (solo) and 7.02 (sidecar)

Top = 5.28 (solo) and 5.9 (sidecar)

[RoyC]

Got the engine sprocket changed to a 17T but now the chain is too long.
The book states that the engine sprocket should be 18T, but someone in the past had changed it to a 19T and the roller coaster parts were not a good match, but on the 17T that I have just fitted they are a perfect match.
Looks like the chain wants shortening by about 1 to 1½  links   (Renold's chain).                                       
The book states Primary chain ½ x .305,  is that the same as ½ x 5/16 ?

Will a chain splitter fit both primary and rear chains ?

[JulianS]

1/2 inch is the pitch and 0.305 inch the diameter of the roller.

[bikerbob]

The reason for lowering the gearing when fitting a sidecar is to  lower the stress on the engine, you can get away with increasing the gearing on a solo but you do run the risk of going faster in third than you will in top. Years ago a friend of mine had a Norton 99 he increased the gearing via the engine sprocket and his bike would do about 95mph in third but when he went into top gear it did not go any faster it just reduced the revs. Also about 50 years ago my brother fitted a sports sidecar to his 1957 Gold Flash and did not change the gearing most of the time he had a mate in the sidecar the bike lasted about a month when the crankshaft snapped through the big end journal. Now at that time the Gold Flash still had the small journal crank shaft but would the same have happened to the larger journal crankshaft I would not be prepared to take that chance and would always lower the gearing if fitting a sidecar. Too expensive to take the risk of not changing.

[RichardL]

I had to go to the book so I could put my comments in context. My bike is a '55 A10, which is listed as having a 21T engine sprocket stock versus 18T for a stock '58 A7SS. So, my going up from 19T to 22T seems OK for a scrambler gearbox on the street and Roy's going down one tooth to a 17 for the sidecar also now makes sense to me.

Sorry if I confused the issue, not to mention, myself.

Richard L.

[chaterlea25]

Hi ALL,
While reducing stress on the engine is a good thing, over revving or continuous high revs at a lower road speed
cannot be too healthy for the innards 

My brothers SR on "standard" gearing feels very harsh at 60-70 MPH compared to mine that has a 23 tooth engine sprocket
I ran on a 22 tooth for a while and felt as though I needed a 5th gear 
It will rev out on the 23 tooth without a problem, and runs nicely at 4000rpm at 70MPH
(I know all this is getting away from Roy's A7 sidecar issues  )

John