Short Stroke Crank

Hello Peter
Just something to add to your knowledge base I have just done some work on a friends Yamaha XT500 if you do not know this machine it is an ohc single pot engine putting out about 33 hp with 84mm stroke 86mm bore.
Anyway here`s the good bit they run a very strong forged steel crank with a similar big end to the norton it also has a steel very well machined rod best of all the crank pins are press fit and the same size as norton the overall width of the complete crank looks to be within shimming limits of the norton cases this engine reliably revs to 6800 rpm the going rate for them in the breakers is about £30 I think this has potential I am going to try it anyway i will make comprehensive notes and get back with any results
Keep in touch
Tony Gardiner

Rocker Oil      Feed

  The rocker oil feed is a "T" off the scavenge side of the oil pump; ie low pressure. Some of the returning oil goes to the rockers, some back to the tank. The amount of oil in each direction is proportional to the resistance in each arm of the "T". After a rebuild and using transparent tubing temporarily, I found that there was almost no oil going up to my Model 19 rockers. Clearly because the route there was constricted and it was much easier to return to the oil tank. The solution was as follows:- 

Restrict the Oil Return to the tank. Braze or solder a blanking disc of metal over the oil tank return spiggot and drill this out to 3/32". 

Open the route to the rockers. The small lateral holes in the banjos at the top and bottom of the rocket oil feed tube were drilled out to 1/8" and drilled through to give two routes through the banjo. I went a stage further and unsoldered the copper tube between the brass banjos. I fitted a short length of 3/16" ID brass tube from a modeling shop to the top and bottom banjos which were then connected with flexible oil tolerant tubeing from a supplier of car fuel injection systems.

The result was a healthy supply to the top end, checked with transparent tubing again, and no undue oiling symptoms after more than 1000 miles

I have a similar arrangement on the cafe racer ES2, running at higher revs.

Peter Ashley

Cylinder   Head   Nuts

  On a standard engine and in a pre-Featherbed frame, the head is fitted to the barrels with the rocker box attached. This means that two rhs cylinder head sleeve nuts have to be in place and that they cannot be wound down with a socket. A ring or open ender would have to take many, many swings to wind the sleeve nut down. A length of para-cord looped over the sleeve nut makes this process child's play!

Peter Ashley

Hot Road Cam Comparisons. ES2 / 16H

Hello Peter,

Yesterday ,I had nothing to do but to install a pair of 16H cams on my workhorse (mod50 1956). As I already told you, it's not the first pair I'm trying, but these ones are with Quietening Ramps and it makes all the difference! No more noise (not more than the original"58"cams)but more torque and a more user-friendly engine! I've been told that those cams were original fitment in the end of the 50's.

Their profile is between the "58"'s and your Hot Road Cams with almost 1,5mm more lift than"58" and 0,9mm less than Hot Road Cams. The difference is much less noticeable on the MOD50 than on the ES2  which is equipped so for a couple of years. (That is because the Model 50 had hotter cams as standard anyway - Ed)

Results from Similar Hot Road Cams.

I have not yet fitted these cams but the ones I have that are very similar in lift and just a few degree different in open and closure degrees, I dyno tested last week

The engine is a 84 x 88 based on a 65 degree balance type 50 crank and a B50 84mm piston.The barrel is a 84 mm bore 500T Norton Alfin barrel from Nortons race group back in the 50'sThe head is an early steel scull cap with a 50mm inlet and 44 mm exhaust with a 34 straight through inlet going to a 34mm Mk2 concentric all gas flowed by SRM.

The cam followers, push rods rockers have been lightened.

It gave 26 hp at the back wheel going through an AMC gearbox,  considering you normally loose a minimum of 6 hp in the gear box, and drive  that gives an minimum out put of 32 + hp.

With a specially machined 3/8 output sprocket to fit a 1/4 chain it maxed at 6200 at 93 mph with a beautifully smooth power curve

I would expect your cams to do the same, although this engine is now to be cleaned and sold off under the banner of " done that , try the next engine configuration."

Power Output 

79x100

84x100

84x88

86x86

Peter

Just for interest the previous engines I tested are  a 79 x 100 with a 16H piston and 28 mm bore carb did 19 hp at back wheel, a 84 x 100   555 cc with 28 bore head gave 22 hp and the 84 x100 with 34 bore and lightened every thing gave the same as the 84 x 88 480 cc but at 5,500 revs.

 Wet Sump Modifications 

 Courtesy of Art Bone   Oil leak fix0002.pdf

 Engine Breather Non Return Valve

 Courtesy of Art Bone   Oil leak fix0001.pdf