JD Midnight Special

Harley 1926 JD 1500cc stroker with sidecar

NOW WE TALKIN PART IV

This all started when i heard my friend Stroker Wulf reving his old 1921 stroker engine. He told me about the Truett & Osborn stroker flywheels for old Harleys. Wow, i want one too. So started gathering needed parts, i found one engine case on internet, i ordered a pair of flywheels from T&O and got one cylinders from ebay, and one from a friend,Värmdö Motorteknik was boring the cylinders. High compression pistons, bearings, valves, guides and some other parts form Competition Distributing Co, what really supported me by Express Air Mail, the fastest delivery was 60 hours, Sturgis - Stockholm door to door.  Also very important and skilled help from Nille at Ultramotors with a perfect henenig job on all the bearings. Totally it took me 3 months to gather all parts and 3 weeks for assambeling and tuning.

This is an amzing piece of  precission metal from Truett & Osborn. Very stright and perfect machinery perfomed, the tappets lined up perfect, insdie 2/1000 of a milimeter, also axial tollerance for the rods was perfect from start of the assambled flywheel. T&O are very skilled in what they are doing. High class racing parts to a resonable price.

I did assamble and balance my first flywheel ever and got it finaly inside 1/100 of a mm toally flex and i used/got 52% balance factor, what actually was the factor ive got by not doing anything to the flywheel or rotating weights, no drilling, no adding of mass. Ill gues this will give the engine a nice torque from bottom. I have also added high compression pistons from Competition Distributing Co, Strugis USA. Now i shall work on the camshaft and maybe one injection system.

I did read on the web of some alternative balancing methodes (ill guess there is as many of them as people what use them) and used the most basic know how from these sites for this job. Its actually very elementary and simple stuff when you get the grip of the main point, how to calculate the rotationg mass, bob weight and the balance factor. Of course you need messuring tools, special tappets and a trueing stand.

After i have checked booth wheels with bob wigth on the balancing stand i put them together with rollers and rods and had made the calculation of the balance factor for 55% and the wheels did almoust balance as they was, i added 20 gram on remote side and got it fully balanced and made a reverse calculation of the factor and foud ot it was 52%, what was perfect for my intention of a low rev torque engine.

I have, as usual, no intentions to create a price winner by the visual finish, for me its ok if it runs perfect. Im a user.

Also i have a theory that paint is decrease the cooling effect on the cylinders, what allways is critical for these old pocket valve engines.

I have added a fat boy rear wheel hub with disc brakes and a 4 speed gearbox from Electra Glide. The bike is totally different to handle and the torque is much more heavy then with the 3 speed gearbox.

Almoust togheter again after 2 months without engine. Last run was 19 of March, the ice race.

   

RIDE ON . . .

Special Thanks to;
Roffes Motor & Raceway, Stockholm, Sweden (www.roffesmotor.se) 
Värmdö Motorteknik & Willes Marinteknik Nacka, Sweden (www.motorteknik.se) 
Ultramotors Södertälje, Sweden (www.ultramotors.se)
Truett & Osborn, USA (www.truettandosborn.com)
Competition Distributing Co, USA (www.competitiondist.com)
Lars Wredenberg, Stockholm,
Stroker Wulf, Broken Spoke, Stockholm,
Ronnie Petterson, Broken Spoke, Stockholm,
Micke Västertorp, Stockholm
E-bay mfl