Telephone: 01443 742791
Address: 18a William Street, Abercynon, CF45 4RW

Harley-Davidson® Engineering Services

Harley-Davidson Engineering Services

We have been specialising in machining Harley Davidson® engines since 1981.

Over the years we have built up a huge selection of the specialist tools needed to recondition these engines which contrary to popular myth are not agricultural and were designed to exacting tolerances from  the very early years of production.



Engine Top End:


  • Rocker boxes Vapour blasted or Polished


  • Rocker arms rebushed, line reamed & finish honed


  • Cylinder heads Vapour blasted


  • Cylinder heads overhauled, including valve guide replacement & honing to correct tolerances & fitting valve stem seals


  • Oversize or Performance modified valve guides made & fitted – We supply high quality valves and guides from Kibblewhite precision machining


  • Valve seats multi angle cut using Serdi & Mira seat cutting equipment


  • Valve seats replaced. All our replacement seats are unleaded fuel compatible


  • Gas flowing & Cylinder Head Porting


  • Cylinder heads machined & set up for high lift/long duration camshafts


  • Cylinder head decking, Squish correction, combustion chamber volume correction (cc’ing)


  • Angled squish bands machined


  • Thread repairs, broken studs removed, oversize thread inserts made & fitted


  • Cylinders rebored and honed to correct tolerances in torque plates. – We use Van Norman, SPS and Kwikway boring equipment and Delapena honing equipment to hold our bores within 0.0002″- We supply pistons from S&S, Wiseco, Keith Black, aftermarket stock replacement and genuine Harley Davidson® – We have torque plates to fit Harley Davidson®, S&S , Ultima and Revtech cylinders in all bore sizes from 3″ to 4-3/8″ 


  • Cylinders vapourblasted, cast iron cylinders painted


  • Cylinders refaced or decked on gasket faces


  • Cylinders relined


  • Tappet blocks machine/honed for oversize lifters. – We supply quality tappets from S&S and Jims machining and adjustable pushrods from S&S (and others)


Engine Bottom End:


  • Crankcases Vapourblasted


  • Crankcase/cylinder base gaskets decked


  • Crankcases bored for big bore cylinders and centre bolts modified to suit


Case boring for big bore cylinders

Big Bore Crankcases


  • Twin cam cases converted to Timken style sprocket shaft bearing;- This style of bearing was fitted from 1956 until 2002, Harley Davidson continue to fit it in their performance engines. This conversion is a ‘must have’ for stronger more reliable engines

    Twin Cam Timken Sprocket Shaft Bearing Conversion

  • Crankshaft rebalancing; – We individually set the balance factor to the rods and pistons being used with that specific crankshaft and balance each flywheel individually, so there is no chance of setting up a rocking couple across the flywheel , a condition that we have witnessed on many occasions on stock cranks.


  • Crankshafts rebuilt & trued. – Factory tolerance is 0.002″ total indicated runout at the bearing surfaces.We view this as a maximum and strive for as close to zero runout as possible, although with some flywheels it is not achievable. Flywheels that will not true correctly are replaced with S&S or Truett & Osborn depending on application because they are better than the factory flywheels and competitive on price


  • Camshaft and pinion shaft bushings replaced and line reamed


  • Main bearings replaced, lapped to size, Timken bearing end float set


  • Centre case throughbolt hole machined & spot faced


  • Stroker crankshafts supplied and fitted;


  • We have extensive experience of building stroker and big bore Harley motors from stroker Knuckleheads to large capacity Twincams®


  • Gear drive conversions for Twincam® motors;- forget cam chains, our gear drive conversions offer a fit and forget solution. combine with S&S easy start cams and S&S uprated cam support plate & oil pump for the performance bottom end needed to complement top end improvements or extend the life of your stock engine


S&S 3 Chamber Twin Cam Oil Pump

S&S Cam Support Plate & Gear Drive Cams – No Whizzy Chains To Wear Out Or Tensioner Debris In Your Oil Pump


If you have an queries please don’t hesitate to call or email us.