SRM's Engineering Services (electronic Engineering PDF) (new Products PDF)
At SRM we rebuild over 250 classic motorcycle engines every year, and our engineering team are committed to the highest standards of rebuild. We pride ourselves in giving you quality engineering and rebuilds for all aspects of motorcycling; we like to ensure our customers that you will get oil-tight, trouble-free motorcycling when your engine is returned to you, be it for road or racing purposes.
Needle Roller Bearing & Oil Feed Conversions
Our SRM crank needle roller and oil end feed conversions completely eliminate the troublesome timing side bush. This is replaced by a combined ball and needle roller bearing which withstands substantial radial and axial load; the combined bearing eliminates end float locking the crankshaft to the timing side, so no more shimming!
The oil ways are altered and rerouted so the oil is fed directly from the feed pump to the big ends via an oil seal housed in the timing casings, and through an end feed pipe quill situated in the end of the crankshaft - nothing is visible from the outside. Oil pressure and delivery to the big ends is uprated by at least 40%, and usual overhaul time for replacement of the big end shells is 80,000 miles - for main bearings this is 100,000 miles! They can last even longer with regular service and oil changes.
The troublesome Triumph 3TA and 5TAs etc can also be converted in this way, to give long reliable mileage.
To carry out the conversion we need the following components:
1. Crankshaft;
2. Both crank case halves;
3. Inner and outer timing covers;
4. Oil pump;
5. Idler pinion gear;
6. Crank shaft pinion gear;
7. Oil pressure release valve.
NB. The conversion can be fitted even if the main journal has worn below the last regrind size!
Cylinder Head Engineering
To run your classic four stroke engine on lead free petrol, contrary to popular belief and misguided information, only the exhaust valve seats have to be replaced. This is due to the intense heat produced around the exhaust valve seat area, the compatible materials required for the valve and valve seat insert.
We replace the seats with a steel insert comprising of a 12% Chromium Ledeburitic structure with a work hardness of 50HRC. This gives very high resistance to shock, wear, deformation and heat oxidation. Out compatible valves are made as per the following specs:
- All inlets are EN52 material with stellite tip on the stem and Tuftrided to 70-74HRC;
- All exhausts are 214N with stellite no.12 tip and tuftrided to 70-74HRC;
We also strongly recommend to use our Colisbro material valve guides that comprise of a copper, nickel and silicone alloy which resists wear, corrosion, spark erosion, has a high tensile strength and can cope with rapid temperature changes - again, the ultimate in modern technology for your classic motorcycle! Beware of imitation Colisbro guides from other suppliers - Colisbro is a trademark brand material and only available from one material supplier in the UK.
Valve seats can be fitted to any cast iron and aluminium cylinder head, motorcycle or automotive. To achieve this we use the latest in workshop technology - the Serdi Millenium 3.0.
The valve seats can be cut to any angle required, plus the correct relief radius can be attained, thus allowing a more efficient flow of gas past the valve seat opening and valve head, which means a more efficient engine.
Engine Reconditioning
All our engines are assembled in a purpose built dust-free assembly room, with no machine tools present. This ensures the engine components and the partly assembled engines do not get contaminated with swarf, grit or dust.
The standards for engine rebuilds are extremely high - SRM will provide oil-tight and trouble-free motorcycling, be it for road or competition purposes. On average we rebuiled 250+ engines per year, and at any one time we can have up to 65 engines in the workshop. Therefore, each engine is booked onto its own numbered Jobcard with a unique reference number. Each of the engines components are also discreetly marked with this number, which prevents any confusion between varying customers' components and also ensure that each job is worked upon in turn, preventing unneccessary delays in the reconditioning service.
Your engine and any components are stored within their own crate in the workshop. All work (for example head conversion, crank grinding, cylinder boring) is done in batches at various times in our relevant workshop departments. By the time your job comes up for assembly, it has 'visited' the relevant departments and had all necessary work carried out, and is assembled by one specific engineer over a period of a few days. During the course of this assembly, all the new replacement parts are logged out of our extensive engine component stores, and any final problems that are not apparent on strip down (such as misfit of casings, alignment problems etc) are rectified before completion. It is extremely important, when you first send your engine to us, that specific instruction on finish, specification etc are put in writing - if in doubt you can always telephone and discuss these matters with the engineer responsible for the assembly of your engine.
We can also give a strip down and autopsy before we commence work on your engine. It is stripped down and inspected for wear, damage, problems and assessment. An estimate is then typed out listing all new parts required, repairs required, engineering work required, and a list of options such as exterior cosmetics, and other options such as dynamic balancing, lead free conversion, tuning and so on. You can then discuss your estimate with the engineer responsible, and make any alterations required.
Please note: on any estimate we cannot forsee any potential problems, and further work that only becomes apparent in the final assembly stage. The estimates are thus provided as a close guide.
Race Engine Builds
On racing engine rebuilds, or engines built to order, the same rules apply as per standard rebuilds except for the extra attention to detail in some areas. This includes:
- Setting the compression ratio (by checking dry assembled engine, measuring combustion chamber volume and setting as required);
- Checking valve to piston clearances and setting;
- Setting up special cams (and dialling in the opening times and peak lift);
- Lightening engine components;
- Replacing bushes with needle roller bearings on the camshaft and idler shafts;
- Strengthening up the crank cases with gussets;
- Fitting special outrigger bearings to the gear box for extra load capacity and less flex;
- Fitting special billet crankshafts, Carillo racing conrods, dynamic balancing, special race diaphragm type clutches, special gas flowed big valve heads, shimmed rocker arms;
- Push rod lengths set exact;
For example, the pictured engine (below, built for one of our customers living in the USA) is a 900cc BSA A65 unit engine. Capacity is achieved by using long stroke one piece billet crankshaft with 90/270 degree configuration, SRM big bore top end with 34mm gas flowed big valve head. The cam is 320 degree duration Nourish Z profile, 9:1 compression ratio.
The power outputs at the crankshaft as tested in SDD Developments Engine Dyno Centre are as follows:
- Max: 71 BHP at 5,800 rpm;
- Max torque: 66ft lbs at 5,400 rpm;
- Max rpm: 6,500 rpm.
Prices on full engines are quoted on specification required - please contact our engineering department for more details on any of the services listed above.