Pictures and technical info on a water-cooled Seeley TR500 from the UK
by David Maskell


I bought new Seeley Suzuki at the start of the 72 season from Eddie Crooks, complete rolling chassis 350, new std T500 engine 250 with racing parts in exchange for std road parts returned - that's some of the help Eddie gave us in those far off days( I am still playing at it 28 yrs on) you are supposed to grow old gracefully.)

About 1989 I was lucky to come across brand new genuine factory parts for a XR05 w/c 500 twin. advertised in MCM ( motor cycle news). These parts camefrom the famous BARRY SHEENE stable hidden under RG500 /TR750 spares he was selling. The guy that bought them had no reason to keep them so I managed to clinch a deal, lucky me.

10YEARS later, now retired, I completed the project. We ran it at OULTON PARK 29 Oct last year. My test rider was the 1981 250cc TT winner Steve Tonkin -3 times British 250cc champ- riding an Armstrong-Rotax (Australian Jeff Sayle was his teamate).

INTRO- Steve started out racing my Seeley in 1973, the following year, he moved up to full sponsorship on 250/350 TZ's. (I was his race mechanic until 1984 TT ) racing a RG500 the g/box sprocket sheared off thro' the drilled radial holes (made by suzuki) chain locked the rear wheel throwing him and bike into the wall at Handley's cottage, RG burnt out, Steve lived to tell the tale,lucky lad. He retired after this bad crash from professional racing. He now owns/ runs a very succesful bike restoration workshop and enjoys our gallops out on the Suzuki track days and parades. He has a wealth of racing knowledge ie setting up, giving the best feed back I could wish for.

The track day started 8am. very cold (air temp. 50F - air density 112% ) must start off rich, weather fine all day, after briefing the bikes are let loose on the track in 20 min sessions mostly the latest superbikes R1's, Fireblades, 901's, fast stuff. My Suzuki was the oldest bike there. This was the first time out on the w/c, I have fitted an EGT meter sent over from a contact in the States so it was new to our setup. FANTASTIC after jetting down from 420 - 360's m/jets 38mm mikunis, taping up the radiator to get some heat in the engine, temp increased from 55deg-75deg's water temp) EGT,s readings increased from 800 - 1200F as carburation was leaned out to get the rev's, boy does this engine rev easily, power from 5,000-10,000 and if you dont keep your eye on the tach - 11,000rpm. No vibration or buzzing like the turned down T500 road cranks, FANTASTIC! I have raced bikes since 1956,( 250cc MOV Velocette) at last the machine I have dreamt of owning, yes a WORKS FACTORY ENGINE. Granted 27 yrs too late but hey who cares.

Martin Crooks suzuki 40th anniversary lap,exiting the QUARTER BRIDGE

TR500 SEELEY conversion to w/cooling using genuine factory parts XR05 parts I obtained 1989
3-barrels - 1 nicosil plated, 6 pistons, 2 cyl/heads, waterpump, last but not least 1 crankshaft .

STD.T500 crankcases need welding to fill up transfer cutaways, cylinder stud holes etc, this together with all the machining operations, re-drilling stud holes for cylinder, facing off case to accept new barrel correcting slight distortion thro' welding, care here makes for very good motor.

Next the crank is definitely a special item crankpins integral with inner wheels,balance holes size/location non std. I fitted my own tried & tested 4 bearings, centre lab.seal as fitted to my air-cooled TR. No sucking oil out of the g/box. Total wgt. crankshaft complete 18.5lbs. std 500 - 27lbs. a big difference, short 130mm rods, ie 750 kettle are fitted. Waterpump is driven of oilpump drive, no problem here making up spacer for case clearence.

A dry clutch conversion made by NOVA in 1990, is fitted from the old aircooled together with a 5-speed box st.cut primary's complete's the bottom end, no clutch drag here. Chassis mods required specialist frame builder Roger Titmarsh (Seeley replica's) to alter front down tubes and engine mounts to fit straight out forward exhausts. Suspension upgraded by Maxton Eng.(Ron Williams) fitted HRC racing inserts to my Seeley forks reworking rear konis to suit. Brakes are cast iron discs, front master cylinder to suit both Steve and I, small bore to give 2 finger operation, combined with all up weight. Stopping indeed outbraking all but those on a suicide mission no problemo!

Power to weight ratio takes some beating. Putting all this together has given me tremendous satisfaction not forgetting all the advice, help and hands on exspertise you pick up over the last 45 years.

Steve Tonkin on the Seeley. The big Ducati clocked Steve at 160mph on the TR

Now for the technical stuff, all tuning data from Suzuki etc,stuffer rings squish band heads, turned down cranks (more
vibrations) forget it! Granted the barrel has plenty of ports including ported pistons,
Exhaust .op.80deg atdc(200deg duration)
Transfer .op.115deg atdc(130 deg.duration)
Inlet .ops.85deg atdc(190 deg.duration ign.timing 2.5mm)
38mm mikuni p/jets
ign. Hitachi ex tz 350
Combustion chambers none squish same as T500 road bike but has central plugs,
pistons no deck height atdc.
head gasket 1.6mm
ccv.atdc=23.5cc cranking pressure 125lbs.ins
fuel pump
petrol not unleaded 4* or lead replacement.
20-1 oil mix R-30
Expansion chambers are really trick items needless to say I must keep the details under my hat suffice to say tuned length is greatly reduced 200mm , mid section dia increased to 116mm as mentioned power starts 5000 I try to gear it for 10,000 rpm tops but have run out of sprockets the highest we have gives 10500 and still is just too good to be true.

Any advice will be willingly given to genuine queries good tuning everyone!
hope this info gives foodfor thought.

Also enclosed are measurements for 1984 Suzuki wc pipes I have just found in my files, these are Suzuki data. I made a set for guy who fitted them to his aircooled t500 racer he did a back to back test on a rolling road, just hung them on to try without changing any settings gave a 10bhp increase at the top.

Good tuning all,
cheers Dave Maskell.

[email protected]


More pics of Dave's bike

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