Ratfighter conversion: headlight and clocks facelift and redesign, colour changed to matt black; top-end rebuild (cylinder head, gasket, valves, etc.)

Current odometer reading: 51379 miles.

Headlight and clocks rearranged to make more presentable. Colour changed to matt black (new V5C reflects colour change).

The bike required topping up with oil by about 100ml every 200 miles. A compression test was carried out, and low compression was revealed on cylinder 1 (reading 130) and borderline on cylinder 2. This did not improve when engine oil was put into cylinder, so it was surmised that valve stem seals were perished (causing some oil loss) and the valves weren’t sealing properly (causing lowish compression). Complete cylinder head and valve reconditioning/renewal was undertaken to resolve these problems. Full video of cylinder head job here:¬†https://www.youtube.com/watch?v=VyAZE6fFubs

The old stem seals were obviously perished, and were replaced. Following this major work, the engine was harder to turn over at the crank by hand, indicating significantly improved compression. The bike was tested and works perfectly.


Oil and filter complete change; valve clearances checked; fuel tap replaced; naked conversion; Brunswick Green paint job; new exhaust silencer fitted

Odometer reading: 50179 miles

Complete replacement of oil with semi-synthetic 10W40. Oil filter replaced with new Putoline filter. Fuel tap replaced with generic Suzuki-style fuel tap as the brass nipple had come loose from the original one (fuel tap is now a standard on/off/reserve one, and not vacuum-operated). Valve clearances checked and all are within spec. Valve cover gasket refitted with blue Hylomar.

Deep Brunswick Green paint job (unsatisfactory and will change to matt black in due course). New V5C applied for, to permit colour change (black and green). Front cowl/fairing was removed, and the headlight surround was cut down. The original headlight and clocks have been mounted to the forks, using standard headlight clamps and fabricated brackets. The original clocks surround has been cut down and reaffixed in order to smooth the aerodynamic flow between the headlight and clocks. The headlight and clocks turn with the handlebars. This is a complete naked conversion.

The end-can/silencer of the existing exhaust (Motad Nexxus) had rotted through, so this was cut off and replaced with a generic steel one.

Leaking sump replaced, complete oil and oil filter replacement, carburetors replaced with newer rebuilt versions

Current odometer reading: 48700 miles

Oil sump pan had been leaking profusely, due to the previous practice of using the oil level sensor hole as a means to drain the hole having cracked the said oil level sensor. It was therefore decided to replace it with an intact one, including a new oil level sensor. A replacement oil pan and sensor was procured, and was installed with a new Athena gasket and blue Hylomar. In addition, a new oil level drain bolt and new Wemoto oil drain washer was fitted. A new Demon Tweeks oil filter was installed, and the oil replaced with new oil: Shell Advance 15W40 mineral motorcycle oil.

Exhaust leak type of noise was noted while riding the bike. It was considered that the cause was worn out exhaust gaskets, so new ones were procured and installed. However, this was not the problem. The problem was traced to a vacuum leak from the carburetor 3. The vacuum leak had a serious cause: the top of the carb had come off, and the spring and main needle had flown out from it. As replacement carb parts for these original Mikuni BDST28 x 4 were unavailable (a new plastic carb top, new diaphragm spring and needle would have been needed) it was decided to obtain a complete set of replacement carbs. The only ones available were a set of Mikuni BDS28 x 4 (from a 1999 model). These were different carbs, but intended for this model of bike. These carbs do not have an oil-fed carb heating system. The carbs were in a neglected state, and required a full stripdown, including separation. They were thoroughly cleaned, the float levels were set, the mixture screws were set, and they were balanced. The oil feed to and from the carbs (on the bike) were then capped off, and these new carbs were installed and tested. Idle speed set to 1200rpm – dead steady. Working perfectly.

Starter (intermittent) issue was observed: occasionally a single click, followed by nothing, would result from an attempt to start the bike. All connections tested and found to be working correctly. Battery had more than sufficient power. Solenoid and starter relay tested, and found to be working. Problem identified as the starter motor. This was stripped down and the commutator was cleaned. This completely solved the problem. However, it was noted that one of the brushes is significantly worn. The starter motor shall be rebuilt in due course.

Bike fully reassembled and working correctly.

Fork springs shimmed to increase stiffness

Current odometer reading: 48416 miles.

Following the steel braided cable installation, which makes the braking work much more quickly and with less lever travel, the bike tends to dive excessively when the front brake is applied. It was therefore to decided to increase the standard fork springs’ stiffness slightly.

Shims were fabricated from 3-4mm steel wire, and placed between the fork springs and the washer that goes beneath the standard fork collet/tube, at the top of the forks.

Braided steel front brake cable fitted

The existing front brake cable was rubber-coated PTFE, and was showing signs of wear, and was suspected of not fully exploiting the braking power of the recently changed brake pads and brake fluid and reconditioned caliper. It was probably the original brake cable (25 years old). It was therefore decided to replace it with a new braided steel cable. The copper crush washers around the banjo bolts on the old brake cable were reused after being re-annealed by heating until red-hot. Tested and working, with greatly improved braking performance.

New (4-degree advanced) ignition timing plate fitted

Current odometer reading: 48072 miles.

In keeping with normal practice with the XJ600S, which has a slightly retarded ignition timing in order to retain compatibility with low octane fuels, a corrected (4-degree advanced) ignition timing plate was procured and fitted, and the old one put into storage. This was in order to make the engine run as per standard specifications as set by the manufacturer.