dadof2

Crystal ball anyone?

Either buy a decent tachometer of pop round to your local garage or engine diagnostics centre. They can attach a sensor to the spark plug lead and tell you the exact RPM using a scope. 1800 RPM = 66.6 m/sec sparking intervals (on a 4T). This should take less than 5 minutes.

I would'nt bother about it, the pint at your local pub is likely to have a more significant upgrade from year to year than most trial bikes.

Following is speculation not definite fact. High tickover needed to generate sufficient electric to run EFI. Some say engine can stall unexpectedly if tickover turned down. I rode a friends bike with the tickover turned down and it seemed OK Large bore throttle bodies do not give stable air flow at low RPM. Makes bike performance jumpy / inconsistent during initial throttle opening. A four stroke cannot produce the same power as a two stroke (of same capacity) without having valve timing to suit high RPM power output. Without VVT this high power / high speed valve timing compromises slow speed running. At early stages of 4RT development the works riders favoured engine characteristics similar to 2T this means a 4T has to rev twice as fast as a 2T for the same number of power strokes.

The suggestion I made was a generalisation for bikes of the 1970s where a thickish oil like EP90 or 20W-50 was originally specified. On a gasgas pro or a Sherco switching from thin ATF to thicker light gear oil or 10W-40 generally improves the gearchange. Just out of curiosity what bike are you referring to and from which oil to which oil did you try with unsatisfactory results?

Lube the cable with a mix of gear oil and molyslip. Han the cable up and make a funnel from duct tape so the oil runs through overnight. The creaking is often the cable nipples sticking and rotating in jerks. Lube the nipples, pivot points and actuating spindle with moly paste. Ossa clutches are heavy. The standard clutch springs are quite strong because the clutch has to bite through 20w - 50 oil. You might be able to change to lighter springs using a modern light synthetic or semi synthetic gear oil.

If your 305 has two piston calipers and short pads wavy discs might cause pulsing. Drilling is mainly to reduce weight and improve cooling. I would be inclined to go for round discs with a minimal amount of drilling - just enough to help cleaning and improve wet braking.

I never owned a 247 but did help a couple of others sort gear problems on theirs. I can't remember exactly but parts of the selector in the primary case are pressed together and come loose resulting in a less positive move of the selector forks. TIG welding the selector parts improves this. The gear dogs and holes into which they engage could do with a bit more undercut. The dogs can be done with a diamond file or wet n dry paper on a stick. If the dogs are already rounded off as a result of sliding out of gear they may need a bit of metal adding by tig welding. The holes into which the dogs engage can be undercut with a dremel and drum grinding stone or a bit of dowel in a drill and coarse grinding paste. You also need to check the gear selector forks are not bent or too loose and move the gers fully into position. you can check this movement with the gearbox built up in 1/2 the crankcase. Thinner synthetic gear oil will give better changes and less neutrals than the originally recommended EP90.

Regarding the sump plug. Some riders used to shim the sump guard down a bit. The method I and quite a few others used was to slightly countersink the hole in the sump, then turn Lathe) nearly all the head off the sump plug leaving just a couple of mm to match the countersink in the sump. A screwdriver slot was then cut in the plug with a small diameter slitting disc in a grinder. Plug was then fitted with threadlock or PTFE tape. Some riders had special plugs turned and threaded from the head of a large socket head cap screw.

That looks like a 1972 to 1974 model. The 350s (Actually 310cc) had a red stripe on the tank as well as the green. Easy to measure stroke through plughole and bore through exhaust port ten work CC out. Usual mods were to replace the IRZ? carb with a Mikuni, replace the front mudguard stay with Sammy Miller items, replace the sump plug with a countersunk / headless item and fit a kit with an extra rear wheel bearing to stop the spindle bending.

Malcolm Rathmell (as a ex montesa rider) the owner of MRS the Sherco importers might have or know where a handbook is. Same goes for Sandifords, although no longer Montesa someone may have a handbook laying about or know someone who has one. The trials fraternity generally being a helpful bunch the above would be worth a couple of phone calls just in case

In late 1996 a TYZ was £4,695 and you could only expect to get £200 ish off for a cash / no trade in deal. At about the same time they were selling off the last of the TY pinkies for about £2700 / £2900 A new Gasgas was £4269 but you could get £1,000 off that for cash / no trade in. Regarding the RTL Hondas in the mid 1980s I can remember them being much more expensive than anything else.

A speedometer is not needed for the MOT but it is a legal requirement for road use. Most MOT testers will pass a number plate which is not strictly legal - see previous posts If the bike is to be used at night or in poor visibility you need lights. If 2017 bikes are type approved with side reflectors fitted then it is probable that they will need them for a MOT. Without reading the EU type approval relating to the specific vehicle I cannot give a definite answer. We should be out of the EU by then. Slightly off topic here but I would hope after we depart the EU the ACU will lobby for trials bikes not to need a horn or speedo and be able to use reduced number plate sizes.

So did I

Dismantle it, then clean with HG stove glass cleaner then repack with new wool.

The original handbook that came with the bike had full exploded parts diagrams and torque settings. All you needed for a rebuild. Perhaps someone will have one laying about. If you are in UK try Sandifords or MRS (the sherco imported)

I fell that from the 1970s to late 1980s trials bikes (and other expenses associated with trials) were typically a much lower % of a typical wage than they are today. The probable reason for this is the increasing complexity of trials bikes and a drop (in real terms) of wages. When I was a third year apprentice a new bultaco 325 was about 21% of my basic annual wage. Today a new trials bike is typically 30 to 50% of a third year apprentice wage. At least the cost of watching UK WTC is now exactly same as it was in the 1970s

Not often you get the chance to put Toni Bou et al to rights

The fat wire windings on the stator are the power windings for things like lights, horn and fan (on a liquid cooled engine). The black box is almost certainly the trigger coil to time the ignition. The fine wire coil - not on the stator is the ignition source coil. This produces the power for the spark.. Resistance should probably be about 250 Ohms but this is not a reliable guide to condition. The only proper way to test it is on the engine and measure the output (or look for spark at plug) when turning the flywheel with a power drill. Does you bike have a CDI box or are the CDI functions integral with the HT coil? Bradford Ignitions may be able to help.

Almost any suitably sized inductive type crank or cam position sensor should do, even an ABS sensor. You probably want one with a resistance of between 800 and 1250 Ohms. Takes your to a local motor factor and see what they have. In UK I would compare sensors on Euro Car Parts website. You will have to adjust / shim the sensor so it is correct distance from flywheel. You could possibly even rewind your own with fine enamelled copper wire.

Possible reasons for oil pumping out are Wrong grade of oil - unsuitable oil can foam and expand Too much oil - check level Water in oil - this will be accompanied by discoloured oil - usually turns grey / milky / cloudy Leak into gearbox from crankcase - porous casting or faulty gasket.

Yet another win at Assen for Rossi and Cal only just beaten to 3rd by Marquez, brilliant race.

Those oils are as different a chalk and cheese. 800 is for an engine that is run hard and will probably be expected to be rebuilt fairly frequently. 710 is definitely the one for trials use especially if fuel with ethanol is being used. From the data it looks as if 800 is not TBN rated to combat acidity in fuels which comes from sulphur or ethanol.

Backfiring and non or difficult starting is often a sign of a faulty HT coil, an easy item to test or swap with a known good one. Thoroughly clean the filter, airbox, tank and carb and use new fuel. Water in fuel can cause these symptoms. My next move would be to check for a sheared or part sheared ignition flywheel key. The TRS stator is a different set up to most bikes - is there a hole in the casing where you could put timing marks on the flywheel and check the timing with a strobe. other than that all you can do is check the stator outputs (source and trigger) at the wires outside the case whilst cranking the engine. Edit - If its a Sherco then you can remove the ignition case to put timing marks on flywheels and spin flywheel with a power drill both to check timing and stator outputs.

You say your 50 is rich - rich means too much petrol for the air. An engine will happily run and stay clean with a fuel to oil ratio of 25:1. I have lost count of the number of time riders think they are putting too much oil in when the real problem is too much fuel due to incorrect carb settings / jets. Before you decide on the oil ratio for your 50 check what the bore material is. Some 50s have cast iron liners, I do not know about Sherco. A problem that can give rise to false assumptions about oil ration / carburation is the fact that many trials engines spend much of their time running below proper working temperature. Use an infrared thermometer to check the temperature where the plug enters the cylinder head. It wants to be a minimum of 88 Deg C. 94 to 98 Deg C being much better. If its over 105 Deg C then detonation and piston damage is a possibility. If you engine is being frequently stop / started and pottered about it might only be getting up to 65 or 75 Deg C which will mean it looks rich or oily when in fact its the way its being ridden is the problem.