feetupfun

If you have a TK that is working OK I would stick with it. They work beautifully on the 434 model. Different story if it has a worn slide, needle or needle jet. My 434 still runs the original TK carby and it is the best running of all my TY250s I have often wondered why Yamaha went away from using TK carbies on the TY twinshock 250

I find that all the TY250 motors stall quite easily in some riding conditions if there is no weight band on the flywheel. If there is only dirt with good traction, I had no problem with running a flywheel with no band. If there is slippery or loose riding, I found a reasonable risk of stalling. After experimenting with no weight band on B and D model motors, I now use a weight band that is approx half the width of the BCDE model band and run standard spark timing on my B and D model motors. I run the standard flywheel with standard weight and standard spark timing on my A model motor. B C D E models here came with weight bands about twice the size of the A model weight band. By personal preference, I ride everywhere without touching the clutch which is maybe why I like a bit of flywheel weight.

Guy with the B and later model motors you can run them with an earlier spark than the A model without fear of stalling, unless the B or later model flywheel has been extensively lightened

Mine is an Australian SP370 and I'm pretty sure it was 6V, but the lighting circuit went to about 18V during normal riding without a battery. I only rode it with a battery until the motor was run in, then it morphed into an enduro bike using RM250C parts

Blowing bulbs was pretty commonplace at the time they were new. Yes they did not come with a voltage regulator so the voltage goes up and down with RPM. A simple way to avoid blowing bulbs is to fit 12V (or 24V) bulbs instead of 6V but they will not be as bright. Another option is to fit a ballast resistor in series with the lights to drop the voltage. Another option is to fit a rectifier and battery to stabilise the voltage. Another option is to fit a voltage regulator. The one I use on an SP370 that I ride without a battery is from a 1980s Husqvarna and it limits the voltage to about 13V so is perfect for 12V bulbs.

the routing of what looks like the ignition wiring up past the rear of the clutch cover is odd, with the magneto being on the other side. The standard wiring route on these is vulnerable to impact because it emerges from the bottom of the magneto case. A common mod is to reroute the wiring through the front of the magneto cavity in the engine casing to avoid problems. Maybe your wiring has been rerouted a different way to avoid problems. A skidplate from any of the MAR models should fit your bike. The first model MAR had a skidplate made from a composite material that was easily smashed to pieces with use. Later MARs had a nice aluminium skidplate, so there are less aluminium bashplates in existance than there are OSSA MARs

Those footpeg brackets have been added by a previous owner. Same for the bizarre sidestand mount It looks like a Mk1 MAR to me

Very likely to be the reason woody. From memory it was about 1mm that had to come off the steel spacer

yes the Yamaha OEM TY plastic bushes fit the Godden Majesty 250/320 swingarm. I did find that I had to slightly shorten the inner bush (the steel one) that came in the kit from John Cane.

Even with standard chain adjuster cams on a TY175, it is best to fit them one way when the axle is nearly at the front end of the slot, and the other way when the axle is nearly at the back end, because that way you can keep the handles/tabs away from passing rocks

The TY175 rubber carby connection to the reed block is offset to the left relative to the reed block, presumably to place the carby further away from the exhaust than if it was straight. As a consequence of the offset built into the rubber part, the inlet path hole in the rubber part does not line up with the inlet path hole in the aluminium reed block. By fitting a rubber connection from an RD350, the holes line up, resulting in less restriction/drag in the inlet. Further reductions in inlet drag can be gained by fitting a 26mm carby instead of the standard 22mm and using a better breathing airbox

that oil/petrol ratio should be OK. If the tank has not been relined to protect it from the damaging effects of modern petrol, I wouldn't put any petrol in the tank unless you are sure that the petrol you are using has no ethanol in it

When it reaches the rev limit of 2500, does it die, 4 stroke, 8 stroke or misfire unevenly? Does throttle position make any difference to its upper rev limit?

Making it the same number of links as the one that comes off is a recipe for problems because the previous owner probably took links out as the chain and sprockets wore.

I think it is the sliders that are machined rather than the staunchions The Norton sliders are machined to a larger ID The modern sliders OD are machined down to fit inside the Norton sliders (and held there with glue)

on some other Montesas that share that same casting, that cover is the cover for the two-stroke oil injection pump

http://www.yamahaty.com/english/ty250en/technique250en.html use the info for TY250 type 516

If this is twinshock TY250 forks, the sliding contact areas in the fork sliders are integrally cast with the sliders ie they don't have removable bushings. The seals John Cane sells work well. Some others do not. Standard oil volume is fine. The first model TY250 oil volume is slightly different to BCDE model forks. Oil weight is personal taste. I find the standard forks work fine with 10 WT or 15 WT fork oil. Spme people use 5WT. The springs may have become shorter if they are originals. New aftermarket springs are available.

Scorpa 2T was Rotax water cooled motor then Yamaha TYZ motor then Sherco motor

In Australia we ride trials in river and creek beds. Some public land is protected from use by any motorised vehicle, but privately owned and privately leased land usually has few limitations relating to vehicle use

When Scorpas started coming out with the Yamaha 250 two stroke motor, I went to my local Yamaha shop and told them I would like to buy one from them but it had to come badged as a Yamaha like the one I had seen photos of in Japan - so I didn't get one

I would get the original casing repaired to reduce the potential for reassembly dramas If it is just the hole that the kickstart creates in the magneto casing, I would not pull the motor apart to fix it, but would fix it while it was apart if I had to pull the motor apart for some important reason

The Alpina/Frontera/Pursang front hub does look very similar to a Sherpa T front hub, but it has a larger diameter brake drum. The similar appearance is why I suggested it. It is hard to tell the difference visually unless both wheels are close together. I can arrange a photo showing this if you like. There is a slight weight penalty with the bigger brake drum. I have a couple of spare front Alpina wheels and brake plates I would be willing to sell if someone wants to make this change, but I am Australia so postage to overseas would not be cheap

yes I would think there is a pretty good chance of there being something unusual inside your 247 motor seriously - if you are using a different LH crank casing it would be a good idea to do a test-assembly of the gearbox with the correct centre gasket before you fit the crankshaft

or use an Alpina/Frontera hub