feetupfun

Bultaco brake pedals don't usually have a return spring on the pedal, or the rod, or the cable, but there is no good reason not to fit one if you want to. If its the hole I'm thinking of it's for the brake light switch actuating link/spring. Some rear brake light switches mount on the swingarm and some mount to the frame above the swingarm pivot

It's standard thread direction

If you measure up a set of modern footpegs you will see that there is not enough space to fit them between the bike frame and the kickstart lever. Options for using modern pegs include: A device/method (locking pin, wire hook) that holds the peg up while you kick (popular) Lift the peg to let the kick lever go past it, kick start the motor, then let the lever retract past the peg. If you have a suitably light return spring on the peg this works fine. The kickstart doesn't engage until it is at peg level anyway (popular) Don't use a RH footpeg spring and keep the pivot action free. The peg will stay up if you lean the bike a bit too the left as you kick (popular but not legal in some places that require spring-return pegs) Reshape the kickstart lever to clear the peg end (not recommended due to the kickstart lever knuckle already being a bit flimsy and this method puts extra load on the knuckle)

The Yamaha Ty175 clutch cable works very well

Sherpa T rims are not meant to be central to the spoke flanges on the hubs, but sometimes are respoked centrally, which puts the tyres off-centre

Yes they are a bit zippy I think on watercooled bikes people sometimes use two base gaskets instead of one base gasket to reduce the compression ratio if needed. Yes it changes the port timing too but that is what I've heard. 3mm spacer under the head would be way too much anyway. I would think 0.5mm to 1mm would make a noticeable difference to compression ratio

Guy, young riders who ride twinshocks set a faster idle than you or I would usually have and they use the clutch almost everywhere so it is not really a "bike" thing, more of a "rider" thing when or if to use the clutch. I confess to using the clutch sometimes on my old trials bikes

If the sleeve is big enough to be touching the 8mm cylinder studs and is concentric with the PCD of the studs, then you should be able to go to 72.5mm bore

If you post a photo of the piston and the important dimensions of the piston it will make identification more likely

you should be able to change the condenser on a Ty175 without taking any stator coils off or taking the stator backing plate off the bike When you spun the motor with the drill and got 3.5V AC, did you have a sparkplug connected between HT and earth, and what RPM did you spin it at? You used a term for what you did to the killswitch that I thought I had better ask about. Did you bypass it or did you disconnect it? For what it is worth the most common loss-of-spark issues with TY175s are caused by (in no particular order) Worn main bearings Not enough points gap Dirty or wet or stuck or worn points Failed condenser Broken or cracked points or condenser wire Broken or cracked LT wiring Sheared flywheel timing positioning key Failed stator winding insulation (the last few inches) causing a leak to earth Less common: Loose stator coil mounting screws Magnets rubbing on coil laminations Repaint of frame causing poor earths of motor casings or HT coil Pinched or rubbed through insulation on killswitch or LT wiring Faulty HT plug cap

HDPE

for the adjustment problem: you didn't mention the ball between the pushrod and the mushroom rod. They can fall out unnoticed while you work on the clutch for the heavy action: inspect the camshaft for wear where the rod end rubs you might have been sold springs that fit, but are stiffer than TY175 springs. A lot of Yamaha models use similar but stiffer springs. Try the old springs lube the cable Because you have a combination of heavy action and lack of adjustment, it is also possible that you have too much plate stack height. Compare the thickness and quantity of the old plates with the new plates

Two strokes don't usually have oil filters

I think you want bigger front sprocket not smaller

As for the question of there being a need to remove mass from both ends of the shaft, it makes no difference to flywheel effect which end of the crankshaft the mass is removed from. It will however cause the bike to balance a tiny bit off vertical if you only remove mass from one end of the crankshaft

If you really want to, it is possible to calculate how much a difference a given change in flywheel arrangement will make to the total "flywheel effect". This will involve working out the total flywheel effect for the crankshaft (all 5 flywheels in the case of a Sherpa T) and the clutch and comparing it with the calculated flywheel effect after making the proposed changes. In the case of the machined-down drive side flywheels in taff_d's photo, I suggest if someone wants to reduce the flywheel effect, only machine the wheels narrower rather than reduce both their width and diameter. This will give you a much bigger (gravity) weight loss for a given reduction in flywheel effect.

I think there are new aftermarket tubes available from the US and the price is pretty much the same as getting the originals redone. Those tubes on Greg's bike came from a different bike that had 30mm tubes. From memory they might be from a CR80. I have seen other TY175s with shortened tubes from 80cc MX bikes. Early DT100,125 and 175 and early Yamaha AG bikes had 30mm tubes too, but because they are just as old as TY175 tubes it is rare to find good ones. Last time I had a set done (in Brisbane) they were $150 per tube plus postage, but it has probably gone up since then

If your "new" condenser is from 40 years old stock then it may have failed due to age. I use "recently-made" condensers and fit them externally. Another possibility is that you have not fixed the root cause by fitting a new condenser. There are lots of possible causes for an intermittent ignition problem Depending on your attitude to life, there are lots of options for how to get your bike reliable. Some people love to fault-find logically, some people like to have a completely original bike, some people want to spend the least amount of money possible, some people like to take a random approach changing things here and there and some like to minimise their stress levels. Modern electronic ignitions are very popular for good reason

My friends bike (175cc with the shorter extension (35mm I think) and 5mm lower axle slot) has the standard frame loop and feels lovely to ride, slightly more stable than standard. I'll see if I can find a photo of his bike Mine is 205cc and 45mm extension and is also very nice (more stable than standard) Photo of friends bike attached. Note his bike has non-standard fork tubes (much longer than standard)

Thanks Biff. I told my wife and it sounds like you aren't the only person who thinks Silhouette are good. Also sounds like "we" might be getting one

You can tell if this mod has been done without measuring by looking at the position of the axle slot relative to the shock mounts. I moved the slot 45mm rearwards and followed the same line as the old slots (not higher or lower). It is fairly obvious in my photos (above) A friend of mine did a similar mod but moved the slot less rearwards, and 5mm downwards

photos of Ty175 swingarm lengthening using home-made extensions

If you are talking about the weld-on extensions, I posted such a thing years ago and will look for the photos. In the mean-time, a brief sequence of events so you can decide if the job is for you; Remove the swingarm Cut off the first axle plate at the correct location and angle Prepare the first side for welding. I used double vee butt welds and manual arc Weld the first extension piece on Make a dummy spacer to replace the wheel, spacers, brake plate etc Fit the axle and spacer to hold the second extension piece in position Prepare the second side for welding, using the axle to make sure that the second extension plate is in the right spot to make the axle slots the same height, parallel with each other and the same distance from the swingarm pivot axle Tack weld the second extension in place Check everything is aligned properly Finish the welding Dress the welds back flat Make a longer brake tension link Extend the side stand a bit Move the brake arm forwards on its splines, or make a longer brake rod Bend the rear frame loop upwards a bit to miss the tyre on full compression

My wife had a Cricut for scrapbooking which sounds very similar, and it was also great for making custom motorcycle graphics. I didn't try making gaskets though. I say she HAD a Cricut because it broke down and we couldn't get parts. Has your machine been reliable and have a good parts backup?

Yes bb that is kind-of what I meant The reason why we use C3 bearings for the crankshaft main bearings is because there is differential expansion, meaning that the amount that the crankshaft gets longer and shorter as the motor warms up is different to the amount that the crankcases get wider and narrower as they warm up. If there is not enough axial movement provided by the two C3 bearings for the amount of differential expansion generated, then axial force will build up in the crankshaft and in the cases until one of the bearings moves sideways on its seat, which will relieve the force, until the motor cools down again, when the force will build up again until it is relieved by one of the bearings moving sideways on its seat. The sideways moving of bearing on shaft or bearing in casing will be repeated each time the motor heats up and cools down, gradually wearing away wherever the movement happens. I've seen it on the crankshaft where a bearing inner sits, and I've seen it in the engine cases, where a bearing outer sits. By using a roller bearing as one of the main bearings, the force never gets to build up because the roller bearing allows for load-free axial differential expansion, so the bearings don't move on their seats, so there is no bearing seat wear on the crankshaft or in the cases