feetupfun

Mine went from 67mm to 72.5mm bore and from memory the only thing I needed to change was to go a half-size richer on the pilot jet (25 to 27.5)

Yes Jon, the silver motor. The original TS-based motor RL250 with the fragile frame is all we have over here apart from a few Beamishes that were imported privately. I've been working on one (motor-apart type of working on) and noticed that the shafts, gears and bearings are massive compared with the 250 Yamaha and 250 Kawasaki. For interest I put Sherpa T 250, TY250 and TY175 crankshafts near the Suzuki crankshaft. The Bultaco 250 crankshaft (crank wheels, big and little end bearings, main bearings and shaft diameters) is similar sizing to the TY175. The Suzuki RL silver motor crank is markedly bigger in all diameters compared to the TY250 and way bigger than the TY175 and Bultaco. The Suzuki clutch basket and gearbox shafts are also massive. Funny though how all the Japanese mid-1970 250 trials bikes weigh about the same overall. From what I can tell the KT has a light motor, heavy frame and heavy wheels, the TY250 has a heavy motor, moderate weight frame and light wheels and the RL250 has a heavy motor, light frame and moderate weight wheels. I reckon it would take a lot of trials riding to wear out the Suzuki RL silver motor. I've only ridden a 325 black motor Beamish and it felt light to ride and had wonderful steering, but had massive flywheel effect.

Yes Guy the TY250 TS motor is flippin' heavy. Not as heavy as an RL250 motor though. The KT250 motor is quite light in comparison.

Maybe the crankcase is full of fuel or oil and some of it is transferring up into the combustion chamber, causing a hydraulic lock. Maybe the exhaust pipe is blocked.

You may need to provide info about which website if you want people to know what you are looking at. If it is the TY offroad website photos you are talking about, the frame in those photos is a modified TY175 frame. It has the swingarm pivot location moved forwards of the frame upright so it does look a lot different to standard in that part of the frame.

If an organiser wants to prevent people doing this, they only give out score cards for the next lap when the previous lap card is handed in. Sometimes permitted, sometimes not, some people care, some do not. Sometimes mentioned in rules, sometimes mentioned at riders' briefings. I know when my kids were little and needed lots of parental support, I preferred them to ride sections using this pattern so I only had to walk the loop once instead of 5 or 6 times.

No. Some TY175 models have the sidestand mount on the left side footpeg bracket, so if you use aftermarket footpeg mounts on that model you lose the sidestand. As far as the aftermarket footpegs kits are concerned, the are designed to fit all TY175 models. There are also quite a few other frame differences between the two types of TY175 frame, but I suspect you are only asking about differences that affect using an aftermarket footpeg kit.

That is quite a big difference in chain length. Option A If you change the front sprocket instead of the rear you MIGHT get away with using the same chain length. If you say what number of teeth are on the front now, someone can work out how many extra teeth on the front will give you the same change in gearing (I'm guessing one or two extra teeth on the front) Option B If you buy a second split link or a one-and-a-half link you SHOULD be able to use the piece of chain you remove when you put the bigger sprocket back on again. For both these options, the likelyhood of success depends on how far back your axle currently is in the slot at the moment and what your adjustment range is and if you have 428 or 520 size chain.

This flywheel is from an OSSA 250 Explorer. The thread the puller screws into is 27 x 1.25 RH

Here is what the RL250 clutch parts looks like. If seeing these doesn't clear up your mystery, let me know what you want measured

OK I'll find the clutch parts on the weekend and take photos. I've got an RL250 motor apart at present

Have you got the washer that goes between the basket and hub?

Thanks Jon I saw he was from Ipswich and thought it was (Aussie) Ipswich

I'm intrigued as to why do you want to make it a 125

Tagging this to remind me to have a look at mine

Yellow or orange or red means weak spark. A good spark is blue. It can have a weak spark and still run OK but start poorly because the spark voltage drops off with reducing RPM and kickstart RPM is lower RPM than running RPM. Problems with the HT lead or cap will reduce the spark voltage. The spark when you look at it with the plug out of the cylinder will always be a better spark than what happens inside the combustion chamber because the pressure in there is higher (a higher voltage across the plug electrodes is required for a spark when gas pressure is higher) Another way to test for a weak spark is to reduce the plug gap and see if it makes an improvement to starting. Try about 0.5mm gap. This makes it easier for the spark to jump the gap but is only fixing the symptoms not the problem. What I've written here about the spark is just for diagnosis. The fact that it starts better when up to temperature makes me think that your starting issue is more likely a fuel/air ratio issue. If it revs up a fair bit with the choke on when starting cold, that can mean that the starting circuit is not letting in enough fuel. The "leaning the bike over" test is good for diagnosing this. You can also see what happens when the bike is up to temperature and idling then you put the choke on without touching the throttle. If the motor stops or runs very rich then your choke is working OK but if it revs up or runs normally with the choke on and throttle closed when at running temp, there is too little fuel going through the starting circuit for cold starting.

Here are some possible things you didn't mention Air screw maybe set too lean Spark plug cap failed inside Spark plug wire failed inside Colour of spark Reeds sitting against seats What you are doing with the throttle as you kick it Is it any easier starting hot or cold The SY250s I've been involved with won't start unless they get spun over fast enough but run fine once running.

If the parts are clean, smooth and lubed the aluminium part will slide off the damper rod under it's own weight. No thread, no need for anything. It is held there between the damper rod and the slider by the screw that holds the slider on.

Yes the tapered aluminium tapered piece has to come off for the damper rod to come out the top. It could be stuck on by gunky old oil sludge

A common cause for slow fan is fan rubbing against something. You didn't say if the 2 Volts is with the fan connected or not. Test for open circuit voltage to see if it is a fan problem or a power supply problem.

The length of the spacer is not particularly critical, as long as it is a bit longer than the distance between the bearing seats, which you should be able to measure. The thin disc near the middle is not important. It is there for when you are fitting bearings. You can hold a plain spacer in position with the axle while you fit the bearings.

You will need to say where you are because rules are different all over the world

Maybe the clutch plates are a bit thinner than normal

TY175 push rod 122.4 mm TY175 mushroom 62.5 mm Have you got enough clutch plates in it?

If you do go the honing route, there are imperial-sized big end rollers made for Harleys that are slightly bigger diameter than the Bultaco rollers. I'm not surprised that there are a few things wrong with your motor because I have never encountered a second hand Bultaco engine that didn't need extensive internal attention before being re-birthed. One I bought recently the crank was so chewed up on the magneto flywheel taper, that half of the crank is unusable. The other side of the crank had the nut welded on, but should be OK to use. Another Bultaco I bought had the primary drive chain welded together. I figure someone couldn't work out how to get it apart so they ground the end off two chain pins, then welded the cover plate back on the chain afterwards. I haven't pulled either of those motors fully apart yet (saving the fun for a rainy day) At least the price of Bultaco conrod kits has come down in the past few years. I remember doing up a 350 Alpina engine about 15 years ago and back then, the piston kit and conrod kit cost about twice as much as the same parts cost for a M49 Sherpa T motor I did up recently.