feetupfun

On some old trials bikes, anything but the plain standard type of chain can be too wide to fit at the front near the front sprocket. Another thing is that O-ring chains have more parasitic drag than a lubricated non-O-ring chains, and weigh more. Standard chains used for trials riding last many years here where it doesn't rain much so there is little reason to use anything else. O ring chains last a lot longer (in distance ridden, not necessarily age in years) than non-oring chains especially in wet, muddy or dry sand riding.

you shouldn't have to take the brake caliper off to take the wheel out

First off does it have USD forks or slider-at bottom forks? My memory is telling me that on slider-at-bottom forks, you loosen the clamp bolts at the head end of the axle and unscrew the axle. The axle has a socket hex head (maybe 12mm hex) at one end and the other end has a male thread that screws into the fork slider

There are two different standard TY175 carbies. One has a stamping 525 - ***** and the other is 1N4-*****. They have different jetting and are that way because there are two different TY175 end muffler designs and the 1N4 carby bike comes with a rubber snorkel on the airbox lid. Have a look at your carby and see which one it is. If you want the alternate jets on hand for when you test ride the bike, you can take the pilot jet and main jet out of the carby and read the sizes that are stamped on them and maybe buy jets one size bigger and smaller. You can buy genuine Mikuni jets from a Mikuni agent or aftermarket jets from multiple sources. The non-genuine jets are sometimes not size stamped. Pilot jets for those carbies go up in intervals of 2.5. For example 22.5, 25, 27.5, 30, 32.5, 35 etc Main jets for those carbies go up in size in intervals of 5. For example 130, 135, 140, 145, 150, 155, 160, 165 etc Both jets are commonly available types. You can look at Mikuni parts listings on the internet. Look for Mikuni VM type carby parts. You can probably also buy them as Yamaha TY175 parts from a Yamaha shop but that would be quite expensive. You may not need to make any changes to the jetting

How much a bike weighs on scales does not always match how heavy it feels to ride.

Yes Jon. I think I've even measured it up (KT motor in TY250 frame), but motivation to do such a thing is low because it is then neither fish nor fowl. I've also briefly tried a TY250 front end on a KT, but again it then isn't a KT any more and if I want to ride a bike that steers like a TY, I just ride a TY.

If you can kick your bike over fast enough, there is a good chance that some of the liquid might get deposited onto the plug tip, but there is no guarantee. However it sounds to me like you can only kick it over slowly with the plug installed. Turning a two-stroke bike upside down with the plug out and rotating the engine with the throttle open is a definitive test, and a good way to clean it out. Be aware that the crankcase might be where the liquid is sitting and causing the hydraulic lock. The crankcase will drain via the transfer ports and squirt out the plug hole as you rotate the motor when you do this test, if there is liquid in there.

If you are dead set keen on using the original tank to hold fuel, you could line it with epoxy.

You could always use an aftermarket (Clarke Manufacturing) plastic tank on a 247. It would no longer look like a 247 though.

If you weigh 25 kg then yes it is completely normal. If you are of average weight or above then it sounds unusual. It has been suggested to you that the kickstart problem might be caused by "hydraulic lock" due to oil or fuel or water in the combustion chamber, but you have not acknowledged that this might be the cause, or explained that you have tested for hydraulic lock and proven that it is not caused by hydraulic lock, but are asking again for possible causes for extreme compression. A good way to test for hydraulic lock is to remove the fuel tank, remove the spark plug, activate the kill switch, invert the bike completely and look for fuel or oil or water coming out the plug hole. If nothing comes out, open the throttle and slowly rotate the motor using the kickstart or the back wheel. If nothing comes out, then the problem is something else.

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