feetupfun

Are you sure that a 1W1 pushrod is the right length? The 1W1 series motors have a different clutch camshaft and a different clutch to a TY175. I'll measure the TY175 parts later to tonight if I can find them

If you are serious about saving money, the big end hole in the conrod can be honed out and oversize diameter (imperial sizing) rollers can be used to refurbish it.

OK thanks. The TY175 I rode that had a TY250 mono front end also had a standard TY175 tank and it had a huge turning circle. If the owner had modified the stops to get a better steering angle then the fork tubes would have hit the fuel tank. I can see that if you use the right type of Majesty style tank then there might be clearance for the fork tubes and have a decent turning circle.

Yuk

Seeing the corrosion damage on the one-way valve in your photo, I suggest you also have a good look inside the tubes where the damper piston runs. The swept area in the tubes may have corrosion damage that will affect the damping performance even it you make or buy replacement damper pistons

Is see that the photo shows a Majesty frame. What did you do to the steering stops to restore the steering angle?

That aluminium part with the taper on it is a hand-slip-on fit on the damper rod when there is no corrosion. This part is the anti-bottoming cone.

The forks you bought are from a TY250 mono which is a completely different bike to a TY250 twinshock. The brake plate on a TY250 mono engages with the lug on the LH fork slider on the forks you bought. Those triple clamps will not match well with your TY175. They will have very limited steering angle side-to-side unless you get a different fuel tank and modify the bottom triple to suit the TY175 frame. TY250 twinshock models forks and triples can be interchanged with TY175 forks and triples without modification. TY250 twinshock forks look a lot like TY175 forks but have bigger diameter tubes and sliders. TY250 twinshock forks are also slightly shorter (about 20mm shorter overall) Your new forks have tubes that are too big in diameter to fit TY250 twinshock triples without modification, and your forks are leading axle, so the steering geometry will be wrong unless you also use the TY250 mono triples.

That seal sleeve is normally a light push fit. I haven't had to heat one up to get it off. Yes the big end should not have that much side play. Should be more like 0.5mm. Might have had the wrong conrod kit fitted. Some Montesas do have the conrod kept central by the top end of the rod, but Bultacos like yours use the bottom end of the rod to guide the rod and depending on the piston used, also may have centralising spacers on the gudgeon pin. Fairly standard Bultaco failure to shear the drive side key when something goes wrong. One Bultaco I bought recently had that nut welded to the crankshaft! Being a Sherpa T it was a slow process grinding the weld away inside the drive side flywheel recess. It's hard to see how much clearance there is on the outsides of the crank wheels in your video, but is it possible that the crank wheels have moved apart to cause that side play at the big end?

Also when you tighten the shock mount screws, do it in a way that avoids the shock mounting rubbers being gripped. The shock mount rubbers need to be free to rotate on the mounting pins to avoid side-loading the shockie oil seals as the swingarm goes up and down. Falcon shocks and many others have mounting rubbers that are wider than the Yamaha mounting pins are long. For this you can use spacers to effectively lengthen the shockie mount pins and tighten the screws up against the spacers, or don't bother with spacers and just Loctite the screws in the position that allows free movement.

If you are never going to dent a steel tank, then a stiff tank sealer that is compatible with modern pump fuel (epoxy resin) is OK. If you do dent a metal tank that has a stiff tank sealer, the lining will probably crack away from the steel and you won't be able to get the dent pulled out with heat and you won't be able to reseal it with epoxy again. So for a bike used on the road an epoxy lining is probably a suitable cheap fix. If the hole is in the tunnel it should be able to be welded or soldered up without the repair being visible when the tank is on the bike and won't damage the paint on the pretty parts of the tank. If you use a flexible tank sealer in a steel tank, it will eventually swell, go floppy, come loose and cause you lots of dramas while you try and get the liner out through the filler hole. I have had to do this in a TY80 (steel) tank and it took hours. The tank didn't leak, so it looks like someone had lined the tank just because it looked a bit rusty inside. You can find metal tank leaks by slightly pressurising the tank (lung pressure is usually enough) and brushing soapy water on while looking for bubbles. Using work shop air pressure or tyre filling air pressure can cause the tank to go way out of shape (permanently).

Can also use a bottle jack to push the tubes down. Push against the junction of the frame tubes near the front of the seat (to avoid bending the top frame tube) If you do it just right the mounting holes will line up nicely too. It's a common maintenance job on twinshock trials bikes that get ridden in trials.

Fabulous looking bike there Gary. Thanks for the photos. M27s are not often seen on the forums and I've never seen one in real life. I did look at an M49 that was for sale nearby years ago (pre-digital photos) that still had the original triples with the U bolts and the welded-on control levers on the bars. I'll see if I can find the photos I took at the time. I remember the seller had some parts that went with the sale, including spare crank seal carriers. He told me it was routine maintenance on the bike to change the crank seals every couple of months, so he bought spare seal carriers so the bike would be pulled down for the minimum time. I'm glad that crank seal life has improved since then.

Here are a couple of photos showing two of the types of top clamp that are being discussed. The upper photo is an M80 and the lower is an M49

If you have standard TY250 fork tubes and they are positioned with the top ends of the tubes flush with the top edge of the top triple clamp, the fork seal will get to 57mm from the underside of the lower triple clamp on full compression. I've put a black pen mark at 57mm in the photo

When you change the fork seals, put in at least 175ml of oil per leg. My previous post mentioning 125 millimetres is a distance measurement, not millilitres (volume). Sorry for the confusion. I see the pits in the tube chrome and will post again here when I've checked if your pits are high enough not to worry about. It looks like your fuel tank has previously been quite rusty inside and someone has treated it chemically to remove the rust. It is possible that your leak is a tiny rust hole somewhere in the tunnel above the seam weld and may be very hard to see. This would explain why it only leaks when the tank is near full. Another thing that may help is maybe you aren't loosening the top tube clamps when you remove the fork caps. These clamps need to be loosened whenever you take the caps off or put them on. The clamping action causes the fork tube to reduce slightly in diameter which can cause the cap threads to jam.

First work out exactly where the leak is. If you are lucky it will be underneath the rear end where many of the A model tanks develop a crack. That way it can be welded without damaging the paint job. No don't line a steel tank with kreem. If it is a fatigue crack then a repair with anything rigid like JB weld is unlikely to work for long. If you have some repair compound that can do a flexible repair on the outside then you might get away with it. Before you buy new springs, change the fork seals and set the oil level to 125mm from the top of the tubes, forks fully compressed with springs out. Use 5 or 10wt fork oil. Using the air space in the forks as a spring by running the oil level at that height will provide better bottoming resistance. When you have the springs out, measure their lengths and post it up here for advice on if you should add anything to the length of the preload spacers to set the sag to a good number.

If it's the one that uses U bolts to grip the handlebars, it will probably be the same as early M49 in which case there are plenty around

I saw a full set for sale on eBay yesterday (top and bottom triples and the stem) http://www.ebay.com.au/itm/Montesa-yokes-trials-pre-65-twinshock/222632902124?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

No, the M27 pipe runs higher where it goes over the head. M49 Sherpa T head is the same except it has cut-away fins to allow the pipe to run lower. If you are not worried about it looking like a M49, you could fit an M49 head. They are way more common than M27 heads because the head from the M49 is used on M80 Sherpa T and Alpina M85 and all three of these models sold very well while the M27 only sold something like 1200. Using a head with cutaway fins would also allow you to use that M49 tank, which would be too low underneath for a M27 pipe to fit under. Another option would be to cut the fins away to provide clearance for a M49 header. Please don't do that though. I would be happy to do a head swap with you because I would like an M27 head and have spare M49 heads.

My money is on the blue and red stickers being road rego stickers from 1987

Have a look first, you will have a good chance knowing it is in an odd place

oldaz please post photos as you bring it back to life. They are a nice bike

There are no windows or test holes or dipsticks for the gearbox or the primary drive compartments. While you are changing the oils, I challenge you to find the gearbox breather without the help of a manual or help from someone.

I have no idea who Steve is. The extra neutrals may not necessarily be due to a shimming issue, and may not require splitting the cases to fix. Whether you want to investigate what is happening yourself depends on how confident you are with this sort of work. We have OSSA specialists here in OZ that could fix whatever is wrong, but I suspect you might be in the UK.