feetupfun

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.

http://www.southwestmontesa.com/manuals.html Many photos of what they should look like on the internet too There are plenty of people on here who are intimately familiar with your bike so if there is something you aren't sure of just post up photos here of what you are wondering about

Use a M212/213 Alpina tank

I've got some early Bultaco front hubs and brake plates that might be what you are looking for, but I need photos to identify exactly what it is you want

Q1 yes you can buy 428 chain sprockets for Ty250 Q2 Chain size/type has nothing to do with gearing. It is the ratio of the sprocket sizes that determines gearing 14/53 ratio = 3.79 = too fast for trials 12/44 ratio = 3.67 = even faster! 12/53 ratio = 4.42 = good for trials - good choice for 428 chain 10/44 ratio = 4.4 = good for trials - good choice for 520 chain

This shows the thin flat sticker I bought in 1975 when I repainted this M99 Alpina

My memory is that the thin flat stickers were all you could buy at Frasers as replacements in the early and mid 1970s

Yes with a 14 it will be crap for trials competition. The BCDE models had 13 as standard. I would need to look up a book to see what A model had. No Idea about the number of links. I usually just buy a 120 link and shorten it to whatever is needed. Going from 12 to 14 on the front makes very little difference to the chain length. If the axle is near the rear end of the slots with a 12, it should allow a 14 with no extra links. You will need bigger than 14 to ride at highway speed.

The modern ones are much more crash resistant, but use a decent adhesive. Some modern ones come with a pressure-sensitive adhesive that does not work well when confronted with petrol, heat and vibration

Sad to hear, Guy