feetupfun

I use rattle can epoxy enamel on engine covers (inside the magneto cover too) because it is good for preventing corrosion and easily be retouched on the outside when scratched. Powder coat is a tougher finish, but not tough enough to avoid being scratched by rocks, and then will need stripping off and recoating to look good again

Yes the cutaway does make a difference but it may still be OK. Certainly no problems with trying it out with the slide you have Also it is a common tuning method to increase the cutaway dimension, so while yours might have started out as a 2.5 it might actually be a 3.0 or 3.5 if someone has resized it. If you can still see the anodising on the edge of the cutaway then it has not been resized

I just looked in two Yamaha parts books. One was for TY250B and the other was for TY250C. Both have the carby with the main jet holder in the float bowl. These models have different jetting, but both showed the same part number for the slide and listed the standard slide as a 3.0

This is a fascinating subject. I am greatly enjoying reading about people's experiences. My 2c worth at this point is that the flatness and surface finish of the hub surface is a critical factor with new linings. Because of what you found with your chalk test I'm wondering if maybe the bead blasted finish on the hub surface cannot hold enough friction material

The wedge ring will seal the air in the tyre. You can plug the extra holes with anything. It just has to keep the water out to avoid corrosion under the wedge ring. Neutral cure silicone rubber would do the job

Guy, this is the sort of thing I am talking about http://www.ebay.com.au/itm/Mandrel-Mild-Steel-Exhaust-180-Bends-O-D-1-5-8-41-2mm-/261818493610?hash=item3cf5992aaa:g:7DwAAOSwv9hW2RQx

Did you refit the ignition cover with a thinner gasket or with no gasket? That would have the effect you described

Guy I make TY header pipes from pre-formed tube bends (from an exhaust repair shop). One 180 degree bend and one 90 degree bend is enough for one TY250 header pipe and they are not expensive. I don't know of anyone selling off-the-shelf headers that fit close enough to the head to suit raised motor TY250 and use the aluminium tank.

My Alpina 138 still has the original chrome brake drum surfaces and both brakes work very well. I wouldn't bother changing the drum surface just to change the coefficient of friction

The standard Alpina drum has a chrome liner, but like the Sherpa and Pursang drum, the chrome sometimes lifts and people get a steel sleeve fitted

As for power you can take it to about 270cc with the standard sleeve. Some people fit reed valves. In my experience that particular motor is a dream to use in completely standard tune running well so maybe you just need to ride it some more and it might grow on you

That hub did not come with a chrome lining. Later Bultaco hubs did have a chrome lining Like every other drum brake, just because the pieces are all in place, it doesn't necessarily mean it will perform well Even if everything is perfectly set up perfectly in that particular hub, it will not work as well as many other twinshock trials bike front brakes, so don't get excited about it ever working strongly. As with all drum brakes, here are the things that need to be done right for it to work as well as it can: The drum surface needs to be smooth (shiny) The drum surface needs to be concentric with the axle The drum surface needs to be parallel with the axle The drum surface needs to be clean The curvature of the show friction material needs to perfectly match the curvature of the drum The outer surface of the friction material needs to be concentric with the drum surface The friction material needs to be of modern composition and designed for the purpose The friction material needs to be bedded in (smooth) and clean The wheel bearing races need to have minimal running clearance The bearings need to be solidly mounted in the hub The axle needs to be installed so that the friction material is centralised in the hub The camshaft needs to have minimal clearance in its bearing The cam needs to be almost flat against the shoe pads as the friction material touches the drum The camshaft arm needs to be at 90 degrees to the cable inner as the shoes touch the drum The cable outer needs to be kink-free and clean inside The cable inner needs to be kink-free and lubricated The camshaft lever needs to be the right length The handlebar lever needs to have the correct leverage ratio and be free-moving There are businesses that can do the relining and machining of the shoes and drum for you A common mod for Sherpa T front brakes is to fit the front hub or front wheel from an Alpina from M115 onwards or from a Frontera. They have bigger brakes that work well, but being bigger, do have a slight weight penalty. Alpina front wheels are commonly available on eBay. They look like the later model Sherpa T front hub. Most people would not tell the difference unless they were side-by-side. I can post a photo if you want

I just read again and see that you had the cases apart to swap the gearbox over, which introduces the possibility of air ingress via the centre gasket leaking

flywheel weight change is unlikely to be the cause. Pretty hard to diagnose from your description. It sounds like it might be lean at near-closed throttle position. This could be poor jetting, or a restriction in the pilot circuit, or air ingress downstream of the carby or a combination. Modern fuel is notorious for blocking the pilot jet if you let the fuel in the bowl evaporate The magneto side crank seal going hard is a common source of air ingress. If it is leaking, there will probably be a witness of oil near the seal behind the stator. There are also plenty of other possible air ingress sites Are you sure that there is enough fuel flow to the bowl, to keep the level up? Original Bultaco fuel taps are notorious for poor fuel flow rate Is it geared low enough in first? M97 Alpina?. The first Alpina 250 was M85 and the first 325 Alpina was M99

A Yamaha 3U5 carby is a bit small for a 325. Marginally OK on a trials 250. I run that size Yamaha-Mikuni on my 210cc TY175 and it goes great

Don't know that one, but do know that Honda CR125/MT125 friction plates fit into Montesa Cota 348 clutch baskets, if you remove every second tang

Maybe your AMAL Mk2 is different to this one? This shows one with the "choke" on (plunger out)

While it is possible to successfully degrease fibreglass tank internals in preparation for an epoxy coating, if you get it wrong, you may end up with a gooey mess on the floor instead of a fuel tank. I've successfully degreased and internally epoxy coated 3 or 4 old Spanish tanks that had contained premix and the results have been very good, but the degreasing process needs to be done with a full understanding of the risks and consequences before you start

Your description of the problem is not very clear, but if the piston is in backwards in a Sherpa T or any other bike with piston port induction timing and a piston with uneven length skirts, it greatly affects the inlet timing which can make a bike quite gutless and greatly affect the jetting requirements. If it hasn't been pulled apart since it last ran properly then it won't be this Please don't take offense but I hope you are using the "choke" lever the right way. I'm pretty sure with AMAL Mk2 the "choke" lever operates in the opposite direction to the "choke" lever on a Mikuni. AMAL Mk2 lever up = on, lever down = off. An easy way to check is "choke" plunger in = off, "choke" plunger out = on If it is not that, the consider that the "choke" on an AMAL Mk2 only has a significant effect when the throttle is in the closed position. It is not really a choke, but is an extra fuel circuit that only allows fuel to flow when the throttle slide is at the bottom. If the bike runs normally with the "choke" on, then the problem is in the pilot circuit of the carby. It is not unusual for the pilot circuit to be blocked in a used carby and it makes no difference what you do with the pilot jet if any of the pilot passages are blocked. I suggest if you can, to test the bike with the carby from a similar engine that is known to run properly.

Possibles: piston in backwards blocked exhaust worn rings pilot jet and starting circuit jet in each other's locations (they are the same type of jet but have different size holes)

The sale price sounds pretty normal to me

The other thing that would make it look a lot better would be to fit a replica of the original rear mudguard. You can get them in red or white and it would make the rear end look much better

They are rare indeed, mainly because the 349 sold alongside the 248 was seen to be a better bike (they were not desirable when new which is why they are rare now) However nowadays some oldies like me who still love riding twinshocks see things differently than we did when we were kids, and nowadays I would prefer to ride a 248 than a 349 of the same year As far as making it look nice, I've recently seen Montesas of that era that have modern build, shapely aluminium fuel tanks, and I prefer that look to the original Montesa seat/tank design. The TY tank doesn't look quite right in a single colour, but with some clever design input, it could be re-painted to make the bike look very attractive

Kickstart - yes Engine number - yes

People call lots of things Sammy Miller Replicas. You could buy lots of aftermarket parts for Sherpa Ts from Sammy Miller products that were developed by Sammy Miller and used on the bikes he rode, including distinctive-looking frames I've even seen a standard Honda TL125 advertised as a Sammy Miller replica