feetupfun

Yes some model DT175s had the same diameter (but longer) fork tubes. TY175 is 30mm so you are looking for for DT175 ABCDE. F and later are bigger diameter. Unfortunately they are as old as TY175 fork tubes so good luck finding any that are in better condition. You may do OK with some models of CR80 and other 80cc MX bikes which also had 30mm fork tubes and are newer than TY175 era

Both. They take up no floor space that way. The black frame is Bultaco Campera (project). The red 348 frame came with an almost-complete 348 which I was doing up to ride, then got my "good" 348, now that other one is spares. That red 348 frame is fairly rusty but might be useful for something one day. That other frame is a Yamaha frame that is very sad but I couldn't bear to throw away (spare/project). I can only lift them up to hang them if there is no motor or wheels fitted.

I've seen it done successfully on a TY250 twinshock using a 3/8" UNC bolt at each end

Better late than never. Here are a couple of photos of 348s. One has the loops and I think it is the final model 348 frame. The other one is my 348 ride bike and the side pieces are made of curved 3mm steel plate welded to the frame rails. It was like this when I got the bike 15 years ago and it works pretty well so I have left it as-is

Fork spring preload spacers are used to tune the preload to give you the right "sag". You adjust the sag with the bike assembled by taking the caps off. If someone rode it successfully before you got it there is a good chance that the sag will be in the ballpark already. With fork seals in your 349, you can use two skinny ones or one wide one. You are only limited by the depth of the hole below the retaining clip. Yes, In Motion sell the skinny ones and using two skinny ones was common practice when the bikes were new, and is still commonly done and it usually works well. Some people seeking to reduce the friction fit only one (wider, double-lipped) seal and some people reduce the tension on the tiny springs that hold the lips against the tubes. It's a free world. What you are doing has a good probability of success. SKF have started making fork seals from some modern fancy low friction material and they are available in your size and are expensive. I've yet to try the SKF seals and the Spanish forks I put together last week (Bultaco M85) have the In Motion seals in them. The Spanish forks I did before that I fitted a single 10.5mm wide seal (Bultaco M49) and they worked fine too. One problem cropping up with our old bikes is that the sliders can develop enough wear to cause the tube to move about too much (radially) in the slider for the seal to work properly. Modern forks have replaceable bushings in the sliders but the old bikes don't have this. If the play is causing problems, they can be machined out to take a sleeve or maybe replaced with less-worn second hand sliders.

The big lips point downwards. Small lips (if any) point upwards. The side with the writing faces up. If you have two seals per leg, yes both seals go the same way up. What spring spacers are you asking about? Those forks sometimes suffer from a plastic part at the bottom of the damper rod becoming a tight fit in the hole they go into as the forks bottom. You can test for this by working the sliders. If they stick at the end of the travel, it is a good idea to machine the part back to size or make aluminium replacements while the forks are apart. They are white/translucent plastic tapered cylinder shape and fit between the bottom end of the damper rod and the slider. They are called anti-bottoming cones

Yes it is good to make a drain hole. Whatever way the water gets in, by condensation or by getting sucked in with the cooling effect of the warm casing going under water, a drain hole will allow the liquid water to drain out. I use both a vent and a drain on my magneto casings. I usually make a plain hole about 5mm diameter in a place that is unlikely to be blocked by debris. Depending on how free-flowing the vent system is and how cold the water is in the creek, some water may be drawn in through the drain, but of course any water drains straight back out again. The only weakness with the drain concept is that if the bike engine is submerged for a long time, the casing will fill up, whereas if there is only a vent it will suck a bit in, then stop filling. It is good practice to remove or loosen the magneto cover after a wet ride or after washing the bike so that it drys out fully inside, even if there is a drain and a vent, to minimise corrosion.

Alternatively, you can buy the bolt as a Yamaha part. I've seen them advertised on eBay Can't see any at the moment though

Pretty sure I machined the nut, leaving just enough hex there to tighten it with

There are two reasons why people remove the bottom rails and fit a structural bashplate on Montesas (and Bultacos). One is that the original tubes become so badly damaged from impacts that fitting a structural bashplate is cheaper and easier than replicating the original design. The other is the improvement in ground clearance without raising the C of G. Montesa and Bultaco eventually moved to using the structural bashplate design in the late 1970s (Cota 349 and Sherpa T 198/199A). From what I've seen in old photos, it is a concept that appeared in about 1968 or 1969, initially on the Sammy Miller Highboy Bultaco frame. I reckon if you did it to a Cota 247 or an early Bultaco, you would have to be very careful with the design to avoid reducing frame integrity, which is marginal already on those bikes.

The third model 348 (1978?) also has those tubular loops for case protection

are you saying you can make this gear from a drawing at a lower cost than buying the part from Beta?

From what I remember, the narrow spacing was considered a success for making the front end narrower and a failure because it jammed up with debris too easily and they went back to wider spaced fork tubes again. I'm thinking the narrow spacing triple clamps came out in about 1981 and by 1983 they were back to wider spacing.

I'm lost now. I thought this was about front tyre side clearance on an MH200

That's true that the exhaust header is probably the same shape, but the Alpina frame on some of the models with the Pursang triple clamps is different to the M199 and M199A Sherpa T frames and those same Alpina models have longer fork tubes than the Sherpa T, which increases the clearance to the exhaust. I have a M138 which is one of the Alpina models with the Pursang/Frontera triple clamps and preventing the front mudguard from touching the exhaust (and also making sure the front tyre knobs miss the mudguard on full compression of the forks requires a great deal of care when setting it up. Yes the bigger Alpina/Frontera front hub/brakes are amazing, but are a fair bit heavier than the Sherpa T front hub/brakes

Some people do use Pursang/late Alpina/Frontera triple clamps on their Sherpa Ts to increase trail, but beware that the front guard may then hit the exhaust pipe if it is a standard exhaust header. I didn't notice what was done with the steering stops and haven't tried it myself. I like the way standard late model Sherpa Ts steer when the suspension is set correctly so am not tempted to make changes.

What you have described is an indication that the trail dimension is currently less than ideal. You can increase the trail by lowering the rear of the bike or raising the front, or both. It can also be increased by reducing the offset as you have said. Riding technique also has a big effect on what you are experiencing. For the front end to work properly in tight turns on many twinshocks, the bike needs to be leaned towards the inside of the turn (probably a lot more than you think is normal) and the rider's weight should be on the outside footpeg.

I've bought some of these to get the pads https://www.ebay.com.au/itm/New-Chain-Tensioner-Tentioner-Universal-Fitting-kit-and-pad-motorcycle-classic/222778684239?hash=item33dea4f34f:g:hnQAAOSwqu9VJP1M When I look at eBay it says 12 UK pounds

What does your tensioner look like? There are few different types and some are easily available at low cost

The same can be said about early to mid 1970s 250cc vs 325cc Sherpa Ts. They both have a similar rated maximum output, but the 325 has much more power at low to mid RPM (from memory they are rated at 21 and 22 horsepower at their peaks) The reason for this is that the gas volume throughput of both motors is limited by them sharing the same size carby and the same size exhaust system. My Alpina M138 350 is also an amazing tractor like the M116 at low to what would be mid-RPM on most other big two stroke bikes of the era so I know what you mean. It doesn't stop you going fast in the bush though, because it has enough gears spaced apart enough to suit the power spread. I find that it is the suspension that limits how fast I am game to go in the bush (so I can still hang on) I'm currently rebuilding a M85 and am greatly looking forward to riding it too. I expect it will be much more like my Sherpa T 250 in handling and motor than the M138, because the early Alpinas share frame and steering geometry with the early Sherpa Ts, while the M138 is longer and has the Pursang triple clamps

If you mean increasing the offset so the kickstart clears the brake pedal fully, not a good idea because if the kickstart rotates much past the brake/footpeg, the kickstart mechanism stop punches a hole in the magneto case. Standard practice is to use the footpeg to stop your foot taking the kickstart lever past there, and don't mount the kickstart too far forwards either or the stop will hit the mag case even before the lever goes past the footpeg. Unless you are very tall, lengthening the kickstart will make it even harder to kick over because your knee and hip will be at even worse angles. Try putting the wheels on something to lift the bike a bit higher and see what you think Yes freight from the UK is horrendously expensive to here too. I usually minimise the cost as a proportion of the total by doing big orders, and making sure I buy all the big light things like mudguards at the same time. Also do joint purchasing with friends. I don't know how NZ sales tax works for imported goods, but here if the order is valued under $1000 it doesn't attract australian sales tax (GST) There is a lot of help available on the internet about cleaning up oxidised plastics and even discoloured fuel tanks. I usually break mudguards before they get too grotty-looking, and don't like plastic tanks so have never tried doing it.

Large capacity single, short kickstart lever located high up and too far forwards. I ride a 348 and find that in the course of riding a trial, kickstarting the thing at each section on the first lap tires me out more than riding it, and mine starts perfectly. I'd hate to try and ride one that was a cantankerous starter. It's too hot here to leave it idling while you walk a section, but I am certainly tempted. I think the decompressor is there to ease it over TDC before having a decent lunge at the lever, and to make rude noises with. As for the mudguards, you can buy new replica mudguards easily. I can't tell if yours has the new-fangled lopolene? plastic tank, or is a fibreglass tank, or has a fibreglass cover (shelter) over an aluminium tank. Fibreglass gelcoat can be polished.

GasGas GasGas 280

That's the reason I got one

pmk, those bikes are all in the same class in Australia. Our classes are Pre-65, Twinshock Pre-87 (air-cooled mono excluded) and Air Cooled Mono. For a while the middle class was Pre-84 (to exclude air cooled monos), but the cut-off date was later extended to allow the (1985) TLR250 in