feetupfun

How well did the multi-drill deal with the hardened bolt shank? I've got a similar problem but with a handlebar clamp bolt and am trying do decide how to deal with it

The visor came with my trials helmet and it is still there and I've never used it. If I'm going trail riding on a trials bike, I use a motocross helmet

The standard fuel tap thread in an Alpina tank is a metric thread M12 x 1.5

Viton rubber is the go for petrol o rings

Looks like it's been through hell. Has it been chewed up by an animal?

1 I can't understand your question. 2 There are usually anti-topping springs on the damper rod that have this effect. The intention is to avoid harsh metal to metal impact when the forks extend fully (like when you riding up a steep bumpy hill). It's also possible that the fork spring preload is too small to hold the forks at the top of their travel. 3 Some fork caps have vent valves that hiss when you compress the forks. Some caps don't have venting. Sometimes with vented caps, the valve sticks shut and doesn't let air out. If yours are the vented type, you should be able to find a small (1 mm) hole on the cap where the air comes out.

What's wrong with yours? There's not much to them. Anyway if you want a new one, In Motion has push-in type Bultaco caps list price 24 british pounds. If you can bear having the wrong logo on it, the Montesa Cota 348 push-in cap will fit your tank. A friend uses a rubber foot from a tubular framed bar stool as a cap for his tank.

Both Mont and Beta 4 strokes are very nice to ride but are quite different in power delivery and both are quite different to a 2 stroke. People changing from 2 stroke to 4 stroke in trials either persist long enough to eventually become as good as they were on a 2 stroke, or give it up as a bad joke and get another 2 stroke, or an electric, which is yet another learning curve. Probably the easiest thing to do would be to tame down your GasGas and then when you have got used to trials competition riding you can change it back to standard and have a ball.

What is the problem with lacquering over stickers?

I recently went through rehab for a broken pinky/5th finger and something I learned from the rehab people in the process of getting back on a trials bike was that your "grip strength" fingers are your 4th and 5th fingers while your index and middle finger are comparatively weak for grip strength. However the index and middle fingers are much better connected to your brain for fine motor control than your 4th and 5th fingers are. They called the index and middle fingers the "clever" fingers. That's the reason we use our index finger and sometimes middle fingers on the levers and leave our 4th and 5th fingers to grip the bars. It certainly rang true for me when I tried to ride trials with a broken 5th finger and found I had way less than my usual grip strength on that end of the bars.

To answer you question, the cable travel required of the thumb control is the same as the nominal venturi size of your carby which is usually 26-28mm on a 2 stroke trials bike.

I've got more life out of TY175 and TY250 kickstarts by fitting a screw into the lever to adjust the preload on the spring. M6 x 1.0mm screw - drill and tap job. The problem is partly because the pivot wears which reduces the spring force on the ball. It is also because a groove forms which lets the ball climb out of the hole easier. You can fill the groove if that is an issue.

Some fuel taps have a reserve position. Some don't. I couldn't see your fuel tap to know. If you've got the original fuel tap it would be a good idea to use a new (modern) tap instead to get a more reliable flow stream. When you do the liner, take care to avoid letting liner harden in the threaded hole for the tap. On a couple of the Spanish fibreglass tanks I've lined, the thread required cleaning out of liner and for that I used a thread cutting tap when the liner was solid but not fully set.

1. I use different fork oil in different bikes, ranging from 5WT to 30WT. Bel-Ray, Maxima, Motul, Castrol, Penrite. 2. I have no knowledge of the dimensions of the forks from the first model 247. They are probably 35mm tubes, but may be a different length, travel or axle offset to the later 247 forks.

The spring and the square piece that the spring acts on function as a non-return valve or maybe a better term is an excess flow valve

Photo A is correct

It's usually easier to fit the damper rod and piston (plunger) in from the top but sometimes there is rust in the upper part of the tube so if yours is rusty you should either make it smooth or fit the damper rod from the bottom end. As for your other questions I don't understand what you are asking.

I've got a 1960's rear rim that width taken from a Bultaco so I'm not surprised to see that your old Cota has one too.

It certainly is 1975 vintage and looks exactly like mine apart from yours having a British fuel tank. I too have looked through on-line OSSA ID lists and not seen a prefix 43 model mentioned. I have a suspicion that your bike model may be very rare hence not well known enough to be listed. The production sequence number on yours (92) is extremely low which could also align with there being not many of them made. I'm wondering if it might originally been a 175cc Mk2 MAR rather than a 250cc Mk2 MAR

The tyre clamp size is the distance between the flanges in inches. 1.85 clamp fits rim with 1.85 inches between the flanges

Same here in Gladstone so far with small engine shops. I'm still waiting for a reply from Aspen

I'm in the process of trying to find an Australian supplier for Aspen 2

There's a photo showing the spring fitment on this expired ebay listing. Photo found in about 10 seconds using google search. After you open this link, click on "see original listing" for a big photo of it https://www.ebay.com/itm/Montesa-Enduro-125-H-Cota-247-Rear-Brake-Plate-p-n-3855-148-NOS-58M-1977-1978-/293384263589

I have no idea but there are lots of possibilities apart from him not bothering