feetupfun

Yes the other stem with no hole is probably the rim lock/tyre clamp. Front wheels on trials bikes usually have one rim lock. The leaning tube stem may not be due to the tyre slipping on the rim. The more common cause for the tube stem leaning is that the tube has moved relative to the tyre and rim. To determine what is causing your tube stem to lean over, you can put marks on the tyre and the rim that are in alignment. If the marks separate during riding and the stem lean changes, then the tyre is slipping. If the marks stay aligned but the tube stem lean changes, then the tube is moving within the tyre. If you want to get the tube stem back perpendicular again at any point, let the air out, loosen the tyre clamp, push the beads inwards off the rim and rotate the tyre relative to the rim, then pressurise the tube to reseat the tyre and tighten the tyre clamp. To prevent the tube moving inside the tyre, you can either make the contact between the tyre and the tube very grippy (clean the tube and tyre internals thoroughly) or very slippery (clean the contact area and when dry, put lots of talcum powder in there). If neither of these methods stops the tube moving inside the tyre, fit a different size or brand tube. If your tube is on the big side for the tyre, fit a smaller section tube. If your tube is on the small side for the tyre, fit a bigger section tube. If your tyre really is slipping on the rim, check the size of the rim lock is the right size for the rim and check for damage to the rim lock. If you can see a decent witness inside the tyre beads where the clamp has been gripping them, it is most likely doing a good job.

Are you sure it's a Montesa?

Possibly air got into the clutch hydraulics while it was lying down. Alternatively, if you pulled the clutch or pressure plate off, you may have let the clutch pushrod ball fall out and not notice it. I doubt the shift shaft has anything to do with it.

Andy, which bike are you asking about?

You didn't mention checking for a clear air inlet and exhaust gas path.

It should start easily at 2-3mm BTDC. Did you do anything else at the same time as fitting the new ignition?

I've not had to work on the steering bearings on my 348 yet, but 1970s Spanish bikes usually have a light interference fit between the stem and the yoke. I just went and looked at mine and it looks the same as yours, which looks like there is a head on the bottom end of the stem. For an interference fit stem, clean up the surface of the stem above the bearing seat. Set up some way to push the stem downwards through the yoke (press/vise/leverage). Heat up the yoke and the bearing. Yoke to just over 100 degrees C. The bearing can be made hotter but be careful to avoid overheating the aluminium. To maximise the effect of the heating to loosen the fit, minimise the heating of the stem. Push the stem down through the yoke and the bearing.

Excellent. Model 49s are a wonderful looking bike.

The motorcycle frame and engine casings are the earth/ground for the motorcycle. Most people ground their kill switch at the HT ignition coil mount.

Values are quite sensible where I live

Hi Wes. We are the same age and I still ride competition trials. Make sure the bars and pegs layout allow you to ride with comfort standing up. A lot of old trials bikes have relatively high pegs and when they were new, they also had high bars. Modern bars are not as high as the old bars. I find when practicing that I ride for 5 to 10 minutes on trials stuff, then stop riding and sit on the seat to recover. Riding competition can be easier on your body than practicing because you usually have to wait to ride each section, and also on a twinshock you can usually ride between sections sitting down.

There is no reason to assume that the big end pin will be OK to reuse after a motor suffers a failed big end bearing. When the crankshaft has been pushed apart, the pin can be inspected for damage.

If someone posts something new, it is visible to everyone who looks at the Trials Central forums, whether the topic started recently or many years ago.

I enlarged the steering stem hole in a spare top triple clamp and made an eccentric to fit in the hole to move the top triple clamp forwards slightly. I did not aim for parallel. I can't remember the concentric dimension for the eccentric piece offhand but there is still some angular offset. From memory, the goal was to move the front wheel axle rearwards by 5mm. To get the fork tube holes to line up again, I twisted the bottom triple clamp then twisted the upper triple clamp. What I wanted was for my KT250 to steer like a TY250 and it now does exactly that.

Ah OK. I guess it's a bit different here where there are lots of derelict TY250s lying around. Plenty of TY250 parts in the US as well.