feetupfun

Yes that swingarm is one inch longer than a standard TY250 swingarm. It was one of the first things I measured when I got the frame kit.

Pretty sure the Series 1 Godden frames were yellow (not plated). My NOS series 1 Godden frame came bare steel. Here is a photo after I bead blasted the surface rust off and primed it (photo taken in 2006/2007) soon after I got the frame

Steve what fork tube offset dimension do you have in those zero angular offset clamps?

If you have a modified rear end, you can work out the spring rate by calculating the leverage ratio on the shocks. 1960s trials bikes like the M27 and series 1 M49 have a leverage ratio of about 1:1 and use 40 or 50 pound springs depending on rider weight. Work out the leverage ratio for a modified bike and multiply the original spring rate by that ratio to get the new spring rate. Leverage ratio = wheel axle travel / shock shaft travel or Leverage ratio = distance from swingarm pivot centre to wheel axle centre / distance from centre line of shock shaft to swingarm pivot centre measured at 90 degrees to shock shaft

we have to put them in the fridge for a while to cool them down enough (joke - it is very hot here at the moment)

If you want to check that your timing is right after setting it, you can use a strobe type timing light on your timing mark. Its a bit of a pain with the 348 though because it means either bump-starting the motor, or taking the flywheel cover off after kickstarting it.

Yes that is a good reason. Another reason is that the gap between the faces, and the diameter of the faces, determines the size of the charge that the capacitor is required to store (the points gap and the diameter of the contacts are tuned to the size of the capacitor)

what about Ittle-jet

You use that gauge to find TDC, then make a TDC mark on the flywheel in line with something on the casing. Then measure from the mark to the position you want the points to open (either using a degree wheel, or by using geometry and measuring around the circumference) and make a timing mark. You then only have to be looking at the timing mark on the flywheel instead of having to read that tiny scale on the TDC tool

It sounds like the clutch is slipping. The kickstart on Bultacos drives the motor through the clutch

Yes its a M115/116 Alpina tank. I think they normally have a threaded aluminium insert in that hole. I think I have some spare tanks the same as that one. Can you measure the diameter of the hole I might have one of those inserts if you want to fix it properly. If you are going to use that tank just to test the bike out, a homemade bung should be OK but do include a vent in it. That tank doesn't have a separate vent

I had similar with a 2003 Nissan X Trail 2.5 petrol. The source of the problem was quite elusive and after doing all the cheap things, I ended up replacing the crank position sensor, throttle pedal position sensor and throttle body before it would decelerate without going into limp mode. It did go well when it was a new car, but by the time it had the engine control problems (about 350,000km), the rings were getting a bit worn and I gave up trying to keep it going (traded it in) Something like that wouldn't stop me buying a trials bike with EFI though, because I'm a stickler for having an trials bike engine that runs super smooth and evenly, at any cost. I ride twinshock trials exclusively nowadays, but if I wanted to ride a modern it would be one with EFI

I've ridden models M10, M49, M92, M124, M158, M198 and M198A. Yes I would say the handling improved with each frame type, and from other things that were improved within a frame era. Improved mass centralisation (relocated exhaust and reduction in height of frame), longer swingarm (relocated pivot point), reduced component masses (frames, airboxes, rims, hubs), increased front end rigidity (triple clamps) and increased rear wheel suspension travel. In the late 60s, the M10 was considered better handling by some than the M27 because the M10 was a bit shorter in the wheelbase. The final model (M198/199B) has a steeper steering angle than previous models which is seen as a plus for that model

The heat generated by new rings rubbing against a newly finished cast iron bore is way more than the heat generated by riding the bike in normal trials operation. Because of this, on an air-cooled bike, the cylinder and rings can easily get hotter than the oil can stand, should the bike be ridden continuously on the first run. I find that on the initial run following a rebore, the cylinder fins can go over 100 degrees C within 60 seconds of a cold start, even with no load on the motor. Each successive engine run sees the temperature rise rate reducing and after about 6 runs of the motor going from stone cold to operating temperature, the bike can then usually be ridden gently continuously. A liquid cooled motor with electroplated bore is completely different because the heat generated by the fresh rings is probably less, and the heat can be removed from the rings and cylinder bore surface much more quickly.

To start with it can't be a M10 Sherpa T, because it is a 5 speed motor By the numbers, it's a M106 (360 (325cc?) Astro) motor in a MK4 Pursang frame (a great setup for ice racing) - yeehaa!

good footage but I think it is in Italy

The speedo drive housing has a flat on it that needs to be positioned against the fork leg. The photo shows that your speedo drive housing is sitting wrongly, which is probably the cause of your problem

but that would be a 100kg rocketship

Photo of DT175A motor to illustrate the mods mentioned by jc2

Here is what the TY175 with DT175E motor looked like

The early series DT175 cylinder will fit to the TY175 bottom end (twinshock DT175 models ABCD sold in 1974/75/76/77) 78 model (E model - first monoshock - radial fin head - plastic flywheel cover) has different cylinder stud layout pattern so would need work to make it fit to a Ty175 bottom end Yes I think you might need to trim the DT head fins to clear the TY175 exhaust pipe The higher top edge for the exhaust port will reduce the low-RPM power compared with the TY175 The higher compression ratio will make it very slightly easier to stall at extreme low RPM If you use a bigger carby than the TY175 carby you will get the full benefit of the exhaust port height difference For a while I rode a TY175 with complete DT175 motor including the 26mm carby from the DT175, but with TY175 flywheel, and it was fine for trials riding, and magic for trail riding. It had a fair bit more power on top and the gears being equally spaced made for very easy trail riding. I didn't mind the slightly less bottom end power but only first gear was any use for trials. Second gear was like third on a TY175. The DT175 motor I used was the E model which looks a lot different externally, but appears to be very similar to a DT175A motor I also have, as far as compression ratio and porting goes. The DT175E motor requires the TY175 frame to be dented in one spot under the motor for clearance, and the standard TY175 exhaust pipe is a very close fit without trimming fins at the front of the cylnder, or over the top of the head. The Ty175 flywheel needs to be trimmed a bit and the inside of the DT175 casing also needs trimming for there to be clearance

Maybe broken fork spring. Should be easy to check without pulling much apart

the ignition stator coil can probably be rewound by someone locally

also check the exhaust system for loose or broken mounts or touching something where it should not