feetupfun

I think that it isn't really the length of the swingarm per se that is important, but that the relationship between the upper run of the chain and the location of the swingarm pivot is important. Changing swingarm length on a bike can affect the geometry of the chain run, and it also changes the fore/aft weight distribution of the bike+rider.

Hi Brian yes I like your M159 too - almost as much as your avatar but I'm sure you didn't look like that when I saw you last Regards David

Be careful with your engine temperature. Wiseco pistons are made of an alloy with a relatively high expansion rate compared with many other pistons. If your machinist has given the Wiseco piston a clearance significantly less than Wiseco recommend (to avoid piston rattle), it will be susceptible to seizure if the motor gets hot.

If it's advice you want you may get help at www.ozvmx.com.au

The actuating lever at the case is completely different (being push from cylinder retaher than pull from cable) but the TY250Z arm and camshaft could be substituted. Not sure if there would be clearance for the cable though due to the location of the exhaust on the Scorpa

The term used for bikes that can be started in gear by pulling in the clutch is "primary kickstart" and has nothing to do with whether the primary drive is by gears or chain or whatever. "Primary kickstart" means that the kickstart turns the clutch basket. "Non-primary kickstart" (Bultaco and many others) means that the kickstart turns the gearbox input shaft.

I have looked at my spare 348 frame for a while with a similar idea, but the problem with the 348 frame is that it relies on the bolt-on braces from swingarm pivot to the head, and the brace from the head to the frame, to provide triangulation for the main frame loop. Depending on the shape of the proposed motor going in, it may be possible to fit braces that will provide triangulation.

It says it in the catalogue what they are (eccentrics for Sachs monoshocks). One is for +/- 3.5mm and another for +/- 2.5mm

Sorry I can't help you yet because I haven't worked on my 2011 Gas Gas Boy 50 yet, but please tell me more about the clutch mod you are about to do. I think the (auto) clutch engages at too high an RPM. I want it to engage at lower RPM. Is that what you are seeking to do also?

There is a newly made instructional DVD for Twinshock and Classic trials bike riding available through Sammy Miller and probably other places too. Rider/instructor is Mick Andrews

Stator coils can be rewound by auto elec specialists Also consider possible loss of magnetism of the flywheel magnets

I have a set of M116 Alpina forks and yokes available but if you are the person who was asking about Matador forks last week and are located in the UK, I suspect the freight cost to you from Australia would be prohibitive

Ok I have had a look at photos of original Mk4 Matadors and the Matador triple clamps do look different to Sherpa T and Alpina models of the same era (that also have the tapered top end on the fork tubes). I don't have a good enough picture of Mk4 or Mk5 Pursang triple clamps to see how they compare with the MK4 Matador, but Pursang forks are in-line axle anyway. You can fit a later front end off an Alpina (M115/116, M137/138) but the top clamp will look non-standard (if that matters to you)

Soft drink (soda) bottles made for carbonated beverages are made from PET (not affected by petrol) and have an extremely high pressure rating. I've tested them with our petrol (pump gas) here and never had a problem with leakage or materials degradadation and they resist abrasion well too. I'm not saying they are suitable for all fuels though as I haven't tested anything other than our petrol in them. A few small bottles is probably safer than one big one and would fit better in a pack. Depending on what country you are in, they are probably not government-approved for carrying fuel. Toddlers accidentally drinking from the bottle is a potential hazard when reusing these bottles.

About pushing the dents out before welding on the inside - the dents in your photos should move back into position without further cracking and the reason you would do this is to preserve the external detail (logos and lines). If you are worried about the process, either do nothing or just weld the inside without pushing the dents out. It's your choice. I've got a clutch cover with bigger dents than yours on my M49 and it still holds the oil in and looks OK. I will not be doing anything unless it starts to leak. The material in those Bultaco casings is very good to work with compared with many other engine casings so if you give the casings to someone who is experienced at this sort of work you will have no problems.

For dents with internal cracking, push dents out from inside then weld repair on the inside

25kW is about what a high performance 250cc 4T or low performance 650cc 4T would produce

35mm leading axle Bultaco Betors and yes very likely that the forks and wheel and maybe triple clamps are shared with other Bultaos but before you go too far you should tell us which model Matador, not the year. Using a year for Bultacos is a bit rubbery for ID purposes. Look at the frame and motor ID numbers and the prefixes of these numbers will identify which model Matador you have.

NGK BP5ES

maybe cooling system problem - fan not running? radiator air path blocked? insufficient coolant quantity?

We are lucky here. The noise police haven't cottoned onto chainsaw racing yet so our racing chainsaws look like the one in the photo except there are no end mufflers on the chambers. The chainsaw racing is easily the most popular thing at our local (rural) show - all the bogans (me included) come out to watch Funny thing is the competitors have ear muffs and safety visors but the juiced-up spectators 10 feet away dont have to wear any PPE at all

yes you can change that seal without splitting the cases but my memory is a bit different to what Woody said. he may be right its a while now for me but my memory tells me that you will need to pull the clutch cover off and remove the clutch pressure plate to allow the actuating arm cam shaft to slide out.

What seal? What shaft? Sounds like you are asking about one of the crank seals or maybe even the seal behind the sprocket