feetupfun

TLM 50s are a good choice for sub-adult size youngsters wanting to ride twinshock class as they are a bit smaller all over than a full size bike and quite light for a twinshock. The motor performance is very good for a 50. Standard size trials tyres, while not leaving much clearance at the swingarm, can be fitted. As far as I know they were only sold new in Japan, but there are quite a few now which have been imported second hand (to Australia) from Japan. Motor parts (not that they usually need them) are not too hard to get as the motor is shared with a Honda moped or scooter. Body parts are scarce. The photo is of a youngster in our local club on her TLM50.

Yes, good quality industrial and automotive rubber hose bought from the reel nowadays is usually ORTAC (oil resistant tube and cover). It's not too bad with high temperatures either. I have had some on an exhaust join (main section to muffler on a 2 stroke) for 5 years now without any problems either.

It's not just a bigger piston job to get to 200cc. You need a bigger cylinder sleeve, head machined and also crankcases machined for the bigger sleeve. Various pistons are available. Some pistons require a spacer under the barrell. Some pistons need the gudgeon pin holes bushed down. It's a big job. Are you still keen to do it?

What is a Razor?

There are options for getting the old oil out. You can drain the gearbox through the filler (inverting the bike) but it is a lot of trouble and quite messy. You can drill out the remains of the plug. You can drill a small hole in the plug and use an easy-out tool. You can work on loosening the plug by tapping against the sealing flange with a pin punch. On the 348 the clutch/primary drive oil is seperate to the gearbox oil and usually has a decent drain plug so you should be able to change that oil without any hassles. By the way, there are many species of snakes here in OZ that are more dangerous/venomous/aggressive/poisonous than the US (or Mexican) rattlesnake. It is a well developed habit here to look before you put your foot down when riding or walking.

Our local club doesn't include twinshock class ie they only run rider grading classes so I ride on my twinshock against modern bikes. Most open trials include a twinshock class so I usually ride that. Some other open trials are for twinshock and classic bikes only. Last year my wife sold her modern bike so whatever trial I ride now it is on a twinshock bike. Before that I sometimes rode the modern bike.

You can do whatever you like with the clutch. It is whether the bike stops or not that counts as far as scoring goes. If you are a died-in-the-wool stopper, you might find that to start with you will do less accidental stopping if you leave the clutch alone. Personally I find it so much easier to ride using the clutch that I prefer to use it and pay close attention to keeping the bike in motion.

Your message was a bit hard to work out, but it sounds like where you ride, the twinshock class rules include a stopping penalty while the modern bike class rules allow stopping. Contrary to what are saying about the rules in the 1970s, events then were almost exclusively run to no-stop rules. If you were allowed to momentarily stop and balance in the 1970s, you were riding under different rules to the convention at the time. There are reasons for using a stopping penalty for twinshock class nowadays. Depending on the nature of the sections, a bike with poor clutch action by nature of it's design may be disadvantaged by allowing stopping. If the organisers are trying to attract riders, it is useful to make the playing field more level by reducing the advantage gained by having good clutch action. To replicate the feel of the events of the time the bikes were made, orgainsers sometimes like to use the same rules as those used at time. Yes it can be tricky and sometimes quite amusing riding to the no-stop rules after years of stopping and balancing. We have one (twinshock and classic bikes only) event a year that runs to no-stop rules and that is one of the reasons it is such fun to ride. And yes lots of us ride twinshock bikes in modern bike classes (with great satisfaction too)

I have no experience with the Castrol 747 but do know that if you use Castor oil (Castrol R40) as the pre-mix oil in your two-stroke trials bike, the carbon formed on the piston crown and in the head will form very quickly and be extremely hard. To remove it will require emery tape/grinder rather than the usual wiping with a 3M scouring pad that removes the carbon formed when using modern oils. Another consideration is that switching from one type of two-stroke premix oil to another without washing out the motor internals can cause accellerated wear rates until all the old oil has worked its way out of the engine. The concentration of Castor oil used as an upper cylinder lube or odour agent in the fuel for a 4 stroke should be kept much lower than what you would use in two stroke premix - mainly to avoid causing carbon buildup in the exhaust ports and valve/s.

I thought this might be the right time to show a photo illustrating how popular Cota 348s are in our local trials club. Photo taken before a club trial October 2007.

Those fork caps are standard on some model Cota 348s. I have 3 sets of 348 forks and thay all have those caps but I have also seen 348s with plain fork caps. It was a popular thing to do at the time. It provides another way to adjust the front suspension. There is a drawback though that increasing the pressure inside also increases fork seal drag.

Here's the other side of DabDab's 348 brochure. Sorry if its upside down or sideways - remember it was uploaded in the Southern hemisphere!!

These are scans of a 348 brochure I am posting on behalf of DabDab. They are in pdf format so I'm not sure they will display properly.

1 The brand/size that you personally find easiest to ride. For me it would be a toss up between Scorpa SY250 and Beta Rev3 250. 2 It wouldn't be a factor because the all the brands are well supported by their distributors here.

Stripping paint from fibreglass tanks is easy if you use an electric heat gun to heat the paint and then scrape it off with a paint scraper. I've successfully done fibreglass Spanish trials bike fuel tanks this way. The latest was an OSSA MAR tank that had three layers of paint and lots of spray putty. Warnings: Make sure you have removed all the fuel fumes before you use the heat gun Don't overheat the fibreglass (or it may catch on fire). Just heat the paint surface to about 50 degrees C - about as hot as you can stand to touch with bare hands.

The head on the bike in the photo from the France Trial Classic website looks like a DT175 head.

Clark Maunfacturing in the USA make high quality plastic tanks for old MX and mini MX bikes. Some of them would fit the KT but the look is nowhere near as sleek as a steel KT tank.

I like the way you show what you are doing to the bikes as you go. I'm usually too keen to finish to stop and take photos along the way but your show and tell webpage has motivated me so a current resto (M198 Sherpa T) is getting the progress photo treatment. When you put the front guard back on the TY, please put it on the other way round even if it means ending up with holes where the mudflap was. Yes you should use tank stickers that look right - even if they are for a different model TY250. You have invested lots of effort already in the paint job and it would be wasted if the tank ended up looking strange. If those stickers in your "goal" photo are too expensive, the yellow and white TY250B paint scheme looks great and the correct stickers for that would only be about 5 pounds and the pinstripe less than 1 pound.

I've tried running a Rev 3 200 Beta on AVGAS which is high lead petrol made for piston engined aircraft. Once I adjusted the float height for the big difference in fuel density (AVGAS is very light), it ran beautifully, and was probably a bit less powerful overall than when run on you guys across the Pacific would call 98 octane "pump gas". No problem with lead deposits on the sparkplug either. The only problem here is that for competition use we must use (unleaded) "pump gas" or homologated unleaded ELF racing fuel so unless you never compete, here it pays to stay away from the user-friendly leaded fuels. About the ethanol content, I have never heard it promoted here as a performance improver in fact the fuel suppliers have to keep the price about 4 cents/litre below the cheapest non-ethanol "pump gas" to sell it (we have a choice of buying "pump" fuel with either 0% or 10% ethanol). "Pump gas" of all types is still very cheap in Australia (approx $1.15US to $1.25US per litre). Most trials riders use the highest quality 98 octane non-ethanol "pump gas" they can get.

Knobby tyres are terrible on anything that has hard surfaces like rocks and logs.

I would expect that if you have a standard pinky it will have needle roller bearings with rollers that will stay in position within the bearings until you slide the bearing inner bushes out ie you should be able to slide the swingarm axle out and remove the swingarm from the frame without having rollers fall out.

The chain will slowly wear the swingarm away unless there is a protector. The protector is sacrificial and wears out slowly. It is no big deal in the short term to have the chain touching the swingarm. Pinkys have steel swingarms so the wear rate will be slow. Yes the swingarm has to come out. I expect it would take a motorcycle mechanic about 30 minutes to replace a protector on a clean bike. Sounds like you haven't done much work on bikes yet so it would probably take you a fair bit longer. You will need tools to fit the swingarm pivot axle and both shock mount bolts. Make sure you clean the bike well before you start or you will get dirt in the swingarm pivot bearings. I would suggest buying a new protector and fitting it when convenient ie when you have to take the wheel out next to clean the brakes or replace the tyre.

Ah the fun of buying a bike in pieces! A standard TY175 head has only one plug hole and there is no place to fit a second plug or decompressor. Your TY175 probably has a head from some other model Yamaha. There are lots of interchangable parts between Yamaha bikes of the same era as the TY175. Having a different head may not be a problem. You may have a few other non-TY175 components so if you want to know, I suggest you start off by checking a few things; Have a look at the number cast into the barrel between the bottom two fins on the right hand side. It should be 52500 if it is TY175. Have a look at the engine number stamped into the top of the right side engine casing. It should start with 525 or 1N4 if it is TY175. Have a good look at a brochure photos of TY175s and post a photo on the forum of anything you are not sure about.

It may be something as simple as a ring stuck (with gum) in it's groove.

Maybe it was just the execution of the idea in the case of the Rotax jetski motors that was crap. The most successful 250cc road race GP bikes in recent years (Aprilia) have rotary valve induction. They are noticably faster than their reed valve competitors (Honda and KTM). In the case of bikes for Joe Public, yes they are a bit more complex than reed valves but do produce the goods. In twinshock trials the SWM with the rotary valve Rotax motor is a beaut and the SWM enduro bikes of the late 1970s with similar Rotax rotary valve motors were at the top of the performance tree at the time.