feetupfun

OEM VM26 from DT175 works. Haven't tried a VM24, didn't even know they made one

I usually use no washers but do use loctite. The reason I don't use the washers is that I fear that a piece might come loose and cause damage

Sometimes people use Loctite on the threads of the bottom screws, and a rattle gun will not undo them using the inertia of the damper rod alone - the damper rod needs to be held stationary

I rebushed a TY175 basket that was pretty sloppy and used punched-out discs of insertion rubber (the discs are round in the TY175) and made new rivets. It got rid of the sloppiness but didn't make the slightest difference to the way the bike went. That was 35 years ago and those discs of insertion rubber are still going strong

manufacturers don't grease them properly when the bikes are assembled

Fuel tank is IT Yamaha 1977/78 It's a TY250 frame and they never had tubes under the engine and the original A model bashplate was rubbish It looks complete enough to me to be resurrected for trials use here in Australia It has a TY250 B model carby The motor and frame look like A model A model frame and motor should have numbers that start with 434 I'm intrigued with the extra bolts through the frame plate where the swingarm pivot attaches on the RH side of the bike

http://www.mijossi.com/3ty/bibliographie.html

The effective length (the distance between the spring seats) of the spring guide/spacer is 123mm. The steel section is 24mm OD. The plastic spring seat is 23.8mm OD. The peg on the plastic spring seat that goes inside the spring is 15.5mm OD. The hole through the middle of the plastic spring seat is 12mm. The four holes in the necked-in section of the steel bit are 5.5mm diameter. The steel that the spacer is made of is 1mm thick. The opposite end to the plastic piece is formed inwards about 3mm to make a flat spring seat The oil deflector is also formed from 1mm thick steel. The OD of the cup section that goes inside the top spring is 16.3mm. The cup section is 52.5mm long and has a single 1.75mm hole in the side near the bottom. The original long spring is a slightly smaller OD on the bottom end to the top end, and the oil deflector will only fit in the bigger end. I am yet to work out why the arrangement for the springs in these forks is so elaborate compared to every other set of 1970s forks I have worked on. I will leave the springs out for a while in case you have any more questions

I thought you might ask that so I left them on the bench last night and will measure this weekend

I have posted a photo of the fork spring assembly to the Trials Australia forum topic "Basket Cases", at the bottom of page 64, because I couldn't get it to upload to Trials Central http://www.trials.com.au/forum/viewtopic.php?f=16&t=4785&p=36482#p36482

I can take photos of the parts laid out in sequence if you need it

There is meant to be a spacer between the two springs, and an oil deflector. So from the bottom it is damper rod, then spring, then spacer, then other spring, then oil deflector, then cap. If you have some TY250 springs handy they work just fine in there with a spacer sized to give about 20 to 25mm preload. If you want to retain the venting on the caps, you will need some sort of oil deflector. I use TY250 (unvented) caps on my KT forks

also consider that the quality of the frame earthing for the motor casings and the HT coil may have been affected by your restoration

Dont just blow out the jets. Remove the pilot jet and look through it and clean it until it is clear. Your symptoms sound like a blocked pilot jet. They commonly block up from either a particle or from gunk if you let premix dry out in the float bowl between rides

as for your other question about the lack of a circlip above the seals, that is quite normal for those forks. The friction fit of the seals in the fork bottom section is all that is needed

You are right. Parallel yokes means that the tubes and the steering stem are parallel. If the tubes are in the same plane as the steering stem, that is called zero offset clamps. Zero offset clamps may also be parallel clamps. Angular offset clamps add another degree of complexity/sophistication because they can keep the steering geometry closer to ideal through the suspension travel. In my opinion, Bultaco Sherpa T and Yamaha TY twinshock clamps have a very well chosen amount of angular offset. The total offset of a front end includes the amount the axle is forwards of the fork tubes centre line, as well as whatever offset is built into the triple clamps, and the length of the forks from top clamp to axle. It is possible to reduce the steering rake without modifying the frame. The most common method is to lower the front (slide the tubes upwards) or raise the back of the bike (increase the spring preload, or fit longer shockies). Another way is to use eccentric sleeves on the steering head bearings.

what's the question?

also check for: a twist in the swingarm (wheel axle not horizontal) (common) the arms of the swingarm being bent off to one side (rare) the rear frame loop being bent to one side (common) the wheel rim not being centered on the spoke flanges (rare) the main frame bent in the middle (puts one swingarm pivot hole ahead of the other) (rare) The shockies being a different length when fully compressed (maybe only one has a bump stop) If you haven't worked out what the problem is by this point, I suggest to start with, you take the seat, seat surround, rear guard and end muffler off, pump up the rear tyre, set the axle adjusters on the same notch, set the bike up so the steering axis is vertical and have a look at how vertical the back wheel is and what the chain alignment looks like Then take the shocks off and see what happens when you move the wheel to the top of its travel

I am pretty sure there is no such thing as cheap shocks that have a good action. I have been using Falcons for about 15 years now and can say that they work beautifully straight out of the box and are lots cheaper than Ohlins The most popular trials twin shocks where I live are Betors, which are a bit cheaper here than Falcons, but I find their action is not as agreeable

Kevin, we are about the same weight. I found that my TY175 forks were OK most of the time, but there were a couple of things that they did: When you are loading up the front end under brakes, like when going downhill on dry, grippy rocks, there was noticeable flexing of the front end When you do medium or bigger landings, sometimes they would bottom out I tried quite a few things over the years to improve them including stiffer springs (from a TM125), air caps, heavy oil and while these things improved the bottoming resistance, they made the action of the forks worse in small stuff, and didn't reduce the fork flex Some time in the early 2000s I fitted a TY250A front end and ran it standard to start with and was pleased with the bottoming resistance and reduced flex. A while after that, I saw a video of myself riding a rocky stream bed and realised that I was using less of the fork travel than I wanted. First off I reduced the preload from standard until I got the laden sag to 50%, then later I replaced the preload spacers with short pieces of fork spring (this reduces the spring rate) and again set the laden sag to 50%. I run 10WT oil 125mm from the top, fully compressed, springs out. I'm quite happy now with the spring settings of the forks but may yet do some development on the damping. As far as how high to set TY250 tubes in the clamps, you will find that the TY250 tubes are shorter than TY175 tubes by about 20mm, so your front end will be 20mm lower than your current setup if you set them flush with the top clamp. The TY250 triple clamps have the same geometry as the TY175 triple clamps, they just differ in the size of the tube holes To get the right preload setting for you and your springs, you can measure the laden sag with you aboard with all your weight on the footpegs with the standard preload spacers, then fit shorter and shorter spacers until you get the sag up to around 50%. You will probably end up somewhere around the 1 inch preload as suggested by bestrcpilot. Yes PVC pipe is OK.

I had a ride on that EM5.7 used in the youtube video last weekend and greatly enjoyed it. It is certainly very different in response to a petrol motor, but I reckon I could get used to it. The thing I liked the most was that there are less things for your mind to deal with while riding. It was uncannily relaxing to come to rest, balance, then ride away without any brainpower being used managing a clutch and avoiding stalling. I recommend having a go on one of you get the opportunity

it is very hard to get the goo out of the pilot circuit and your symptoms do sound like that might be the problem

It might be what Tony says, or it may may be the shift mechanism centring spring. There is a centring spring for the shift mechanism that lifts the shift lever back up after you shift down a gear. It is visible when you take the clutch cover off

Another option for the rear axle: I used a TY250 twinshock swingarm axle as my OSSA rear wheel axle because mine had been straightened a few too many times, and I don't think that one was the original either.

The induction tract is under vacuum when the motor is idling, so if there is a leak, air will be getting in, causing the motor to run faster and leaner than it should. If carby cleaner or WD40 gets sucked in through a leak, the motor will change RPM. This helps to locate the site of the leak.