feetupfun

Another benefit for using a roller bearing on one end of the crank is that it allows for zero-load differential expansion of the crank and the cases, which can otherwise lead to a loose fit for one or both of the crank bearings with the standard deep groove ball bearing arrangement (even with C3 bearings), from the bearings moving on their seats

Welcome bb. You will fit in well

They are only 12 HP when the motor is in perfect nick so to achieve 60 MPH you have to get the gearing so that you are a bit below the RPM that gives peak HP at 60 MPH. You made a huge change to the gearing going to 42 rear if you had a 49 previously. Front sprockets are much cheaper than rears so I suggest you get a smaller front. If you had a 49 rear 15 front, you had a ratio of 3.267. When you went to 42 rear the ratio went to 2.8. If you fit a 14 T front and stay with the 42 rear you will have gearing about halfway between 49/15 and 42/15, which will be closer to what you want As far as the carby goes, if you are going to ride at sustained full throttle or near full throttle and high RPM along a road, you had better be sure the jetting on the main jet is right or the motor might seize. You need to say what jetting you have in the carby to get feedback on if it is suitable. The carby settings have nothing to do with the gearing. It is the way the bike is used that can make the jetting critical

I can answer that one b40rt. Wiseco pistons expand more with temperature rise than original Yamaha pistons. The extra heat created while new rings bed into a fresh bore can take the piston temperature (size) to the point of being at risk of piston-to-bore seizure, more so than with the lower expansion rate Yamaha piston. Of course as well as the way the break-in is done, the risk of piston/bore seizure also depends on what clearance the rebore was done to.

Increasing the TRAIL will reduce the tendency for the steering to be pulled towards the ends of the steering travel and reduce the steering effort when riding in rocks. I would not describe it as slowing the steering. Rotating the bars forwards generally increases steering effort and rotating them rearwards generally reduces steering effort, however for many people riding a TY175 the bar ends get in the way of your legs unless they are rotated well forwards. Having the ends of the bars further forwards allows for better bike control because you can move around more. However there are limits for having the bar ends a long way forwards because you also need to be able to get your backside way back for big drop-offs and so arm length, body length and handlebar width are important factors.

Twinshock era aftermarket shocks are all different visually so can usually be IDd by letting someone who has lived through the era have a look at them. To answer your question though, I don't think there is such a list, but there are many places on the internet where you can see brochure photos of old trials bikes that show which shocks they came with

One thing I probably should have asked is why is it important to know who made the exhaust header?

Before you spend $$$, try it with the tubes slid through a bit. Sliding the tubes up and down affects the trail and rake, as does changing the ride height at the rear. The way yours is set up, the standard rake is retained, but the trail is reduced compared with standard. Standard bike steers very well (neutral) with tubes about 20mm through and 340mm shocks.

The header section could be what Sammy Miller products sold many years ago, or it might be home-made. The SM products item was made from pre-formed bends like yours is and like many home-made headers were/are. I would tend to think it might be home-made because from what is visible in the photos, the radius of the bend that goes over the head is too big to be the old SM Products item. Yes the main section is a WES with a home-made heat shield. Can't tell from your photos if it is the one-piece WES or the front part of the two-piece WES Looks like a fairly non-standard frame. Any chance of photos taken side-on, showing the whole bike? That will also show the shape of the exhaust header better

http://www.ebay.com.au/itm/AFTERMARKET-IGNITION-COIL-YAMAHA-TY250-TY-250-74-78-NEW-/282088176043?hash=item41adc3f9ab:g:4XgAAOSw-KFXd8hp

Yes to both. Makes perfect sense and is more obvious on smaller motors than bigger motors

MCS brand make replacement HT coils for TY250. It is a HT coil that suits lots of old Yamahas (and I even use one on my Sherpa T) You should be able to get one from a motorbike shop or from an ebay seller. I will find a link to one after work if you haven't got it sorted by then

You probably should look under the tank and identify which wire goes to the HT ignition coil. The black wire coming out of the magneto casing should run to the HT ignition coil and also to the killswitch. The other two wires coming out of the magneto casing are for the lighting circuit PS by the look of the cylinder and carby, it looks like a 75 model to me not 76

possible causes: original fluid contaminated with water or particles remaining from manufacturing processes not cleaned out prior to assembly or item left wet and unprotected from corrosion following machining

To get the pressure you want, you pump the tyre up above what you want (with whatever source of compressed air you have) and then let air out until it is down to the pressure you want. If you are a novice at setting trials tyre pressure, use a low pressure (trials) gauge to measure the pressure. Once you have done it enough times, the gauge becomes unnecessary because you will be able to judge when the pressure is right by the appearance of the tyre when you put your weight on the bike, or by pushing against the tread with your knee Be aware that the tyre pressure will change with the temperature of the tyre, and with change in altitude

I use rattle can epoxy enamel on engine covers (inside the magneto cover too) because it is good for preventing corrosion and easily be retouched on the outside when scratched. Powder coat is a tougher finish, but not tough enough to avoid being scratched by rocks, and then will need stripping off and recoating to look good again

Yes the cutaway does make a difference but it may still be OK. Certainly no problems with trying it out with the slide you have Also it is a common tuning method to increase the cutaway dimension, so while yours might have started out as a 2.5 it might actually be a 3.0 or 3.5 if someone has resized it. If you can still see the anodising on the edge of the cutaway then it has not been resized

I just looked in two Yamaha parts books. One was for TY250B and the other was for TY250C. Both have the carby with the main jet holder in the float bowl. These models have different jetting, but both showed the same part number for the slide and listed the standard slide as a 3.0

This is a fascinating subject. I am greatly enjoying reading about people's experiences. My 2c worth at this point is that the flatness and surface finish of the hub surface is a critical factor with new linings. Because of what you found with your chalk test I'm wondering if maybe the bead blasted finish on the hub surface cannot hold enough friction material

The wedge ring will seal the air in the tyre. You can plug the extra holes with anything. It just has to keep the water out to avoid corrosion under the wedge ring. Neutral cure silicone rubber would do the job

Guy, this is the sort of thing I am talking about http://www.ebay.com.au/itm/Mandrel-Mild-Steel-Exhaust-180-Bends-O-D-1-5-8-41-2mm-/261818493610?hash=item3cf5992aaa:g:7DwAAOSwv9hW2RQx

Did you refit the ignition cover with a thinner gasket or with no gasket? That would have the effect you described

Guy I make TY header pipes from pre-formed tube bends (from an exhaust repair shop). One 180 degree bend and one 90 degree bend is enough for one TY250 header pipe and they are not expensive. I don't know of anyone selling off-the-shelf headers that fit close enough to the head to suit raised motor TY250 and use the aluminium tank.

My Alpina 138 still has the original chrome brake drum surfaces and both brakes work very well. I wouldn't bother changing the drum surface just to change the coefficient of friction

The standard Alpina drum has a chrome liner, but like the Sherpa and Pursang drum, the chrome sometimes lifts and people get a steel sleeve fitted