feetupfun

OK photo time

Excellent thanks and you are welcome to try out my bikes. Yes I'm coming down and planning to ride Open Twinshock blue line

It's because the motor on a motorbike rotates a lot faster than the ideal rotation rate for a bicycle pedal crank

I recently bought a set of magicals springs for TY250 forks. They are dual rate of a similar design to the standard TY250 springs. On the magicals, the first rate is a bit stiffer than standard springs and the second rate comes in earlier in the stroke than the second rate on the standard springs. I found the magicals springs made otherwise standard TY250 and KT250 forks feel even more under-damped. Very good in combination with Majesty damper rods though which provide more damping. Rod after reading your last post I was wondering did you check how good was the piston/bore sealing in your Marzocchi forks. Yours may have a ring for all I know - I haven't worked on Marzocchis from a 240 Fantic, but Betors from the same era have sealing rings on the damper rod pistons. I'll be very interested in what you find with the HFS setup.

It's not a flat bracket so you will need more than a tracing to replicate it exactly. I have a TY175 frame that is undamaged if you want photos. I'm assuming yours is the competition frame because they are the ones with the weak bracket. There are other 1976 model TY175s that have a much more substantial bracket. The frame type I'm thinking you have is frame number prefix 525

Seems to be a very common mod to the 123

Mikr do you have tyres for your 123?

You can put it back in no matter where the shift drum is sitting. All that thing does is hold the shift drum in the positions that suit where each gear is correctly engaged. Your photo appears to show a dip where the plunger goes. If there is a dip there it means that the drum position is right to have the gearbox in a gear. If there was a bump in line with where the plunger goes, the shift drum would either rotate as you fit the plunger until the plunger goes into a dip, or the spring under the plunger would compress with the shift drum staying still. In the second case as soon as you do anything that moves the gearbox shaft, the drum will rotate and the plunger will slide into a dip and stay there until you shift gears with the shift mechanism.

Looks fairly normal for that seat

Jay if you are still on here, what change did you make to the location of the swingarm pivot?

Did you get a plastic-base original seat? Around here, depending on which upholsterer you use, they cost between $80 and $150 total for foam and cover if you give them the seat base ready to go. The johnnyjazz photo seat has the thin skeletal steel frame which can be tricky to separate from the rest of the seat.

Yes that does look like the right seat to suit the A and B model fibreglass seat surround. I looked at the remaining photos on that listing on eBay and had trouble seeing if there were holes for the rear mounting bracket bolts or not. I see you have a C, D, E rear guard fitted. You may need to shorten the front end of that guard to fit the fibreglass seat surround.

section swept, the A model seat that T5avs1 is seeking is nothing like what you have shown in your photos. You have shown the seat for C, D and E models TY250. The original seats on the A (and B model TY250) were also a very poor design with a thin steel skeletal frame glued to a foam pad and a vinyl cover glued to the pad and wrapped around the underside of the steel frame. The thin steel frame had captive nuts for the mounting brackets attached and 6mm steel bolts went through the brackets and the fibreglass shroud/surround/fairing. Because these original seats fell apart quickly, Yamaha developed an improved design that had a moulded plastic base which fitted very well to the original fibreglass shroud/surround/fairing and were sold as a replacement part. I only know this because one of my TY250Bs came with this plastic base seat design, with part number sticker still attached. I do not know of anyone still making replica seat bases that fit on the A, B models fibreglass shroud/surround/fairing. It wouldn't be too hard to make from scratch a seat base that will fit against the fibreglass shroud/surround/fairing if you were really keen to retain the original look. However most people I know do away with the fibreglass shroud and buy an aftermarket (C,D, E) seat or seat base as shown in section swept's photos and weld on a couple of mounting plates to their A or B model frames to replicate the C, D, E model seat mounting plates. The brackets shown in the T5avs1 photo are seat brackets for A and B models seat design and their lower ends attach to the inner ends of the upper shockie mounts. The small hole in the end of one of the brackets is for a spring that pulls the end muffler forwards. I don't know of any supplier of the A, B model seat brackets, but they would be easy to fabricate.

That terrible noise may be big end (conrod) bearing failure

Are you asking about brackets to replace the original brackets to suit the original design seat or brackets to suit a new aftermarket seat or something else

and as done by Yrjo Vesterinen with his Bultaco in the early 1980s. Nothing new under the sun

Aftermarket shocks for your bike have become available in the last couple of years and probably have a superior action to the original Yamaha unit even if it was in perfect condition. You probably need to ask yourself how serious you are about suspension performance.

I've just bought a pair of springs from majesty and am keen to try them out in the forks that already have the majesty damper rods fitted.

Frame is a few years earlier than M198

Those "weld seams" on the white tank are present on all the original fibreglass MAR tanks I've worked on

I ran a BPR5ES for trials in a hot part of Australia in a Beta and it seemed to be the perfect heat range. If I was flogging it along tracks or on the road I would use a cooler plug

The window tinter who showed me how to put stickers on said that he used the cheapest brand of trigger pack window cleaner. He reckons it worked better than an expensive brand of window cleaner.

James (on the blue TY250) could do with stiffer fork springs

The TY250 springs I have bought from B&J are quite a bit stiffer than standard springs. Your springs may be a tiny bit shorter than standard but do not exhibit much wear so their rate should be pretty close to standard. If you use additional spacers with the standard springs, anything longer than 9mm additional to the standard spacers will cause the fork springs to coil bind on full compression.

If you are stuck, replacement crankshafts can be made by suitable machine shops