Okay, I can clearly see the Flywheel on the right has a thicker ring on the outside and I can't say for sure but it looks like mine has a thinner outside ring. I guess without weight and O.D. dimensions I have to assume that the flywheel I have is from a TY250A. It'll still work, but my son says he remembers that the bike was easier to ride with the original fly wheel. Thanks for the pictures. Now I guess I'll go with it. Perhaps I should ask, does anyone know of a source for the heavier wheel?
Well after returning from our Thanksgiving celebration, my pictures had arrived from my phone to my laptop. I will post them with to see if any one knows by the diameter if not by looking at it, if it is the correct one for my 493 series TY250. I think the number on the outside face of the flywheel is F143-3073. I am not sure what that means or refers to. I have found nothing in my research mentioning those numbers.
LaVern
It's not the original type of flywheel for a TY250D but it will work fine. As expected, it's a TY250A flywheel. Do you still want dimensions or photos of a TY250D flywheel?
Are you saying that all of the DT covers will require a longer kickstart shaft length?
I'm saying that I believe ABCD models DT100, 125, 175 covers are all the same part. They changed the cover design with the E model. If you want to check that out for yourself you can look up their part numbers.
I just did a search on these forums on this topic and from that, it seems you can use a TY175 kickstart shaft with a DT cover, but need to make a spacer for the shaft to stop it floating towards the right, so that sounds like both shafts are the same length overall but have the shoulder that bears against the casing in different locations.
I have a DT175A motor that I can compare the kickstart shaft and cover from with TY175 parts if you want.
Yes, also DT100, DT125 and DT175 ABCDE models clutch covers will fit on the TY175 and yes the kickstart shaft length is different. The DT type cover is also more robust than the TY175 cover
The TY250A flywheel has a smaller steel band on it than the TY250B, C, D and E models, but is otherwise the same as the BCDE flywheel. I can do photos if you need.
Yours is a D model bike
The part number for the TY250A flywheel is 434-81350-10
I did some more investigation. One fork moved pretty well without oil and spring but when checked over full length had 0.030" run out.
The other side would stick intermittently and the tube was 0.006 TIR. It must have been the one with the cavitation feel and has a pretty nasty gouge inside the slider near the top. I can't even imagine how it got there, maybe previous owner maintenance. It is not an interference fit because the tube can at times slide freely through. It feels more like like the right combination of oil and air in the gouge creates a vacuum and sort of attaches tube to fork leg. Have you ever fixed anything like this? I found some 30 mm bushes but suspect the fork leg would be very challenging to set up on a lathe.
It is interesting that you mentioned polishing because I did a quite bit of that. When I got the bike there were quite a large number of deep gouges and burrs on the tubes so the seals would not seal. I filed burrs, filled big gouges with epoxy, filed and polished smooth. I don't remember the sand paper roughness but they look pretty shiny. It was done in a lathe. The entire fork action felt very stiff until I went to the thinnest oil I could find. After that I just felt stiction. Is there a way to reproduce the original ground finish? With the right paper it seems like you could create something like the honing finish in a bore.
Are all old forks likely to have issues? I'm a little tempted to buy new tubes but hate to do that and find no change. I may try straightening.
The yokes have a machined surface on the bottom that looks perpendicular to the bores. They sit flat on a surface plate so are straight. The fork brace is not perfect but seems close. Is there a way to get a perfect fit?
Pushing on the assembled forks off the bike seems OK. If anything, I may feel a little uneven damping sort of like cavitation of the oil at times. That makes no sense to me. I'll try without springs and oil.
Yes you can replicate the original cross hatch finish with fine paper.
Old forks only have issues if there is something wrong.
Checking the yokes: Fit one tube and do the clamps up. Slide the other tube through the bottom hole and up to the top hole. If it lines up it's likely that the bottom yoke is straight on that side. Do the same again but insert the tube through the top clamp towards the bottom clamp. If it lines up, it's likely that the top yoke is straight on that side.
As for the fork brace, it's made of thin mild steel so should be pretty easy to shape it to fit perfectly.
If there are slight bends in your tubes, align the bends fore and aft with both bends the same way and you will minimise the friction.
A good test for if you want to tell if you are making an improvement in alignment is to make an axle spacer to replace the wheel, suspend the bike, remove the oil, fork seals, springs, mudguard/fork brace and assemble the front end without them and move the axle up and down by hand.
There are left field things to consider as well such as on one TY175 I bought had a fairly twisted lower yoke that was causing alignment issues. When assembled, the tubes looked fine but if you slid one tube down out of the upper clamp while the other tube was still in the other side, the bent yoke became very obvious.
Another TY175 had a bent fork brace which was pushing the sliders away from each other (causing friction).
Another way to look for the cause of friction is to look for areas on the tubes that are more shiny than others.
Another cause of sticky forks is dents in the sliders. This is easy to test for by feeling for stickiness with the spring out and cap off and the fork slider disconnected from the fork brace and the axle.
To answer your first question, TY175 forks working properly have very little friction and TY250 forks working properly are no different.
I'm unsure if polishing the tubes is a good idea because the standard ground finish is intended to hold oil to lube the seals and to lube where the tubes rub against the sliders. Polishing the tubes may make the seals feel sticky and may also overheat the seals if you ride along a corrugated dirt road.
feetupfun thank you for the details. I just placed an order with InMotion, they don't carry the Magicals anymore or any TY springs according to their web page.
The dual rate with increased rate sound perfect. Now to find them.
France Trial Classic. They don't call them Magicals but they have the same dimensions. They are black whereas the Magicals are bright plated.
I recently purchased a 74' TY250 which the prior owner rebuilt the forks. The forks feel very soft and offer a very flat rebound feeling.
I decided to rebuild them again since the stanchions are rusty. I ordered new replacement stanchions and new aluminum damper rods "including all the factory works modifications" 🙂 for what that's worth.
I also ordered a set of OZO Pro Trials rear shocks (340mm and set up for a 230 pound rider).
I am looking for a set of replacement fork springs and possible rebound springs (if necessary) that will work with the above setup and my weight and I am having trouble locating them. BJR doesn't have any stock on fork springs at this time.
Can someone lead me in the right direction of where to purchase, or if another spring would work?
What is the stock spring rate? I feel I may need a little stiffer spring for my weight.
The standard Yamaha rebound springs will work fine in combination with the aluminium damper rods that In Motion sells and with aftermarket fork springs.
I'm 95 kg and have three bikes with TY250 twinshock forks and all have aftermarket fork springs in them. Two of the bikes have the aluminium damper rods and the third has modified Yamaha TY250 damper rods. Two of the sets of fork springs are Magical brand and the third set is from France Trial Classic. All three sets of forks work great for my weight with the standard quantity of 10 weight fork oil and 31 mm spring preload. All three bikes have standard Yamaha rebound springs in them. I haven't tried them without rebound springs.
The Magical TY250 springs (dual rate) have an initial rate 0.36 kg/mm and a final rate of 0.54 kg/mm. Spring travel to reach the higher rate is 134 mm.
Standard TY250 springs (dual rate) have an initial rate of 0.26 kg/mm and a final rate of 0.42 kg/mm. Spring travel to reach the higher rate is 137 mm.
I also have some B&J Racing TY250 springs (single rate) that I shortened by 8mm for use with Gold Valves. They are 0.39 kg/mm.
The France Trial Classic TY250 springs (dual rate) share dimensions with the Magicals springs.
I need to replace the rear shocks, I’m staying with Betor for originality but their website lists black springs for the 213, but the originals were chrome. They do list others for earlier Alpinas with chrome springs with the correct length and mounting size, but will they fit? I have tried their customer service but no help. Inmotion list the same shock for all Alpina models soI guess I should be OK…
You'll need to say which Betor shocks you are referring to if you want fitment help on here
I am curious if this thread is still active. If so I am trying to figure out what was left to me. The engine and frame both show m-5100493 and B-5100493 (no letter before the M and B). The best I can figure is that it is a 360 Montadero. I would love to restore it and ride, any help is extremely appreciated.
Thank you in advance,
Dino
Yes 360 Montadero. It's a very rare trail bike with a Pedrables engine design which is quite different to the common 5 speed Bultaco motor and hard to source parts for.
Ordered new crank seals and they sent me 2 thinner ones of the same size instead of the size that was in the bike originally. am I supposed to double up? i would show a picture but 25kb is not enough? not sure why they limit so much of file size?
Probably because of the cost for photo hosting. I think if you become a Supporter of Trials Central you can post large images
Having now fully cleaned up my 198B barrel and cylinder head, the top of the barrel and the underside of the head are stamped 137. It has been over-bored to 73.75 giving 256cc.
Do the Bultaco Sherpa gurus suggest my head and barrel came off an older 250 Alpina 137 from 1974/1976?
The bike was apparently supplied directly by Comerfords in early 1982 as one of about 110 bikes supplied and sold by them, and was allegedly billed as a 'Vesty Replica'
Or perhaps just put together by Bultaco factory using what was just lying around? And presumably over-bored to the max early in its life?
Ideas appreciated. Thanks
Bultaco cylinders are usually stamped with the model ID of the first model that came with that design.
I would have thought however that the 137 had a protruding sleeve cylinder while the Sherpa T 250s went to a soft metal head gasket/flush sleeve before the 198B. My 198 has a flush sleeve and soft metal head gasket. They did do lots of strange stuff to get bikes out the door towards the end and a 137 Alpina type cylinder and head would be fine to use on a 198B.
As for the large diameter bore, yes it's fairly common to bore a 238cc motor much bigger than standard to get more grunt rather than because the bore is worn.
montesa 349 1980 mk1
in General Trials Talk
Posted
The pre-Honda front wheel has the rim centred on the hub spoke flanges