tony27

It should work but you'll need the head as well, fairly certain the base gasket is the same for both size motors

Have a good talk with the guys when you order the puller, they'll tell you exactly what you need to get things sorted.

Winding the screw in richens the mixture, sounds like you need a bigger pilot jet. The pilot jet in the TY mikuni is different than most other mikunis which means your local shop won't have 1 in stock, with my modified airbox that breathes a lot better I took the advice on TY trials site & ordered a #37.5 which has worked out well B&J racing is closer to you than TY trials so I'd see if they can supply you a couple of different sizes

If you do decide to replace this should help, unfortunately the site doesn't show a 1980 model. There are a few different bikes that used the same basket & gear which would increases your chances of finding a good 1. The friction plate is used in a lot of bikes which means the fingers are the same in other bikes so it could be possible to change baskets onto the TY gear https://www.partzilla.com/product/yamaha/525-16150-00-00?ref=5d9cf591dcd36ebb53a7b0646d447d9ab6f350c1

Yamaha won't have a cable, try TY trials or possible venhill cables

My 250 have a lot of the same mods. The magicals springs etc & the lengthened swingarm really make a big difference

You would be surprised how much of the noise in the motor comes from the rubber dampers inside the clutch going hard & shrinking. I replaced the dampers & basket a couple of years ago & it difference it made was huge

TY175 & 250 use the same wheels, there won't be a weight difference. The dished sprockets aren't the easiest to get but most places that deal with TYs can supply a spacer that lets you use flat sprockets My biggest concern would be your comment about the spacer, sounds like the rear wheel will be off to the right side now Personally I've always found the 175 to cramped for my height of 181cm which is part of the reason I ride a 250 even though most people say the 175 is the better trials bike

My TY250 has quite a few mods & I was offered mono forks to fit but I didn't feel it would look right. Most of the mods could have been done back in the day like the steering pulled back which was done previously, the only non period mods are not something that are immediately noticeable like the v-force reed block In theory I have to ride against Fantics & SWMs etc as there is no era splits, this doesn't worry me as most guys with the newer bikes aren't actually that good & I enjoy riding a bike with a lot of my own work in it

That grooving would definitely cause your leaking issues, new valve & needle will seal & lower the fuel level to where it should be The o-ring wouldn't be the cause of the overflowing but may help with the lack of snap if you're getting main jet bypass

#4 is the part. Here is the kit for replacing all the o-rings & bowl gasket, definitely worth doing for the price & should get rid of most carb problems https://www.tytrials.co.uk/trailandtrialsuk/prod_189299-4-9-14-24-Carb-Repair-Kit-TY250-Twinshock.html Could be worth ordering either the ignition tune up kit at the same time unless you plan on upgrading to electronic ignition https://www.tytrials.co.uk/trailandtrialsuk/prod_147767-911-Ignition-Tune-Up-Kit-TY250-Twinshock.html Do you have a manual for the bike, the only 1 for 250s that seems to be easily gotten is from cycleserv for the B model but it works for the later bikes as well. I can check with a guy here in New Zealand who sells copies of manuals to see if he has ever copied the genuine Yamaha manual if you need 1

My C model definitely has a lot more snap than that but it has no flywheel band & runs electrexworld electronic ignition on a freshly built motor. Seeing as you're in Canada the best place for a new throttle cable is B&J Racing, they should be able to supply a domino throttle as well. Don't worry about the listing saying 74-77 as the 78 is the same apart from colour scheme. I've heard that Bob's TY motors are amazing, if postage wasn't so expensive I would have sent my cylinder to him for the porting work http://www.bjracing.com/id115.html If you want to use the standard throttle then TY trials has this cable & is 1 of the best source for parts around. I bought all the bearings, seals, gaskets etc for the rebuilt from them & had the parts in New Zealand in around a week. John is great to deal with & knows his stuff https://www.tytrials.co.uk/trailandtrialsuk/prod_43441-24-Throttle-Cable-TY250-Twinshock.html When you are changing the needle & seat pay attention to the condition of the o-ring that fits into the float bowl, when these get damaged it allows fuel to bypass the main jet

Sounds like you had it dieseling which can do damage to the piston & rings. As feetupfun says I'd remove the flywheel first to check the state of the key before pulling the header pipe & looking up the exhaust port to check piston condition For the revs to rise like they did there are only a couple of things that could be the cause. Either the throttle cable was displaced at either end meaning the slide couldn't return fully or less likely you had a major airleak develop - would need to be something like the manifold coming loose/split but airleaks normally don't just suddenly happen

My top race stuck out a few mm which made me think that the steering head had been modified, glad to know that it isn't the case. The lower inner race can be removed by removing the bolt through the lower clamp & pressing the shaft out, you have to make sure the relief for the bolt is lined up when refitting but it's a pretty easy job 1 of those sets of races is definitely scrap, normally it would be the lower as that's where water can collect. You do want to use the lower seals for this reason

I found when I fitted the taper roller kit to my C model that I needed to leave the seal plate off the top bearing to get enough thread for the nut to do it's job. Apart from that it was a pretty straight forward job

Seem to remember the studs have flat ends on the longer thread which are the ends that go into the barrel, the shorter end is slightly domed

If it's anything like the 2 strokes I'd leave the radiator until the engine is in

It's your bike so if you want it british racing green then do it. I suspect it will come out looking great I know what you mean about the time & money thing, I recently bought a CZ sidepipe to restore for racing & with it needing the forks rechroming & the back end of the frame straightening out it won't be cheap or quick to do

If they are anything like the older bikes then I'd say yes, leave everything connected & you won't need to bleed the brake. The hose running inside the swingarm is great for protection but makes servicing harder

Being in the states have you tried www.bear-sports.com The list of manuals they have on their site is just a fraction of what they have, I've bought several of their manuals for CZs & they're well worth the $18. I see 27 different Bultaco manuals in the list that came with my last manual but none showing on the site

Makes balancing much easier, generally the kits that are sold also move them rearwards a bit

When I get in to sorting my C out fully I'll probably order a 28mm from mid atlantic trials as well, I have extensive mods to the airbox & a WES muffler so it definitely fits what they say is required to run the bigger carb. They are certainly well priced & now that new airbox to carb tubes are available stretching to fit the larger carb is not so worrying

You have the standard carb, parts aren't as easy to find as they are for the later mikuni carbs EBay is probably your best chance for finding what you need

No special tools needed to remove the plates, only if you're removing the hub & basket Probably nothing wrong with the friction plates, have the feeling the only steel in the clutch is the drive plates & that the friction plates are plastic but I could be wrong. If you do strip the clutch either deglaze the steel plates with wet & dry sandpaper or get them blasted

Same fibre plates as used in Betas What condition are the fingers on the clutch basket in? If there are any notches from the plates I'd order a new 1 along with rivets & rubber dampers off Splatshop, actually quite cheap & there is a page on their site showing how to do it. When I did mine I also upgraded to the later hub which flows oil better but it wasn't really needed, motor was much quieter after doing that as well