Mark97 Posted March 10, 2018 Report Share Posted March 10, 2018 Hi, I am a newbie member but I have purchased a Yamaha TY 175 1980 to do some twinshock trials for fun. I have stripped the bike down for a light restoration, but on removing the flywheel cover spotted some black silicone to the front and slightly above the front sprocket and behind the clutch adjustment screw/bolt. Removing the silicone revealed what looks like Quick Steel type repair putty had been used. The bike had not been leaking from this location, and the area of damage looks quite small. My concern is that in this location there appears to be a small steel cap pressed in to the aluminium casting, what is this for? Am I OK to ignore it as the sproket seems to rotate freely and smoothly or should I look at getting it welded properly? I would need to locate someone who welds alloy in Essex. I have looked for replacement crank case halves but they seem to be in short supply. any advice would be greatly appreciated. Regards Mark Quote Link to comment Share on other sites More sharing options...
tony27 Posted March 10, 2018 Report Share Posted March 10, 2018 If it hasn't been leaking then you're probably safe to use as is Getting it welded should involve stripping the motor fully & takes some serious skill to do it properly without causing distortion. Not familiar with the 175 motor so I don't know about the steel cap, a photo would help to confirm that welding isn't needed Quote Link to comment Share on other sites More sharing options...
Mark97 Posted March 10, 2018 Author Report Share Posted March 10, 2018 The red mark on the image above shows the location of the damage, the steel cap is the black circle. I have not split the crankcase so was wondering what is behind the piece that is damaged? does a shaft of some description sit in there? Regards Mark Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 10, 2018 Report Share Posted March 10, 2018 The black circle is a bung fitted to seal a manufacturing hole in the gearbox casing. The hole is there to allow the casing to be machined to provide the left end bearing for the shift drum. There are no rolling element bearings on either end of the shift drum. Provided the crack doesn't allow misalignment of the shift drum, it should be fine without a weld repair 1 Quote Link to comment Share on other sites More sharing options...
Mark97 Posted March 11, 2018 Author Report Share Posted March 11, 2018 Oni, the screw and bolt for the clutch adjuster arm is still intact, it sits slightly ahead of the piece that's damaged, in my image its obscured by by the index finger, so hopefully the clutch adjustment will not be an issue. Looking at exploded diagrams as Feetupfun says the shift drum seems to sit there, I did not know whether a bearing of some description (i'm new to this) so hopefully as shifting does not seem to be a problem and there was not an oil leak I will keep it as is, at least for the time being and look for a replacement casing or someone who can repair it in the longer term. Are all TY175 casings from all years the same or are there differences on different years productions? Thank you. Mark Quote Link to comment Share on other sites More sharing options...
tony27 Posted March 11, 2018 Report Share Posted March 11, 2018 Reading what Feetupfun has written I wouldn't bother about replacing the case if the shifting hasn't been affected & there aren't any leaks. Looking at Partzilla's listing the B & C model used the same cases which are unique to TY175s so I would say any TY175 case should be the same if you decide you really want to change cases Quote Link to comment Share on other sites More sharing options...
shakennstirred Posted March 11, 2018 Report Share Posted March 11, 2018 As said if not leaking leave it be. just add some new sealant Quote Link to comment Share on other sites More sharing options...
bikestat Posted March 11, 2018 Report Share Posted March 11, 2018 on the ty175 the damage was caused by the chain tensioner spring becoming weak and allowing the chain to come off and cause this damage a common problem on that bike Quote Link to comment Share on other sites More sharing options...
Mark97 Posted March 12, 2018 Author Report Share Posted March 12, 2018 Thanks everyone for your comments, I will rebuild with a new chain tensioner and keep the existing crankcase half but keep an eye out for a replacement. Thank you. Mark Quote Link to comment Share on other sites More sharing options...
goudrons Posted March 12, 2018 Report Share Posted March 12, 2018 It's already been mentioned it's a hole machined to hold the shift drum and should have a plastic cap inserted from inside, but most got damaged there as it's were the chain hits if it comes off the rear sprocket. So finding a good case is very hard! I remember buying up 6 or 7 complete cases to try and find a decent one when I did my refurb. The old trick was to jam a coin in there from the inside, any oil that spilled out lubed the chain! Just remember to top the gear oil up before use. A 2p piece fits perfectly. There's a weak point on the case at the other side too, around the post for the kick start return spring. Usually once the splines on the kick start shaft wear away, owners get a bit brutal with the kick starter, repeatedly smashing it around until either the spring breaks of more often, the post snaps off and rips a hole in the inner case. This can also crack and take out the lowest, rear most point of the case at that side too. 1 Quote Link to comment Share on other sites More sharing options...
Mark97 Posted March 12, 2018 Author Report Share Posted March 12, 2018 Goudrons, thats good to know, so if I do split the cases i can drop a 2p into the area of the casing where the plastic cap was I am assumin it needs tapping into position or is it held in position by the change drum? Regards Mark Quote Link to comment Share on other sites More sharing options...
goudrons Posted March 12, 2018 Report Share Posted March 12, 2018 One will just drop in and the shift drum holds it in, though it won't be oil tight, just keeps some of the sh*t out. Best advice is, don't fix what ain't broke. If it's ok now, leave it and have some fun. Splitting the cases when you don't really need to (like crank rebuild, mains bearing or seals) will more likely cause a load of other issues. They aren't overly complicated, but they can bite back, I've seem plenty mullered by guerilla engineers. You can put far too much into one of these and to be truthful, you don't get much out. There are a few useful mods that help them a little, adding an inch to the swinging arm, modding the top yoke to move the bar clamps over the top of the yokes and dropping the forks down the clamps around an inch helps them steer a bit better as does moving the foot rests back and down a little. They don't really ride that great compared to most, if not all the competition of the day and they can swallow a lot of money quite easily that you'll not see back. But sometimes madness takes over and I once got hooked on one. Just don't ask what I spent, I prefer to try and forget! 3 Quote Link to comment Share on other sites More sharing options...
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