Is that a YDS 5?

I have a 1979 TF 185 and it's fitted with a 12/28 sprocket set - don't know if that's the factory fit. It doesn't like going more than about 65kph so i'd like to gear it up.
Doesn't look like i can get a 13t on the front but What did the TS185 have on it?
38T for a rear is already pretty small

You said 12/28 but then said 38 so I will assume 12/38.
Sorry I don't remember stock gearing, but a TS185 will easily do 70 mph in stock trim. They do REV (somewhere around 7500 is power peak) and perhaps it's just revving / making more noise than you expect?

Your dealer should be able to tell you what stock sizes are on the TS vs TF.

A little searching for parts fiches found https://www.partsfish.com/oemparts/a...c/transmission and it says 12t front is stock on the R, and 38 rear https://www.partsfish.com/oemparts/a...881/rear-wheel
So that sounds like you just need to rev it!

Huh, so this would have explained why the '73 TS185 I used to have kept needing new bearings every 5 minutes ... you live and learn!

Thanks for posting that info :)

er, yeah! Suzuki had the very best oiling system available, the direct bearing lube went a long way to their reputation for reliability and longevity. On my TS185 RACE bike, I adjusted the pump higher - to the max setting, but still variable according to throttle opening as it was often plonking along at low speeds, and ran pump gas. As I recall, the standard Suzuki race kits simply said wire the pump full open, and run straight pump gas. The factory TR500 I raced ran this way and worked fine, as did a TR250 I know, and my own TR-ized T20.

Note that the Suzuki bearings that were direct oil injected, had a shield to keep the oil IN the bearing, with of course lots leaking past to lube elsewhere - but that shield would largely PREVENT oil from getting TO that bearing from the PREMIX.

I got it as a very tired "field bike", it was a real death trap, lol

Didn't keep it long, and I had my street-legal looking DT100 so I just went back to that (the oil pump on the DT never gave me problems, but lots of people hated them at the time)

Next model along - YDS 6.

You can remove the oil pump and run Yamahas on pre mix as all they do is pump the oil into the inlet manifold and, essentially, make two stroke mix there. There are oil ways drilled through the castings to the various engine bearings and excess oil drips down into them. Not so on Suzukis and Kawasakis from that era - their oil pumps split the feed, with some going to the inlet Yamaha style, but the second feed line pumps directly to the engine bearings. Take those pumps off and, as mentioned, the bearings will eventually run dry and fail.

All of that supposes the pump actually works of course. Mine, it turns out, was only putting out 1/3 the oil it was supposed to. This was the result a few months after that picture was taken -



https://i.postimg.cc/Hxc0XcNp/IMGA0002s.jpg




Getting the bits of piston out of the crankcase required a full engine strip. It's now back together again but in the meantime I've learnt more than I ever wanted to know about Yamaha oil pumps. :rofl:

Carnage! I'm sworn off of 2-smokes these days, apart from my TY175 which I want to convert to electric sometime anyway, lol

That doesn't look like oil pump issue to me... usually not enough oil just seizes the piston. That looks like bad jetting or timing, most likely jetting. Be sure the carb is set correctly to stock and of course check timing too.
GOOD thing about Yamaha oil pumps is you can dispense with them easily and just run premix. (That's the only good thing mind you).

Very well observed Grant and it just goes to show that posts here don't just vanish into the aether when you press send :rofl: No, the oil pump was only one amongst a number of issues, some of which I'm still working through.

The rule of thumb back when I used to run these things in anger was that hole in piston = timing too advanced, and that was my first thought. The dial gauge however told me different. It was set according to the book a few hundred miles before and still was at the book setting (1.8mm) when I checked it afterwards. The jetting - main, pilot, needle, clip, cutaway etc - also was exactly what the book said it ought to be. So maybe the compression was too high? The book said 7.5:1 but a day with a burette came up with both cylinders a fraction under 7.0:1. Squish band was 1.2mm, plugs were NGK 9's - a grade harder than necessary, and exhausts were factory standard. I'd only been doing 45mph on a trailing throttle when the piston holed. By all the numbers that should not have happened.

I contacted a well regarded two stroke tuner about 50 miles from me and took the engine to him. His first thought was an air leak causing a weak mixture and did a leak down test. A couple of small gasket leaks showed up but nothing serious enough to point the finger at. Next suspect was the cylinder head profile on the affected cylinder. The head had been reworked by a well known - probably the best known - two stroke engineers in the UK to repair some previously existing (before I got the bike) chamber damage and the correct profile hadn't been restored. He remachined the head and tightened up the squish band slightly. That's where I am at present. I'll see how it feels on the road but I think a few dyno runs to check fueling and timing will be in order come the spring.

Back with oil pumps, I was surprised to find out exactly how little oil mine was putting out. It looked perfectly ok and the bikes had only done 12k miles from new. There is a Yamaha service bulletin about oil pump output (as there is for Suzuki pumps) and, armed with those figures, I built a test rig to check mine. That's how I know how little it's pumping. There is someone who rebuilds these things as a 'side hustle' but he's swamped with work (or, I suppose, he could just be very slow!). I contacted him in March and he said August. That's now slipped to January. I mentioned the pump problem to a friend in the US who has a barn full of old Yamaha stuff and he sent me over three more pumps to test. Two of them put out exactly the correct amount but one was way down - even worse than mine. All four of them looked exactly the same externally - no damage or anything to tell them apart. I've used one of the good ones for the rebuild but I now have two non functional pumps and need to figure out why they don't work. Leaking internal seals are, I'm told, the usual suspect but we'll see.

You’ve been doing your homework!
I presume zero sign of any issue on the other cylinder?
I look forward to hearing more!

Interestingly (to me anyway!) the other cylinder shows no sign of problems. Plug is the correct colour and there are zero marks on the piston - no blow by or anything. As there should be (or not) after 300 miles really. I'd taken both cylinders to the hotshot engineers for repairs just before Covid hit last year - the previous owner had really 'done a number' on the internals. He rebored one and resleeved the second. The problem cylinder was the ... no, not the resleeved one as you might guess, but the rebored one.

While I was waiting (they took nearly six months!) I had the crank rebuilt and paid for some new OE pistons / rings by mortgaging my wife :rofl: I got it on the road this time last year, did a couple of hundred miles and put it away for the winter. This spring I checked it over, did a couple of short trips and then one 25 miler. The piston holed about 1/4 mile from home so fortunately it was a short push! The only thing that - pre hole anyway - distinguished between the cylinders was that the 'faulty' one constantly ran about 10C hotter than the other one on my IR thermometer. That was on my list to investigate when the problem happened.

As I've said before, the idea is to ride the bike to Morocco. The trip was meant to be last year, then this year and now next year - all Covid postponements but perhaps fortuitous in the circumstances. It was meant to be a solo trip but the friend who supplied me with the oil pumps said he'd like to come along and bought another YDS6 for himself. He's going to ship it over and we'll go on one each. The bike he bought came with recent dealer receipts for $1200 of engine rebuild work. He managed 55 miles on it before the clutch thrust bearing broke up, jamming and wrecking the clutch basket and the primary drive. Fortunately he had enough parts to rebuild it himself but that's a grand total of around 375 miles so far for two wrecked engines. On that basis we're going to need around 15 bikes for the trip! :rofl:

The picture below was Photoshopped together to show Then and Now, but as time goes on I'm more convinced that Zen and How might be a better title. :(

https://i.postimg.cc/bwMbCxCS/70-20a.jpg

Hmmm... 10C hotter on one side is a LOT wrong. In the absence of anything obvious thus far, I'd also be looking at piston clearances, exhaust pipe obstruction - baffles, carb synch, and worry about crank seals - was the cylinder on the side where the outer crank seal is against air/ignition?
Love the then and now photos - hope to see more when you get there!
good luck

Attention Neil!
 

I've forwarded the link to this story to a good friend who is a former professional 250 privateer rider on TZs and has one of the finest collections of Yamaha 2-stroke twins you'll ever find. He restores them professionally now and is a meticulous mechanic . I'm sure he will have some input.

It's nice seeing the old thread still has some life.

Best regards

Nigel in NZ

Yes, I agree about the temperature difference and that was under active investigation when the piston holed. Whatever was causing it wasn't the obvious stuff - I'd checked that as mentioned above. I was quite specific about piston clearances when I had the cylinder work done. Yamaha say 1.5 thou and that's the figure I gave the engineering co. Not being one to take this on trust I checked it when I got everything back and my measurements came out at between 1.6 and 1.7 thou on both sides. I don't have pro grade measuring equipment so there may have been some slight errors in that but it seemed near enough to what it should be to put my mind at ease. The engine specialist checked it (once a new piston had gone in), came up with 1.8 thou and he was happy with that.

Crank seals were new on both sides. You can't get OE seals (or I couldn't find any) so it has to be aftermarket, but there is a YDS specialist supplier in Scotland and the seals (plus a lot of other bits) came from him. Because of the centre labyrinth seal you have to leak down test the whole engine - you can't do it one side at a time. The seals passed that test. The faulty cylinder is on the primary drive side so oil would be sucked in if the seal was faulty. Often that results in a one cylinder smokescreen but there was no evidence of that.

Exhausts are std - as you can see from the picture - so no half developed expansion boxes setting up obscure pressure harmonics. The inside of the silencers had been cleaned out both chemically and physically - and a messy job it was. I got about a kilo of carbon out using a kind of wire flail I welded up. Baffles are std, cleaned back to bare metal, and most importantly, in there.

Carb balance is a bit more of an issue. It's easy to balance the carbs themselves - the lolly stick method works well and I've used it for years (decades) on two strokes. You can't really use vacuum gauges on these old two strokes. However that's the idle balance. Keeping that balance when you twist the throttle has (and is) proving more tricky. The cable is a one into three via a junction box type and is inconsistent. I have three cables at present - the OE Yamaha one that was on the bike, a specialist co (Venhill) custom replacement and a DIY one that I soldered together myself. All three of them behave similarly - the carb balance varies depending on cable routing and handlebar position. I'm still messing around with this as it's unacceptable but I have a feeling I'm missing the obvious. While in that area I'm currently looking closely at fuel flow. The carb jets may be std but if there was some restriction before that point the cylinder could still run weak. So everything from the tank filter to the float chamber is being tested. Similarly the oil flow from the tank to the pump. No point having a good pump if the oil feed isn't fast enough.

I'm going to resolve the cable issue one way or another as carb balance does need to be maintained, and then it's going to be gently gently to get a few more miles on it before it goes on the dyno. That hopefully should identify any fueling weaknesses and optimise the ignition settings. In the meantime I've been trying to get some luggage capacity sorted out and spent a happy few days (!) welding up a custom fit luggage rack. I just hope I get a chance to use it.