Looks pretty good to me too. Not much blow by on the piston which suggests the rings are good but as Grant suggests it would be a good idea to check the end gaps before reusing them - or, if you can get suitable ones, replacing them. If you are replacing them (and they are almost a service item with two strokes) a very light hone would give them the best chance of bedding in but you need to remove almost nothing. Certainly new little ends - and circlips - and have a close look at the gudgeon pin for wear.

The crank looks ok although the bluing on the flywheels does seem odd. Because of that I'd check the con rod side shake to get an idea of the state of the bearing. Check the rocking side to side movement at the little end of the con rod - anything up to about 1.5 / 1.6mm suggests the bearing is ok. Other than that I'd be happy with how that looks.

Sorry for the late response, I dont get time very often, but I really appreciate all your help and advice.

I decided to replace the piston and rings, then lightly honed the cylinder. I then stripped the head, and it is now painted and back on the motor. I will post up some pictures soon, but for now I'll show how the bike itself is going.



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You've got a posher shed than me!

This is one I'm just finishing off -

I wish that was my shed, it's my spair room lol.

Really nice bike mate nice work

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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!

__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com

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 -








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.

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).

__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com

Very well observed Grant and it just goes to show that posts here don't just vanish into the aether when you press send 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.

Hi Nigel I live in the same part of the world as you.

You mentioned how the oil infection is important on a Suzuki 185 TF/ TS engine, and not to run premix

I recently bought a go kart for the grandkids and it has a 185 TF engine on it and no oil injection.

Apparently the engine had been recently overhauled, and maybe that's why.

Do you know if the oil injection system is still available, and if not, can one be made up.

Thanks.

The Suzuki 2-strokes were NOT designed to be converted to pre-mix, the oil injection went straight to the crankshaft bearings, and routed via stamped steel "slingers" to the rod bearing, and the piston via a separate line. The crank bearings iirc would be somewhat shielded from a premix, so you'd have to run heavy and pray.
IF the rebuild was done with that in mind, probably removing the slinger, it might be ok. BUT - Suzuki's design was VERY good and they even ran it on the factory race bikes, albeit wired open to a max setting. The TR500 I raced was set that way, as was the TR250.
I would want to know who rebuilt the engine and what if anything they did to modify it.
If mods not done, absolutely get an injection system on it. It shouldn't be too hard to get a used system off a wrecker/breaker. They were extremely reliable, I never knew of a failure when I was a dealer.

Edit: Thinking more, could be a problem getting premix to the big end bearing of the rod because it's expecting to be lubed from oil coming OUT of the crankpin, and RETAIN some of it as long as possible - so it may not get premix INTO the bearing very well.

__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com

Yep, that's right, Grant. One of the needed mods to run on premix is to enlarge the oiling eye in the big end of the connecting rod.

Cheers

Nigel in NZ

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