TF/TS gearbox problems
 

A question for Nigel.
Our little tf 125's have been suffering from gearbox semi siezures when cruising in top gear in hot weather. They get noisey and eventually tighten up but recover after a 10 minute break. There are no problems when riding in towns or the hills using all the gears, its just prolonged top gear travel.
Perhaps you have heard of the problem before and can give me an idea which of the bearings is giving up the ghost. I am only a little nervous that it might be the clutch bushing, which would be a bugger to get a new one machined in.
Any ideas mate?
It might be India oil related but I doubt it, its gone on thro' several oil changes. Just in case, we will be taking out the best gearbox oil we can get, synthetic, do you have any recomendations with viscocity?


Andy

ps. won't be taking it apart untill its on the verge of explosion. (destructive testing)

What makes you sure it's the gearbox? Sounds more like a plain old piston seizure to me. A gearbox seizure would be very weird. I've never seen one of these gearboxes fail in any way, and I've thrashed them thoroughly. Note that the 125 uses the same box as the 185, and THEY never fail. Terrible oil might cause a problem, but it's unlikely.

Pull the barrel off and have a look - if the piston is anything but perfect that's probably it.

You can remove any aluminum off the barrel with a little hydrochloric acid, and a light sanding with 240 or so wet dry sandpaper. Wash very thoroughly with gas.

Take a fine file to the piston seizure marks and gently file them off, working around the piston, not up and down. DO NOT sand the piston.

You'll usually find that the seizure marks are on the "corners" in relation to the wrist pin. Just file what you need to get the worst of the marks off, no more.

Note that they shouldn't seize, it's very unusual for them to do so, so something is wrong.

Be sure you are using the right plugs - BP7ES normally, BP8ES in hot / hard driving conditions. Also make sure you have good 2 stroke oil. If not, adjust the oil pump up a bit. Also check the plug colour - if it's white or light tan the main jet is wrong, too lean.

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Grant Johnson

Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com

I was scratching my head over this one, Andy, until I read Grant's reply. I would like to know why you think it is gearbox troubles before passing any comments re. the gearbox. It sounds to me that it may be they are jetted too lean on the main jet. This is not usually a problem on TFs as they are not tuned for performance, but I guess if the bikes have been set up for extra fuel economy from the factory, then maybe going up one size in main jet might be a good idea. The fact that it is happening to both bikes adds to this argument too. Jets are not too expensive. If they do have a smaller main jet, then that might be good to keep for higher altitude riding. Running with a non-standard (free flowing) air filter or exhaust will also act to lean off the mixture too. Grant has very good advice regarding repairing the piston and bore. If it is piston seizure, then be mighty glad you are running those little Suzukis. If it was a small four-stroke and it was seizing, then it would have destroyed itself many time over by now. I have a 1968 A50 Suzuki which has locked up on me several times, to the point of jamming the back wheel, but by the time I have got off and checked everything, it had freed up and would start again. The A50 is in a different state of tune to to TF. It can run up to 90km/h but to do that it is at a much higher state of tune and much more susseptable to temperature, altitude and even fuel type.
Let me know what you think, and I will keep pondering as well. Isn't good though, to see more and more people going the "low tech, small bike" way?

Regards

Nigel

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--"How can I be lost if I don't care where I am?"--

Thanks for the reply's gentlemen.
Loads of info and greatly appreciated, between the two of you there is a wealth of knowledge on the 70's suzukis.
Ok, a bit of info that I didnt mention;
A wine from top gear when cruising at 85 kmh slowly gets worse. Slow down and the gearbox is stiff. When stationary, in neutral, they rev, tick over as usuall, but selecting any gear,clutch in, starts the "shaking a tin of bolts" noise. Wait 5 minutes and ride off buisness as usuall. Its happened about half a dozen times now, always when cruising the long straight roads.
I see where the piston siezure idea comes from my first post, but that can't be it(almost sure ;-).
Internet diagnosis is a swine, just thought I would give it a try.
We fly out in a week to ride the bikes Nepal/Greece and this problem was playing on my mind.
So any more ideas are more than welcome.
Andy

Ok, let me get this straight - you're in Holland at home, the bikes are in Nepal, and you're going to fly out and ride them to Greece?

If so, then since it does indeed sound like gearbox trouble - although how BOTH of them have the same problem I can't imagine, but ...

I'd recommend visiting a bike wreckers and buying a coule of used bottom ends, strip and rebuild the innards as needed, and take the innards with me to Nepal. Swap out the innards on the spot and you're good to go. They are very easy to work on, and you can do both in a day easy. Especially when you've had a chance to have a little practice at home beforehand and know exactly what to do.

It would be nice to just swap out the whole crankcases, but the numbers won't match so that won't work.

I'd also take a spare piston and rings set as spare, and a couple of rings sets and small end bearings and circlips to put in while it's apart. Deglaze the cylinder and you're good to go. A couple of quarts of good 20W-40 oil too.

Good luck, and keep us posted! You should do a blog on this trip, should be worth watching! See the Travellers stories link on the left.


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Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

Thanks Grant
I already have the top end to take with me, but never thought of getting in touch with a breakers for a couple of gearboxes etc. I will look into it.
Strange things have happened to the two bikes, both have about 25,000km on them. Bolts go loose at the same time, wire connections also. If it happens to one then the other goes out in sympathy.
Andy
(writing is not my favourite passtime;-)

Andy,

Good luck with the trip, did I mention my local Suzuki garage has an original parts manual for a TS. If you need part numbers and have your chassis nos I'll happly look into it !!

cheers Matt

Hi All
Problem was fixed in Pokhora. I drained the gearbox oil and there was 1/3 too little. We changed the crank oil seal, which was pretty hard rubber, and since then the little buggers are running fine, for the last 3000 km.
Number of times I had checked the oil with the level screw and it seemed ok, but measuring the drained oil told the true story.
Thanks for the help.
Andy

That's great news Andy! Thanks for the tip too. Now that you mention it, I have noticed that there was a time that I filled the required amount and noticed that the level was already higher than the hole in the side. I just assumed that it was just slightly over or that I had slightly over-filled the gearbox but maybe not huh!?! It just shows again how robust these little buggers are, if they have been underfilled by 1/3 and still been so reliable. Keep the faith mate, and one day i willsee you on the road.

Kind regards

Nigel in NZ

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--"How can I be lost if I don't care where I am?"--

Hi Gents
Kept the faith and thrashed the little bikes for 13000km to Greece and all held up well.
I found new pistons in Shiraz/Iran and slipped them on as the power was down a bit but it made no differance, must of been the petrol/altitude or thick 2 stroke oil that was holding them back. Piston and ring set for $14 and did both bikes in less time than tappets on my transalp ;-) When we got half way through Turkey they picked up speed again.
Promissed myself not to get different bikes untill these blow up but at this rate there going to get me a long way yet, only 37000km on the clock.
A big smile still on my face still, even here in cold wet Holland.
Andy

Good going Andy, good to hear all went well!