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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Gearchange return spring retaining post problems
Post Info TOPIC: Gearchange return spring retaining post problems
TTRider


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Gearchange return spring retaining post problems
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Hi all,

I was out a couple of weekends ago on the TTR for the Borders Rally - first rally and a fantastic weekend... until the bike lost all drive!

To start with the bike was having trouble finding gear - I'd kick the gear change lever up but it wouldn't find it. From what I remember this was third to fourth. This was infrequent though. Not too long after, it happened again but now even when engaged, I'd need a lot of throttle to keep the bike moving at all (maybe 5-10mph?) At this point I was thinking I needed new friction plates.

A couple of minutes later all drive was lost and I had to get towed!

Whilst waiting for my mate to come get me I noticed that the bike would idle fine in any gear (when I could find one), even without me using the clutch i.e it wouldn't stall.

I've taken the clutch cover off to take a look but this is the first time I've gone into the clutch and to be honest, I don't really know what I'm looking at!

Part of me has stopped thinking its the friction plates now but that maybe its the actual change mechanism itself or maybe it needs a clutch adjustment?

If anyone has any ideas as to what it could be I'd appreciate your input - I'm not quite sure what to try next!

Cheers!



-- Edited by TTRider on Thursday 12th of May 2016 07:43:12 PM



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mossproof


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RE: Gear problems
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If the clutch cover's still off, take the spark plug off, put the bike "in gear" and turn the rear wheel by hand. If there's nothing turning in there, it's not engaging gears in the gearbox. If things are turning but the engine's not, the clutch is slipping. Has the long actuator lever seized, or the cable, or is there something jamming the clutch release arm (where the cable pulls it)? I think if something was broken in the gearbox you would either have drive or not so it's pointing to a clutch problem of some sort. Keep delving in there,

Good luck,

Simon.



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TTRfan


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Just a thought.

You may be getting "false neutrals" if the gear change mechanism isn't working correctly.

The only thing I have come across that has caused this to happen is a loose post in the crankcase.

Gear spring retaining peg.JPG

 

I have had (I think) three cases where the casting around the peg has broken - presumably though over enthusiastic gear changing e.g. stamping on the gear lever! See below:

Gearcase needing welding 001.jpg

 

If this has happened to yours then all is not lost. Find someone who can TIG weld to relocate the peg securely.

Crankcases2.jpg

 

Just a thought....

Brian



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Robin


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Good morning,

I have gear change problems, this is predominantly when changing down. The issues has been identified as a damaged casing around a pin (see photo).

I have looked at various forums on this subject and it appears all is not lost, a repair is possible.

The questions I have regarding this repair having spoken to a couple of local 'experts' are:

  • can the repair be made in situ 
  • do I need to find and remove the broken piece of casing (the TTR was ridden for a couple of hours with this issue)TTR support pin.jpg
  • has anyone done the repair and subsequently the weld has broken
  • is it possible to weld the casing support to the pin or is it repaired by applying weld and then machining a new hole. 

As you can see I have no experience of welding and what is possible or not. The general consensus is that the engine will have to be stripped for repair.

Any info would be appreciated.

 



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TTRfan


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Hi Robin.

I hope you don't mind me merging your post with a previous thread but it shows some photos which may be helpful. 

In my repairs, I have always had the post in place whilst TIGging around it.

That was until the last welder I used decided that wasn't a good idea and, without asking me, proceeded to weld with the post removed. I now have the nightmare of trying to drill through the weld and find the exact location of the original hole no



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mossproof


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Some welders will be happy to do it as long as there is room to get the tig torch in. Others will demand a complete strip down. In either case, the area has to be spotlessly clean. Also, you MUST find the missing bit. Otherwise it will eventually get ground up, go through the oil pump, damage journal bearings and cam bearings, get stuck in main bearings or the big end... You cannot afford to bodge if you want the engine to last.

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Rossyboys


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Hope its a simple fix


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TTRfan


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Any progress on the welding Robin?

If you give up and decide to change the case then Steve has one in the shop that fits "blue" TTRs - see here 



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Robin


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Hi Brian, the welders I have spoken to all are of the opinion that the crankcase must be split. The area would be welded and then machined out for the pin. The engine is out of the frame and I will split the crank next week, on the rebuild I plan to do a top end refurbishment. Not quite sure how much to do, but looking at the following areas:
Piston rings
Timing chain
Valve stems

Any other info on the top end rebuild would be appreciated.
Regards


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TTRfan


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You should be able to find all the info you want in the "Stickies" section but this is quite a good one to start with - see here



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Ttboof


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if you have the crank case apart, the gearbox bearings are cheap (if bought from your local bearing shop) it's a good time to replace them. 



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TTRfan


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RE: Gearchange return spring retaining post problems
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It is a coincidence that after having the problem raised, I have my own problem with posts that have broken mountings in some spare engine casings that I had put at the back of the shelves hoping perhaps that they might magically fix themselves! Although, obviously that didn't happen cry

It was (or should have been) easier for me as my cases were stripped out but my welder conspired to do the repair differently to how I asked and caused a whole new problem!

I had asked for weld to be built up around the post as I had had done in the past. However, without conferring, he decided it would produce a better and stronger repair if he welded up the hole without the post in evileye

You may ask why this would cause a problem but, if you think about it, how do you find and drill out the capping of new weld in exactly the right spot to match up with the remains of the original hole?

Once again, I called upon my brother to help as two heads are better than one plus I only have basic tools with no fancy milling machine, etc.

This is what we started with:

Gearchange return spring post refitting_1.jpeg

To make sure we drilled at 90 degrees we had to use the drill stand so made sure before we did any work that the case could be made to fit in it and that we had a way of holding it firmly in position in exactly the horizontal.

Gearchange return spring post refitting_2.jpeg

We decided to make up a template from plywood that located the hole in a good casing and bolt that to the repaired cases to use as a guide for the drill in the drill stand. Plus we added a cardboard guard to prevent swarf getting into the bearings that were still in the casings. Not a five-minute job!

This is what it looked like:

Gearchange return spring post refitting_3.jpeg

Thankfully it worked out fine and the pins tapped home very nicely and are tight and secure biggrin

Gearchange return spring post refitting_4.jpeg

I hope that helps someone now or in the future and  perhaps is an example of what can be done without expensive engineering tools and equipment. My drill stand cost me £25 second-hand a few decades ago wink

Brian



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JOHNYBOY


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very clever engineering skills brian

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mossproof


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Nice job Brian (and Trev)!
You could offer to machine casings for people for a fee - cover the cost of all that expensive mdf



-- Edited by mossproof on Monday 11th of March 2024 05:14:22 PM

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