TY250 jumping out of gear

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tat ty
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TY250 jumping out of gear

Postby tat ty » Wed Nov 08, 2017 8:29 am

I guess this is a question for David, but I thought I would put it out there, as others may benefit from his advice.

My TY250A has developed a habit of occasionally jumping out of gear.

It's not so much a selection problem, as that will usually present as you attempt (poorly perhaps) gear changes. In this situation It can happily be cruising along in 5th gear for quite some time and then simply jump out of gear.

My thoughts are that possibly the detention plunger is not doing its job. Perhaps after 40 plus years the spring below it is not quite doing holding its own,so to speak. I had thought it may be an idea to place a couple of fiber washers below the spring to give it a hand.

My issue is I don't quite understand how the plunger functions. I suspect it is the candidate but of course there may be more complex issues. I'd rather the easy road first.

Any comments would be valued.

Alastair



Guy53
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Re: TY250 jumping out of gear

Postby Guy53 » Wed Nov 08, 2017 10:09 am

Is it just in 5th gear ? Does the gear change feel's right ? Often the plunger is dirty, 1st I would unscrew it and give it a good cleanup.

Guy



llewdaert
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Re: TY250 jumping out of gear

Postby llewdaert » Wed Nov 08, 2017 10:55 am

Either the gear has not been selected correctly or fully,

or the gear and /or main shaft itself is worn [if the bike has done lots of road miles in top gear this is my bet].

The gear is held engaged by the angle of the dogs[spurs] on the actual gear itself. Not so much by the detent ball and spring[but it worth a try to repair if it is faulty.

Good Luck

James



David Lahey
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Re: TY250 jumping out of gear

Postby David Lahey » Wed Nov 08, 2017 8:10 pm

There are two easy things to check before you get too serious.
The first is that the plunger that holds the shift drum in the right spot might be sticky due to oil sludge or particles building up inside it like Guy said, or maybe the spring inside has sagged so yes cleaning it out and adding something to compress the spring a bit will help it.
The other easy thing that I have seen is that sometimes the weight of the shift lever is too great for the spring that centralizes the shift mechanism after each shift, and the jiggling that the lever does just riding along can be enough for the shift mechanism to override the detent plunger which is trying to hold it in gear. This sometimes happens if people fit an aftermarket (heavier) shift lever without adjusting the centralizing spring, which is located inside the clutch cover. If you need to do this I'll post up something from the workshop manual showing how to do it.


relax, nothing is under control

David Lahey
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Re: TY250 jumping out of gear

Postby David Lahey » Wed Nov 08, 2017 8:18 pm

The plunger has a rounded, hardened, polished steel tip that interacts with a wheel on the left end of the shift drum. For each gear ratio, there is a smooth depression in that wheel that the plunger goes into.


relax, nothing is under control

tat ty
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Re: TY250 jumping out of gear

Postby tat ty » Thu Nov 09, 2017 8:14 pm

Thank you all.

The issue does appear to be a 5th gear issue. Bike has roughly 3500 kms on its speedo.

Running the original shift lever.

I'll give the plunger a bit of love and we'll see how things go.

Thanks again gentlemen.

Alastair




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