Gearchanging problem

[fuzz]

For some reason I cant seem to change down gear properly. The gear lever doesn't seem to engage lower gears. I'll change down into 5th, say, but then the lever becomes spongy and won't go into fourth. It only seems to happen when using the brakes though - if I use engine braking only it will shift down the gears. At first it started only happening from 2nd to 1st about a week ago, but now it's happening in the higher gears too.

Another problem now occuring is the engine losing power. Only occasionally, but for a couple of seconds it will almost die. It feels like it's run out of petrol - no engine braking occurs. It also splutters on occasion. I have a feeling it might be the air filter, as it's coming to the end of it's life (1000 miles left before scheduled replacment) and I also took the baffle out of the exhaust yesterday, which is when this problem began.

Any thoughts?
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Bikes: '99 NSR125R, '00 SV650S, K1 GSX-R600, '97 CB500, K3 SV1000S, '16 VFR800

[alains]

about your gearbox , it seems that drums & forks are loosen so the gears do not engage properly , may be it's your ridding habits , but nothing much to do . the best is to buy a second hand engine (with little mileage) , have a good look on it then change it . about the other problems , certainly a good cleaning of tank , air filter , carb and a new plug will resolve them . in case have a look here : https://cgi.ebay.fr/moteur-HONDA-125-NSR_W0QQitemZ4601579957QQcategoryZ117479QQrdZ1QQcmdZViewItem
i can help you if you want and about the fact it's a french engine do not worry your top engine will fit it and the seller accept to ship it at the buyer expense (france-uk around £15 in first class)
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the worst day fishing is better than the best day working

[fuzz]

Sorry, should have said, this is on my SV650S.

Having gone through the manual, I can rule out it being a clutch problem. Possible causes could be bent selector fork, although it's never been dropped, lever return spring or stopper arm spring. Of course it could be something else entirely.

Oh, and with the engine problem, could it be that the carbs need synching? That's a job that's now overdue.
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Bikes: '99 NSR125R, '00 SV650S, K1 GSX-R600, '97 CB500, K3 SV1000S, '16 VFR800

[Guest]

[G]

[fuzz]

Well I changed the engine oil completely, and also cleaned the gunk from around the gearchange shaft but the problem remains. I find it odd that it only happens if each gear is not put under load for a short time. This is fine during normal riding, but if I need to stop quickly I can't change down quick enough to get it into first before I stop. I can, however, rev the engine and let the clutch out while holding the bike back at the lights/crossing etc. and go through the box that way.

I'm going through the diagrams in the manual to try and understand how the gearchange mechanism works. From what I can gather, when the shaft turns, the pawls on the selector arm turn the cam plate, and then the spring on the selector arm sets it back into position. The stopper arm locates into the cam plate to make sure the gear is engaged properly.

If this is correct, could it be that the centralising spring is weakend, and therefore not returning the selector arm back to it's starting position straight away? Or, is it possible that the stopper arm spring is worn and the cam plate is not locating properly, so the selector arm can't find the pins as they are not in the right place, until the gearbox is under load?
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Bikes: '99 NSR125R, '00 SV650S, K1 GSX-R600, '97 CB500, K3 SV1000S, '16 VFR800

[sickpup]

As the bike changes up the gears ok I think we can rule out bent selector forks although I would love to know how dropping a bike bends them.

I think what you have is under cuts on the dogs.

Put the baffles back in and you will probably find that magically the engine problems will disappear.

[finpos]

Just went through this with my mate and his SV650. Don't know the model, maybe yours is the same.

Fearing bent selectors, worn dogs and all manner of engine-in-bits type trouble, the problem was...

The gear lever height adjustment.

Every time he changed down, his foot would never let the gear lever return quite to it's centre, so the the selector drum wouldn't fully rotate to the next position. Pressing down on the gear lever again, he was just selecting the same gear.

Used the adjuster rod to lower the lever a cm or so, problem vanished.

Hope it's as simple.

finpos.

[fuzz]

Thanks finpos, it was the lever height. Could also have been the lever pivot as this is as greased up as I can get it. I couldn't remove it from the footrest, but it rotated more freely once it was put back. The gear down changes now though are a bit clunky, maybe I haven't adjusted the height properly? The clutch is adjusted properly.
____________________
https://www.bikepics.com/members/fuzzbcf/
Bikes: '99 NSR125R, '00 SV650S, K1 GSX-R600, '97 CB500, K3 SV1000S, '16 VFR800