NC30 JUMPING 2ND GEAR

[fourfingers]

Hi all.
I need some advice.When I got my engine rebuilt after a cranksaft failure I decided to change the standard nc30 gearbox for an nc35... suits me beter for road use.
I bought a set from GF. everything went fine during runing in (1000km), but when I started twisting the throttle harder, 2nd gear starts fine, then jumps and inmediately reengages. Looks as if the gear cogs where jumping out of place under power. I kept the original nc30 selector drum, so I am not sure if this could be part of the problem, or if it is just worn gear cogs. So... any imput aprecciated

[fourfingers]

Well, I finally got a very clarifying answer to my problem fron Chrisxr, dynoproracing.I will post it, just in case anyone is interested.

" The problem will be eoither worn gear dogs on the gears or damaged or incorectly fitted paddels at the star drive.

you need to inspect the gearbox for damage to stubs at the very ends of the gears especialy the 2 sliding gears 2nd gear is favourite after race or misuse, These gears are 90£ each to replace you may also test the fork thickness on the selctors check them against the manual tollerences. The gear cluster shold be built also with the correct shim spacer and the correct circlips thiscould also be cause of your problem but a comon fault on these is the sliding gears becoming damged chipped, or rounded.
The selctor etc on the rvf and vfr are identical to my knowledge we have fitted rvf gears in shortcircuit bikes and vfr gears for isle of man with no complaints.

Hope that helps"

[Andync30]

Am having the same problem with my nc30 when in 2nd at 8k and 11k it feels lik its slipping but no other gear

[tanuki]

sounds like worn dogs in the gearbox...

cant be that though as it only happenbs to NC29s

[Neosophist]

What oil you got in the engine? It sounds like the clutch to me. Fully synth can add too the clutch slipping, spesh in 2nd.

[fourfingers]

Neosophist Oil is definitely not the problem, since this only happens in 2nd Gear. It´s just a matter of the gear engaging normally, and missing under acceleration for a second, and then reengaging without the need of pedal imput. More likely to be worn cogs slipping out of place , selector forks... whatever.

Tanuki Nc29 and nc35 do share (to my knowledge, and to be more precise, L and N models) the same gears, excluding mainshaft, with its integrated 1st gear, and countershaft. Apart from that , the rest of the geas will fit the 35´s gear shafts.

[RickOliver]

This is common problem on high mileage/well thrashed NCs - it is caused by wear on the engagement dogs on the sliding 6th gear pinion on the gearbox countershaft (it`s the one which locks into the 2nd gear pinion when 2nd gear is engaged). The cure is to replace that 6th gear pinion, and the selector fork will normally need replacing too as it tends to get worn &/or bent by the pressure of the faulty gear trying to disengage under load.

List price for the gear pinion is £85.50 (NC30) or £77.73 (NC35) and he selector fork (same for both models) is £68.73.

It is an engine out job to make the repair - the one scrap of good news is that although the official shop manual says that you can`t, you can in fact split the cases and do the job without taking the cylinder heads off.

The parts were still available from Honda last time I checked and I can supply them if required...

[tanuki]

Tanuki Nc29 and nc35 do share (to my knowledge, and to be more precise, L and N models) the same gears, excluding mainshaft, with its integrated 1st gear, and countershaft. Apart from that , the rest of the geas will fit the 35´s gear shafts..

I kow they do mate...however there has been a fair bit of dicussion in the past that people seem to think that its only a problem with the NC29...generally NC30 owners.

twas a little dig thats all LOL

[fastdruid]

This is common problem on high mileage/well thrashed NCs
List price for the gear pinion is £85.50 (NC30) or £77.73 (NC35) and he selector fork (same for both models) is £68.73.

Nice to know the actual prices, when this happened to NC35#1 instead of go this route we spent 120quid for a replacement engine (and carbs) off a 20k bike.
Especially as you need to remove the engine even if you're fixing it a replacement engine for less than the bits was a bit of a no brainer.

Druid

[fourfingers]

Hi Rick, nice to hear from you. First of all, thanks for the zxr fork fitting kit you sent me some months ago. Everything is running perfect. About my gear prob.. I was planning exactly what you mentioned above. I have 2 spare sets of forks(checked tolerances against manual), and bought a complete nc29 used gearbox just for the c6 and c2(just in case). Unfortunately this gears have also been abused. So I think I will end up buying a c6.
Talking to a friend (motocross racer), he told me about a guy who repaired gear cogs with an electroerosion machine. They reshaped the cogs with a slight negative angle, so that, once engaged the gears tend to stay together. I guess this works better on castelated(square) type cogs... wich is not the case. I also read about gear cog failure... Mike´s 80bhp machine... mine is nothing near that, but shaving material from the cogs might not be the most intelligent thing to do.

Druid, I wish I could find a real 20k 120quid nc35 engine... But taking into account there might be 40 to 50 ncs in the whole country where I live, this is very unlikely to happen. Not many people in the UK are willing to send engines overseas, and even if they are, it is quite expensive +-140GBP. Been looking for nc35 engines for a while, the cheapest I´ve seen 300+ postage. Plus you never know what you are going to get.

Cheers, Emilio