Jumping out of first gear

[unknown pleasures]

Hi,

I am just about to embark on another, a third, engine rebuild and to help ensure i fix the fault this time i would be very grateful for any advice you can offer.

Background:

I have an italian gp 125 and last summer uprated the engine to a GT 186, lots of new parts, all quality and proper job done. Also had it hand-painted- unknown pleasures- if you've seen it about.

Anyhow since the build i have had trouble with it jumping out of first gear. In the rebuild i put in a new sliding dog, a new first gear, mb uprated gear selector springs,and the rest of the gears looked good.

The problem has got worse and because i had to split the engine to tighten the endplate in the pouring rain at smallbrook on the IOW last year i thought the problem might be due to the shimming - you never do your best work by the side of the road so you:). I took the gear box apart, checked all parts and then played about with a range of shims, the original shim seemed best and ten attempts later the 0.3-0.07 spacing was acheived. I rebuilt the engine only to find the problem persisted. I repeated the above a second time but could not fix the problem.

Now i am thinking that it could be as simple as my cableling - both gears seem fine but maybe the clutch is dragging a little - it doesn't pop back quite as it should, feels a little sticky, so could that be it?

Otherwise i am tempted to put an old sliding dog in, it never gave me any problems before but i was recommended to change it during the initial rebuild.

What happens is as soon as i rev it in first it pops out, if i'm two's up this is almost instantious so i have to drop it to second straight away and slowly allow the engine to catch up with the gears.

I am desperate to sort this as its driving me mental and i do not want to damage the sliding dog with the gear slips

any help will be hugely appriciated

thanks

Andrew

[a.j]

Pull away in 2nd.

Here to help.

[rbgaz]

Pull away in 2nd.

Here to help.

:bigsm:

[tomdavid1988]

I've had this before and it did turn out to be shimming of the gearbox, but most likely is incorrectly set up linkages, i.e the swivel is just catching the retaining nut not allowing it to fully pop into gear, although annoyingly seems to be fine when running on blocks, it's only when back together and under load it plays up.

Have also had gear selection problems like this simply down to s**t, misrouted, broken or stretched gear cables, also had it from misrouted clutch cable jamming the gear tube in headset and knocking it out of gear.

[unknown pleasures]

Thanks tom, will give the cables a good look over before i get knee deep in the engine