Hi all,
I am going to replace the gearbox in my NC30 engine with the one from my 35. The reason being, i have found that it is not going into 3rd very well . I was planning on doing this swap over winter in anycase for racing, but this problem has brought the job forward.
My question is;
Can this be done without removing the heads, and splitting the cases to get to the bottom half?
If it can't be done no problem, will just take them off.
Many thanks

Unless theres a magical way you can't change the gearbox without splitting the cases. You can leave most of the top end crap in though and just lift the top off the bottom, shouldn't really be any need to get the pistons out unless you want to do some work while you have it apart?

Neosophist wrote:Unless theres a magical way you can't change the gearbox without splitting the cases. You can leave most of the top end crap in though and just lift the top off the bottom, shouldn't really be any need to get the pistons out unless you want to do some work while you have it apart?

Thanks Neo,
Yer thats kind of what i thought. I dont plant to do anything to the pistons or the top end.Do you think it would be okay to have the engine upside down to split the cases?
Is it possible that the shims could come out?

That's major surgery in my book.

I think you'd be best pulling the whole engine down to get this done, then you could attend to other bits and pieces while you're in there.

Cammo wrote:That's major surgery in my book.

I think you'd be best pulling the whole engine down to get this done, then you could attend to other bits and pieces while you're in there.

Yes that is true, but with all things like this, it tends to get out of control, and very expensive
I think i will see what the cash flow is like over the winter and perhaps change the rings and get the barrels honed. I guess it saves taking the engine out twice

No need to get the rings / barrels honed unless theres problems with them.

Shims won't fall out unless you take the cams out / move the rocker arms out of the way.

You can leave it the right way up, when you lift it off you'll probably find the pistons / crank stay in the top end anyway, they have done when i've had them apart before.

Might be worth getting some plastigauge and checking the wear on the bearing shells etc while it's apart, see how worn the motor is.

Mostly they run forever so you should be fine.

skinnydog0_0 wrote:Yes that is true, but with all things like this, it tends to get out of control, and very expensive

Amen to that!
When you go ahead I'd be interested to see how you go and what you find if you do a thread on it. Lots of rebuilds on here but not many that go the whole hog.
Best of luck with it.

I tend to forget about taking pictures until its all back together and think aw crap.

When you have engine oil all over the place and valve collets etc knocking around it can be a bit fiddly to keep getting the camera out

Neosophist wrote:I tend to forget about taking pictures until its all back together and think aw crap.

When you have engine oil all over the place and valve collets etc knocking around it can be a bit fiddly to keep getting the camera out

LMAO
Yer our digital camera is the wifes toy, so she gets very upset when i try to sneak it into the garage. I did try to get her to take pics when i replaced the heads, and did the valves and shims, but it was like pulling teeth so i gave up asking
I will try to make notes and take pics as best i can. If i can get the gaskets i think i will do it this weekend.

Well i have started getting the engine out, so here goes with the thread.
Please feel free to offer advice if you think i am doing something stupid
Anyway, this is how the bike looked before i got it in the garage.


It doesn't always rain in Wales

So it is now in the garage and i am just about to start to get it apart


I will add some more pics in a bit, need to recharge the batteries on the camera.