Well I've read a bit about this mainly on the old forum and the basics are the CBR600 engine fits into the NC29 without a problem but if you want it in the NC23 then you need to chop the frame. Specifically I remember that it is the front spar that needs to be chopped and extended, and due to this I've not fancied it but always wondered by how much it needed to be hacked by. So imagine my surprise when I stumbled across this on eBay.

Yes the guy is advertising a NC23 with a CBR600FL engine in it. What made this stand out from the others is that he has helpfully provided photos without the fairings on. So why can't I see any cuts or welds in the frame? I presume that it is the 600FL engine as advertised as friend thinks that it is and I'm sure its not a standard NC23 engine.




So we are back to that age old question for the NC23 will a CBR600 engine fit without modifying the frame and if so what will I need? Or can someone provide, preferably with pictures a modified NC23 sporting the 600 lump so I can make a decision on this aspect of my long running project?

CBR600 engine fits into the NC29 without a problem but if you want it in the NC23 then you need to chop the frame
>>other way round.....cuts to the frame are inside the front frame ONLY so the rocker cover can be removed for maintenance work, so cant be seen from those pics.

Do cbr600rr engine fit to NC29 ? Or only cbr600FL ?

most people use engines around the same age as the NC29. 600FL i think as RR is newer

Ok I'm getting further confused. I've gone back to the old forum and did a quick search and I'm getting conflicting results some say that you do need to cut the frame others say not.

Sticking only to the NC23 with the 600FL engine will I need to cut the frame?
If the cut is only to make maintenance easier when removing the valve cover where exactly should it be cut?

Is it only the 600FL that will fit without frame modification or will other models fit?
Again if other models will fit which ones are they and which require the modification?

You will need to cut your frame. As said above the front spars need modification .Im fitting a 600fl motor to my nc23 atm.
Good luck

take a safe bet and cut the frame...
where?
this you can see only when the donor lump is in place. you need to cut a V or D so the rocker cover can be removed for shims/valve clearance etc. if you dont cut a small amount out the frame.. it will cost you £££s and 1-3 days labour just to do a 1/4th day job.. why? as they will have to remove the whole engine to get the rocker cover off!

The problem lies with the cyl head being about 25-30mm wider than the 400 lump also when you put the rear engine bolts in, the front fixing points are out about 10mm also . Im not to bothered about the rocker cover removal problem,but i will be cutting the front spars that connect to head and front crankcase and moving them to line up with front fixing points before rewelding. I will post pics as i go with this to give a better idea .

I'm not bothered about having to drop the engine out to do the valves as I'd be doing it, but I am bothered about cutting the frame.

Drew70 if your doing this yourself then pics (and lots of them!) would be great.

Will do squirrel