1984 aero cbr400 blown motor, Brocken piston valves help

[04colyZQ8]

Hi guys I'm a newbie to the forum from bc canada, I'm hoping to get tips and help from you guys, your forum seems like it comes up on every search that I've done for my bike so far.. Hehe

Ok so it's a 1984 cbr400 twin cam gear driven 399cc inline four with adjustable valves since it's an areo. Now is this also called a nc23? Cb1? Does mine have the vetec system that runs on 2valves, then switched to 4 at high rpm? It's currently a tripple since I have a dead slug!

Looks like motor swaps, nc29, f2, or fireblade, hurricane 600s have been done! But I can't find any motors anywhere, other then the f2, but that looks like a lot of work to fit in?

I'd rather repair the nc23, that I have. I can't find a head anywhere!! All four valves broke at the stems on cylender four, and holed the piston. The heads damaged but repairable, how ever I can't locate new valves of new guides, and no mechine shop had pilots small enough to cut the seats.

Are the nc23 valves from 89 and up inerchangesble?

[04colyZQ8]

I'm thinking about buying a set of used guides, freezing them, and heating the head, then buying newway seat cutters. From what I've found the ex should be 19mm and the intakes 22mm. I'm hoping the 30degree cutter that works for valves 18-21.5mm will be close enough? And that the 45 cutter that's for valves 20-22mm will work? The 60dgree cutter will do for sure do both valves. I'd like to do this with only three cutters, at 78.00 usd each I can't afford 5 cutters!

I'm also confused on which pilots to use? I've heard the use 4mm Id guides? But the Haynes manual for 89-91 nc23 says they are 3.80-3.89mm Id

So do I order the 4mm, 3.8mm, or 3.82mm pilots for neway small diameter cutters?

I'm leaning towards the 3.82mm one?

I found a set of china aftermarket valves for the nc23, they say they are 4mm id, stem, 58mm long, 19mm ex, 22mm intake will these fit my early 84aereo?

What about the aftermarket ebay piston, and rings gaskets for 89-90, nc23 will those work?

I'm a comp mechanic by trade I'm sure I can cut the seats, lap in new valves, but any tips for parts and tools would help me out!

[jim157]

The aero was manufactured in 1986 and 87 and was replaced by the tri arm in 1988. The bikes are completely different although the tri arm engine is based on the aero's. Afaik the two models share very few components apart from some engine internals.
As you probably discovered both the aero and tri arm share the nc23 designation to make things even more difficult. None of the CBR's used the VTEC system, that was only featured on the naked cb400 super fours.

Aero parts are also pretty difficult to locate, so it might be worth considering your options before you start spending lots of money on a restoration.

A tri arm or nc29 gull arm restoration would be a far easier and cheaper project due to the availability of parts.

[04colyZQ8]

Well, I'll likely scrap this bike, take my losses. I cannot find an exhaust valve or piston anywhere?? The aero valve stem is close to 5mm, the tri-arm is 4mm stem ID, the aero valve is 80mm long, the tri-arm is 85mm long. So looks like the tri-arm valves won't work. The piston OD, pin bore ID are the same...but looks different, so that likely wont work either.

I can't even find a tri-arm motor to save my sole? But by some miracle that I did would it be a direct bolt in, to my aero frame?

[fastrob691]

A guy on here in the parts section had engines for sale in the last couple weeks.

[04colyZQ8]

Really were was he from? I found some motors but they are in the uk! Cost 450pounds to ship to me! Which is around 670.00cdn:(

Now I found a 89 nc23 head that has shim and buckets, instead of my adjustable rockers! If I get the head complete with cams, gear drive, rocker cover, and nuts. Will it work? Also like to run the mv4 style aftermarket piston? I've been told they will work in place of my kt8s? I've also located a used set of ky2 pistons.

[04colyZQ8]

Bump!! Still looking for info I found a 88 nc23 jugs, pistons, and head, on eBay will this bolt to my 84 AERO block?