Topic: To 466 or not?

[krksquared]

Just wondering how the performance improves by taking the engine to 466. I saw a Forseti big bore kit for less than $300. I'm guessing another $100 needed for gasket(s) etc. Worth it? Forseti any good? More torque would be really nice. I'm not looking for gobs of power. My CBX does just fine in that department. If stock is 37hp - 24ft/lb, what might 466 generate? I really like the CB400F overall. It handles & stops nicely. It just needs a little more torque in my opinion. This probably contradicts a cam change as I don't want to move the torque curve up in rpms. So I guess I'm asking what another 58cc's gets me? Anyone here gone that route? And don't tell me to get a 550 

[jakec]

I talked myself out of a 466 because as people have said here the real power is to be gained by boring the carbs. Why do a 466 if you aren't doing that as well as a hotter cam and springs, polished head etc. It was a bit of a give a mouse a cookie situation for me, so I just went with stock for my rebuild and will maybe revisit the idea later.

[krksquared]

The hotter cam is a bit ambiguous to me. Some cams increase hp by moving the hp peak up in rpms. I don't want to have to rev it high just to keep up with Accords & Camrys etc. Some cams keep the rpm range about the same but help torque (probably by increasing lift). Not much helps like increasing displacement except supercharging . As for a polished head, I assume you mean polishing the ports? Without a flow bench and some experience, head work could ruin performance. I've never heard of boring the carbs. Are the carbs a significant impediment on the CB400F? Sure would be interesting to see some before & after dyno results. Anyone?

[Tim2005]

I've done the Yosh 460 route- with everything else standard it's like riding the 400 in a very strong tail wind.  No need to do cam or big carbs, but you might want to raise the gearing a touch otherwise you tend to cruise along in top & still keep trying to change up one.  I've not heard of Forseti, the Cruzinimage kit is well regarded and cheaper than that though.

[krksquared]

Thanks Tim. Never heard of Cruzinimage. I'll check them out.

[krksquared]

I think part of my motivation is that my SL350 seems to have as much or more "grunt" than my CB400F. The 350 is lighter and is actually rated as having a bit more torque. Dang ain't bikes fun! 

[Tim2005]

That's mostly as it's a twin - low down they are gruntier. Oddly enough I was talking with someone earlier about CB450K0, which I'd like to own- he said much the same as a 400f up top, but much gruntier low down. Also expensive and unreliable, but that's another story...

[jakec]

I would agree, when I ride my 550 it's like the same exact power band.

[Stev-o]

I'd say not.  $300 for the kit, $100 for gasket kit, how 'bout boring? Another $200.

Buy a 750!

[RFogelsong]

From everything I've read, the 400 heads are the only ones that aren't choked up by restriction in the intake and porting these for street doesn't amount to much past removing the casting lines at 9 and 3 o'clock, so you're not missing much there. 

Common Motor in Texas is now advertising they're refacing and welding cams and rocker faces.  I'd lighten and match the rocker arms and maybe petition them about doing a 400f cam and rocker set.  They don't list that they currently support the model, but they do list the service for the 550's for the same prices, so I don't see why it'd be too different.  If they needed a good cam as a template I'm sure it could be arranged.

I recently stumbled across a company called BRC on webike Japan and they make 1st and 2nd over piston sets, complete with rings and wrist pins and all, for $250.  It looks super-high quality and I'm curious to try it if my cylinders ever need taken out that much to regain spec.  https://japan.webike.net/products/21727438.html

To open up the exhaust a bit, I've heard that the reproduction headers now available from David Silver are single wall vs. the original Honda double-wall...which should aid breathing a bit.  There's a mismatch in diameters between original and reproduction stuff, it can all be made to work together with collars and sleeves though.  I think the header is only like $350...a relative steal compared to the 350f's $1200 replica set.

All of this together should add up to a 400f that's "everything it ever was out of the factory" and possibly a little more while maximizing parts you already have and not taking everything off the deep end financially with excess "while you're there" ideas. 

[Bodi]

It's a bit of a rabbit hole but you will notice the power gain from a 466 kit. If you can stop there, all is well.
I put in the Yoshimura 466 kit, no opinion on the cruisingimage kit. I found it worth the cost and work, I did everything except the cylinder boring and valveguide replacement plus valve seating. Cleaned up the port finish without any reshaping.
A mild cam, and there are several, with slightly stronger springs adds more power and cost while being fully streetable. The cam I have, Megacycle but I don't have the number at hand, idles well with good low end power and considerable improvement mid to redline.The hot "race" cams barely idle and sacrifice low and mid performance for high rpm horsepower, not good for a street bike, and the heavy springs necesary require a heavy duty cam chain but still eat tensioner blades.
A good header will probably help, I put a Kerker on but mostly because the original organ pipe header was damaged.
Next stage - that I have not done - is stronger rods to increase redline, and bored carbs. The stock carbs don't flow enough for full benefit of a 466 at near redline. The oval throat bored to round helps a lot. For racing, CR carbs were used but they are useless for street. Maybe there are aftermarket or repurposed carbs that would be good now, that was decades ago. Denoonsp still bores the carbs I think. Carillo might make a rod set but they aren't in the current price list.
That "full monty" hop up gets you into several thousand dollars, price of an older used CBR600 or R6... much better bikes overall than any 70s 400F can ever be.

[krksquared]

Thanks Bodi. I'd never heard of Megacycle. I checked out their catalog & they list two cams for the CB400F, 131-00 and 131-20. Sounds like you went with the 131-00 which would be my choice too. Your build sounds like what I am contemplating. RF mentioned the Silver headers. That's what I have. The originals (which I still have) were kinda messed up. The headers on a 400F are really important for the bikes appearance and my bike otherwise looked almost new so I "went for it". I'll check the wall thickness & other dimensions & report back. I can say that the Silver headers fit with no problems and they sure look nice. It's hard to quantify what I'd like but I'll guess that another 10ft-lbs of torque would be sufficient. It's not so much what the torque peak is but the shape of the torque curve. If I want to go really fast, I have a CBX. Someday I'm going to have to try out a modern bike. I hear they are significantly improved over my fleet.