Topic: Complete Piston Sets for my cb400f... requiring help (or patience)...

[takeitdk]

Hi all-

Rebuilding the top end of my stock '75 cb400f.  Haven't done this before so I need some advice and help on sourcing piston sets.  My machinist recommended +0.5 due to the rust he saw.  +1.0 would obviously be a sure thing. 

The reason I'm leaning towards +1.0 is that I'm afraid of the possibility that +0.5 won't clean up all the rust and I'll be stuck with a +0.5 set.  My machinist is very knowledgeable and he said he is not certain that a +0.5 bore would clean up 100% of the rust.

That said, a quick search proved hard to find sets for +1.0.  David Silver Spares only has 1 complete set for 1 cylinder.  CMS looks to only have +0.25 and +0.50 sets.  I plan to call them on Monday to inquire about +1.0.  Western Hills Honda can put a complete +1.0 set for 4 cylinders together for me but at a cost $$$.  On the other hand, it looks like both DSS and CMS can get me complete sets for +0.5... now.

So, I need some advice.  Should I be patient and hold out that I will come across 4 piston sets at +1.0?  Are there other vendors out there I don't know of that you can point me to to source +1.0?  Or should I just go +0.5 and hope that all the rust cleans up?

Thanks for any help you can throw my way...

DK 

[Kong]

If I were you I'd tell the machinist to bore it as far as is necessary to clean it up, and then report back.  It will cost you a second setup fee when he has to go back  to hone it to the final fit, but at least you'll start off knowing exactly what you need and will avoid the false start and expense of buying the wrong parts.

[gsnorcal]

I had the same wonder/worry about being able to source the parts. I ended up ordering the 466 big bore kit from Japan on eBay (member "cruzinimage_co"). Only a few members here have tried them, so the jury is still out as to quality.

Anyway, it may not be a solution for you, but it's an option. I figured this way I'm only making one trip to machine shop.

Dave

[takeitdk]

gsnorcal... thanks for the suggestion.  Yeah, I've seen the big bore kits out there.  Not really wanting to go in that direction with this bike though.  Looking to keep the bike as stock as possible. 

DK

[camelman]

gsnorcal... thanks for the suggestion.  Yeah, I've seen the big bore kits out there.  Not really wanting to go in that direction with this bike though.  Looking to keep the bike as stock as possible. 

DK

The jury seems to be pleased with the big bore kit quality.  Also, the bike will look completely stock, but you'll have a lot more power.  You can also bore out the carbs to flow more fuel/air, and get even more power with a totally stock looking bike.

CMSNL has piston kits, but I think cruzinimage_co has access to smaller bore pistons too.  The CMSNL kit will cost you $300 or so, but I think cruzinimage_co can get those second overbore sizes for more like $150.

Camelman

[Bodi]

I would go with the Ebay 466 piston set. This will be probably cheaper than finding OEM +1 parts. Without further mods, the 16% displacement increase probably won't require any retuning. To get a really noticeable power increase you need a hotter cam and a better exhaust as well as the bigbore kit.
If you don't like that idea, 400F cylinder blocks are on ebay quite often and you should be able to find a rust-free one that would be good for a .25 or .50 rebore fairly cheap.

[camelman]

Bodi, one word of caution on those hotter cams.  They'll raise the max rpm of the engine, and the con-rods in these engines don't do well when held at high rpm.  Other than that, you have a good power mod plan.

Camelman

[crazypj]

I'm about 90% sure we used to fit XL100 pistons into CB400 (I know it was one of the singles)
 There was no such thing as a big bore kit at the time so we had to adapt something 'off the shelf'
 The diameter is 53mm and pin size is 12.99mm so that would work. (never found a cast iron liner Honda that wouldn't take a 2mm overbore  )
Maybe it was the 'original' 460 kit?
Unfortunately it was over 30 yrs ago so I just can't remember any details.

[Bodi]

I wasn't really suggesting the all out hot-up, he seems to be going stock. I just think the bigger pistons may work fine with stock jetting if nothing else is changed - and the price is right.
The con rods are not too good for racing but I use an 11K redline for my street use and have no problems (so far). I don't "hold" it at redline, that would be way too fast for the ancient frame to be safe even with the higher gearing I run. It's just for acceleration to semi-legal speeds when I'm in the mood. Carillos would be sweet but I have other good uses for that much $$$.