CB400T

[longhorn717]

On here again looking for inspiration, information, and ideas. I've got some ideas already and would love some .02

I've got a 1980 CB400T that looked decent albeit plain when I got it 2 years ago. I raced it like I had something to prove and blew alot of seals in the engine. My question here is what should I look at/replace when I crack it open to replace seals? how much to paint/polish the engine?

I read a thread on using other-than-stock carbs. Any ideas on what to look for? I'm thinking of a unique version of an x-pipe for my bike and need to make sure I have enough air/gas mix to match the exhaust.

suppliers of stainless exhaust pipe/sheetmetal?

sources for gas tanks and seats?

Is an airbox with K&N filter better than a pod set-up? Thinking of building a combo airbox/battery holder/electrical holder.

What do y'all do to clean up the internal space? battery under seat with electrical?

Anyone know if there's a rear wheel with a disc setup that would fit my 20mm axle? I can make new spacers if need be and mounts for the caliper.

Are there any larger and/or upside down forks people have used on this bike? I'm a larger rider at 260lbs. but love this little frame. any way to bore/stroke the motor or add performance other than adding more efficient carbs/intake and exhaust?

Lot of questions hope I can get help on most of these. Would love to get the hard stuff (engine) done before the weather gets too hot again. lol gotta love Texas.

 

[longhorn717]

Bump. C'mon on guys any help?

 

[Gissmo50]

let me try and jump in here,

do you know what seals have gone on the engine are the rings/pistons in good order?
im currently tearing my CB apart and i'm going to replace all the seals i can after having it vapor blasted. As far as polishing painting it goes its a personal thing although to much polishing on the head and cylinders can cause the engine to store heat personally once mines blaster im going to polish the clutch and genny covers the edge of the cylinder and head fins and the rocker cover and have everything else black.

tanks you can fit anything you can make fit the CB and n have quite large back bones but i believe the 500f and 400f tanks are quite an easy fit.

seats if you can make a mold and glass it you can make your own if not there are hand made items available from vonzeti on eBay UK or just seat pans that are pre-made and need fixing points and upholstery.

you can use other carbs but there inst much info on doing it and most dyno centers want the bike running b4 they tune them ive been looking at using mikuni TM-36's but you could use Vm32-36's or any cab that you can fit in the mount's but you will have to go to dual pull throttle and work the jetting out for yourself for a base value and then go have it tuned on a dyno but it can be done have already spoken to a place that will do it here in the uk.

under the seat you can use sheet metal welded/riveted/bolted into place in someway shape or form

there aren't any bore/stroke "kits" that i have found if you stroke it then you lower compression and the largest over bore i can find is +1mm which only gives you 405cc from 395cc

thats the extent of what i have for these bikes hope it helps

 

[longhorn717]

Thanks a bunch. as far as I know I probably need new rings because there is oil leaking from between the jug and the head. I have an extra set of jugs if one is bad I should be able to use one or the other.

As far as paint goes I was wondering what brands and types are people using?

Thanks for the info on the carbs and I got a bunch of extra parts including a new throttle grip that came with a dual throttle cable set-up. just have to look out for some carbs that will fit.

Thinking bout going custom on the seat. Haven't decided if it's gonna be a solo or two-up seat yet or maybe one of each.

I knew from looking at the jug I got on ebay that an overbore was unlikely to have large gains for me. Didn't know if there was room to stroke though. But I'd forgotten about compression.

 

[Gissmo50]

paint wise anything that can withstand high temps so vht or bbq paints are good or you can use 2k or 2 pack paint as they can handle heat also,

for carb size they run 32mm body's standard so i don't see why you couldn't go up to a 36mm or 38mm body's is you can get the jetting to match and can get inlets the right size inlet and mounting rubber then anything is possible but you would probably have to have the head ported and polished to allow the engine to use the extra a/f mix and you would deff want some form of free flowing exhaust.

if it helps i am planning on running mikuni TM flat-slides having the head gas flowed and running a single exhaust for each cylinder and either a uni foam filter or a pod filter and then having it dyno'd to suit all of it, its probably not going to idle at all well but it should give it a good kick up the arse.

 

[longhorn717]

I've seen vht on here before but not sure what it is exactly and haven't taken the time to look it up cause I'm not there yet.

Can any machine shop do a p&p job? and how much am I looking at on that?

Here's what I have in mind for the exhaust except for a twin. That's why I'm interested in bigger carbs and a high flow filter.

 

[Gissmo50]

http://www.ebay.co.uk/itm/PJ1-GLOSS-BLACK-ENGINE-CASE-HIGH-TEMP-TEMPERATURE-SPRAY-PAINT-CAN-MOTORCYCLE-/280802300571?pt=UK_Motorcycle_Parts&hash=item41611f129b#ht_2182wt_1396

that's what i use over here in the UK, you can remove the casting marks and smooth out the inlets and exhausts yourself if you handy with a die grinder or dremel tool there are plenty of videos on YouTube about porting and polishing but the basic idea is to make a smooth entry into and out the combustion chamber, there are two views on the inlet weather to leave it a little rough or to smooth it right out again searching the internet will explain this.

I like the exhaust system it will let it run faster but keep some of the back pressure to help idle.

ive found the basic ethos to building any bike is if you can think it and you or someone you know can make it then its possible do what you want to do and as long as your happy with how it turns out then its a good result

 

[tsbigdog]

You seem to be at a crossroads with this bike. Especially since the engine is shot. Your ideas are all valid points for improving the bike. The problem is, you have to ask yourself if you are trying to turn your CB400T into a Ducati Monster? Don't get me wrong, I would love to see you get it done and have it come out great. All of us CM/CB owners welcome any new ideas and projects. Just make sure you wouldn't be better off with a different bike. Just my .02

Get a manual for the bike if you don't have one. Best 35 bucks you'll spend. It will have all the clearances and tolerances you'll need to check.
Mac makes a 2 into 1 exhaust, but it's not stainless. It's about $275 for a complete system. Comes in chrome or black.
Airbox with a K&N will probably save you a lot of headaches in the carb dept. These CV carbs are notoriously difficult to tune.
Several companies make engine paint. VHT, Duplicolor, etc.. and can be found in any auto parts store. I bought mine at Advance. I used the duplicolor on the head and cylinders. I'm still deciding what to do about the cases.
Gas tanks are available on ebay. You should be able to use any 78-82 CB/CM400 tank. Some other tanks will fit with some modification. CX500 comes to mind, but check with some others to make sure.

Good Luck.

 

[longhorn717]

Thanks guys. Right now I need to clean it up and get it running. Then ill decide whether or not its going. Its a fun little bike and I like the frame size just not crazy bout the handling.

 

[longhorn717]

Hey guys its been awhile. Just started a new job and am hoping to get back on this project. I've spent countless hours thinking about all the possibilities for this bike. I know I'll get a modern streetbike for longer trips and maybe some touring, but this is a great little bike for around town and day rides through the hills here in central Texas. I've got a mile long list of things to do but first is to get the motor in working order and get it put together at least temporarily and tagged so I can ride it back and forth to work as the weather warms. I'll be doing weekend projects to it for a few months but that way I can use it and test it as I go along.