Topic: CB400F - My first bike

[JParty]

Hi friends,

I excitedly got my first street motorbike - a CB400F. This is my first forum post so please go easy if there is anything I screwed up.

I have experience working on cars and grew up on thumpers like the 1983 XR500R. But it was time for an old school four banger.

I had a couple of questions for the experts of this bike.

1. The engine appears to be painted in black(?). Is there any recommendation to tidy this up beyond stripping the whole engine? The crankcase/gearbox housing also may have been chromed(?) – it looks like it’s lifting a fair amount. Any pointers on how to clean this up would be great!

2. I’ve not seen any 400Fs with this seat? Was it a factory option? Same with the bars, looking at pictures they don’t look stock.

3. There is oil seepage once it gets warm about the engine fin where the rocker cover meets the rest of the engine.

4. Any other insights or pointers about this bike would be mega!

Thanks!

[JParty]

Had major difficulty uploading pics - told you it was my first every forum post!



Leak is along this interface - enough to make her smoke at stop lights.

[grcamna2]

Welcome to the forum JParty;I see the work it needs with the oil leak,aside from that I really like how it's set-up now:for Caf'e.The PO who had this work done really cared alot to make that a great Caf'e Racer.

[robvangulik]

None of the things you mention, the black cylinders, the chromed covers, the seat and the handlebars are stock, BUT the bike doesn't look at all bad and as long as the leaking isn't too bad, ride it while the weather is fine!

[Tim2005]

That leak is easy enough to fix- just take off that cover and fit a new gasket, it's basically a big o-ring. What you may well find is that some of the threads that hold it down are stripped, make sure you have an M6 helicoil kit available & that's easily fixed. That whole job is do-able in an evening.

Stripping that black paint won't be easy without stripping the whole motor, I'd be tempted to add a fresh coat over the top unless you are planning a strip-down. As for the chrome plate on the covers, that might sand off, never tried it.

As for the seat- it's aftermarket, but still ok. Your bike has many aftermarket parts, mudguards, headlight mount, wheel rims, exhaust, rear shocks, ignition coils and more I expect.  Enjoy it and ride it.

[BenelliSEI]

Welcome to the forum, nice looking bike! Before digging in, try soaking the engine with a good degreaser/ “engine cleaner and then doing a hot wash with a high powered spray washer. Unless the surface was really well prepared, it’s amazing how much of the black paint may just wash away....

Good advice earlier. Ride it now and get into it when the weather forces you to stop!

[Bodi]

Nothing major appears butchered, so all good there!
The front mudguard has been replaced, which is not a great idea as the OEM mounting bow is also a fork brace, and the 400 has thin fork tubes that rather want a fork brace.
Seat and bars are definitely aftermarket. If it's rideable, you may as well keep them? Likely you will need new control cables for standard bars, but maybe not. Seats are available from Vietnam (I think) but I have not seen one to vouch for the quality.
The oil leak is probably easy to fix. The engine is serviceable in the frame once the tank and coils are removed. Remove the vent cover and valvegear cover: loosen all 8 tappets all the way out first. The gasket thing is available, it's a formed shape in O-ring material. Generally it has to be prised out and the groove cleaned super well with solvent and elbow grease. The new one should be glued in with automotive weatherstrip adhesive or whatever works for you. The 6mm cover bots are tricky: there are several lengths and they have to go back in the right places. On a test fit - putting the bolts in the valvegear cover off the motor - the threads on all of them should stick out about the same distance. Be very careful tightening them, the head metal is pretty soft and it's too easy to strip out the threads. You want the cover down tight to the head but you don't need to super crank on the bolts! Be very very careful installing the valvegear cover- tappets can wedge behind valves and if you force the thing down via the bolts, expensive damage results. Running rubber bands between opposing rockers, pulling them up, is useful.
Chroming aluminum alloy is a fools game, the electrochemical potential is extreme - doing it successfully involves multiple platings of different metals under the final chromium layer and is ridiculously expensive... and even then a tiny perforation from a rock strike or whatever will corrode underneath and the chrome layer peels off. It's OK for a show bike but for a bike that gets ridden ... no. I would look for a used clutch cover if I wanted to delete a chromed one: the chemicals that eat chrome also eat alloy (but much faster) - it's OK for steel parts but not for aluminum alloy. Chrome is much harder than the alloy so removing it with sanding is not so good.
The black paint might come off with a pressure washer, and definitely will if you spray "aircraft stripper" on it first. But that stuff will take almost any kind of paint off almost anything, so the engine will have to come out for that.

[JParty]

Bodi, BenelliSEI, Tim2005, robvangulik, grcamna2 - thank you for your replies. I got a lot of joy seeing your responses. I wanted to only reply once I had a little update!

Since my post I took your advice and got some degreaser to see how well the black paint was prepped. I warmed up the bike, let it cool a so nothing was too hot and sprayed on an engine degreaser. I let it soak and then took to it with a hose (don't own a pressure washer unfortunately!). The result was, yes the paint certainly wasn't prepped well as some definitely came off even with the feeble water pressure I had available.

Here are some pictures mid cleaning/degreasing.




The plan now is as follows:
1. Adjust valve clearance
2. Compression test dry then wet to see if I need to new rings/cylinder hone
3. If compression is good then buy a pressure washer and use BenelliSEI approach. If they doesn't get it all off then take Bodi's idea of stripping the existing engine paint outside of the bike frame. Do the top end seal following this.
4. If compression is bad then pull down the engine and get the parts vapour blasted (my wallet is telling me "NO" already)

Now, in response to your helpful comments:

The front mudguard has been replaced, which is not a great idea as the OEM mounting bow is also a fork brace, and the 400 has thin fork tubes that rather want a fork brace.
Seat and bars are definitely aftermarket. If it's rideable, you may as well keep them? Likely you will need new control cables for standard bars, but maybe not. Seats are available from Vietnam (I think) but I have not seen one to vouch for the quality.

I had already thought about trying to find an original front mudguard as I didn't really think the one on the bike fits great. Your structural assessment is even more convincing than just thinking about aesthetics! I'm still thinking about which seat I want to go for; original or something smaller and more tidy. I shudder at the thought of cutting the rear subframe given it has lived this long without anyone hacking at it. I'm UK based and had a looked for a used example but couldn't find much - may have to go the DSS route.

Chroming aluminum alloy is a fools game, the electrochemical potential is extreme - doing it successfully involves multiple platings of different metals under the final chromium layer and is ridiculously expensive... and even then a tiny perforation from a rock strike or whatever will corrode underneath and the chrome layer peels off. It's OK for a show bike but for a bike that gets ridden ... no. I would look for a used clutch cover if I wanted to delete a chromed one: the chemicals that eat chrome also eat alloy (but much faster) - it's OK for steel parts but not for aluminum alloy. Chrome is much harder than the alloy so removing it with sanding is not so good.

Yeah it mustn't have been prepared well as I was sitting in the garage last night flicking bits off with my finger nail. Not sure if I'd ever get a result trying to scrap off the bits I can with something soft that won't gouge or scratch the aluminium like a windshield scrapper or whether I'd just end up with something more unsightly. Fitting a different cover is an interesting idea.

The black paint might come off with a pressure washer, and definitely will if you spray "aircraft stripper" on it first. But that stuff will take almost any kind of paint off almost anything, so the engine will have to come out for that.

Any recommendations for an "aircraft stripper"? I assume you are talking about chemical product not something else right...  I assume I'd have to be quite diligent in masking off any seals so they didn't get attacked.

Before digging in, try soaking the engine with a good degreaser/ “engine cleaner and then doing a hot wash with a high powered spray washer. Unless the surface was really well prepared, it’s amazing how much of the black paint may just wash away....

Is there a particular product you recommend? I just went to a local hardware store and got some generic automotive engine degreaser. I think with a pressure washer plenty will come off because there certainly was some that came off even with hose pressure.

That leak is easy enough to fix- just take off that cover and fit a new gasket, it's basically a big o-ring. What you may well find is that some of the threads that hold it down are stripped, make sure you have an M6 helicoil kit available & that's easily fixed. That whole job is do-able in an evening.

Stripping that black paint won't be easy without stripping the whole motor, I'd be tempted to add a fresh coat over the top unless you are planning a strip-down. As for the chrome plate on the covers, that might sand off, never tried it.

Thanks for the advice Tim2005. I assume even if I managed to strip all the black paint off that you factory paint needs to be applied or from factory were they just the bare metal with some kind of high temp clear coat on them? I guess you are suggesting adding black paint to the existing? To be honest the current paint is in pretty bad shape and appears to be have been painted within the frame so wouldn't be super optimistic about adding more black paint.

Any advice is greatly appreciated!

[Nurse Julie]

Not a bad bike you have there. As you are in the UK, it would be worth you joining the UK branch of this forum. Many of us over here in UK own 400/4's and it may be useful posting to more 'local' owners as well.
SOHC.co.uk
http://www.sohc.co.uk

[Tim2005]

Hi again. Yes, as that paint is falling off then over-coating it won't work well. It'll be interesting to see how much comes off when you pressure wash it. Try scraping along each fin with a stanley knife too, it's surprising how much that can take off sometimes.  When new the barrels and head were basically bare alloy, with a surface finish from the original casting process, but the rocker cover was clear lacquered. The top crankcase half was painted silver/grey originally too.

As for degreasers- gunk is still as good as any, while decent paint strippers are hard to get. There are some industrial ones like Paramose that are decent. Though I think only sold in 5L cans and pretty dear.

As for the compression test, you need to be a little cautious of the figures it produces as most gauges have a pretty long hose, which for a big car-size cylinder is ok but for a little cb400f pot it can throw theresults, there being more volume in the hose than there is in the head. That said it's good way to compare the 4 pots are pretty equal.  How does it ride & run? If it'll pull over 90 then the compression is ok!

[BenelliSEI]

+1to above. Any good engine degreaser will do. I prefer the ones that “spray on, let soak” I usually do a couple of applications. I paint came off with a hose, try a real pressure washer (not the drive in car wash kind). Don’t poin it anywhere you want to leave paint.

[grcamna2]

+1to above. Any good engine degreaser will do. I prefer the ones that “spray on, let soak” I usually do a couple of applications. I paint came off with a hose, try a real pressure washer (not the drive in car wash kind). Don’t poin it anywhere you want to leave paint.

+1 A real pressure washer with a Fine nozzle and just don't point it directly into any gaskets:a general blast will do the trick.

[JParty]

Thanks for the replies.

Engine out yesterday!

[Stev-o]

Welcome.  A long handled wire brush will persuade the paint off the engine. If you plan to repaint, not every spec needs to come off.

I had my Kawasaki H2 motor vapor blasted, to do it right, every little part will need to be removed.
I would not recommend to you to do this, you may be opening a "can of worms".

Good luck

[Bigglen1]

Congrats on your "new" bike. Just got one me-self.

[914eener]

For engine cleaning/degreasing I’ve used scrubbing bubbles bathroom cleaner for ages.  Sounds crazy...right.  Follow the directions on the can.  Spray it on and let the bubbles do their thing.  After a few minutes hose it off and the engine will be squeaky clean.  Doesn’t damage metals in any way.  A big can only costs a few bucks at most any grocery store and lasts forever.  Works really well for cleaning chains too.

Learned this trick working on old Porsche’s that almost always have leaky pushrod tube seals.

[JParty]

Hello!

I’ve got the bike stripped back and ready to send to the blaster. I’ve not had a chance to ride the bike much, but the short stint I did before stripping down had a pretty big flat spot. I didn’t play with setting up the carbs as I knew I’d be tearing the bike down.

I’d originally planned to send the carbs assembled to the soda blaster and get him to just tidy up the outside. I wasn’t sure whether to tear the carbs down as I wasn’t sure I’d get them back together! I opened up the bowls and I can see there is a bit of gunk and coloring in the bowls. Is there any ways I can assess the carbs to know if I should be putting a carb kit through them? Is getting just the outside of the carbs soda blaster foolish (should I be tearing down and getting ultrasonically cleaned instead?

Thank you!

[bryanj]

The clips holding thecarbs to the head rubbers are too wide and will cause air leaks, also check the rubber manifolds for cracking

[Bodi]

Ultrasonic will clean the dirt and goo out (using the right fluid) but won't super clean the cases. I would not have them blasted all assembled. Even if you do get them shiny and looking new, they go gray again pretty quickly. Some fluids will attack the rubber bits, some will turn the alloy bodies dark. I can't say what to avoid but Crest cleaning solution is safe.
The rack throttle mechanism doesn't come apart easily and is much harder to get back together again. Clean it as much as you want without taking it apart then oil all the pivots.
Carb kits... step back a sec. No carb kit I know of is a good idea. The brass parts really don't wear much at all: the needle and its orifice do after a lot of miles but inspection can show that, a worn needle will be pretty obviously worn and one can assume the orifice is as well then. So if you don't use the brass bits, all you have is a gasket set which is almost always incomplete (no fuel tube 0-rings).
Honda still (I think) sells the carb gasket kit (complete set) and the float valve. Just the Keihin valve costs more than most "complete" carb kits but the cost is worth it. You can find lots of posts here about aftermarket carb kits and their issues.
Genuine Keihin jets are not so easy to find but are mostly available. Needle and orifice (emulsion tube, actually) not so easy to find.
If you do take the bodies off, measure the slide openings as accurately as you can. On reassembly, use the "sync" adjusters to get back as close as is practical. The settings for the idle adjuster and choke throttle advance depend on this adjustment and are a bastard to get right again if you don't.