Topic: Anyone care to answer a few questions?

[rk]

Hey guys,

75' CB400F has been an ongoing project all winter. Re-did the carbs, installed dyna-S ignition, chased a few electrical gremlins away, and put the thing back together. This thing has really been a love-hate... mostly because I'm learning as I go (hopefully I did everything right and it doesn't fall apart on me whilst whisking down the freeway).

1. With electronic ignition installed, such as a Dyna-S system - am I right in thinking that kick-starting the bike without battery power is futile? I'm no electronics whiz but from what I understand, the points and condensers of the old ignition system created enough spark to start the bike, battery or no. Correct?

2. I bought the bike 3rd hand with a 'new battery'. It had some life in it when I got the bike, so I kept it warm and dry in the closet all winter. Put in on the charger a few weeks ago for a day and a half... now it's dead again. Is the battery ruined or am I doing it wrong? Also - I'm planning on finishing the cafe conversion that it's in the middle of... so I'd like to remove the stock battery and wiring altogether. I've been reading about smaller new-tech batteries... but I don't know where I'd find one. If I'm going to have to replace this battery right away, I'd rather just get a smaller one that I can use once I get the rest of the parts to finish the job.

3. Had it running today, and it started leaking oil (a few drops) from the alternator. I popped the cover off and it's dry in there. Is this normal? Is there a seal that's missing? I was under the impression the alternator was oil-cooled but maybe I'm wrong and it's leaking from elsewhere?

4. I rebuilt the carbs this winter, but now #3 seems to be leaking when the fuel is on and the bike isn't running... and tips I can try before I go ahead and take all the carbs off again and figure out what the issue is?

5. I've been reading a few thing about fuel petcocks recently. Does anyone have a step-by-step 'DIY new seals' guide? Mine leaks a little bike.

6. Finally - I haven't had my carbs synced or tuned yet, and I really have no idea where to start. The bike seems to idle at 2000rpm until it gets hot, and then it idles around 3000RPM... normal?

Thanks for the time and input, this forum is a lifesaver. Love this bike... just wish I knew what it needed sometimes!

[tomkimberly]

You need a battery to engerize the electrical system.
You need to repair your petcock.
You need to clean your carbs.

Etc, there are no short cuts...............

Tom

[Tews19]

Check the float on carb 3. Not sure the factory spec for float height. A stuck float is a common problem for an over flow.

The battery may be salvageable. Bring it to a battery store to have them charge it.

[Jerry Rxman Griffin aka MuthaF'er]

Bench sync your carbs FOR STARTERS then get them done correctly.

[Cut]

Sometimes my carb float sticks as well.  I simply tap the float bowl of the offending carb with the back end of a screwdriver and that seems to clear up the issue.  I have a cafe bike and can say that you will need an Absorbed Glass Mat (AGM) battery.  Given the size of your bike you could get away with using a 4 or 6 amp hour (6ah) battery.  I stayed away from lithium due to the fact that you cant use your regular battery charger on these batterys and that the cost just doesnt justify the expense.  Seals are wear items for which the petcock is one of the easier ones to R&R. I suspect, but am not sure, that your leak may have been from the slip fitting where your header pipe meets your exhaust pipe in that area.  I just started my bike up for the first time in 4 months and had a carbon/condensation puddle in this very area.  Purchase a manometer and master the art of carb synching. Lastly, If your RPMs are running away from you as the bike warms, this is symptomatic  of a lean condition that can occur when your carb floats are low (too much air and not enough fuel).  By chance, are you bottle feeding the bike when this RPM runup occurs?

[Bodi]

If the alternator is dry inside, probably the oil isn't coming from inside? The alternator should be dry. There is an oil gallery plug beside the alternator, held in by the cover. This seals with an O-ring and it could be leaking. Also, DO NOT run the engine with the alternator cover off: the gallery plug will pop off and a very messy gush of oil will spurt out.

There are two petcock styles, both are serviceable but the riveted type needs extra work to drill out the rivets then procure machine screws to fit and then tap the holes. The screwed type is a bit weird (hard to describe) inside and usually just cleaning and applying some silicon grease to the sealing surfaces gets it to seal. The riveted type has a rubber "valve" disk with 4 holes. Usually just flipping the disk over, adding some lube, and reassembling it (with those screws) does the trick.

You need a battery with any ignition system (except a magneto of course). There is no electrical voltage to make a spark with no battery, the alternator makes zero power without a battery to supply field coil power.

You can use a smaller battery if you don't want electric start. Changing battery technology is dicey: the charge requirements of different battery types are different and you may have an over or under charged battery... in particular that can get pretty flamey with a lithium battery (see Boeing 787).

Carbs take a lot of work. You should be good at removing and installing them by the time you get them sorted. You will need to do a proper vacuum sync. Fule leaks are either bad float height or leaky float valves or broken overflow tubes (they can split almost invisibly). Avoid aftermarket carb "brass parts", get OEM Honda is you need them... and usually you don't, except for thr float valves.

[splitt]

On your leaking carb. Turn off the gas first, then loosen the drain screw to drain the leaking carb. Tighten the drain screw and turn the petcock back on. There may be some dirt or rust holding the float valve partly open. The debris should flush out when the bowl is drained. This may fix the problem without pulling the carbs.

[Stev-o]

1. You need a battery for spark.
2. Buy a good battery, I like the sealed Scorpions.
6. Adjust idle when bike is fully warmed up, about 1400 rpm.

[Matt Chapter]

This thing has really been a love-hate... mostly because I'm learning as I go (hopefully I did everything right and it doesn't fall apart on me whilst whisking down the freeway).

I've put over 20,000 miles on my 400, it's a pretty reliable bike once it's set up correctly.  Get the manual, it's not necessarily extremely obvious, but the info is there.

I can't speak to electronic ignition, but you definitely want a reliable battery.  Most likely with the abuse yours has been through, you'll have to replace it.  Going forward, keep it on the charger when not in use and away from large temperature changes should extend the life at least a little.

3. Had it running today, and it started leaking oil (a few drops) from the alternator. I popped the cover off and it's dry in there. Is this normal? Is there a seal that's missing? I was under the impression the alternator was oil-cooled but maybe I'm wrong and it's leaking from elsewhere?

I just replaced my alternator gasket, after starting the engine with the cover removed.. doh.  Make sure the gasket surfaces are clean, relatively oil free when you replace the gasket.  I used a razor blade to get some of the tougher stuff off, like old gasket.  I ordered my gasket from these guys, they have two, I got the vesrah for 1USD more. 4into1.com/vesrah-alternator-cover-gasket-vy-1003-honda-cb350f-cb400f/

4. I rebuilt the carbs this winter, but now #3 seems to be leaking when the fuel is on and the bike isn't running... and tips I can try before I go ahead and take all the carbs off again and figure out what the issue is?

My first guess is float height.  Unfortunately, you have to take the carbs off, especially for the interior carbs.  I need to do the same thing.  One temporary fix may be to use the center stand instead of the side stand so that the angle to leak isn't as great.

6. Finally - I haven't had my carbs synced or tuned yet, and I really have no idea where to start. The bike seems to idle at 2000rpm until it gets hot, and then it idles around 3000RPM... normal?

Both of those idles are high, start with a bench sync then move to the vacuum sync.  I'm about to go through this process, just ordered a carbtune that should be here next week.

Love this bike... just wish I knew what it needed sometimes!

Patience, a nice full wallet, and tiny hands.

[rk]

Thanks for all the info guys...

I was able to repair the petcock with some new seals I bought at Princess Auto. I can't remember if the original seal was an O-Ring or not, any input?

It's still leaking a little bit of oil from somewhere near the alternator. The alternator itself is dry... still haven't tracked down the source yet.

I took it for it's first ride since I've owned it today and noticed a few things...

1) When it gets hot, it's hard to get it back into neutral... normal?
2) After it's hot, it's a PITA to get going again - kicking it over is really tough...
3) The idle is still a little weird, seems to idle high (around 3000RPM) unless it's in gear (2 or 3rd) at which point it idles down to around 1500RPM

I did a little reading about breaking in a new engine (it's been totally overhauled) and it talks about riding it at high RPM and not loading the motor up too much... anything else I should be cognizant of?

Happy she's on the road! I'm going to take it to a bike shop here in town and get a real mechanic to give it a once over (he says he can sync the carbs too) just to make sure it's all good to go... hopefully my 400 is as reliable as advertised!

[kghost]

Sounds like you need a clutch adjust and some carb work.

[EDU]

I stayed away from lithium due to the fact that you cant use your regular battery charger on these batterys and that the cost just doesnt justify the expense. 

Finally a thread I can contribute to! 

Now, I don't know @#$ about vintage bikes and I'm struggling big time with my CB500F... having said that, I do race a 2010 ZX6R which runs a total loss system (basically meaning it won't charge its own battery). I have a Lithium battery on it and I bought a charger for it (for obvious reasons), all up it cost me around $120 for everything but that was a couple of years ago. The battery gets charged every 3rd session on the track but it can easily do 5 (I've done 6 but it's a gamble) and it has lasted me 2 years and counting!

What I'm trying to say is that $120 (probably a bit more by now) is not a lot of money for a battery and charger that not only will outlast most lead/etc batteries but also weighs around 400grms and save a TON of space! I use the 4-cell battery on the ZX6R and I have used it many times on the CB500F. It starts both bikes without any struggle at all.

Ps: This is where I got my stuff: http://www.motydesign.com/ and no, I have no affiliation whatsoever with them.

[rk]

I've been playing around with the clutch settings, I backed it off a bit and then went for a ride - as soon as I laid into the power the clutch would slip... so I adjusted it back the other way and it seems to work better now.

I'm still chasing the oil leak, its a few drops here and there while I'm stopped at a light. I'm going to inspect the aforementioned oil gallery in the morning to see if its coming from there.

How are these tanks vented? My tank doesn't appear to be vented (I can hear it sucking air when the bike is shut off).

There's also a vent line from the top of the crank case (I think), it's a fairly large diameter... is it supposed to smoke? Is that indicative of anything? Too rich?

There's a guy in town that's going to sell me a few hours of his time to go over the bike (this is my first rebuild... don't want to die on it if I can avoid it). He's got a manometer and some serious CB experience, I'm hoping he can figure out my idling issues.

Otherwise! She rides like a dream! Put a few miles on her today ripping around town making noise!

[lucky]

Another reason for a leaking overflow is a float needle that does not seat because it is worn or distorted.

Almost never discussed.

[Fritz]

installed dyna-S ignition,

Why?

Put a few miles on her today ripping around town making noise!

So, what are you aiming for? Learning on how to make your bike reliable and fix it or just making noise?

Seriously, installing an electical ignition and then "chasing electrical gremlins", finding out that the battery is toast, is the wrong order, IMHO.

There are tons of threads that cover your questions. Also read Honda's workshop manual for your model. And follow their instructions.

The oil leak might come from anywhere - it just drops off at the lowest point of the engine. But I think you should take care of that after everything else is working smoothly.
The tank vent is in the lid. There's a tiny hole in it that can get clogged and might not be easy to find.
The "breather" or crank case vent is smoking either from blow-by and / or water vapour. The water vapour will dissapear after having ridden the bike for a longer distance letting your oil heating up to operating temperature. The amount of blow-by depends on the conditions of your pistons, cylinders and piston rings.

Remember to always warm up the motor before you ride it hard. This takes about 10 miles or fifteen minutes or even longer depending on the weather conditions. If you redline her regularly without a warmup, you'll wear out the motor and transmission...


Cheers
Carsten

[rk]

The bike was missing pieces when I bought it, so I figured I'd upgrade what I needed to replace anyways. The electrical issues were unrelated (lights, horn, blinker, etc.). The battery was brand new, however it was dead when I put it away for the year and subsequently it didn't take a charge months later.

Thanks for the tip about the hole in the cap though, I had the tank re-sealed and likely that covered over the hole. I'll take care of that tomorrow.