Project CB400 Four, Round 2

[.RJ]

wozers - mad prawps!

[PGK]

It lives! And runs! Well, more or less. It still counts as running, even if it's only 3 cylinders.

I took it out of RJ's garage the other day. On a whim, I decided it was high time this bike was running and on the road. So I spent all day today fixing up a couple of odds and ends that it needs to be on the road. I had a long list this morning, and I didn't quite finish everything, but I'm happy with the progress. You can see in the previous pictures what it was like when I got my hands on it. By the end of the day I had this:





Front brake sorted, rear brake sorted, headlight installed, taillight installed, airbox removed. some wiring sorted. I'm gonna need to make a harness, probably.

Front brake works properly, new pads, piston, seal.





CBR600?? lever?

Kaan gave me a CB750 headlight, which is larger than the CB400 headlight, so I had to add some tabs to the headlight bracket.





And I made a taillight bracket, the light is from a '73 BMW. I think it looks pretty good.





It's not rideable yet, 'cuz the engine isn't running, but it is close.

[Ginger]

LOL! Where'd you get that master cylinder? Excellent progress!

[.RJ]

The master came from my F4i

Did you cut the front fender down too? Whys it only running on 3 cylinders?

[PGK]

The master came from my F4i

Did you cut the front fender down too? Whys it only running on 3 cylinders?

I did cut the front fender down. I'm gonna use one of the pieces to make a little rear fender.

I'm not sure why it's only running on three. One of the carbs is flooding, i need to set the float heights. Where do you measure the float height? near the float valve? at the other end? in the middle? Resting on the tip of the float valve needle or with the spring depressed? I'm not sure. I need to do something about float bowl gaskets too.

I put in new plugs and set the gap. I set the points gap. I don't know where the timing mark is to check the timing, or to set static timing.

It seems like compression on one cylinder is low. I need to look at it some more though, it was near the end of the day today when I started troubleshooting in earnest.

[CaptainHenreh]

AWESOME.

That header gives me a chub.

[.RJ]

I'm not sure why it's only running on three. One of the carbs is flooding, i need to set the float heights. Where do you measure the float height? near the float valve? at the other end? in the middle? Resting on the tip of the float valve needle or with the spring depressed? I'm not sure. I need to do something about float bowl gaskets too.

I think float height is ~26mm from the base of the carb body, with the float contacting the float pin but not depressing the spring. I think on my 400 I ended up setting them a little higher (22-23 mm?). I've got a gauge if you want to use it. Also if its flooding make sure the o-ring on that float is ok and didnt tear on install, its pretty easy to do.

Static timing is the 'F' mark (should be a mark for 1-4 and 2-3). Check the spark advance at ~2500 rpm with the 'T' marks.

Do you have spark on all 4?

[PGK]

Pretty certain I've got spark. I'll check out the o-ring too. The sohc4.net says float height is 21mm. I just used the depth gauge on my calipers. Where on the floats do I measure? closer to the valve, or in the middle?

I didn't really get too deep into diagnosis, I spent most of the day taking care of other things. Tomorrow I'll check it out and see what I find.

[.RJ]

Measure the base of the carb body to the bottom of the float - 21mm sounds right - I think I was using a clymer manual, it was pretty worthless, at ~26mm it would fuel starve on the highway.

[PGK]

I know that it's the bottom of the float to the carb body, but since the float pivots, i'll get a different measurement depending on where i measure in relation to the float pivot pin.

[.RJ]

Well, whatever the lowest point on the float is when it touches the pin.... or just eyeball it

[PGK]

It ran tonight! On all four, too. I had installed the idle jets for #1 and #2 in the wrong spot. There was something fishy with the points too, but I cleared it up and set the timing/points gap. I checked the valve clearances, and did a compression test. got 160 psi on three cylinders, but 125 on one of them. I think the rings just need to seat properly in it. One of the float valves wasn't seating, so I lapped it with some lapping compound and it cleared up. The carbs still leak a bit though, I'll probably put some hylomar on the float needle valves and the float bowl gaskets, and spend a little more time setting the float height.

One of my coworkers is bringing in some handlebars tomorrow, I'm gonna try and make some clubman bars for it, and make a better headlight bracket. I've also got a line on some new mufflers, I know someone with a pair of Dunstall Decibel mufflers, one with baffles, and one that's just a straight megaphone.

I also made and installed a braided steel front brake line today. It's money. Only thing is, with the F4i master cylinder and the single piston caliper, the brakes are kinda binary. Very stiff lever. I guess that's what happens when you use a master cylinder designed to operate 8 pistons and have it operate 1.

I'm gonna try and make a wiring harness too. Theres a bunch of extra crap in this one I don't need, I want to simplify it a bit. Really I just need it to power lowbeam, high beam, taillight, brake light, coils, and starter. When I'm doing that I'm gonna make a battery box and stick everything in the tool tray under the seat.

Down the road I'd like to make a cafe-style single seat.

Another coworker might have a line on a rolling chassis with rearsets, tank and some other stuff. I'd like to have another frame and swingarm that I can add bracing and gussets to, the stock frame seems pretty noodly.

[.RJ]

the stock frame seems pretty noodly.

It is

Good work on getting it running - if the the floats are leaking, it might be those o-rings too.

[PGK]

the stock frame seems pretty noodly.

It is

Good work on getting it running - if the the floats are leaking, it might be those o-rings too.

i think that's what it is, so i'm gonna put 'em together with hylomar.

[PGK]

I need a battery. A small, 12V battery. Anybody got ideas? suggestions? A battery?

[Chris]

I need a battery. A small, 12V battery. Anybody got ideas? suggestions? A battery?

I used a security board battery (my company installs security systems in homes) to lower the windows on my BMW for a while... I haven't read through this whole thread, but something like this might help you out.

<!-- m --><a class="postlink" href="http://www.homesecuritystore.com/ezStore123/DTProductZoom.asp?productID=446">http://www.homesecuritystore.com/ezStor ... ductID=446</a><!-- m -->

[Evan]

I need a battery. A small, 12V battery. Anybody got ideas? suggestions? A battery?

drill battery?
build a pack with 10 NiMH AAs ?

[.RJ]

I need a battery. A small, 12V battery. Anybody got ideas? suggestions? A battery?

YUASA YTZ7S - thats what I've got the CB750. Its small, but a little pricey ($80).

[white_2kgt]

Odyssey PC680,
<!-- m --><a class="postlink" href="http://www.odysseybatteries.com/battery/pc680series.htm">http://www.odysseybatteries.com/battery/pc680series.htm</a><!-- m -->

Use it in the bike, then use it in the car.

[PDenbigh]

I put and Odyssey in my ATV a little while ago and it works REALLY well. I managed to hydrolock the engine and get mud in the carb, and through a whole lot of cranking (5 minutes or more) the starter didn't even suggest that it was slowing down. Then the ATV sat for about a month, and then started right up.

Also, I have an Odyssey in the XR. It sat for nearly 8 months unstarted, and fired right up when I turned the key.