Topic: Progress on my '75 CB400F Garage Find

[carnivorous chicken]

I still haven't had a chance to remove the carbs and reset the floats. I ordered a Motion Pro SyncPro, but it won't arrive until next Monday.

Also, the timing might be off and, while I can set the static timing, without a working tach and the carbs being all weird, I can't set the timing with a light while the bike is running. It jumps around too much.

The frustrating thing is that the bike fires right up and idles nicely on its own. If it weren't for the rattling sound and the fuel dripping out the bottom I'd be tempting to just leave it as it is!

Anyway, I rode it to the bottom of my driveway and took some pics. I figure it's all I can really do for now.

Don't want to be the bearer of bad news but... Others may have a different opinion, but if it's possible for you to return you Motion Pro sync tool I would do it in a heartbeat. Those things are pretty crappy compared to others. I've used mercury filled tools in the past, which are great, but am using a Morgan Carbtune tool -- and it's pretty fantastic too. Others are into gauges. But if you poke around you'll see that most people aren't that happy with the Motion Pro tools -- the blue liquid is crap, they get air bubbles, and flutter. It's better than nothing, but for a few bucks more the Morgan is way, way better.

And just a thought -- after you tightened the lock nuts on the valve adjust, did you recheck to make sure the gap hadn't changed? It can be tricky and take a few (or several) tries to make sure that it's just right after you tighten.

But MoMo is also right, could be a rattling cam chain (search this site for instructions on how to adjust) and a carb sync will help.

[Master_Moose]

Don't want to be the bearer of bad news but... Others may have a different opinion, but if it's possible for you to return you Motion Pro sync tool I would do it in a heartbeat. Those things are pretty crappy compared to others. I've used mercury filled tools in the past, which are great, but am using a Morgan Carbtune tool -- and it's pretty fantastic too. Others are into gauges. But if you poke around you'll see that most people aren't that happy with the Motion Pro tools -- the blue liquid is crap, they get air bubbles, and flutter. It's better than nothing, but for a few bucks more the Morgan is way, way better.

And just a thought -- after you tightened the lock nuts on the valve adjust, did you recheck to make sure the gap hadn't changed? It can be tricky and take a few (or several) tries to make sure that it's just right after you tighten.

But MoMo is also right, could be a rattling cam chain (search this site for instructions on how to adjust) and a carb sync will help.

Hopefully the sync tool works ok. It looked better than round gauges, which bounce around, and I didn't want to wait for shipping from the UK for a mercury one. Though I wish I'd seen the videos on how to build your own before I'd spent money on this one. I may still return it.

I did check after locking the nuts. Basically I just left the feeler gauge in the gap, tightened the nut, and then made sure the feeler gauge was still able to move without being too loose.

As far as the chain, I'm guessing I'll need to remove the blanking bolt and push on the end of the plunger (it took me a while to figure out where that even was because 90% of the pictures that have been posted in the past are no longer up). Hopefully the pivot on the arm isn't seized. If I'm not mistaken the engine needs to be partially disassembled in order to replace it.

[Stev-o]

Don't want to be the bearer of bad news but... Others may have a different opinion, but if it's possible for you to return you Motion Pro sync tool I would do it in a heartbeat. Those things are pretty crappy compared to others. I've used mercury filled tools in the past, which are great, but am using a Morgan Carbtune tool -- and it's pretty fantastic too. Others are into gauges. But if you poke around you'll see that most people aren't that happy with the Motion Pro tools -- the blue liquid is crap, they get air bubbles, and flutter. It's better than nothing, but for a few bucks more the Morgan is way, way better.

And just a thought -- after you tightened the lock nuts on the valve adjust, did you recheck to make sure the gap hadn't changed? It can be tricky and take a few (or several) tries to make sure that it's just right after you tighten.

But MoMo is also right, could be a rattling cam chain (search this site for instructions on how to adjust) and a carb sync will help.

Hopefully the sync tool works ok. It looked better than round gauges, which bounce around...

I have the "round gauges" they have damper valves that can be adjusted til the needles dont bounce.

[Master_Moose]

Don't want to be the bearer of bad news but... Others may have a different opinion, but if it's possible for you to return you Motion Pro sync tool I would do it in a heartbeat. Those things are pretty crappy compared to others. I've used mercury filled tools in the past, which are great, but am using a Morgan Carbtune tool -- and it's pretty fantastic too. Others are into gauges. But if you poke around you'll see that most people aren't that happy with the Motion Pro tools -- the blue liquid is crap, they get air bubbles, and flutter. It's better than nothing, but for a few bucks more the Morgan is way, way better.

And just a thought -- after you tightened the lock nuts on the valve adjust, did you recheck to make sure the gap hadn't changed? It can be tricky and take a few (or several) tries to make sure that it's just right after you tighten.

But MoMo is also right, could be a rattling cam chain (search this site for instructions on how to adjust) and a carb sync will help.

Hopefully the sync tool works ok. It looked better than round gauges, which bounce around...

I have the "round gauges" they have damper valves that can be adjusted til the needles dont bounce.

lol, well damn. I'll probably return this tool and get one of the other things available. The first thing I need to do though, is get the float levels correct so they stop overflowing.

[carnivorous chicken]

lol, well damn. I'll probably return this tool and get one of the other things available. The first thing I need to do though, is get the float levels correct so they stop overflowing.

Yep on the float levels.
Depending on where you are, you might be able to find someone with gauges or a good sync tool to borrow to get those things dialed in (or even a crappy one just to get them close) so you won't spend any more time waiting -- we all know how frustrating it is putting down a project to wait for parts or tools to ship.

[Master_Moose]

I haven't had any time to pull the carbs back off yet, but for now maybe you all can let me know your thoughts on something else.

First off, I'm not getting any power to the headlight circuit. I've replaced all of the fuses, but I'm not getting anything at all at the headlight plug. I'm not entirely sure which fuse is for the headlight though, since there doesn't seem to be a diagram anywhere.

Also, sometimes the starter will start running as soon as I turn the key. I've replaced the right switch assembly with a repro version from 4into1.com. Would that mean the new switch is faulty or is it possible there's something else? Is there a relay for the starter?

[MoMo]

Off the top of my head I'd bet the right switch is defective...Larry

[Master_Moose]

Off the top of my head I'd bet the right switch is defective...Larry

So the Yellow/R wire is the one from the start button. If I turned on the key and the starter automatically started running, I could disconnect that wire to make the starter motor stop. But when I connected a test light to it, it would suddenly work normally again and the tester would only light up while the button was pressed. After about 20 tries the test light FINALLY remained on after releasing the button, proving that the switch is bad. I then tried to get video, but it went back to working normal again! Anyway, the pic I have should at least be enough to get the switch assembly exchanged for a new one.

[MoMo]

When you open up the switch the clear plastic housing is most likely cracked.  Seen it too many times ... Glad you figured it out...Larry

[Master_Moose]

When you open up the switch the clear plastic housing is most likely cracked.  Seen it too many times ... Glad you figured it out...Larry

On a brand new one though?

[MoMo]

When you open up the switch the clear plastic housing is most likely cracked.  Seen it too many times ... Glad you figured it out...Larry

On a brand new one though?

Didn't realize it was new

[Master_Moose]

I got my carbs off today and did the clear tube test. Carbs 1 and 2 are way too high, even though I set them all of the floats at 23mm instead of the factory recommended 21mm.

Also, I noticed the sliders in 1 and 4 have a bigger gap than 2 and 3. Is that something that gets sorted out when I sync them or is something else wrong?

[jas67]

Get yourself four of these to accurately set your float levels.
https://www.z1enterprises.com/fuel-level-gauge-tool-kawasaki-suzuki.html


It's the only way to know for sure what level the fuel is getting to in the float bowls.

[Master_Moose]

Get yourself four of these to accurately set your float levels.

It's the only way to know for sure what level the fuel is getting to in the float bowls.

I feel like maybe you intended to include a link or a picture.

[carnivorous chicken]

Also, I noticed the sliders in 1 and 4 have a bigger gap than 2 and 3. Is that something that gets sorted out when I sync them or is something else wrong?

Short answer, yes. But while you have your carbs off you can bench sync them -- search here for how to posts -- but you want them as close as you can get them, and then syncing with a tool will dial them in.

[jas67]

Get yourself four of these to accurately set your float levels.

It's the only way to know for sure what level the fuel is getting to in the float bowls.

I feel like maybe you intended to include a link or a picture.

Yep:
https://www.z1enterprises.com/fuel-level-gauge-tool-kawasaki-suzuki.html

[Master_Moose]

Yep:
https://www.z1enterprises.com/fuel-level-gauge-tool-kawasaki-suzuki.html

Sadly they're out of stock and I haven't been able to find them anywhere else. I've even tried just find an M6 to barb fitting screw, but haven't had any luck, which is I why I went with the plastic vacuum fittings with plastic hose instead. For $50 for a set, are the ones from Z1enterprises.com going to be significantly more accurate than what I'm using?

I went ahead and set all the floats to 25mm and #1 is still way too high and leaks out of the overlow, #2 is way low, and #3 & #4 both look the same.

[Master_Moose]

Could my float not actually be floating? I figured since these weren't hollow they wouldn't have a leak or anything, but is there something else that could cause them to sink?

[jas67]

Sadly they're out of stock and I haven't been able to find them anywhere else. I've even tried just find an M6 to barb fitting screw, but haven't had any luck, which is I why I went with the plastic vacuum fittings with plastic hose instead. For $50 for a set, are the ones from Z1enterprises.com going to be significantly more accurate than what I'm using?

I went ahead and set all the floats to 25mm and #1 is still way too high and leaks out of the overlow, #2 is way low, and #3 & #4 both look the same.

If what you're doing doesn't leak, and you can see the fuel level, then the Z1enterprises ones will do no better.    Please keep in mind that the thread pitch is a fine thread, 0.9mm, not 1.0mm, which is the normal thread pitch for a 6mm screw.

Could my float not actually be floating? I figured since these weren't hollow they wouldn't have a leak or anything, but is there something else that could cause them to sink?

Yes, if your floats are not brass, it is entirely possible that ethanol has attacked the plastic and rendered it no longer buoyant.

[MoMo]

The brass ones if you have them can develop pinholes and sink to the bottom.  I've seen it more than once...Larry

[Master_Moose]

Sadly they're out of stock and I haven't been able to find them anywhere else. I've even tried just find an M6 to barb fitting screw, but haven't had any luck, which is I why I went with the plastic vacuum fittings with plastic hose instead. For $50 for a set, are the ones from Z1enterprises.com going to be significantly more accurate than what I'm using?

I went ahead and set all the floats to 25mm and #1 is still way too high and leaks out of the overlow, #2 is way low, and #3 & #4 both look the same.

If what you're doing doesn't leak, and you can see the fuel level, then the Z1enterprises ones will do no better.    Please keep in mind that the thread pitch is a fine thread, 0.9mm, not 1.0mm, which is the normal thread pitch for a 6mm screw.

Could my float not actually be floating? I figured since these weren't hollow they wouldn't have a leak or anything, but is there something else that could cause them to sink?

Yes, if your floats are not brass, it is entirely possible that ethanol has attacked the plastic and rendered it no longer buoyant.

The last time this engine ran (~1982) they hadn't started putting ethanol in fuel yet

[jas67]

In any case, you might want to put some gasoline in a small open container, and put the floats in, and see if they float or sink.

New floats wouldn't be a bad idea.    The CB350F has brass floats.    The carbs *look* the same as the CB400F carbs.    It might not be a bad idea to buy CB350F brass floats and put in your carbs.   They would be way more ethanol resistant than the plastic ones.

[Master_Moose]

In any case, you might want to put some gasoline in a small open container, and put the floats in, and see if they float or sink.

New floats wouldn't be a bad idea.    The CB350F has brass floats.    The carbs *look* the same as the CB400F carbs.    It might not be a bad idea to buy CB350F brass floats and put in your carbs.   They would be way more ethanol resistant than the plastic ones.

Interesting idea. Not that I'll put ethanol fuel in this bike if I can help it, but there is trace amounts even in "ethanol-free" fuel.

Anyone ever use brass cb350f floats in their cb400f?

[Master_Moose]

I bought all new floats and it has new needles and seats, but carb #1 still overfills and leaks. 

[jas67]

I bought all new floats and it has new needles and seats, but carb #1 still overfills and leaks. 

Did you check the fuel level in the floats with the clear tube method?   Maybe the float level in that carb set set too high?