Author Topic: 1975 Honda CB400f Project - Beginner (Read 48388 times)

Clinto · « **Reply #25 on:** December 29, 2012, 06:57:05 PM »

I have to second swan's recommendation on keeping the stock exhaust

Apexxn · « **Reply #26 on:** December 29, 2012, 07:08:22 PM »

You're in LA, I say sell that scratched up stock exhaust to me.

You want a really loud bike right, make a lot of noise, sell that quiet exhaust to me.

No chrome shop will ever touch it, please sell it to me.

gjunkie · « **Reply #27 on:** December 29, 2012, 08:05:09 PM »

Haha settle down Apexxn!

Well look here's my rationale behind this. I've seen a few CB550s with a 4-4 exhaust which I think looks beautiful. But I've been unable to find something like that for a 400. I eventually realized why I liked the look so much, the fact that the stock exhaust has so much pipe covering its underbelly. The 4-4 splits and gives it a less cluttered look. The MAC exhaust seemed like a good compromise. It's not a 4-4, but looks very clean and sort of hides the fact that there's 4 pipes by overlapping them a bit. I'm also a fan of the black... Sorry Swan.

@Swan: when you say they're OK but not great, what does that mean?
Also, what's the deal with Gasket sealant? Do I need a specific kind for the head gasket?

** EDIT **
After doing some research, Swan, I can see why you want me to keep the original exhaust. I'll be honest I had no idea that 400f club members were such purists! I'm about 27% more intimidated now.

swan · « **Reply #28 on:** December 30, 2012, 10:42:04 AM »

"@Swan: when you say they're OK but not great, what does that mean?
Also, what's the deal with Gasket sealant? Do I need a specific kind for the head gasket?"

Mac exhaust workmanship, chrome (or black) is fair but not really nice. I assume they are made overseas and a step above Harbor Freight quality.

it is your bike, do what you like, but again focus and function then worry about fashion. I do not use any gasket sealant (other than a light wipe of motor oil) on modern gaskets. You do not need sealant for your head gasket, tighten down the cylinder nuts in the correct criss-cross pattern in your manual and to the correct torque.

gjunkie · « **Reply #29 on:** December 30, 2012, 10:49:22 AM »

@Swan thanks! I'll be testing the electrical today. I found the electrical diagram for it. After that ill start on the leak. The #1 thing I'm focusing on right now is do as you said and getting it in as good running condition as I can. Then move on.

swan · « **Reply #30 on:** December 30, 2012, 11:04:48 AM »

Atta boy....

Stev-o · « **Reply #31 on:** December 30, 2012, 04:10:51 PM »

+1 - keep your stock exhaust, much better than the Mac. If the chrome is in bad shape, you could have it coated.

gjunkie · « **Reply #32 on:** December 31, 2012, 03:18:28 PM »

In the middle of removing the motor. Any tips on removing the master chain link? I bought a tool for it, but they assumed I had a newer chain.

Tews19 · « **Reply #33 on:** December 31, 2012, 04:38:30 PM »

Are you planning on replacing the chain? If so, cut it off.. You may want to replace the sprockets too... I have replaced all the sprockets and chains on the bikes I ride.

gjunkie · « **Reply #34 on:** December 31, 2012, 05:13:04 PM »

Update:
Ok. Day one of taking the motor off was a pain. It's not even off yet really. Following the instructions from the owners manual, we got stuck on the second to last step... Removing the chain. We didn't have the proper tool for removing it so we had to take the rear wheel off enough to loosen the chain. That was very difficult. We bought a tool to remove the chain, but it seems to be for newer chains where there's no master clip. In this one there's one specific section of the chain that has to be removed.

After all that and getting the last remaining bolts off, we still couldn't get the motor off of the frame. There's about 1 inch between the top of the motor and the frame, which isn't giving us enough room to play with. Tomorrow we're gonna try to jack up the motor enough to be able to pull it out. We'll see.

Stev-o · « **Reply #35 on:** January 01, 2013, 11:58:07 AM »

Lay the bike down on it's side (on moving blankets to protect the engine side covers).
Lift the frame up.

gjunkie · « **Reply #36 on:** January 01, 2013, 07:51:39 PM »

Updates:

Ok! Successfully took it apart. Took off oil pan/oil filter cover and their gaskets, which were falling apart and essentially fused to the motor. Spent a good amount of time carefully getting those pieces off and replacing them. Cut up my hands quite a bit thanks to the razor sharp oil pump.

After taking off the layers from top to bottom to get to the head gasket, we were surprised to find that the gasket was essentially brand new! So we have NO idea where the leak is coming from... Regardless we replaced all the gaskets and O rings.

Also, while taking off the cylinder head, the bolts were definitely not torqued right when they were last put on. Some were VERY tight, some very loose. Perhaps this was part of the leak problem?? We put them all back and torqued everything to specification.

We wanted to put as many things back onto the motor and plug any open holes to be able to spray some stuff down and clean it, but while I was putting back the spark plugs, I messed up... I put one back a little crooked, and it messed up the threads on the cylinder head... $#@!

We were so close... SO, tomorrow morning we're taking the motor to a local shop, very knowledgeable guys, to re-thread it and double check all our work. Make sure the timing was set correctly, valves are good, etc. Perhaps they can also provide some insight as to what the leak could be. Here's some pictures from the process today, pre-disassembly:

Took some shots of the exhaust. It's in much better condition than I originally thought, tho it's rusted throughout:

Also, the air box doesn't really seem to be plugged in to anything... I don't really think I need it. The electrics and fuses are bolted on one side of it, so I would need to figure out how to bolt them down without...

Can someone tell me what this is? There's two of them (I think). If they're the same, the other looks brand new, this one is in pretty bad shape.

We cleaned the frame as much as we could without taking everything off.

And, the '34 Ford that my buddy and his dad are working on in this shop. Pretty sweet ride.

gjunkie · « **Reply #37 on:** January 02, 2013, 07:45:29 PM »

Almost completely done. Today we took the motor to a local mechanic who rethreaded the spark plug cylinder. He also reset the timing which we had done wrong. Another thing he told us, the CB400f's had faulty Oil Control Orifice valves which caused too much oil to be sent to the heads causing too much pressure. This was the source of my leak! He told us that either they have been fixed already and were just dirty, or they'll have to be fixed soon... which means I'll be taking the heads off in the near future again.

We got the rear wheel back on, cleaned the motor a bit and got it back on, and almost all wires hooked up. We have one left to hook up, and we're not sure where it goes. Can someone shed some light on this thick wire with a red tip? The battery wires are accounted for already. This seems to go inside the starter cover, but we just can't figure out where.

Also, we think we hooked up the ground from the battery to the right spot, but Im hoping someone can verify. The book isn't very clear.

** EDIT **
Looking at these schematics, I think I see where this cable should go.

** /EDIT **

Putting the master chain link pin back on was awesome...

Heading back to work tomorrow, so I won't be able to finish up until Sunday unfortunately.

gjunkie · « **Reply #38 on:** January 06, 2013, 09:42:18 PM »

OK! She's back together in one piece. Took a little longer than I thought, but I was pleased that the bike started on the first try.

Only thing that gave me trouble at the end were the coils and in which order they should be plugged in. I knew that coil 1-2 should go to plugs 2-3, and coil 3-4 should go to plugs 1-4. But what I wasn't sure of was which plug in each coil was which. We sorta guessed and it seems to work just fine.

Took it around the block and it's obvious that the carbs still need to be synchronized. It won't idle and it won't pick up speed very well. I'm hoping a little sync will do the trick. Here she is back together and cleaner.

iron_worker · « **Reply #39 on:** January 07, 2013, 06:12:36 AM »

The coils fire each of their leads at the same time so it doesn't matter if you reverse 1&4 or 2&3. When the number 1 cylinder is at TDC on the compression stroke, the #4 cylinder is at TDC on the exhaust stroke. Both #1 and #4 will fire at the same time from the one coil. The ignition event on the exhaust stroke is considered "wasted spark". Hence wasted spark ignition system. (same can be said about #2 and #3)

If you mix up wires between the two coils ... then you're in trouble. ha

It's a good looking bike. Enjoy riding it.

IW

gjunkie · « **Reply #40 on:** January 07, 2013, 09:28:15 AM »

@IW thanks for clearing that up for me! Makes complete sense.

I wasn't able to ride the bike home from the shop due to the carbs, so hopefully I can get back this week and finish that up. I've got some parts coming in this week (replacement oil caps for forks, new tripple tree, clip ons) that I don't wanna start installing until she's up and running well.

Does anyone know what the ratios are for the tach/speedo with stock wheels? I can't find any info on that...

** EDIT **
Found this, does this look right? http://forums.sohc4.net/index.php?topic=87443.0

gjunkie · « **Reply #41 on:** January 07, 2013, 11:22:48 PM »

I have a question about overflow lines. It seems like I have about 6 overflow lines for carbs, battery, etc. I'm going a little crazy because it looks like I've got nothing but tubes coming out of the bottom of my bike. Is this normal? How do people hide these??

Apexxn · « **Reply #42 on:** January 09, 2013, 10:58:02 AM »

Thats where the battery ground was on mine.

Your pic of the master link. Did you push it all the way on it's not seated correctly.

gjunkie · « **Reply #43 on:** January 09, 2013, 11:38:24 AM »

Quote from: Apexxn on January 09, 2013, 10:58:02 AM

Thats where the battery ground was on mine.

Your pic of the master link. Did you push it all the way on it's not seated correctly.

It literally would not go in any further. I'm not sure what else to try. What would you recommend?

iron_worker · « **Reply #44 on:** January 10, 2013, 06:22:28 AM »

Move the chain over so the master link is on the rear sprocket on the back side. If you pull your chain cover off you can use a flat screw driver or punch on the back side of the master link and drive it downwards.

IW

Apexxn · « **Reply #45 on:** January 10, 2013, 11:12:23 AM »

In addition to what iron-worker said remove the clip and make sure your plate is pushed in as far as it will go. I chain tool works wonders here but if you don't have one a needle nose vise grip or other tool of this sort clamped over the outside plates will help seat it.

gjunkie · « **Reply #46 on:** January 13, 2013, 08:00:11 PM »

UPDATES:

OK! So today's task at hand was to synchronize the carbs. It was a bit more difficult than we thought it would be.

The book recommends each carb to be set at 16-24 cm-hg. The synchronizer I got is in inches, so I just did a simple conversion to get 6.2 - 9.1 inches. The carbs were definitely not synced, but they weren't that bad either. The book says that I can allow for a 3 cm (.3 inches) difference. Here's a picture of the gauges. You can see that carbs 1, 2, and 3 are pretty even, and 4 is a little low.

We ended up getting all of them around 6, which is definitely on the very low end. However, we had a hell of a time getting them to match at even that. So I figured at least get them synced. The rattling noise I heard before went away when they were synced. And as I tweaked, if I went too far it would come back.

Can someone tell me what the bolts circled in red are? there's one per carb and they hold down a spring inside of them. No idea what they are, and the book doesn't mention them.

A potential problem we found.... The idle screw (circled in green), can't really do much. When screwed all the way in with its spring completely compressed to idle at a higher rpm, it barely reaches the lever it is meant to push up. So it seems like it's not really doing much... Did we put something back together wrong?

After riding it around for a bit we noticed that the oil leak is NOT fixed. I definitely have to get the Oil Orifice Valves fixed. It leaks onto the motor and it burns up. Not good.

Also got to ride it in some long straight aways to see if I could finally get her over 45mph. I got it no higher than 55mph. And at 40mph in 6th gear I was getting 4000 rpm. That is awful high... how am I ever supposed to get to 70mph?? Could this be due to the oil pressure inside? Could the carbs have been set too low? Can anyone provide any insight on this?

hondamatteo · « **Reply #47 on:** January 13, 2013, 08:50:41 PM »

Your throttle cables are probably set to far, therefor holding up the throttle and not letting it return to where it will hit the idle screw. What rpm is your idle at? Should be around 1000-1200 I think. I wouldn't worry too much on what reading you are getting on your carb sync gauges as long as they are all in sync and reading the same. 4000 rpm isn't very high for these bikes. My 350f doesn't make full power till like 5-6k and red line is at 10k. But you can check your sprockets and see if you have the stock number of teeth on there, front and back.

Tews19 · « **Reply #48 on:** January 13, 2013, 08:51:14 PM »

I have the same sync tool. You don't need it at specific level but should have them all reading in the same vacinity. Alsoi would tweak the plastic knobs to have less vibration with the needles. If you search on here you can see me sync a set on a 550. It will give you and idea how it was from the start to the end product.

hondamatteo · « **Reply #49 on:** January 13, 2013, 09:05:50 PM »

As far as not getting full power did you sort out your electrical/charging issue? Just running on the battery you won't be getting a very good spark. And what jets are you running in your carbs with those pod filters? That might be giving you another issue, running too lean. Just a couple ideas

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Author Topic: 1975 Honda CB400f Project - Beginner (Read 48388 times)