Topic: 1975 Honda CB400 Four Project - Rookie

[RickB]

Malcomgb,

I detailed it back a couple page (page 19 to be specific):

http://forums.sohc4.net/index.php?topic=51957.msg1138842#msg1138842

If you scroll down to the lower part of that post you'll see what I mean.

As I mentioned, I have now bought this valve adjustment tool from DCC which should make it all the more easier.

Rick.

[Hush]

This little bike certainly keeps you busy Rick.

[RickB]

Hi all,

So I got the head back from the engineers. I had HydroBlast get the broken exhaust stud out and put a helicoil in one of the bolts need the cam chain tunnel that striped last time I took the rocker cover off.

I then took the head over to Head Stuff Development in Moorabin to have the spark plug threads helicoiled as HSD had the tooling to go that small. The plug threads were always a bit dodgy so when I had the head off, I figured I might as well do it all at once. I had them replace the valve stem seals with OEM Honda ones too just to be sure.








But before I got the head back I replaced the plates in my clutch in an effort to fix a lag in acceleration at low RPM when the bike is warm. This was due to Doctorlumen and I having the same issue and he replacing his clutch which apparently fixed his issue, so here's hoping mine is gone too (otherwise it's back into float heights!).

I had no real problems here other than that damn castle nut that you need a special tool for. I bought the clutch removal tool from EBC but that was just too hold the basket in place, not remove that nut. So if you're removing the clutch from a CB400F, you need this tool from Honda 07916-6390000 or a much cheaper alternative to remove a 16mm castle nut.

Ok, head stuff:



For reference, the larger NE Brand tubular oil gasket is on the right, the OEM Honda on the left. Like the smaller oil valve gasket, this one was hard and warped after only 1600 miles. Given the trouble these little bits of rubber have caused, buy OEM Honda if you're rebuilding your head or having head gasket issues.





OEM Honda gasket. See here for how badly the NE Brand one fit compared to this.









Helicoils in the spark plug heads. The guy that did the machine work was worried that the fine edges might cause detonation and pinging as it gets hot. This is the first I'd heard of such a thing but lets hope it doesn't affect me. The threads are now stainless steel, so I shouldn't strip those in a hurry.



A by product of all the machine work. I spent an hour pulling shavings of metal from the head and valve areas. I hope I got it all but I'm almost certain I would have missed a small piece. Other than strip the valves and springs out, I was as careful as I could be.





This is the bold near the cam chain tunnel that I had helicoiled.





New OEM hardware on the inlet manifolds and new OEM exhaust studs after having the threads cleaned up. They went in easy.





Now this prevented me buttoning up the engine. The pillar nut on the left had side pulls the head stud to the rear of the bike when I torque it down. I think it's because the 'meat' of the mating surface was machined away when the engine went back together originally as it had been damaged by the previous owner.

So now the bolt that screws into this pillar nut doesn't line up correctly. I tried pushing the pillar nut as I torqued it down, but it was hard to do with one set of hands. If I had a shim to hold the head stud out it might do it, but I have no idea how that would stay in place.

I didn't have this issue last time I had the rocker cover off, so I don't know what's happening.

Rick.

[RickB]

So I had my dad help me. He came up with the idea of chiseling down a wedge of wood to help hold the nut in place.

After a few attempts (which included swapping those pillar nuts from one side to another, which felt like voodoo but did help) we got the rocker cover back on:





Then disaster struck! I had my torque wrench set to 6 ft-lbs which was on the low end of the scale and this center bolt snapped. This is the same area of bolts I had issues with last time (in fact I had the top left helicoiled just last week).

So I'll run it without the bolt in for now (as that was what I was doing last time with that stripped top left bolt) and when I feel like taking the head off again, I'll get that snapped bolt removed (and some other stripped threads and helicoils I have since found).

So frustrating.

Rick.

[MoMo]

Rick, I noticed that not all the cover bolts are snugged down.  Were you torquing the middle bolts when the others were not snug?  ...Larry

[RickB]

Larry,

Yeah the manual said to torque down the center four then move the others on the outer. Maybe I should have torqued it all down in stages?

Rick.

[Doctorlumen]

I did the same thing, Rick, when I swapped my leaking head gasket for OEM. I only use a 1/4-drive ratchet on my old hondas, unless the bolt is on the frame, or the clutch retainer. I haven't had anything rattle loose, and have suffered a lot fewer stripped threads and broken bolts.

[MoMo]

Larry,

Yeah the manual said to torque down the center four then move the others on the outer. Maybe I should have torqued it all down in stages?

Rick.

Definitely.  After all are snugged down work your way from the center out using an X pattern.  I usually do  two torque increments.  When removing the cover and/or a head gradually loosen working from the outer to the inner using the same X pattern.  Good luck...Larry

[straat-toe]

The donk is out! Yep, I got the engine out and the frame stripped. Tomorrow it's off to the powdercoaters.



So that oil filter bolt just needed a bit of powertool action. I had to cut the head down to fit a 10mm ring spanner over it. I already found a replacement (400fourbits.co.uk), so no worries there. If I could buy complete set of stainless bolts steel bolts for this bike, I would. I've seen some around for the engine casing etc. Should I get phillips-head or allen-key? What's better? I'm certainly not putting all these corroded soft metal screw back on.

Hey Rick, my Oil Filter bolt is giving me the same grief. So soft the 12 just started spinning. I think I'll try your grinder approach before calling in a pro.

[RickB]

Guys, thanks for the advice on the 1/4 drive ratchets, I haven't yet built up the courage to take the head about and fix those threaded bolts, but the good news is the head has leaked a drop since I replaced those second-rate seals and head gasket with OEM! So cheers to all for the advice on that.

I'm back in Australia at the moment and have been on a few rides. I bought a spare carb rack from 400fourbits.co.uk a while back with the intent on removing the retaining pin correctly as I did it wrong the first time.

Well that part went smoothly but the electroplating screwed up. I wrote a post in the SOHC section about it, but I'll include it hear for archiving purposes:

So I drilled out the retaining pin on a spare CB400F carb rack and removed the throttle cam and sent it off to get electroplated.

I went to put it back together and it fell to pieces on me!

It appears the electroplating process has eroded the rivets that hold the cam that the push/pull throttle cables connect to. It's a two part thing which is under a bit of stress, so I want to 'fix it' correctly whilst respecting originality. Obviously I could just bolt them back together but I want to do it the 'right' way.

Has this happened to anyone else and/or can you tell me how Honda originally fixed these two pieces together?

Thanks,
Rick.

[Icarus]

I just started taking apart my '75 400F a couple days ago and looking through this thread has been helpful, and daunting! 

As for how that throttle plate was originally held together, mine looks to be riveted at those three points.

[Timmy]

Icarus: same here! A really good read if you have a cb400f yourself.

I'm about to remove and replace my clutch in a near future. Can anyone link the mentioned tool earlier? Where can it be bought? Dimecitycycles?

[RickB]

Timmy, I bet you've sorted this out by now but if you don't want to order the tool from Honda using the part number I listed, you can find them on eBay labeled 'Clutch Lock Nut Spanner Tool' at various prices.

[RickB]

Hi guys,

So a while between posts, but I've been living in the US and don't have my CB400F with me. I bought an 86 XL600R and have gone on one adventure already, which was a great time.

So whilst I'm away from the 400F, I've had Ryan and the great people at HVR Australia making me an alloy tank and seat. HVR is where 'My Mechanic Matt' now works. A high end historic and vintage restoration shop. Probably way overkill for a simple motorcycle tank, but as I have learnt time and again on this project, the poor man pays twice. I want to be able to be indecisive or fussy and am happy to pay for a quality job.

I never loved the small CB350F tank I had on it, nor the lines of the original CB400F tank. I wanted something bigger, more of a GP racer feel but with a streak of 'meaness'.

I tried to fit a CB500T tank, but it would have taken a lot of work to get it to fit and it still wasn't perfect.

What I really wanted was a tank and seat like on the 'The Coachbuilt 590 Honda Four' featured on the front of a 1975 Cycle magazine I saw on this very forum. My experience making my seat out of fiberglass taught me to avoid it at all costs. Too fragile, too difficult for me to work with. Nope, there's a right way to do this and I knew it was alloy.









So over the last year or so I've been working with Ryan at HVR to get it just right. It took him a few goes with my vague directions via email from the other side of the world, but we got there and I'm so stoked with it. He's just got to screw on the filler cap and weld on the brackets to hold it all in place.

Then we're moving onto the seat. This time, we're gonna' mock it up with cardboard first so my indecision doesn't cost me an arm and a leg!











This was actually the second attempt, the first being way too much of a 'toaster' tank. Once I had seen this in person, I decided it just didn't feel hefty enough. It was still too slender, I wanted more bulk...



So I photoshopped up a little before/after photo and sent Ryan back to work...























Ryan widened the tank an inch either side. The above photos show it after he tacked on the new midfle section.













This is where we're at now. The 'shoulders' of the tank look a little sharp in the photo but I think that's just the way the aluminum catches the light. Ryan asked me if I'd like to polish it, I said no, I want it to dull and age like a vintage GP racer. I think a mirror like Manx style would be too much given the amount of chrome on this bike already.

I plan on dropping the gauge set down into a dashboard type arrangement (I'm thinking one of those new Smiths digital units too) as I feel the filler cap should be the tallest part of the bike.

For the seat, I'm thinking something not as square/flat in the rear as the 590 Coachbuilt Honda. More of a hybrid between that and the CR750 bubble style seat I think, where it's rounded off and kicks up over the rear tire slightly.

Rick.

[Godffery]

I really like the shape of the tank but isn't that underside a bit oversized? It seems to be taking up allot of fuel volume unnecessarily?

[RickB]

Yeah you're right, I actually didn't notice that. I wonder what the capacity will be?

[Godffery]

Other than that issue, they seem to do quality work.

I checked out there web site and saw some absolutely beautiful cars; I'm guessing Motorcycle tanks are a new thing for them?

[RickB]

Hi,

So I'm back home with the bike and have been getting stuck into it. As I mentioned a year ago, my carbs got gummed up from what I suspect was a combination of POR15 tank lining not cured correctly and bad fuel.

So I took the opportunity to replace the rusty carb cam and 'axle' as I wasn't able to have those plated after hydroblasting the carbs. I suspect the rust on these parts was causing the engine casings and other close parts to oxidize quicker too. Anyway, here's me finishing the carb rebuild job I should have done correctly in the first place:



Old rusty parts that weren't plated after hydroblasting (as I couldn't remove the locking pin, see earlier lessons with extracting drill bit).





New and shiny.



Gummed up carb bowls. This grey gum was in the bowls. POR15?

Cleaned everything, replaced gaskets with Nitrile rubber gaskets I got from TTR Kevin I believe. Interestingly enough, these leaked after the bike was in storage for a year. A quick ride around the block and they settled in again.

So now that I have a 70's racer inspired seat, I had to come up with another way of mounting my indicators. So I had a friend mill me up some adapters to mount my indicators to the suspension mounts.



These are the original mounts.



This the new part. It's just the same as above but with an internal thread to screw onto the suspension mounts:



I drilled a hole for the wires to exit out the bottom, and mounted them up.













Next up was fitting tail lights to my frame rails.

Thanks to user greddm over in this thread, I was able to find some small dual intensity LED's that are apparently super bright (although I haven't tested them too well yet, they're essentially hidden under my seat...).

I found some 19mm chair leg stoppers at the hardware store, drilled out a hole, drilled a hole in the frame under the seat frame (out of the way/weather there I figure) and wired it up with my vintage connectors.











Now I've got poor front brake stopping that bleeding hasn't fixed (rebuild of the caliper?), a leaking fork seal and a muffler that looking more and more offensive to my eyes.

Game on!

Rick.

[calj737]

You may need to replace the brake lines themselves if they're original. The rubber deteriorates over time and allows air into the system. Also, the master cylinder may need rebuilding. The piston within it can also suffer from corrosion and not fully cycle.

A full rehab of the master, caliper and lines is a very good idea. Piston seal and possibly new piston, stainless brake lines are great upgrade, and rebuilt master cylinder. Should feel light years better-

Carbs look stunning!

[RickB]

calj737, thanks for the pointers.

The carb rack is indicative of the quality of the rest of this bike. I have braided stainless steel brake lines, rebuilt master cylinder and caliper with new piston and a speed bleeder installed. This was all rebuilt over the last couple years and is what I would consider 'as new' in terms of condition. Functionality is always moving target though!

The brakes worked a lot better before the bike was in storage for the year. I re-bleed the brakes (Speed Bleeder was worth every cent!) and that got the lever returning and piston retracting, but now the piston doesn't clamp down hard enough no matter how hard I pull on the lever. I mean it stops slowly, but it's not a two-finger hard braking. Any thoughts on what's causing that?

Rick.

[calj737]

It sounds like the piston seal inside the caliper is not allowing for proper movement of the piston. Was this also replaced when the brakes were rebuilt? Could be the return hole in the master cylinder is clogged up too, despite a recent rebuild.

And lastly, double check the caliper adjusting spring. Does the caliper move freely on the arm? There's a spindle in the arm that needs to allow the arm to swing with the piston motion.

[Cb400fnoel]

Any joy with the carb issue, did the clutch change help?

By the way the photos, information and tread are Brillant sources of information,

[Godffery]

 I can help with those brakes !   = }
http://www.vinmoto.org/gallery/v/VinMoto-Garage/album03/Godfferys-Garage-123/Parts+and+service/

[Leonardovans]

Really nice build thread, and nice work on those carbs.

i have two now, and I am going to rebuild one soon.

Can you tell me where to get Tims' rebuild tutorial please?

cheers

[RickB]

Hi everyone,

Long time, no posts sorry. I moved out of country for work and only get to work on my 1975 CB400F sparingly. A lot has changed on the bike, I will update this post with some details shortly. Before that, I need some help. I finally got my new exhaust setup on and I need some advice on tuning.



Setup: Other than #38 idle jets (stock is #40), everything else about this bikes breathing is stock. Airbox, carbs, stock jetting (#75), clip position, air mixture screw, needles, headers, coils, plugs. The carbs have been synced/balanced.

I have modified the outlet of the collector to fit a straight through Cone Engineering 'Max Performance' stainless steel muffler. There is no baffle. The muffler specs are:

Max Performance, 304 SS. Main cone 1.50"IDx3.50"x13.6". Reverse Cone 2"x2" long. 15.6" OAL. 2.00" SS wool wrapped Perf core.

The bike runs pretty good, however it feels like I'm losing a power at high RPM.

It doesn't appear to idle from cold nearly as well. Could this be because of my #38 idle jets?

Here's one plug (same plug, multiple angles) after an hour long ride. I pulled all the plugs, they appear exactly the same.











My question to you all is, do I need to adjust the main jets or needle position? Can I just adjust the air mixture screw? Perhaps someone here put a straight through muffler on their otherwise stock CB400F?

Should I just put a baffle in my straight through exhaust?

Admittedly I don't know the causality of changing a muffler on the fuel system.

Thanks in advance,
Rick.