Topic: 1975 Honda CB400 Four Project - Rookie

[Godffery]

You can slide your fork tubes up threw the triple tree clamps enough to relocate your clip-ons above the top clamp. this will give you the room you need for the proper master angle.

BTW; raising the fork tubes will also decrease the bikes rake, witch will increase steering response. 

[dmcgrego]

Rick,

Have you had any luck getting rid of your flat spot right off of idle? I lowered my floats to 23mm and it helped it a little more, but even with 38#s and the lowered floats it still has a little flat spot and doesn't want to rev quickly when you blip the throttle for downshifts. It's great for the first few miles and then when it warms up it starts to stumble a little. I tried jetsrus.com and they don't have anything smaller than 38's so I'm running out of ideas.

Darrel

[RickB]

Darrel,

Good to hear from you. You know what, I haven't had a chance to drop my float height yet. I'm in a different country to my bike at the moment. It's the first thing on my list when I return home in August.

I'm disheartened to hear you haven't had much improvement, I am putting a lot of eggs in this basket! My only advice would be to actually verify your float heights with an external measuring tube. Like the one described here.

I'm going to make one with a plastic nipple from the hardware store and some tubing. What's the thread/pitch of the carb drain screw for the Cb400F though? I suppose it wouldn't have to be dead-on as the plastic would just re-thread itself anyway. I'm going to make up for and actually check what my levels are externally. Only way to be sure.

Rick.

[dmcgrego]

My next effort is going to be to run some thin wire through all of the passages. I've blown compressed air through all of them and carb cleaner and they seem clean and clear of debris, but it sure seems like something is blocking an air passage. Or extra gas is making it's way into the carb. throat, maybe past the o-rings on the high speed jet? I don't hold much hope for that, because the o-ring seal seems pretty tight. If anyone has beaten this problem I sure would like to hear what they had to do to fix it.

The bike is so awesome to ride when it hasn't fully warmed up, I just want the same thing when it's up to operating temperature!

I'll let you know if I make any progress.

Darrel

[RickB]

Darrel,

It sounds like you've got a better handle on the workings of a carburetor than I do, which is an encouraging sign for me because I'm kind of in the dark for the most part.

I fully rebuilt my carbs. Had them professionally hydroblasted, used all new OEM needles, jets, emulsion tubes and Keyster gaskets. Re-plated all my hardware too. I'm confident I don't have anything blocking an air passage. I'm told my aftermarket pea-shooter exhaust is the reason I have lag, but I don't fully accept that.

Your last sentence, "The bike is so awesome to ride when it hasn't fully warmed up, I just want the same thing when it's up to operating temperature!" is exactly how I feel!

Keep me updated with your progress for sure.

Rick.

P.S. I don't know if this is just more red herring's but I found this thread with a guy describing a similar problem. Nothing I hadn't tried but maybe you'll get something out of it.

[Doctorlumen]

Darrel and Rick,

I've chimed in on this topic from time to time, as it is the only problem left affecting the ride quality of my 400. I have also heard that a free flowing exhaust with very little back-pressure causes this problem...but I'm really not convinced.

Lately, I've been wondering if it has to do with timing. Has anyone ever heard of a "floating" timing at or above optimal running temp? When I checked my timing yesterday, it wavered quite a bit between the marks. Never advancing or retarding past them, just kinda bouncing from one to the other, while the idle bopped about with it. Held steady while cold, but once the bike warmed up it started wavering. Really not sure what to make of this, but do you guys' bikes act this way?

[RickB]

When I saw your user name, I was hoping you'd found a solution because I know you've got the same problem!

I agree with your comments on the exhaust, I can't believe a replica Norton Commando muffler would reduce performance so much.

I'm not too up on timing issues. I have a DYNA S ignition with the 3ohm coils, so I doubt timing can 'float' as you suggest on a completely digital system. Right? I wonder if the heat affects that in anyway?

Interesting.

[dmcgrego]

I have been too busy to do much wrenching or riding, but I adjusted the air mixture screws,  again the other days and I wasn't able to make any improvements. The adjusting of the air screws seems to have only a small effect over quite a large adjustment range.

I sure wish one of you guys would figure this out!

[Rob69]

Great documentation, Rick. I wish I would have documented more of my CB350F restoration project. The bike looks great. My brother has a CB400F that he's not doing anything with. I think I'm gonna see if he's willing to part with it.

[Doctorlumen]

Hey Rick! I think I made a breakthrough with the "bog" and it has nothing to do with the carbs. New clutch plates and springs.
Don't know if you (or Darrel) replaced your clutches when you rebuilt your engines, but I just swapped my old stockers for new, and the bike feels BRAND NEW! Take-off is instant, warm or otherwise. Idle is super clean and steady. The "float" I described in the timing is gone.

With all the times I've replaced my Ducati clutches, and been amazed by the the bike coming to life, you'd think I would have figured this out earlier.

Anyway, if you haven't swapped out your springs at least, maybe give it a try and report back. Not saying my carburation is perfect, but a lot of my woes went away with new clutch bits. Gonna pop her up on the Dyno soon to find out for sure.

[swan]

RickB,
I just read all 21 pages, wow, what a ride! I am humbled you were inspired by my one of CB400f's and I believe you have easily surpassed my efforts. Great Bike, documentation, images and moreover the patience to do it right. You have a bike for life and know every nut, bolt and part of it because you did it yourself. Be proud and ride the wheels off it!

[RickB]

Rob and Swan, thanks for the kind words. I've found the SOHC4.net forums to be the most invaluable tool for rebuild my little Honda. Couldn't have done it without all the people here.

Doctorlumen: This is very exciting. No, I didn't replace my clutch. That's actually one of the only things I haven't looked at or considered. When my mechanic took the clutch out, he said they looked fine and just needed a little sanding. However for the cost of new plates, it's worth a shot! Thanks for the great advice. Now I just have to wait another 6 months until I'm back in the same country as my bike.

[RickB]

I know it's been a while between updates but I only got to ride the bike for a day when I was back in Australia recently. It was terrible weather most of the week I was back.

I had to re-bleed my brakes which is such a pain in the neck (especially because I mistakenly thought a speed bleeder would help with a fresh new line. It doesn't.) and I changed out brake pads on the front and back for something I hope stops the bike better.

The front pads I swapped because I thought the DSS sourced pads I had on it where wearing my disc unevenly and quickly. So I went with some EBC organics. The pads on the drum I swapped for some grooved EBC organics to see if they are more responsive. However I suspect it's my MC Again rearsets that aren't allowing me to put enough pressure on the pedal.

I wasn't able to change out my head gasket to stop the leak or get my carb float level issues looked into. The float level thing was hard, I tried everything to get tubing to seal into the overflow screws but nothing would stop the fuel leaking out. You really need the proper screws to do it.





Just jamming the tubing in didn't work. The fuel just leaks down the thread.





I picked up a CB500T tank because I liked it on another forum members CB350F. I like the shape, even if it is a little 'peanuty' at the rear. Regardless, it'll take some serious panel beating to get the stock coils to fit (I don't want to move the coils so panel beating is my only option. The tank is the last thing I need to worry about, I just thought I'd try it if it were easy.















So I bought some 'GP Style' levers from Dime City Cycle to replace the fake chrome ones I bought on eBay a long time ago. DCC said these were a matching pair but when they arrived, they are clearly not matching.

They're from Emgo and when I queried DCC about it, they were nice and said I could return them but it was very difficult to find exact matches for levers and these might be the best I'll be able to do.

I do like that they're solid alloy and not a cheap fake chrome and I figure with them at each end of a handle bar, I doubt anyone will notice they're slightly different shapes. Have anyone got GP style leavers that are exact matches that are solid cast or are DCC correct in that this is the best I can do?





I got these from DCC too (well actually I had to find longer Dzus fasteners from Kurvey Girl). The flat bit of alloy is the seat pan that attaches to the base of my fiberglass seat. Finally I don't have to screw around with nuts and bolts in the cramped space beneath my seat. These are just a quarter turn and they click in. Great!

Ok, merch news!

For a mates birthday, I made up some tool wraps. Well I bought a tool wrap from Duluth Trading and had a leather stamp made with the 'gangs' emblem that I punched some initials into and had sewn onto the wrap.





These guys made me the leather stamp and stamped it into some scrap leather. All for $110. I was pretty impressed by that actually, I thought it'd be way more.



The tool wrap from Duluth Trading plus an Explorer Swiss Army Knife with 'survival' lanyard that I knotted up myself (watched some YouTube tutorials on how to do it).





I bought a letter punch set from Tandy Leather so I could do my mates initials. The trick is to heat, then dampen the leather a bit and give it one good whack.





Came out pretty good I reckon. I screwed up the RV one by making the letters a bit too far apart so I filled in the spaces with a dot. Then I discovered Deus already make a tool wrap and it's way better than the Duluth one. Not to worry, mine are personalized.

So that's it for now. I have bike stuff happening, but nothing I have any photos or meaningful information on right now. I really can't wait to get stuck into the gasket, carb and clutch issues we've all been talking about above but that'll have to wait until I'm back in the same country as the bike.

Rick.

[knowsnothing]

Nice work Rick.  I would be pumped if my buddy gave me that for a present.

[RickB]

Hi all,

Long time between posts, but I'd been in a different country than the bike for a while. I've been home for the summer and have been on a few rides, it's been fantastic.

Now that I've got that out of my system, I'm going to fix some nagging issues. Namely that dreaded head gasket leak.

This engine has 1600 miles on it since a total rebuild.

Jessem, you were right, it appears to be those oil valves and the head gasket.



I'm following the manual to the letter. Carbs off, exhaust off, coils off for better access.



Got the cam shaft out. The sprocket is off the shaft here, don't go thinking I have some special way of removing the shaft with the sprocket on.







You can clearly see where the oil is coming from. The outside oil valves and front corner studs. It's getting pushed behind the head by the wind and baking on.













You can see some of the sealant from the pillar nuts and rubber/copper washers I replaced earlier fell into #2 cylinder. Those studs are bone dry so I'm confident the leak is from the inferior NE Brand gasket kit.







I didn't check if these wear marks were on the cam and valve cover, they may be from the old cam. I'll have to check.











The valves. When I showed these to Matt my mechanic, he thought the amount of carbon build up and what appears to be oil on the valves might suggest a slight valve seal leak.

From memory the valves seals we used in the rebuild came in the NE Brand kit. Which if everything else in that kit is an indicator, is crap.





The OEM Honda oil valve gasket is on the left, the kit gasket on the right. The kit gasket was rock hard and felt more like nylon than rubber.



Hard to see but the difference in the OEM Honda head gasket on the bottom vs the NE Brand kit gasket on the top. Way more meat on the Honda one.









Whilst I had the head off, I thought I should replace the exhaust studs as they were looking a bit rusty. I used the double nut technique and of course the last of the eight snapped off!

So I have the head with Woody from Hydro Blast (the guy that made all my aluminum look so nice). He's going to remove the broken stud and repair the threaded screw near the cam shaft that I striped last time.



And finally. The #4 header has a good bit of rust going now. It's too far gone for polishing, what do I do? These pipes are double-walled right? So it's probably rusting from the inside. Can I paint this somehow? I don't even think re-chroming it would work, right?

I've got some other things to work on, including a Yamaha r1 throttle tube swap, shorten my cables and replace the clutch plates.

Rick.

[gjunkie]

Hi Rick,

Very nice work. Thanks for this update. I'm currently dealing with a similar leak and have been trying to figure out what the exact culprit is... the gasket or the orifice valves. The gasket we took out looked brand new, so we think it's the valves.

Let us know if this fixes the leak!

[MoMo]

Rick,  too bad-2 rebuilds in 1600 miles is a pain.  The quality of that gasket kit is totally inferior, especially  the alignment of the hole around the oil passage-looks as though the gasket is touching the o-ring.  I have used Vesrah kits without a problem and of course Honda gasket sets too...Larry

[malcolmgb]

Take the pipes to a plater and get his opinion, from my dealings with them they would re-chome but possibly not to concours standard though.

[RickB]

@ gjunkie: Yeah I've been told by more than a few gurus here that those NE Brand gaskets are the main culprit, so I'd be suspect on anything from those cheapo kits.

@ Larry: It's quite obvious when you see those NE Brand gaskets next to OEM Honda stuff. I can't believe DSS even sells those things given the amount of issues people have with them. I'm losing sleep just thinking about all the o-rings from that kit that are failing in my fresh engine.

@ malcolmgb: I actually hadn't thought of taking it to the plater and seeing what he says. I've got to get some bits and pieces from a replacement carb rack plated so I'll take it to him then and see what the damage will be.

[gjunkie]

@RickB - I put in an order for OEM oil orifice valve gaskets and an OEM head gasket as well.. I hope this solves my leak issue... If THIS doesn't do it, I'm afraid the block could be warped or damaged. The oil orifice valve gaskets that are in my bike now look like the small one in your picture. CULPRITS!!!

Do you set the timing yourself? If so, kudos. I'm more than comfortable taking it apart and replacing these parts. But setting the valve timing seems like something you wanna get perfect. Which means that once I put it back together, I'll have to take it to a local shop to do it for me... Unless you can give me some words of wisdom?

Thanks.

[RickB]

gjunkie,

Sounds to me like you've got a very similar problem to me. I'm confident the OEM gasket and seal replacement will solve the leak.

As for valve timing, I don't believe I've made it to that point yet. What's involved with it? I've set the tappet height before, I have a Dyna S electronic ignition. All I'm assuming I have to do is put the cam shaft back in correctly, set valve heights and I'm good to go.

[gjunkie]

RickB:

As far as I know, yes, that's all that's involved. However, let me tell you what I did. I took it apart a month ago to fix this leak, but my replacement orifice gaskets were identical to what I took out... hence not fixing anything. We put the Cam back on, but couldn't really tell if what the book was telling us was correct (turn the sprocket to a certain line, etc). So we took it to a shop, low and behold, the book had it wrong or at least it was misleading/confusing. I think in concept it sounds simple, but in my opinion it's one of the few things I would like a pro to do for me (or at least check my work) until I learn how to do it myself.

Today I ordered an OEM head gasket and orifice gasket. Which means I'll be taking this apart again within the next couple of weeks. I'm toying with the idea of timing it myself this time, but a local shop, Yoshi's Garage, is offering to do it in under an hour for $75USD. It's a shop I trust very much. Kinda hard to beat... only draw back, I have to actually get it there first which means renting a UHAUL and finding a friend with a car that has a tow...

I'm not trying to discourage you at all. I'm just personally afraid of damaging the valves.

[RickB]

gjunkie,

Yeah I'm a little hesitant to put that cam shaft back in but I have both the Clymer and Haynes manuals, plus a tonne of photos of things before I took it apart, I think I'll be alright.

If you read back through the last couple of pages of this thread, you'll see I had one of my tappet screws almost come off after over revving the engine on a bad shift change. It damaged the underside of the tappet cover it was that close to coming off. It was making a terrible noise on the ride home.

After that I got pretty familiar with valve heights. I made a tool out of a square decking screw that makes the job so much easier. For this job I bought a set of valve height adjusting tools so I'm expecting it to go quite smoothly. Regardless, getting that thin feeler gauge in there is still a pain in the ass.

I'll keep you posted.

Rick.

[gjunkie]

RickB,

Wow! That sounds bad. Well at least it sounds like you will be pretty set to do it yourself. I need to get myself a set of feeler gauges.

Let me know how it goes.

- Freddie

[malcolmgb]

I made a tool out of a square decking screw that makes the job so much easier.

Can you give me details of how you did this tool and the parts required please Rick.