Topic: things that annoy me on my CB400f

[kajtek]

everyone loves these little bikes and holds them in high regard, but i have some niggles that could develop in to bugbears, and given a rainy day too much bikexif could lead me to selling it, or mothballing it.

i really hope you guys can help me to resolve, or get used to these things as i really love my bike when it runs well.

1. jerky snatchy clutch

ive had the clutch apart, and carefully sanded the steel discs, and lighlty sanded the fibre plates to unglaze them, even got a new to me thrust bearing thingy incase my one had worn badly. worked ok for about 30 mins, then doing it again. doesnt do it when cold, once its warmed up though, gets bad pretty quickly. drives me crazy. my plan is new steel and fibre plates, pull my finger out and file the slight notches in the basket. will have the steel plates bead blasted before assembly. am i missing anything? im using 10w 40 bike specific semi from a uk motofactors (halfords).

2.runs worse when warm

obviously, all signs point to a rich condition, starts easily, and i have to come off full choke on to half in about 20 seconds or it bogs. after 20 mins riding, it feels more laboured, i have to blip the throttle before moving off so it doesnt bog, and coming on/off the throttle is awkward. feels 'laboured'. i expected it to run lean due to the marving exhaust fitted, but current signs point to rich. one exhaust started to blue so i tightened up all the intake rubbers and exhaust clamps. hard to know if it made a difference. current plan: make the carbs spotless. it seems this can be the only starting then work from there. i did not clean the emulsion when i first bought the bike (didnt know they existed..) so that may be a factor? then plug chops etc. also, my intake is standard, apart from a trimmed intake tube for the air filter housing (different seat blocked intake!).

3.jerky drive on/off throttle

this kind of ties in to the above points, but coming on/off the throttle is jerkier than i would like it. recently when the engine was apart to fix seized camchain adjuster, i replaced the 8 primary rubbers. didnt replace primary as bike is on 26k miles, the guides werent worn and it didnt appear worn (little sideways deflection). recent new chain and sprockets, no tight spots, set at 20mm lash.
i do a lot of town driving and on and off the throttle is quite annoying, as it takes up what seems like drive lash it clunks forward.
apart from the gearbox itself, could this be from worn dampers on the clutch basket? min have definately given up, as there is play between the gear and the basket. i did a search and have seen that 3 yrs ago someone was talking of a kit to fix this but nothing since, any ideas?

4.whining

oh my god, this drives me crazy between 3000-4000rpm in traffic. i can only guess its the primary to clutch basket gear causing the whining as it does it under load at standstill, but not if clutch pulled in. with the jerkyness and lash mentioned above, the noise coming in with every jerk makes me wish i rode a scooter. this site mentioned it being fixed (bottom of page) : http://www.cb400f.btinternet.co.uk/trans.htm
they mention replacing the whole assembly, do you think he means the basket aswell? any advice on the cause of the whine greatly appreciated. please note it becomes more apparent the hotter the bike gets.

so, theres a few points to work through, please reassure and advise me as much as you can before i give up and start driving to work..

ashley

[trueblue]

I was using a semi synthetic 15w/50 in my 650 and the clutch was up to sh!t, it was jerky and when I really wound on the power it slipped, I swapped to a 20w/50 mineral based oil and it cleared up and has been fine since.  I can't guarantee it will fix your issue but it fixed mine.  If your pipes are bluing it is running lean, what do your plugs look like, and it will probably pay to clean your emulsion tubes.

[Trevor from Warragul]

There's definitely something wrong with your bike because my 350/4 is an absolute dream/doddle to ride around town!

[sopo400f]

My 400 also wines like crazy and on/off throttle is also jerky.  Your not alone.

[kajtek]

I was using a semi synthetic 15w/50 in my 650 and the clutch was up to sh!t, it was jerky and when I really wound on the power it slipped, I swapped to a 20w/50 mineral based oil and it cleared up and has been fine since.  I can't guarantee it will fix your issue but it fixed mine.  If your pipes are bluing it is running lean, what do your plugs look like, and it will probably pay to clean your emulsion tubes.

Thanks for the input, will be changing oil in a few weeks so will try out a 20w-50 mineral. the fact that it becomes difficult when the engine is hot and the oil is thinner, makes me think that oil could be a factor. fingers crossed it helps! can i ask what brand you are using without starting an oil debate?

[kajtek]

My 400 also wines like crazy and on/off throttle is also jerky.  Your not alone.

will be sure to let you know if i can get it ride better. its so much smoother at speed but i cant ride everywhere at 50mph +!

i reckon a big thing with jerkiness could be fuelling. i think a richer condition just above idle makes the transition smoother (read that somewhere), i also want to experiment with different idle speeds. what i would love is to ride a perfect 400 4 so i could compare. if anyone has one in the south of england, let me know and you can have a go on mine to make yourself happier about yours...

[jessezm]

I was using a semi synthetic 15w/50 in my 650 and the clutch was up to sh!t, it was jerky and when I really wound on the power it slipped, I swapped to a 20w/50 mineral based oil and it cleared up and has been fine since.  I can't guarantee it will fix your issue but it fixed mine.  If your pipes are bluing it is running lean, what do your plugs look like, and it will probably pay to clean your emulsion tubes.

Thanks for the input, will be changing oil in a few weeks so will try out a 20w-50 mineral. the fact that it becomes difficult when the engine is hot and the oil is thinner, makes me think that oil could be a factor. fingers crossed it helps! can i ask what brand you are using without starting an oil debate?

I had the same issues with thinner oil and a hot bike.  After my engine mods I'm running a bit hotter, and I switched to 20w50 fully synthetic Mobil 1 or Valvoline 4t motorcycle oil, and the shifting is now totally smooth even after the bike is totally hot.

[camelman]

I hope you don't give the bike up. It should run better than you describe, and should be repairable.

Your jerky clutch is almost definitely due to the indents in the clutch basket. I've done that repair on every engine I've had apart now. I did a cb450 recently that was virtually undriveable. It had false neutrals, a vague and jerky clutch, and inconsistent clutch disengagent. It all went away when I filed BOTH sides of the clutch fingers smooth.

The carb clean must include tubes and idle circuit cleaning. You might find random washers and o-rings in the idle circuits from POs. Get them set up right and adjust your idle screws correctly and you'll be running much smoother.

The oil statements sound spot on to me.

Drive line jerkiness is often due to excess chain slack. If not, then it could be the rubber pads around the clutch basket to gear rivets. No solution for that other than getting one that is less worn or drilling out the rivets, making new rubber dampers and riveting it all back together. You can tell if those dampers are shot by the amount of slippage between the clutch basket and the gear.

Check your transmission gear bushings too. If they are worn, then they won't slide on the shafts easily. That will contribute to hard shifting. A machine shop can replace those for you easily enough.

I hope you get it running better.

Camelman

[camelman]

By the way, I've totally been there before.

[Lil Red]

My 400f suffers from none of those things. It did have a noisy chain after sitting in a garage for 25 years stored dry thank God...I put some motul 20-50 dino oil in it changed the plugs, set the points timing and fired it up. I finally took the chain off cleaned it with a brush and kerosene, put it in a fresh oil  and ATF bath (ATF because it's all I had lying around)...here lately I also synched the carbs which werent that far out of wack...and it runs like a dream 11k rpms in first and second now...oh new IRC tires 3.00f 3.50r....it's like God's little motorcycle...it starts clean at 40 degrees...a little fiddling for about 3 minutes....easy going for about 3 miles and then she just runs like it's fuel injected...The whine that you refer to may be misinterpreted by me as being mechancal music...all those little valves and fingers and gears and chain....WHIRRING is what I call it. Like a 35hp Bernina Sewing Machine with the flywheel chained to a rear wheel.

All the smells and sounds that transport you back to a time when analog mechanical sweetness had just about reached an apex...needing only electronic ignition to perfect it. When turning a screw could make something happen and Rube Goldberg machines (carbs) worked their magic, ( I still dont really understand how they work, only that if you do "this" and "THAT"...this may result)  all while producing distinct sounds...And that soft perfectly linear power delivery...the lack of real torque...that makes you feel that you are indeed the greatest rider EVER!!! (Wow...I handled the sand at that apex just like Rossi would have...contained all that power well....slid it just right.....when in reality there could have been no other outcome..BWAHAHAHAHA!!!)....and all because that wail...it makes you think it's a power house or something....and the size and weight...it's a four cylinder MOPED with a motorcyle frame...you just cant buy that kind of #$%*....I'm so sorry that you're finding so much trouble with yours...I really am...these bikes being so old now...I would guess they are pretty much individual and singular in their character...I suppose you could fix it up best you can and sell it...get another one and see what fate deals you....or you can double down and tear it down to nuts and bolts and piles, and rebuild the thing from atoms...it might work...it could also be that it just doesnt suit your personality...you may want to go to a CB750...some people just dont have the DNA to appeciate what many would call a limited narrowly focused (in todays context) wimp cycle...But if indeed you ride a good one and are possessed by it's qualities...then you will be rewarded with an experiance like no other...that actually no other bike is designed to give. This strange connection that it transmitts to me the minute I fire it up...I've owned all sorts of Honda products, mowers, bikes, cars...This is the only one where I can actually feel Soichiro Honda's smile go thru me...the small bore high winding complex four stroke...the "WAIL"....whaaaaaaAAAHHHH! WhaaaaaaAAAHHH!...each broken by that snick that I can almost accomplish by flexing my big toe knuckle...makes my Guzzi seem like a trash truck by comparison...listen to like the rc166 or 161's on you tube...to many it's just boring...but to me it's just endless pleasure...takes on a Zen quality...where it becomes like som monastic chant...Sounds crazy I know...I just hope that for your sake...you find it...Call me lucky...or just strange...I'm just thankfull I did. I guess it helps to be a Romantic...not sure the thing can turn you into one though...especially if it's not running right.

Mine the first ride after I changed oil and plugs and set the timing...hadnt adjuste shifter or ANYTHING really...now I have an emgo pipe wich took some of the snortiness out of it...sadly ...

5 - 1975 CB400F Barn Find

400 Four with Emgo muffler

[kajtek]

Jesseszm, 20w-50 going in for sure, not much choice in uk though! Prob have to order online..

Canelman, thanks for the advice, I nearly did the clutch indents when it was apart, I just have very little time due to young kids, so put it back together hoping for the best... Which I didn't get! It's definitely coming apart, will stay up one night with some good coffee and get it done.

I need to get some carb o ring kits if they exist? Honda kit is kind of pricey per carb...

I think it was ttr400 that mentioned a clutch basket rebuild kit? I'm thinking I will look for a better one though, maybe one that doesn't need filing so much, could help the whining noise as well.

Lil red, that is without a doubt the most inspiring reply I have ever read, thank you, I'm gonna stick with my bike and make him work. It just feels like I never got him right from the start, I owe it to him to make him the best he can be! The videos were brilliant, that first one, i just put headphones in and closed my eyes and listened to the wail, perfection.
Your bike seems to be everything I want from mine, I feel invigorated to know it can be like that! Something definitely up with mine, it just feels like its fighting itself, like it's not in sync with itself. I will try record using my iPhone on a ride 2mrw. But for now I'm gonna go outside and get a photo of him so u guys can see who we're talking about.

[camelman]

Get the kit from TTR. It'll be better than anything else you can find.

TTR400, I wanna buy three of those kits!

[kajtek]

Damn, IPhone won't let me upload pic, just imagine a yellow 400 with a homemade seat and clip ons...

[kajtek]

[trueblue]

I was using a semi synthetic 15w/50 in my 650 and the clutch was up to sh!t, it was jerky and when I really wound on the power it slipped, I swapped to a 20w/50 mineral based oil and it cleared up and has been fine since.  I can't guarantee it will fix your issue but it fixed mine.  If your pipes are bluing it is running lean, what do your plugs look like, and it will probably pay to clean your emulsion tubes.

Thanks for the input, will be changing oil in a few weeks so will try out a 20w-50 mineral. the fact that it becomes difficult when the engine is hot and the oil is thinner, makes me think that oil could be a factor. fingers crossed it helps! can i ask what brand you are using without starting an oil debate?

I use synforce oil, it is a local oil company here, I use their oils at work and they make a decent product, but it doesn't matter what type you use as long as it is a mineral based 20w50 motorcycle blend.  You can pretty much guarantee that any oil you buy today would be at least as good if not better than what the bike was built to use.

[Really?]

The only thing that annoys be about the 400F is that I do not have the one that I had when I was 14/15.  Rode the P out of it.  It ran well and smooth.  It ran better when I put a valve through the piston and fixed it myself.  Heck, it ran surprisingly well with a hole in the piston.  The smoke screen was awesome! This was back in '78/'79 so it was fairly new.

[Stev-o]

That annoys me too...that I don't have  one.

[kajtek]

found the thread where ttr400 mentions replacement dampers:

http://forums.sohc4.net/index.php?topic=50127.0

gonna shoot him an email as his website doesnt show them, and that thread is 3 years old so may never have gone in to production. fingers crossed!

so this is my current punchlist:

1. change oil to 20w-50, gonna try mineral first, CASTROL ACT EVO 4T 20W-50.

2. clean carbs! really really clean, off the rack every little orifice, rebuild with new o rings. just need to source the correct sizes from somewhere in the uk. bench sync, install.

3. check all intake rubbers for cracks/leaks. new exhaust gaskets (just in case).

4. clutch basket out and file notches. possibly get seconhand one and file that if dampers are better. replace dampers if possible. im gonna put new fibre and steel plates in also just to be sure. bead blast steel plates. new clutch cable (might aswell to be sure).

i think i might go for electronic ignition too, my points are nearly out of adjustment, and to buy the hond points, possibly codensers, might aswell just go electro. the 2 im looking at are the pamco and one i found called accent something or other. any experience on a 400 with these?

ashley

[trueblue]

Something else I only just thought of, worn cush drive rubbers will cause a jerky driveline.

[kajtek]

Good call but just replaced those, and oh my god that was the hardest job I've ever done on a bike. 3 evenings of swearing, cuts, and broken tools. Never again!

[Lil Red]

Hey, thats a nice bike in the pic....hope you get it sorted out.

As far as h
The ignition...have a loo here
http://forums.sohc4.net/index.php?topic=67543.0

This ignition requires the least energy to run on the already barely adequate charging system.  And it allows for a rehook up the points on the very rare occasion it should fail. (I dont think there's been a single report of a failure?)

You may want to also get a trickle charger to keep the battery up...i do remember a notable difference in running on a flat battery.  In the mean time you may very well want to get the timing rock ssolid, with timing light and the gap right on. you can file down the points and regap them. the bikes are really sensitive to off timing.

Oh and i forgot to mention what I think might be the greatest attraction of the 400...you can use all of its power most of the time...and not get into too much trouble...and all the sounds point to 1980's Z1R...but you look down and you're only doing 50mph....

Best of luck with it. youre at the right place here...stick with it and you'll get it running great for sure.

[grcamna2]

+1 on the HondaMan electronic ignition ! 

[Teatimetim]

Yes I'm quite annoyed I don't have one.

[camelman]

Man, I wish I'd had this much support to keep me from making every bad decision i've made in the past.

FYI, these bikes can handle the dyna S ignition without trouble. The 3 ohm coils might be a little difficult for the charging system to keep up with, but the ignition unit itself will not overly tax it.

Camelman

[Lil Red]

Yeah the Dyna Systems work well, and are self contained...i would think you could find availability in the U.K...The thread I linked has all the discussion on it...the Honda man works with the points acting as a trigger only, the points will no longer arc so they'll last pretty much in definitely...the Dyna just trashes the points and condensers altogether and provides a new assy with light contacts triggering the spark? i have a dyna on my Guzzi and it worked fine for years.

The hondaman ignition is small and light so the post to UK should not be ridiculous.

Both provide better spark and allow for set once and forget it timing, which s pretty nice