1980 cb400n excessive vibes :(

[fimpBIKES]

Hi all,

annie bought a really cool lil honda cb400 a bloke spent HEAPS on restoring

its sweet, goes great for a 400cc old school bike
but man does it vibrate!!!

i adjusted the tensioner for the balancer chain
but that hasnt really fixed it

anyone played around with one of these before and have any hints as to what i should check out next?
its pretty annoying to ride more than 10minutes or so, or over 60kph



oh and before you ask, YEP
we already have installed some awesome drop-down cafe-racer bars and old-school grips [8D]

[Redmohawk]

Tryed putting some lead weight inside the bars? Changes tuning of bars to a lower frequency may make it a little more plesant for her.

Is motor rubber mounted ? Might be another option, if someone has been poking around down there make sure they havent put in a solid mount somewhere.

[Hagarr]

Balancer mistimed??

[xa-mont]

Isn't that called character?

[Hillsy]

quote:Originally posted by Hagarr

Balancer mistimed??


+1

Also, some of these older small bikes need the engine mounts torqued to spec. Might want to check that.

[fimpBIKES]

http://img.photobucket.com/albums/v676/fimpbikes/cb400balancer.jpg

[fimpBIKES]

this is the balancer assembly,
i pulled the RHS cover off the engine and found that slot in item 13 was all the way down
so i took off the two nuts (15&14) and reset the position of 13 as per the manual

there is a little dot punched into the end of shaft 4 to tell you if item 13 has been reset too many times and if so you need to replace the balancer chain (9)
you need to replace if that dot is below horizontal, ours was only at about the "1 o'clock" position so thats cool

was hoping this would fix it but there is still heaps

i know "character" but this is a definitely more than that, it stuffs your knuckles and its not normal
we had the old bars stuffed with sinkers (5 or 6 taped together than forced in there) but it didnt really help
im trying to find some proper barends that are steel to go into hollow bars but they seem to be non-existant these days

anyone know where to score some?

will check over the engine mount torques, the bloke we bought it off seems to have been a bit of a numpty
no loctite on anything and a big tear in the rhs cover gasket when we got it

good thing i have lots of experience on oily back tyres LOL

thanks for your help blokes, the bikes gorgeous and its killing us not to be able to use it

[Benz]

I've got a pair of Geep turbo steel bar ends that would probably do the job. Yours for the postage Fimp.

[xa-mont]

http://cgi.ebay.com.au/HONDA-CBR900-CBR600-CB600-F-F4-F3-F2-Black-CNC-BAR-END-/300501847908?pt=AU_Motorcycle_Parts_Accessories&hash=item45f74e4f64#ht_3825wt_907

[Jockney Rebel]

take the bloody balancer out ,,i know a guy who used to courier with us and did the very smae thing got rid of the balancer and gave the bike better power

[Swordsy]

I blame the mechanic! [:P]

[Hagarr]

quote: this is the balancer assembly,
i pulled the RHS cover off the engine and found that slot in item 13 was all the way down
so i took off the two nuts (15&14) and reset the position of 13 as per the manual

there is a little dot punched into the end of shaft 4 to tell you if item 13 has been reset too many times and if so you need to replace the balancer chain (9)
you need to replace if that dot is below horizontal, ours was only at about the "1 o'clock" position so thats cool

was hoping this would fix it but there is still heaps

i know "character" but this is a definitely more than that, it stuffs your knuckles and its not normal
we had the old bars stuffed with sinkers (5 or 6 taped together than forced in there) but it didnt really help
im trying to find some proper barends that are steel to go into hollow bars but they seem to be non-existant these days

anyone know where to score some?

will check over the engine mount torques, the bloke we bought it off seems to have been a bit of a numpty
no loctite on anything and a big tear in the rhs cover gasket when we got it

good thing i have lots of experience on oily back tyres LOL

thanks for your help blokes, the bikes gorgeous and its killing us not to be able to use it

OK point taken, BUT how does item 4 locate with item 5, looks hard to work out with that diagram but if this is able to be fitted 180 degrees out it will vibrate like fuck, don't forget four stroke cycle you can still be out even though it may appear to line up!

You still need to time the balance shaft so the balance shaft weight/s are opposing the crank forces.

Go back to basics and physically check don't rely on old marks or dots, people may well have fucked with this and not really understood what they were doing.

Late model Jap stuff is impossible to get wrong but I would still go back and physically check balance weight is opposing to crank forces

early Jap stuff you could actually get wrong!!

Not sure of the early Jap twins but I believe they are like an Old Norton or Triumph where you have two of the pistons at TDC together, this gives you huge vibes, to try and sort this they drove the balancer to oppose those forces by timing it to be opposite when the pistons where at their extreme to try and smooth this out.

Similar to a flat plane V8 crank, they make heaps more power but don't smooth out until they really start to rev.

[fimpBIKES]

good point hagarr

the engine mounts all seem good, they dont seem to be rubber mounted
but checking on the net i think thats normal

anyway, i'll take off that other cover and check it out like hagarr said

should i look at balancing carbs, timing or anything like that (or all of the above LOL)

[Jockney Rebel]

http://www.kiwibiker.co.nz/forums/showthread.php/83335-Balancer-chain-adjustment.
try this conrad may shed some light on it

[fimpBIKES]

cheers jim, those are the step i did as per manual

need to check out the other side where the chain is i think

[fimpBIKES]

Ok, we found the issue
Balancers are both installed 180deg out LOL

[Jockney Rebel]

thatll do it ...id investigate removing it ..i kinow it can be done just never doen it myself

[The Mad One]

They`re not called 'bumble beez' for nuth`n :D

[Hagarr]

(In best Smithers accent) ....... eeeeexcellent!

[ALBI]

anne will hate you now !! she enjoyed riding it

ahhhhhhh yep take em out !

[fimpBIKES]

ok, next hurdle is that we stuffed the stator getting it out
not to worry i thought, probably wanted to replace it anyways since its soo hard the get to (inside out compared every other bike i've played with)

trying to find one on the net, strugglin...

[fimpBIKES]

perhaps, shall look into it

did a findapart search, nothing yet but hopefully some come back
might send some photos to re-winding places and see if its salvagable...

[fimpBIKES]

got it sorted
just need to chuck the exhaust on and get some rego renewed now :)

http://youtu.be/rj3runctqBw

[ALBI]

way to go anne !soon you'll be riding and wanting more!

[Swordsy]

it only took 9 months! thats a new record for you isn't it? :p

[fimpBIKES]

its not bad for me :)
ive fucked up the shifter somehow though, the lever isnt returning after the shift

will whip the side cover off when the weather settles

took it for a spin though, the little fucker feels like it has a 90degree head angle :S

[Cruisecontrol]

Was this a difficult fix, Conrad?
My CD250 blurs my vision the vibes are that bad, and that is just sitting in the driveway (still not rideable yet).
I didn't notice any real vibration riding it stock but now with a whole lot of bits removed it is buzzing like the proverbial.

[fimpBIKES]

wasnt too hard once i knew what i was doing

had to get a chainbreaker small enough to do the little chain
took me a while to get brave enough to really force the crankcase apart (had a few beers one night and hung it upside-down off a rafter while smashing it with a mallet)
oh and i didnt use a proper tool to hold the flywheel while undoing the crank nut, so stuffed the stator (which turned out to be rare as fuck...)

there is a certain amount of adjustment you can do from under the cap in the RH engine case, might get you out of trouble
(assuming your bike is similar)

i get into trouble up here in newy cos if you get halfway through something like this none of the local mechanics want to give you a hand or touch it
for instance when i had the cases apart i could see the balancers were wrong, called a few mechanics about getting them to break the chain and put them right then reconnect chain
they either had no fucking idea what i was on about or wouldnt help once they found out how old the bike was (a lot of shops up here wont bother with 10year old + bikes, presumably cos they are lazy cunts)

but i would say YES go for it
if you need a special tool etc im sure someone in sydney will step in and help out