Hello All..new to the forum and new to bikes..400 4 Carbs overflowing..

[vivvov]

Hello Everyone.
I was sitting in a room when a friend of a friend offered up his 400 4 that had been standing for a while (10 years in a garage).  Only ever had a Honda 70 (and that went walk abouts quite quickly..left the night the Fair left town) so I was happy with my 400 4.  Trailered it to work and garaged it some more, did my test, then took the bike to the MOT..limped it to the garage with half of south London sounding it's horn behind me...it passed  but ran terrible..no power on acceleration.  Limped it to a friends drive.  Looked at it a lot.  Then looked at it some more. 
Then took the Carbs out and checked/cleaned the jets and etc..they seemed clean.  Then a friend who used to ride a 400 4 said it wont be the jets..it'll be HT leads or timing or something..but not the carbs. 
Put the Carbs back. Looked at it more. Left it some more.
Last week I put a new battery on it and it started first time..but now petrol flows out of all four carb overflows. I'm sure it didn't used to do that(..guessing the MOT might have highlighted it!).  Guessing some idiot must have messed something up when I (said idiot) took the carbs out first time round.
So I took the carbs out again and put it on a bench.  Checked the floats, checked the float valves and needles. With the float chambers taken off, each float valve and needle cuts of the fuel when finger pressure is applied...and the floats are adjusted to the right cut off depth (22 mm).  No leaks!
However when the leaf spring is added and the float chambers are back on, Turn the fuel on and the chambers fill and all 4 overflows soon start to run nonestop. Plus leave it on and the fuel level raises faster than the overflow can cope with and it comes up through the jets and throttle slide.
I thought maybe I've somehow mixed up the float valves and needles and the wear and tear means that fuel is sneaking in..so I carefully blocked 3 float valves and rotated all 4 float needles in the remaining valve. No luck.  With the chamber back on the one carb (and the other three float valves blocked up), none of the needles did the job of stopping the overflow..the overflow happened with all 4 needles.
Now I could just order some new float valves and needles from DS but the fact that the fuel cuts off when the floats are gently pushed up (with the float chambers  off) suggests to a dimbo like me, that valve and needles are not the problem.
Anybody got the idea what's happening here and how to correct it?
(Once it's corrected I can then start on why it's running so poor).
Vivvov

[K2-K6]

Hi and welcome to the forum.

You seem to have been quite thorough in working at any causes. It's possible that the floats are touching something inside the float chambers, are the floats all the same or are they handed to fit different carbs? if there is a difference it may be very small.

Agree that if valves will shut off fuel with light pressure then they should work ok.

If you turn the carbs upside down and blow through the supply you should be able to hear / feel if they are different with float bowls on or off.

[rigwit]

if you are manualy putting pressure on float needle shut of valve  could be 1 of 2 things   there is a phenomenon with petrol over time that there is a fine muck susspended in it  (comes from filling station tanks)  this builds up around the inside of the needle seat  hard pressure is enough to overcome it  but light pressure from floats isnt---------  other thing is if your floats are of the ,"hollow" type and not the solid  you could have inavertantly punctured them one way is to take them off and shake by your ear  if puntured youl hear petrol swishing about , or get some hand hot water and submege each float in turn and see if any constant bubbeling  is there  if so  new floats needed if  fine crud you can take out each needle valve seat  and clean it with a q tip dipped with fuel...................  ive had this before on my old 400-4  and was a recuring nightmare untill i cleaned out tank with some ball bearings. good luck  and welcome to the site  keep us up to date how it goes  .............

[vivvov]

Going to do all of it. 
The floats seem ok..given them a shake etc already.
Valves and needles.  Reckon you might be right about finger v float pressure. Read somewhere that it's an idea to carefully q tip the valves with chrome polish so as to "re fit" the valves and needles (the ones fitted are all metal..not metal and rubber that DS seem to stock). 
I'll try it all and be back if I'm stumped.
Thanks..
Vivvov

[marineboy]

Hi & hello.
Thought i might as well add my experience of Honda`s little 400/4.
I picked up the bike some 100 milefrom where I live, the previous owner said he would show me the way to the nearest A road, well like you the bike wouldnt rev over 4000 revs, we pulled over at the side of the road & messed about with it a bit, I said I would continue as it would be ok revving to 4000 revs as that gave me about 45mph which would be ok or so I thought...... 3 mile later and the first hill see me down to 20mph, I pulled over to the side of the road & again like you petrol poured out of no 1 carb. I tried running the bike with the fuel off until starvation (the bike, not me) nope, that didnt work, I tried emptying the float bowl and nope that didnt work, anyway the previous seller had been following me and he stopped, we went back to his house, whipped off the carbs & blew through the offending cartb, all seemed well, I went on my way & made it home,but, once home with the engine running the same fault happened.
I ordered a repair kit from DS and a mate changed over all the necessary bits, we put the carbs back on and hey presto.... the carb we had repaired was leak free, but the other 3 leaked like a sieve!!!!!!  mmmm bugger, I then with my mate looked at carb no 2, the small o-ring seal that sits on the float valve had perished badly, we stopped there,,,, I ordered 3 more kits from DS & about a week ago we changed the other seals,jets etc etc & done the float heights. Still the carbs initially leaked when we returned them to the bike.....

I read somewhere that bikes that have been standing do tend to suffer from this problem & that riding them regularly can often solve the problems encountered, I went for a 10 mile thrashing of the old girl down some country lanes & kept on running the system dry by use of the petrol tap & so far...touch wood, things have improved & no leaks.

I am a great believer that modern day petrol is very,very bad for bikes that dont go anywhere & even by emptying the tank & draining the float bowls of fuel the sticky gooey mess residue left behind gums everything up in its path .Obviously the float idea works on the same principle as a toilet ball valve idea. If your ball valve in the toilet wont shut off under working conditions, it always seems to shut off once a big hand is helping it stay shut! I think float bowls are no different.
 I have tried ultrasonic cleaning on another bike I have, but, I wouldnt say from that experience that there was a dramatic transformation in the behaviour of the bike.
Good luck with your leaky carbs, I know how you feel especially at the cost of petrol too!!!
Regards

[colin400four]

A Warm Welcome.

COLIN.

[colin400four]

I notice that in the Haynes workshop manual it states the height of the floats should be 22mm, yet the Honda Factory Manual states 21mm. I have read on a number of occasions that this measurement is critical ?

Colin.

[dave400]

Welcome from up north 

[K2-K6]

That was  good response from marine boy and very thorough, this forum is brilliant for the experienced contirbutions that we can get access to.

I know it's not really of any help, but it's my impression that you get a lot more of this sort of stuff with unleaded than before.

I don't know if anybody knows much about this but I try to avoid "low sulphur" fuel as it seems to be worse than having normal sulphur, whatever that entails. Anybody got any insider knowledge to guide us?

[Spitfire]

Don't know about gasoline but when low sulphur diesel came out we had to put an additive in the diesel to restore it's lubricant qualities, the sulphur acts as a lubricant.

Cheers

Den

[K2-K6]

Yep I noticed that in our family "bike" a VW diesel, it will do something like 40miles more to a tank on some brands than other low sulphur stuff and I heard that the pumps last longer with sulphur so aim to buy that and AVIA fuel I bought in france was the best for range that I've seen (apologies for off topic disesiel! discussion).

I guess this may not affect SOHC stuff so much but may impact on newer Injected bikes with pumped fuel supply.

[vivvov]

Cheers marineboy..got th weekend coming up to check the 0 seals and polish the valve seats..

[marineboy]

You are most welcome, I do like reading stories in motorcycle magazines where someone states " its been laying in my garden uncovered for 20 years, I put fresh petrol in it & charged the battery & away she went third kick" yeah right o!!!!!If mines been laying around for 20 minutes it doesnt go third kick!

From my experience as you can see,what I did for one carb I ended up doing for all four carbs. As long as its not gushing out petrol anywhere dangerous ie; onto the exhaust underneath & the flooding carbs are not causing you to sputter & stop everywhere IMO I would try & ride it a few times & see if things improve, keep on turning the fuel tap off on the journey and letting her run to the point whereby she is begging for petrol, then put the tap back on to fill the bowls back up again, she may just need a bit of encouraging to get things moving...... But do watch where you are going when you are fiddling around for the petrol tap!!!!!!
Regards
as always
Marineboy

[vivvov]

Hello All

Thought I'd update.
Just polished up float valve seats and needles of 1 and 2 carb...leakage reduced to a couple of drips from number one..good stuff....
Then just taken out no. 3 float valve and Marineboy was right, no 3's o-seal is in bad shape (and I'm guessing the minor drip on no 1 carb is due to o-seal).
So it's a combo of the two.  One I can sort out with polising, the other I can sort out with new
o-seals.

Don't want to come across like a Scourge but anyone got any thoughts on sourcing o-seals as opposed to the whole float valve kit x4.

Vivvov

[Bryanj]

In theory the "O" ring is the same as the 500/550 and the original part number was 16171-551-004 IF you can find any old stock anywhere(try westernhillshonda.net) or a petrol proof 5.7x1.3 mm "O" ring if that size exists anywhere except Honda