Running rich

[grantasaurus]

Hi all,

I'm having a problem with my CB-1 running quite rich at the moment, and has me a little puzzled, just wondering if anyone else has had a similar problem?

The bike is running very cold (the temperature needle never moves above 1/5 of full scale on the temp gauge), and is blowing decent amounts of black smoke at full throttle and mid-high RPM. My fuel economy is rubbish too - the bike is drinking around 6l/100km (about 44mpg UK, 39 US) when I was expecting 4.5 -5 l/100 km. All these things make me suspect that it's running rich on the main jet circuit.. but the question is why?

My first thought was that maybe the needle or jet was worn - however, I've torn the carbs down, and can't see any signs of wear on the jet needle or needle jet - and nor would I expect to, the bike has only done 19000kms (12k miles). I've checked the operation of the chokes, and they're moving smoothly and springing back to where they belong when the cable is pushed back. The float levels look standard (none of the tabs are bent) The only thing I didn't check on the carb when they were apart were the main jet sizes, but I have no reason to suspect that they're non-standard (i.e larger than #105s).

I have a sneaking suspicion that it might be the float levels but didn't actually measure them when the carbs were apart. How sensitive is the mixture to float level? If the floats were out like 0.2mm (i.e. not enough to notice by eye) or so would I notice it running this rich?

The air filter looks OK.. but then it really is hard to tell. Could this explain it? The richness seems a little too severe to be explained by simple clogged air filter though.

Hoping someone can suggest something to steer me in the right direction. Don't want to tear the carbs apart again without having an idea where I'm heading, otherwise I might have wasted my time.

[xstreamcanadian]

this is not a helpful reply, but how do you check the float levels? when you say no tabs were bent etc?

thanks

[grantasaurus]

What I mean is that I checked them by eye only - was in a rush and didn't get the verniers out (you can use the depth gauge part of a pair of these to measure the height)

The proper method for doing this is in the Honda Common Service Manual - do you have this?

[chingloy]

Go here:

http://www.vf750fd.com/vf750f/Honda_Common_Service_Manual.pdf

or here:

http://xr650r.barbershack.com/XR650R/Honda_Common_Service_Manual.pdf

or here: 

http://www.hondaxl.it/download/Manutenzione_Honda/Service_Manual_cap_01.pdf

or here: 

http://www.carlsalter.com/aaman/Honda_Common_Service_Manual.pdf

[oldsmoker]

Grant, lets start simple. The choke is off when it is pushed all the way up and on when pulled down . Not trying to be a smartass but you are new to the -1  and the " choke " is really an enrichener, it adds fuel, it doesn't choke off air.

[grantasaurus]

In countries of English / commonwealth descent a "choke" means any sort of mixture enriching device for starting purposes. That's why I called it a choke - force of habit.

In any case, the 'bystarter valve' is not the cause of the bike running rich. All the slides on the bystarter system are moving freely and springing back in to where they belong.

Has anyone experience needle wear on a bike with low mileage like mine? The carbs are apart again, so will be blowing out all the air circuits, and checking the  height of all the floats to eliminate these as causes.

[Falk]

short Question: Do you have a Aftermarket Muffler and Downpipes?

I got this at my CB1 from LASER and there were also some Systems from BOS. The BOS-System came with a 105 Mainjet
And with my LASER-System I had to modify the Airbox to get it in a "green" Level....

(got a Sensor at the Downpipes and a Air/Fuel-Meter installed)

[grantasaurus]

No the exhaust and down-pipes are stock.

I thought a 105 main-jet was stock? That's what I recall reading in the manual anyhow..

[Samuichris]

Correct.
The stock main jet is 105.

[Falk]

mhm - have to check
let me think about - Friend of mine was using 112 with some Mods at the Airbox
I was using 110 with some Mods at the Airbox but orig Muffler....

mhhhm ok could be 105 as stock Mainjet - need to find the description for the BOS-System

[Drewski]

The air filter looks OK.. but then it really is hard to tell. Could this explain it? The richness seems a little too severe to be explained by simple clogged air filter though.

Yup, a blocked air filter can have a noticable effect on the mixture. Also, does your bike have the sub filter located behind the main one? The element in this usualy rots, breaks down and can end up in the engine, maybe the cause of the black smoke??.