Engine still running rich

[WilliamsOliver98]

Hello there, I've been working on my bike (Honda Xl125 1983) and after it not running properly I decided to study the spark plug, its carbon fouled, and I read that it was a sign of the bike running too rich. Since then, I've installed a new air filter and checked for air leaks, which there doesn't seem to be any. I then inspected the carb to make sure the float wasn't sticking and was at the correct height, which it was and even looked to make sure the needle was positioned on the correct groove (as specified in the manual). All this and the plug still indicates a rich fuel mixture? am I missing something obvious? I've tried adjusting the mixture screw on the carb whilst the bike is running but it still runs like shit (despite it being on the recommended settings), ive got it to a point where it idles but it cuts out after a while and has no power. Is it just a case of adjusting the carb screws until it runs smoother? or could something else be the culprit

Any suggestions would be appreciated!

Thanks

[megawatt]

What is the state of the air filter? Does it need choke to start?

[WilliamsOliver98]

It starts better without the choke, the air filter is in good nick, its the original filter that I cleaned and added new foam onto to stop it from getting any dust in. I did try it with a conical filter that i'd bought but it was on of those cheapo ones and didn't seem to make any difference (better or worse). I even started it without an air filter on just as a comparison and there was no difference.

[megawatt]

If it starts better without choke, checkout the choke mechanism and circuit.

[WilliamsOliver98]

I'll give it a once over tomorrow to double check the choke out, but im 90% sure its all in working order, when the choke lever is pulled it moves the arm on the carb so I assume its working. I've put some lubricant on the cable too to make sure its not sticking or anything like that.

[Guest Richzx6r]

Try leaning out the mixture a turn or so if you can and clean the plug and gap it so its correct as although unlikely to be the cause of poor running it may be a contributing factor in a small way.

[megawatt]

Don't assume anything. If you want to fix it , eliminate the obvious. Just because the lever moves , doesn't mean the choke is working properly..

[WilliamsOliver98]

Ok, ill give the choke a more thorough inspection tomorrow and ensure its working correctly so I can cross that off the list for definite, i'll also clean the plug and check the gap, its a new plug so shouldn't be an issue. Any chance that its nothing to do with the carb and is more electrical or something? I've been looking at the carb and surrounding areas for the last few days and cant seem to find anything a miss.

[Guest Richzx6r]

Don't assume anything. If you want to fix it , eliminate the obvious. Just because the lever moves , doesn't mean the choke is working properly..

 

what he said

[Guest Richzx6r]

Ok, ill give the choke a more thorough inspection tomorrow and ensure its working correctly so I can cross that off the list for definite, i'll also clean the plug and check the gap, its a new plug so shouldn't be an issue. Any chance that its nothing to do with the carb and is more electrical or something? I've been looking at the carb and surrounding areas for the last few days and cant seem to find anything a miss.

 

Tbh with the age of the bike theres probably not a great deal that is electrical, I'd guess the lights work on a dynamo and that the spark is probably the only real electrical thing bar the indicators unless it's a points ignition?

[fastbob]

Just a suggestion . You say that the float is at the right height . Ok , but is the actual fuel level in the float bowl correct ? There is a difference . If the carb has a little nozzle on the drain screw you can rig up a simple U tube to determine the actual fuel level . I will include some information from the ER5 manual that describes the technique because it is possible to get a false reading if you do it wrong .

[WilliamsOliver98]

There are only a few electrical components. I replaced the ignition coil a while back. Its got a CDI ignition system, which I don't know an awful lot about tbh. I did run some resistance tests on the pulser generator and the CDI unit itself and they are within the normal ranges specified in the book. The timing on it ive set according to the book also, it starts well so I didn't think that was a problem, but I may be wrong.

[WilliamsOliver98]

Ill also be sure to check the fuel level in the carb too, didn't even think of that and the test looks simple enough! thanks for the help guys. i'm not a great mechanic but ill get there hopefully!

[Guest Richzx6r]

If they are within operating range and fairly new then can more than likely rule that out, I'd probably put most of the time and effort in to setting up the carb

[megawatt]

Is the plug just sooty that can easily be wiped off, or is it harder and baked on? Is there any blue smoke coming from the exhaust?

[WilliamsOliver98]

There's no blue smoke for definite, there's white/grey smoke occasionally. I would say the plug is baked on, it doesn't wipe off easily, ive cleaned It a few times and have to scrub it off. ive included a few images, sorry for the poor quality, its hard to get it to focus. Hope they help.

[megawatt]

Looks a bit oily to me. Does it blue smoke for a few minutes from cold, then clear up? You may have leaking valve seals or a leaking head gasket, leaking oil into the combustion chamber. That's if îts definitely not carb related.