Too rich or too lean?

[tommo903]

I've only had my '55 A7SS about 6 weeks and because of a few starting issues, I decided to get myself a replacement parts kit for the monobloc carb. This has certainly helped and it now generally ticks over quite nicely...but having taken the bike on two runs since (only about 10 miles each), it will only run whilst the choke is partly on. This made me think the bike must be running lean, but when I removed the spark plugs, both are sooty black! So now I'm somewhat confused on which way to approach this and any advice would be gratefully received.

Another thing that I could do with some help with is the operation and use of the advance / retard lever. Having been predominantly a japanese bike rider for many years, I've never needed to worry about such things. When I bought this bike, the previous owner said he never bothered touching it, so up till now, I haven't either. However, if I had a better understanding of when and where I'd need to use it, I might wonder how I've managed to get through life without it!

Thanks,
Steve

[chaterlea25]

Hi tommo
The choke on will be giving you a false plug reading
If it needs choke to run then its too lean
Where have you set the air screw? needle position? fuel level?
did you fit a fibre washer under the float jet? this is not correct on old mono's
Are you sure the tiny passages from the pilot circuit to the engine side of the slide are clear?

Its not unknown or uncommon to find a manual mag and also an ATD fitted 
does the engine note alter when the ign lever is moved?
If manual only it should (probably) kick back when trying to start on full advance ???
Check the ignition timing on full advance, and tell us what you find?

John

[tommo903]

Hi John, thanks.

I'd forgotten to mention that I wondered if the choke might be giving me a false reading, so I'm glad that you'd confirmed that.

I have the air screw set at 2 turns out, so I'll probably try 1.5 instead. The needle position is 3 (in the middle). I don't what the float height is but it's on my list of things to check...is there a method by which to do this please? I use a piece of clear tubing on my bikes with Mikuni carbs but this doesn't look that straightforward. Regarding the level, I've read it needs to be at the 'pip' mark on the back of the float bowl, but when I looked at the plastic float, I couldn't see how it could be adjusted anyway? By the way, I did fit the washer under the float jet so I'd better remove that.
I'm as sure as I can be that all tiny passages are clear...I soaked the carb in some thinners, then cleared it through with compressed air...all seemed ok.

I'm not able to do a test of the ignition lever with the engine running at present...only because of what I have found this afternoon. I drained the oil in the tank and from the sump and noticed that the sump plate has an allen screw securing one of the corners rather than a stud / nut. Unfortunately, the screw has a lot of play from side to side and doesn't tighten up properly...presumably a damaged thread. Not sure how I'm going to deal with this...didn't really want to have to remove the engine from the frame at this stage.

Steve

[chaterlea25]

Hi Steve,
Remove the cap from the pilot jet,make sure the jet itself is nipped up to its seat
push the clear plastic tubing over the jet and bring it to the other side of the carb
The pip is on the chamber cover not on the float !! Some covers do not have the pip ???
so I gauge it to the bottom of the air screw hole,
there are dozens of topics on this subject on the forum so have a look for them
Usually 1 1/4 to 1/1/2 turns out for the air screw

Usually the sump plate threads can be helecoiled in situ ? I make an alloy block that match two of the holes in a pillar drill so they're square to the base of the block
the block can be bolted on from one of the good threads, the hole through the block will keep the tapping drill square, then back to the pillar drill and tap through the block or a tight clearance hole and re attach the block and use to keep the tap straight

HTH
John

[tommo903]

Hi John, that does help, thanks.

My carb does have the pip, so I'll use that. Assuming the level is not going to be exactly correct, how do I make adjustments? I appreciate you've suggested I check for other topics regarding this, but I've just not had chance yet, but will be trying that. So, I'll adjust air screw and float level and see how it goes from there before I touch anything else such as needle height etc.

For me, doing the helicoil in situ will be difficult as I don't have a motorcycle stand and so there won't be sufficient clearance under the bike, unless I lay it down (not too keen on that!). Likewise, I see what you are saying in making an alloy block, but I don't have a pillar drill either so would need to get someone to make one for me...I assume the block can't be very thick as the studs only project from the cases by approx 1/2 inch anyway?

Steve

[chaterlea25]

Hi Steve,
AMAL do a new float with adjustable tang, if needed
Usually they are ok or a new needle will fix it, adding varying thickness gasket washers under the needle seat wil correct if too low a level

The studs can be removed from the cases by locking two nuts together on the threads
They have 1/4 whit threads into the alloy so easy to then use a longer screw to hold the block
around 1inch thick is ok
Remove the battery if its a conventional one before leaning the bike over, find somewhere soft to lean it on!!
LOL
You could always follow Rocket Racers lead and turn the bike upside down 

John

[tommo903]

Hi John,

Appreciate all your help with this...I've obviously got a few things to sort out before worrying about one of my original questions concerning the use of the advance / retard lever! I'll re-post once I'm a bit further along the line.
Thanks again,
Steve

[mugwump]

If I may just jump in here for a mo. Iv'e noticed that many novices to Brit bikes , quote " I've only ever had japanese bikes" unquote, don't fully understand that the mixture screw is only effective on the idling and about 1/8" throttle opening and has no effect on the normal cruising. Also, many people try to set the screw out from closed a set number of turns and expect that to do. I've always tuned the running of the carb by starting with about two turns out, get the engine warmed up and then adjust the screw accordingly to give an even tickover. If the engine speeds up or slows then re-adjust the throttle stop screw. If spitting back through the carb or hesitating on pulling away is experienced then try winding the mixture screw in a tad to richen things up a bit. The richness when normal running is probably caused by a fiber washer under the float needle valve  as mentioned ( causing the float to shut fuel off a bit late, or the float needle is worn. Incorrect slide cut-a-way or main needle position need checking. Also, main jets have been known to rattle loose.
I have had to drill out the idle jet on my Huntmaster as it was stuck solid and trying to remove it just chewed the end up. Nightmare job as drill too deep or off centre and the carb is effectively buggered, still worked in the end.

[edboy]

my a10 has been flooding fuel since coming back from a long run and its been difficult to fathom why?
however with the help of this forum i also wrapped some copper wire around the float tang until i dropped the fuel level to around 1/2 way[ i have a perspex cover] and now runs fine  around town.
i hope the top end wont be affected ? but monoblocs seem very sensitive to fuel delivery. if i turn the fuel tap off the engine revs madly when the fuel drops to empty in the bowl.
years ago before sleeving we couldnt find good , unworn monoblocs so used  new concentrics on old a10s.

[edboy]

it seems in my case the float height was a red herring. it seems i ve worn the needle jet out in less than 2,000 miles . this creates an additional pilot circuit , hence rich idle and hard to start. wish i knew this earlier.