Dead again

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Apr 15, 2004
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Well I'm back to square one. Last week, bike ran great. This weekend, after sitting all week, it's the same old story. Started right up, died right away. Didn't have any new plugs to put in it so I couldn't get the stupid thing running. Blah!!!

I thought the carbs were in good shape after the last rebuild and after the bike ran so well last weekend. Now I don't know what to think.

The problem seems to be that about half the time I try to cold start it fouls the plugs. Impossible to get going again without a brand new fresh set. All I had today was a used set and they didn't work either. Maybe those amals are just shot or could it be something else?? I'd buy a Mikuni kit but what if that didn't fix it either?

71 750 Roadster parts bike
On Sunday 8 Aug you stated
I found it very difficult to get access to the clogged pilot jets so I drilled out the blanking plugs behind them. Now I can see daylight thru the pilot jets and the pilot fuel circuit is clear on both carbs.

But, and this brings me to my question, I tried to push a single strand of 12 awg stranded wire thru the pilot jets as suggested on another thread and I could not get it to go on either carb.

Compressed air is the recomended method for cleaning out the carbys after a good soak in your preferred carb cleaner.

Are you sure pushing piano wire n whatever thru hasn't opened it up and made it too rich ?

Have you tried new needle jets also, as these could be worn ? If they are you will find that you will need to adjust your mixture screw back to say 1.25 turns out or thereabouts.

Are choke slides fitted to your carburetors? If so, make sure they are all the way up imediately after starting the engine. Better yet, don't use the slides for starting the bike.

It sounds like the engine is being flooded, possibly due to the choke sides, so eliminate them from the equation.

Let us know what happens.

Carb details...

Chokes aren't the problem, they aren't fitted! PO removed them and threw them away. I have a set that came with a box-o-parts I bought but have been waiting for colder weather before I install them.

Jetting is 200 mains, 105 needle jets (new), old needles in middle clip, #3 cutaway. Air screws are 2 turns out; before the soaking and poking they were 3/4 turn out. (This is at our mile-high altitude) I haven't done a hiway-speed plug chop reading yet but last weekend the color looked good when I checked them following a ride.

It does seem the first minute or so of running with the flooded engine is critical wrt fouling plugs. If I don't flood the carbs thoroughly it doesn't start. But when I do, about half the time it fouls out. I don't have any sandblasting equipment or anything like that so there's no way (that I know) to clean the plugs. I just have to throw them in the garbage and go spend another $7 for a fresh set. Maybe I can get a quantity discount if I buy a case of them. I've been using NGK BP7ES plugs. Norbsa recommends autolite, says they're more resistant to gas fouling. I suppose I should try some if I can find some place that sells them...

Debby, I get mine from an Advace Auto a chain store up here. Don't feel bad BSA's do this too. Triumphs seem to be the only ones that can run these through the starting phase. It was such a big problem that Bosch made special plugs for the German race cars that cost like 78.00 each. Now if I could just get Auto Lite to nickel tripple plate thier AP 64's.norbsa
Debby, Dave is hot on the trail here follow his advice hours on the dyno have taught him lots. I have the feeling that you have what many here have bad fuel control at certain spots in the carbs. The hot plugs are for getting rid of the fustration and finding the problem. I have often thought that on an old set of Amals, were the slides and needle holes are sloppy, that the needle must be very out of concentric with it's jet as it is pulled out of it's jet. Having this needle off set in the hole can't be good for atomization of the fuel. It's large dropletts of gas that are taking out your plugs and this could happen to someone with all the good parts in the carbs. This is the reason I keep going back to how the floats are set, it's the number one reason that gets Commandos with tilted carbs get into this kind of problem. But if your trying to run sloppy slides with wopped out needle control this also could be at the base of your problem. norbsa
Good Luck Debby,

Seems you have all the experts on your case now.

You must be learning heaps about amals :D
I am way to frugal (cheap) to buy new plugs just because they foul. I wire brush em up, maybe scrape a little with a knife, wipe the threads, if anything comes in contact with the electrode, I brush em again, blow em out and reinstall.
Debby, what is the status of your fuel. I am working on a Combat that came from Texas that has brand new Amals. The innards of these carbs were lacquered something terrible. Both slides were stuck because of the lacquer or whatever the residue is.
I wonder if this residue is just fuel, or is it a combo of fuel and resins from the fiberglass tank. In California here, we had a problem with the additive MBTE. It has been removed now, but some guys are still going to the trouble to drain their fiberglass tanks after every run. What a pain.
I don't know about other states and fuels, any comments anyone??
Still dead

Debbie, I haven't been following this thread so may be redundant, but everything you say could point to bad ignition. Weak coils, bad wires, faulty points/condenser or even Boyer if you have one. A weak spark will allow plugs to foul when they would otherwise be OK, and it could be that your high altitude is aggravating the problem.
A lot of variables aren't there? I'd hate to spend several hundred $$ on new carbs only to find I had an ignition-related problem! So I'm not sure what to do at this point. The spark looks good but maybe some new condensers would be worth a try. They're relatively cheap. Also I think I'll try some hotter plugs.

Mike, do you have a fiberglass tank that's unlined? If so I'd say the sticky goo in your carbs is probably dissolved resin from the tank. Mine did that before I had it lined. That stuff really makes a mess. If your tank hasn't been lined you'd definitely want to drain it after every ride.


Condensation did go through my head earlier after you said you left it sitting. But I discarded the idea as I thought you would notice something like that when you were "doing your float levels"......

So, it could be gunking up from another source then ??

I really couldn't believe you would have had to change slide sizes and the such as suggested as the bike no doubt ran fine with all that in it for years.

Unless of course those items were wrong ever since you got the bike.

Things like this problem can be difficult when you are not at the bike all the same.

Anyway.....what is happening ? Have you got it beat ?

Is it snortin once more ?

Regards from
Debby, There appears to be some kind of sealer on there. I think my case was just bad, rancid fuel. Though I have owned several Commando's, this is my first fiberglass tank. I heard of others with problems, this one appears to be fine.
I haven't had time to do anything with the bike this week but I just scored some autolite ap64 plugs from my local napa car parts place. Will try them out tonight and see what happens. I'm hoping they'll keep the thing running long enough to let me figure out what the real problem is.

The autolites were actually $1 cheaper per plug than what the mc shops charge me for generic NGK plugs! I wonder if they'll give me a discount if I buy like 100 of them? I could save even more money. The more you spend the more you save.

Perhaps the next thing I should do is set the float levels. They're a bit high (rich) from what people told me on that other thread. Perhaps that's enough to push things over the edge into perpetual-plug-fouling-mode.


Be careful. I suspect those Autolite plugs are hotter than the standard Champion plugs; so don't do any high speed riding with them.

And yes, the float level you reported in an earlier discussion did seem way high to me. As mentioined previously, with the bowl updside down the float should be about level with the edge of the bowl. Anything lower than this will certainly contribute to an overly rich condition at idle.

However, this overly-rich theory flies in the face of your need to tickle the carbs to restart the bike.


Jason, AP64's are not that hot they are direct replacements for Bosch WRP7's that I have run for years. CNW come with AP63's one step cooler. But I just did a trip to Ohio and back 250 miles each way at 80MPH straight thru with AP64's and many hard runs since than up to 6500 RPM don't you think I should blow up. Yes they burn white like they should but deep down inside were the ceramic touches the metal core there is a ring of color about .025 thick after my hardest run so I am not scared. The main thing is when I slow way down and tuol around the camp ground at five MPH I can still start the bike even if the plugs get black. I don't like the fact that they have no nickel plate on them main thing is there foul resistent.norbsa
I put the autolites in last night and tried them out. They got the bike running but just barely. When it started it was only running on one cylinder. I kept it running by keeping it revved above 2000 and eventually the other cylinder joined in. It settled down to a nice smooth 1000 rpm idle but seemed to be missing and cutting out above idle. It was dark and my taillight has quit working so the only test ride I did was one pass up the alley. Couldn't really tell anything from that.

I'm thinking there's something else wrong besides carb settings. Sometimes the bike runs great, other times it doesn't run at all or very poorly. Maybe there's some random electrical fault. Or maybe I have contaminated fuel. The last time it ran well was when I put fresh gas in a couple of weeks ago. Then when it sat for a week it didn't want to run. Maybe the lining I had professionally installed in the tank is dissolving and spoiling the fuel??? Just a thought. But I'd think if it was just messed-up carbys it would run bad all the time. Or could bad condensers cause these sort of symptoms? I hate to troubleshoot it by replacing one expensive part after another ("nope, that didn't fix it") but condensers are relatively cheap. Another thought I had is running a jumper wire directly from the battery to the coils to rule out possible wiring problems...

Debby, Bad condensers would put excess sparks at the points and then pit them on even a short ride. Pull the point cover and with your fingers check that the AA unit is smooth and free you may have to bump the motor with the bike in fourth gear to get all the pressure off the cam of the AA unit to see that it is realy free. If your condensers are bad you will see burnt points. Sure sounds like Old wireing. norbsa
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