Bonneville America Forums Forums Technical Forums Performance Mods Probs with carbs

Hi I was wondering if any body has some new ideas on this problem as I cant sort it. I have a bike here which was ridden up to me and now barely runs after cleaning the carbs. I have tried all I know and have had some great ideas off other members but still no luck. The bike is not mine and I only know what I have been told, but here are the specs. Big bore kit, no air pump 42 pilot 120 main after merket pipes that are triumph but say off road only, after market filter.
Now the bike runs rich and will barely idle. I havent ruled out ignition and had the black box done but if you have any tests for coils or electrical let me know.
The carbs have been done and done little filter is clean floats are set, diaphrams are ok slides are worn a fair bit. Needles have one washer. everything seems good and i have checked and double checked most things.
It idles better with the balancing rubber boot removed from inlet port on rhs. It kills plugs asap.Idle screw is way up on where it was prior to cleaning the carbs and it only starts to run ok when the fuel is off and about to run out. Any ideas would be appreciated but as I said most of the std ones I have checked 10 times. Thanks Link

When you cleaned the carbs, did you undo the throttle sensor from the carbs, if so this could be your problem..

...I know this will sound daft, but it is possible to re-assemble the carbs with the plastic "spider" that supports the diaphragms inserted incorrectly. I recall someone else on this site had the same problem and had exactly the same symptoms that you describe.

Hope this helps.

Thanks gus but I didnt move the sensor. It may not work though,is there any test you can do or do they not play up. The plastic spider is holding the needle tightly down and not blocking the hole so I think its ok.It is not really running on the idle circut at all and way way rich but all the airways seem (compressor job)clean. I ran carbie injector clean and blew all passages out as good as you normaly can but it seems like an air way is blocked. Does any one have the airway layout for these carbs that I can have a look at? Link

Sounds like the pilots jets are blocked or air screws ports are blocked. I'd pull them out and look close at the pilots.Also, look at the bowls for corrosion. If there is oxidation clean all the white oxidation out of the bowls. Little bits can break off and jam the piots in a few mins. I'd also pull out the air screws and make sure you have the spring, washer and o-ring on each carb. While they're out blow some carb cleaner through the ports on the pilots and air ports. The new ethanol gas is very corrosive and can reak havic with your delicate fuel systems.

Good Luck

one (or both) of the main jet assemblies has lost a collar. A Carburetor Primer

So it looked like THIS when you put it back together?

What Moe said.
And check the mechanical parts of the choke (enrichener) circuit to insure the ball is still in there. You can unplug the sensor to rule it out as it's a minor player in the scheme of things.

Quote:

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Big bore kit, no air pump 42 pilot 120 main after merket pipes that are triumph but say off road only, after market filter.
Now the bike runs rich and will barely idle.

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With that set up it should be running a tad lean, you've got extra fuel entering the system.

BB with those jets would be more than a tad lean it is burning parts lean. I would fix that right away and hope your problem isn't caused by a burned valve. I would do a compression test.If you have low compression the plug would look like you have a rich condition due to low compression causeing poor cimbustion.As Ed said if it isn't lean and your compression is OK you have fuel entering that shouldn't be. Maybe a float not doing it's job. If you park it anf leave the gas on does it leak?

I was going to say something about his stock jets but didn't want to complicate the issue. 120 mains are wayyyy to low. Sticking float, missing parts under the air mixtures screws, the missing collar syndrome all would work to push too much fuel. or rather leak too much fuel. Are both the plugs fouling out? How about the spark plug gaps? Seems to me that with the big bore kit having been put in place that the problem arose then. Didn't he have another thread where he said he checked the slides diaphragms and such? I hate problems like this and hope he gets it sorted out soon. Thus the collar suggestion. Ed's comment about the fuel enricher circuit was not mentioned before. Hum, So Ed, how would know about that one?

Yeah Moe he did have another thread about the things you mentioned.

Hi I dont remember seeing the collar. This could well be missing. Tha pilots have been blown out heaps and seem really open. The needles and orings etc are really good.I presume the collars are up the top of the emulsion tube chamber at the bottom of the port.Thanks for the great ideas. I'll report back. Link

Ok there is no collar on either carby at the top of the emulsion tube. When you remove the jet and tube there is a 5mm or 6mm hole all the way to the inlet port.There is no buttross sticking up into the port so it is missing. I suppose some clown aka me has lost them but I have never had them come out before without a whack.
New problem the wreckers wont sell me them without the carbies attatched and I cant seem to find them in a shop as of yet. Does any one have one they could measure up for me and I'll turn two up at work so at least I can ride until the new ones arrive. Thanks Link

I have several of those old carbs floating around does anyone know how I can identify weather they will work or not? They are old Honda CB 350 or 360 , can't remember for sure the cc anymore. Have some old Suzuki carbs too of the same type. I can hook you up if they would work but don't want to needlessly part with my parts.

link, I can get the collar measurement for you in the morning.

Hi guys I found the collars after hands and knees on the ground for a while. Thanks for all your great ideas.I'll let you know how it runs!Link

That'll do it, back in they go and Bob's your uncle

I love that Bob's your uncle line.

Thanks to all who assisted with my probs. It ran far better and the only fault now is a slight pop and I mean slight pop in the carbs once in a while. I will balance and set and have a final play tomorrow.The mixture screws are 1 1/2 does this seem right as they still poke up into the inlet port. You dudes are guns!!!!
Thanks Link

Some carb cleaners can play havoc on rubber and platic parts. I had an issue with needles (dynojet kit) one time that caused my bike to run so rich that it was fouling the plugs. Going back to stock needles resolved my issue there.

Are the needlies lining up with their holes? Sometimes on reassembly they won't drop down into the jet passage. Are the floats in good shape? If they get cracked and filled with fuel your carbs will flood.

I think that I would have to take the carbs apart and inspect all the parts and replace any rubber parts such as o-rings that may be damaged. Completely remove the air screws and flush the passages with carb cleaner. Be care with the rubber parts because the cleaner may cause them to swell out of shape. If the passages are not open you might carefully use some light guage guitar string to try and open them up. Do not damage those passages! You said you used compressed air to blow in the passages and may have compacted some debris around the air screw seats or some curves in the passages. Removing the air screws before flushing will help. Spraying into the air screw hole should push fluid out of one of the small holes at the back of the carb intake side.

After you've insured that all the passages are clear, reassemble all the parts correctly, remove the shim from the needles, adjust your air screws about 2 1/2 turns, it should start and idle normally. At that point you should be able to adjust the air for best idle. Once that is established, rejet for the big bore, air filter, and pipes. Syncronize the carbs and put it on a Dyno to verify that carbs are setup for all ranges of operation.

Another thought, could carb cleaner have damaged the throttle position sensors? Also, are you using stock needles or are they dynojets or some other aftermarket or otherwise non-stock item? Needles and needle adjustments can have a big impact. You should always look for and eliminate the simple things first then move on to the more complicated things. After all, the bike ran fine and all you did was clean the carbs. The problem occurred with the cleaning of the carbs.

Hope some of this helps.