Carb issues

[Session101]

well let start from the beginning

put new diaphrams on the carbs and put about 50 miles on the bike easy, and it was perfect

went for about a 100 mile ride with some friends and about mile 80 bike lost power and backfired twice, but made it back home ok.

took the bike out for another ride again and it just didn't have the power that it did before.

i checked my diaphrams and they are good, so i sprayed and cleaned the carbs so you could eat off them, even cleaned the passageways. Also cleaned and scrubbed the coils to ensure good connection.

now the bike is running really rough and the carbs are both acting weird, i don't know which one is the way it should be. the right side carb, vaccum secondaries is going up and down with small revs and goes up upon full throttle, but also bobs up and down on idle too. the left side isn't moving even with high throttle...wtf is going on, ill post up a vid shortly.

basically i need some ideas... Im going to start from basics tomorrow
1)compression test and test again with adding oil
2)going to pull the plugs and dry fire them to see if the spark is blue or red, new spark plugs?? (cheap) but mine are like 400 miles old...
3)Go through the carbs again? or maybe clean the heads as much as i can

[Session101]

[media]http://www.youtube.com/watch?v=3EZMr-l-4zw&feature=plcp[/media]

[markrennick]

the right side carb, vaccum secondaries is going up and down with small revs and goes up upon full throttle, but also bobs up and down on idle too. the left side isn't moving even with high throttle..

(no expert, just guessing really..)

I've never watched the slides in action, but it looks to me like the right one is working correctly. My vacuum guage acts the same way.

Does the left one work when you pull the cable end? If not I guess it needs stripping again.

Hope you didn't swap any of the left & right parts, I've heard of that having strange effects..

[Session101]

no i  cleaned each carb one side at a time when they were on the bike

[Barry]

the left side isn't moving even with high throttle...

Interesting video !

The fact that the good side bounces a little may be due to the fact that flat top Bings have no slide control springs.  Flat tops only lasted 2 years in production and maybe that's the reason. Having said that I have no problems using flat tops.

If the left side doesn't lift at all, logically it's either excessive slide stiction or if the diagram is good with no leaks then there must insufficient vacuum reaching the top chamber. That could be because of a blockage or the fact that the engine isn't producing enough vacuum due to valve or piston sealing problems. Your compression test will tell or a manometer carb balance.

The communicating passage to the top chamber is a small hole on the underneath of the slide. The hole should be oriented towards the cylinder head on both carbs. The hole is not so small it blocks easily though.  

Going back to the slide bounce this is a very long shot and probably unlikely but perhaps worth a mention.  Harley owners and maybe others have been known to drill that hole out to a larger size to improve throttle response. I suppose it's possible a PO did it to your carbs which would result in more slide bounce as the hole size acts as a damper orifice by restricting the flow of air in and out of the top chamber.   Sorry I don't know the correct hole size off hand without stripping a carb.

[Session101]

here is a question... if you use your finger to slide the secondary up, should it fall right back down? or should it stay? or should it fall slowly?

[Barry]

It most certainly shouldn't stay. It should pretty much fall right back down. There is not much damping effect even with the correct sized hole unless the movement is very rapid.

[Bob_Roller]

Do you have cap on the vacuum port on the carb giving you the problem ?

[Mike V]

I'm with Barry and Bob's advice.  

Additionally - A loss of power is often a result of slide/diaphram operation it seems, or lack of.  Check the installation of your diaphrams to make sure the tabs are located correctly in their bosses.  Did you use OEM Bing diaphrams? Any burrs or wear patterns in the slide or slide bore? Just some wild guesses...

[tvrla]

First off, they're not secondaries like car carburetors - it's a slide - just an air valve.

The left one is upside down - or was the camera upside down? It looks to me like the right side is operating normally, but I didn't get much of a look at the left one, and that's the one that needs watching.

The piston moves up due to vacuum and returns because of gravity. Either there's no vacuum, or the slide is sticking. If no vacuum, check the valve lash - actually a good idea since adjusting carbs is the last step in a tuneup after everything else. Valves too tight would have a huge effect on vacuum.

[Session101]

lol, yeah im used to cars more than motorcycles.

so it should be boucing at idle? that's normal?
1) Diaphrams are fine and were working fine when installed
2) vaccum port on the bottom is capped with the screw

I chose to clean the carbs because i was getting oil in the carbs from the engine using the stock air cleaner, so ill check to see where the vacuum is coming from.
also yes i filmed it upside down, i just wanted to show one side moving vs the other.

i get home in the morning and will take off the carbs first for compression test, and bench tear them down.

[Session101]

so finally got some time with the bike
1) checked compression seems to be good, within 10 of each other, the left side the rings are worn because i sprayed some oil in there and it went up by 10, to equal the right cylinder.
2) pulled both carbs, put them on the bench and basically cleaned and rebuilt both of them, and put them back on the bike, ensuring the choke is positioned as well

I did happen to look at this video to test the slides and make sure i have full motion and movement
[media]http://www.youtube.com/watch?v=Q5BGTi6OX1E[/media]

they did but question, what should i do if the slide goes up and doesn't return unless there's a vacuum on it? it doesn't seem to fall right down like in the video..

i switched sides on the spark plugs, they seemed to be blacker on one side than the other, so i bought some new plugs too to swap out just in case.

[Bob_Roller]

Do you have springs under the top of the carb that push down on the slide ?

You may want to take emery cloth and remove any scratches on the slide and the area in the carb body that it moves over, might just be a bit of friction holding the slide up .

[Session101]

no springs, i don't think my model came with any..

but i just double checked and both slides are now dropping and working perfectly fine.

So i started up the bike, and its running really rough...but both slides are properly working and rise and fall at idle

i pulled the plugs to check, swapped with new ones and bike still runs the same, i checked for spark and both are sparking with blue

now im stumped....

i used an IR temp on the exhaust and it shows that the right side is running hotter than the left side, right side at about 140F and the left side 98F but thats after about a min cool down.

so now i have no clue where to go from there.... Got fuel! Got spark! why is it running rough and why is it running hotter on one side than the other?

oh i forgot to add when i pulled the redid the carbs, i put the air/fuel screw at 3/4 turn out per haynes manual

[Bob_Roller]

That adjustment is to start start with, you need to perform a full carb synchrinization after disturbing the adjustment screws .