Popping from cylinder#3

[Mike]

Hi everyone,

I have a 2000 Standard with 160,000 km. This past week while nearing the end of a ride I thought I was running low on fuel so I switched to reserve. Filled the tank the next day and maybe 2km from the station the bike started to backfire and seemed like it was not running on all cylinders.

Have never done anything to the carbs so decided to pull them. While disassembling them I noticed the carb slider in #2 was stuck in the open position, found the spring broken in three pieces. (Wished I had taken the carb caps off before removing the whole carb assembly)

While waiting for new springs I removed the float bowls to check for varnish buildup. To my surprise everything looked like new so reassembled without removing the jets.

The bike started instantly after reassembly but cylinder #3 was continuously popping through the exhaust. I could tell it was #3 due to the fact that I have 2 Brothers exhaust installed.

Changed out the vacuum piston to another carb to eliminate the possibility of the diaphragm having a hole in it. Switched spark plugs. Cylinder is getting fuel. Checked vacuum lines.

I am hoping someone can help me out and give me any ideas on what to look for. 

Thanks
Mike

[Ricky-D]

Popping when..?

1)  At idle only
2)  At any rpm
3)  Accelerating
4)  At deceleration

You get the idea.....

Need lots more information

***

[Michvalk]

You have an intake vacuum leak. Somewhere there is a cracked vacuum line, or intake O-ring, or one of the intake boots from the air cleaner is not on the carb square. Go over the installation of the carbs, and I bet you find the problem!

[Mike]

Popping when..?

1)  At idle only
2)  At any rpm
3)  Accelerating
4)  At deceleration

You get the idea.....

Need lots more information

***

It pops a little at idle and the frequency increases as I increase the rpm's

[Mike]

You have an intake vacuum leak. Somewhere there is a cracked vacuum line, or intake O-ring, or one of the intake boots from the air cleaner is not on the carb square. Go over the installation of the carbs, and I bet you find the problem!

With #3 exhaust popping, would the leak have something to do with carb #3? I will check everything over again tomorrow. Thanks

[Michvalk]

Well, I'd for sure start with #3!

[Mike]

Good morning,

Well, checked everthing over this morning. Made sure the boots from the airbox to the carbs were seated properly, checked the intake o-rings which were replaced last season, vacuum lines, all seems right and #3 is still popping.

Not sure what to look for now, any more ideas out there?

Could it be anything to do with the spark plug wire?

Thanks
Mike

[Ricky-D]

I would think the problem is the carburetors need synchronizing.

#3 is loafing.

***

[Mike]

I would think the problem is the carburetors need synchronizing.

#3 is loafing.

***

I wondered about that, all I did was replace all six slider springs, remove the float bowls and funnel setting plate for inspection.

Sure screwed something up.

Thanks Ricky-D for giving me ideas of what to check.

[salty1]

I would think the problem is the carburetors need synchronizing.

#3 is loafing.

***

If you don't have a vacuum leak, I would also suspect carb synchronization is in order.

[NDFRC]

Popping when..?

1)  At idle only
2)  At any rpm
3)  Accelerating
4)  At deceleration

You get the idea.....

Need lots more information

***

would like to piggy back of this and see if i can get help narrowing down my phat ladies 'popping'.
I know I caused it cuz it didn't start till after my working on it, yesterday I installed a pingle, air filter, and de smog. I did the dsmog to get rid of a slight decel backfire that i had and it did take care of that. I have been checking and double checking all vacuum connections and air box to carb to intake manifold clamps and exhaust nuts. I haven't changed intake orings yet(do they have to leak to be bad?) back to my new popping..  I can do hard accelerations thru the gears and hard, long decels without any backfire whatsoever, its when i have it right there at point where your not accelerating but your not decelerating.. just holding it at cruise and it seems to be worst at a steady 3k..  pop, a couple secs another.. then more.. its a sharp pop, sharper than a backfire seems, more crisp like and definitely on the right side..1,3, or 5.  hope this is okay to spin off on this thread with my problem, i don't mean to confuse the issue.

[Mike]

She's running fine again!

Took the carbs out again, cleaned the jets this time. While reassembling I double checked all connections and vacuum hoses.

Thanks Michvalk,Ricky-D and all for helping out.

[salty1]

Glad it's running again!  I still would sychronize your carbs. FWIW   

[twisted]

Just thought I would add my story to this.... About a month ago I was out for a ride two up... noticed that my 2000 tour was sluggish and a little vibration. Found out I had one dead cylinder... Also over the past while it had started Popping on decel. So Vacuum leak. Decided to do the carb thing... Thanks to D-ray... excellent videos... Well what an odyssey ... I am now an expert no on all things carb and fuel... if it was wrong I had it!!! To make a long story just as long... I had a cracked intake o-ring, sticky floats, cracked vacuum fittings, California smog, leaky petcock, choked jets ( not completely blocked ) previous owner had done some stuff with the carbs and the pilots were set at 6.5 turns and then filled with silicone, #5 intake tube from air box to carb was not sealed properly... and more!!! I had the carbs out 3 times to get them right... I desmoged (thanks to the guy from Quebec) I added the electric fuel shut off and I added a ford inline fuel filter that screwed directly into the electric valve with a nipple on the intake end...installed the 38 jets and run the pilots at 2 turns... put the variable timing kit in and built my own balancer with lots of hose and aquarium valves... and added a "t" into the vacuum line to the petcock so I could add a vacuum tester to hold the petcock open and balance all 6 at the same time ( I use forceps to close the intake end while it is off the intake..) The home built balancer and vacuum tester are well worth the investment of about 50 buck to build. The 3rd time I had the carbs off I used a whole can of carb cleaner ( i don't think the new stuff is as good as the old stuff... just my opinion) I changed the float bowl screws over to stainless allan cap screws and bought a special screw driver to adjust the pilots while installed... can be done without but much easier with the tool...

Anyhow I think I can call myself and expert on all things carb now ... Had the scooter out yesterday for a good hard run... ran better than ever before...