All 4 carbs backfiring.

[fatbiker]

I bought a 2005 Max in great condition a few weeks ago and when I picked it up it ran fine with the exception of one of the carbs backfiring on occasion. I installed an Ignitec computer and COP's kit and while the bike became more responsive it would still backfire thru the one carb. Now after riding the bike a few weeks it backfires thru all 4 carbs. Idle is perfect but when the RPM's reach 2k and above they start to backfire.

Here are some of the things I checked:

Changed the fuel filter as it looked stock. No change.

Spark plugs were gapped at .27 . Installed new plugs and gapped them at .27 as well. No change.

Checked the airbox rubber boots for leaks. Didn't find any. Went ahead and replaced all the rubber boots with new ones. No change. Bike backfires both with and without the airbox on. Made sure the engine breather hose was connected and it is.

When I installed the COP's kit I removed all of the old ignition coils. Have made sure that all wiring is hooked up correctly and not reversed.

Checked the settings on the air fuel mixture screws. The front two carbs were at 2.5 turns out and the rear were at 5 turns out. Adjusted all carbs to 2.5 turns out. No change.

Checked the program setting on the Ignitech unit. I am running the the 97 - 07 program with V-Boost and COPs. Dwell is set to SHORT.

Battery tested out good and has a full charge. Charging system is putting out good amps.

One thing I have noticed is that the fuel pump does not make it's usual clicking noise when I turn the bike on. Even when I removed the fuel filter and installed a new one it did not click. Gas is getting to the carbs as it runs for a long time. Possible fuel pump issue?

Anything I missed?

 

[one2dmax]

You need to be running the 85-89 program on the ignitech I would think.

 

[fatbiker]

On a 2005 Max? I moved the Ignitech and COP's kit from my old 86 Max and used the new wiring harness you sent me. The 85-89 program was installed and the bike would not start. I then installed the 90 - 2007 program and it fired right up.

 

[Traumahawk]

Where are the carbs back firing ? That "poof" thru the airbox? Usually that means that the A/F screws are too lean. Mine would do it, occasionally, then when I enriched it up, never had it again.

 

[fatbiker]

Carbs are backfiring thru the top into the airbox. They are all currently set at 2.5 turns out. How did you go about setting them to the right mixture? Should all 4 be set at the same number of turns or will each carb be set differently?

 

[Traumahawk]

Ok.....when I had this problem, the bike was basically stock.....and had stock pipes. I set all of them to 4 turns out.

Since that time, I have gone to a kerker 4-1, Seans muscle jet kit. I have an IR temp gun from harbor freight. With the bike idling off of choke, I tried to get the temps all of the same. The fronts are basically 3 turns out, and the rears are 3.5 turns out. Lean burns hotter, rich burns cooler.

So, the answer your question, no....they dont all have the be the same turn number. And they arent the same number from the factory.

 

[Traumahawk]

You will have to aim the temp gun at the same place on each of the pipes. I think the stock exhaust are double coated on the fronts....but I'm not for certain about that.

 

[davesax36]

Check fuel filter.
Check gas tank for rusty dust.
I have a video on here somewhere showing my carbs sneezing. It was clogged pilot jets. It might have been that one was a little clogged and running it spread some junk into the others.
Does it idle without the choke?
Do the revs hang when blipped?

 

[fatbiker]

I was able to adjust three of the carbs so that they don't backfire anymore. I just kept adjusting the air/fuel screw out until they stopped. The fourth carb is still backfiring. The air/fuel screw on that carb is very hard to turn. What could be the cause of this? This could be the problem.


Fuel filter was changed. No rust in the tank. It does idle without the choke. The revs do not hang when blipped. Bike only backfires over 2K but idles perfect and starts up great too. May have to clean out the pilot jets.

 

[Traumahawk]

Normally a carb will backfire up thru the carb when it gets lean.


ALSO....if the carb screw is hard to turn....dont force it, and strip it. Squirt in some PB Blaster, and walk away. Come back 2 hrs later and try it.

 

[bazwell]

Sounds like you are on the money there.
Which cylinder is the problem?
Maybe shotgun clean the carbs and check the fuel enrichener diaphragms if it persists.

 

[fatbiker]

Well, I took the bike out for a ride today and once again all 4 carbs are backfiring up thru the airbox. I'm beginning to believe that it's the recently installed Ignitech unit and COP's kit causing the problem. When I bought the bike a month ago it was bone stock and ran good. When I installed the Ignitech unit and COP's kit it ran great for a day or two then all of a sudden all 4 carbs started backfiring. I installed new spark plugs and gapped them at .026 . I've checked for air leaks around the airbox rubber boots as well as the intake rubber boots. No leaks. The Ignitech is programed with the 90-07 V-boost with COPs program. Could it be the Ignitech unit is not programmed correctly or am I missing something completely?

 

[ItsDuckie]

I suggest a carb sync. Mine did that. Sync'd the carbs popping went away.