Right side backfiring exaust??????. Left side fine

[birdhouse]

These carbs (79' BS 38's) have been gone through already. Anything I missed? anyone know how to properly set up carbs for pod intakes? I recieved some advice off here last week and I re jetted it and the bike ran like complete shit. so I put the stock jets back in it and it runs good just has backfire in the right side. All advice is welcome ..Thanks guys

 

[Tech7]

Backfires when? Could be an ignition problem.

 

[birdhouse]

back fires at idle. And is slow to return back idle after reving the motor?

 

[gaps]

Sounds like maybe a lean mixture, try a bit of choke/enrichener...if you loose the pop and the revs drop normal then you are lean. Have you been fiddling with idle mixture?

 

[littlebill31]

The slow return to idle is usually the pilot jet. As gaps said, running lean. Your mix screw should be 2 1/4 out for stock. If you have to go more than 2 out past stock, which for you would be 4 1/4 turns, you need a bigger pilot. Turn the mix screw all the way in, counting rotations to see where it is. When it stops you then turn it back out to 2 1/4, stock. Counter-clockwise=rich clockwise=lean.

Check for air leaks which cause the backfires. The hot exhaust coming out of the engine hits the cooler, ambient, air causing it to pop.

http://www.amckayltd.com/carbguide.pdf

 

[birdhouse]

I have only messed with the throttle stop adjustment. It was mentioned to me to adjust mixing screw 2 to 3 turns out but I never did. Where is this mixing screw located? i am new at this please bare with me!!! Thanks

 

[birdhouse]

Airleaks are the next course of action

 

[littlebill31]

Sorry, I meant exhaust leaks. The mix screw is a little standard head screw. I don't have a picture. If you look at the throttle/throttle stop on the carb, above the spring there are 2 standard screws. The big one is a vacuum screw. The smaller one above that is the mix. Look at the link I added. There is a picture towards the end of it.

The throttle stop actually controls your left carb. The synch screw adjsuts the right. You need to do a "dance" between the throttle stop and mix screw. Gotta read that link for the carb Guide, beleive me.

 

[birdhouse]

I just looked at tha link you sent me and found it.

 

[littlebill31]

It would take all day to explain how to adjust it.

Print that guide out and read it like mad. It IS the carb bible!!

 

[grizld1]

OK, one more time! Before you touch those carbs again, service everything else: cam chain tension, valve lash, and ignition timing (checking both advance and retard positions), in that order. Your carbs weren't "gone through" unless they were stripped (fuel screws, floats and needles, and jets removed), with every passage blown clear with solvent and compressed air, float level inspected, float function checked on the bench, and thorough inspection done for air leaks. If you take anything for granted you'll likely either be selling that bike or still thrashing around this time next year. Do a compression check while you're at it; if you have more than 10% difference between cylinders you'll have an idle stagger. If compression is in spec and everything is dialed in right and you still have an idle stagger, run a leakdown test; that often reveals defects that don't show up on a compression test.

 

[birdhouse]

they were, except for removing mixture screws. This motor only has 2500 orginal miles on and was bought from the orginal owner is all that other stuff need to be gone through with so little miles?

 

[littlebill31]

Most certainly yes. It's 32 years old. Never trust the PO, never! Gas sitting in a carb just over 1 winter can completely screw it up. The mix screw is a major adjustment and easy to clean. So if something that easy was overlooked, what else was?

 

[Classic]

Sounds like the advance springs could be weak and timing is getting thrown off. How does it run with the stock airboxes?

 

[grizld1]

Mileage sometimes doesn't signify. If the bike wasn't being ridden, it wasn't being maintained. Corrosion doesn't come to a halt because things aren't moving and neither does off-gassing of rubber and plastic parts, grease, etc., and springs left under pressure weaken. One more thing: go through the harness one connector at a time, clean 'em up, and apply dialectric grease. Re. carbs, there's no way the idle nozzle in the spigot (the one in front of the butterfly) got properly cleaned with the fuel screws in place, and if you didn't have a reference for the location of the fuel screws I tend to doubt you had one for the float height spec. You can either make up for 3 decades of neglect at the git-go or play Whack-A-Mole with defects for as long as you own the bike.

 

[XSLeo]

If I can get you to listen to one thing from me, that will be to listen to what Grizld1 has to say. He is one of the two carb guru's who wrote the carb guide.
In the factory manuals they have a list of maintainance items and how often they should be done. The cam chain tension, valves, ingition timing, oil change. these thing should be done every 2000 miles.
Your bike has 2500 miles, do you know for sure these things were done at 2000 miles.
They are not hard to do, just follow the repair manual.
At 3000 the book says to clean the carbs.
The bike has set along time. Fuel doesn't age well. It starts to change almost as soon as it gets made. In a few short months it starts to seperate and turn to a varnish like sustance. This varnish plugs up passages in the carb. What doesn't turn to varnish slowly corrodes the internal parts.
So if it sat for years just think how much varnish has built up and how much corrosion has occured.

 

[birdhouse]

Griz,Leo and Little bill you info is invaluble. Im new to bikes and this is my first build and I want it to be done right the first time, no sence in taking short cuts now. I will pull the carbs again and follow all instructions you have given. I did find that my clamps on my rubber in take mainfolds were,nt tightened all the way, so I tightened them until they touched. Just wanted you guys to know also I have coverted my air filters to pod filters. As instructed I went up to a 137.5 main and a 30 pilot and also moved the e-clip on the needles to slot #2. Is this information correct? I live in virginia beach right on the ocean just incase you need to know location. Im trying to figure this stuff out with the help of you guys so I can learn my bike inside and out. I apoligize if im being a pain in the ass. Thanks for all the help once again. I will read manual tonight to get some knowledge on all other maintenence you guys noted

 

[littlebill31]

I live in Delaware, sea level, and run 142.5 main and 45 pilot. Now, I have BS34's, pods, Harley exhaust, but as an example every bike is different and having, as 5twins and
Grizld1 say, a trained ear really helps. My bike was popping not too long ago and I tightened up the clamps...fixed. But even before I did that I started with the standard, cam chain, valves, Timing ( I have a TCI, but should still check) then to the carbs. The carb guide is a must to read and learn! And doing these little adjustments gets you so used to them that they become second nature.

 

[crazyazsredneck]

make sure the plug wires on tight that was my problem

 

[birdhouse]

Crazyaz, funny thing is the boot on that side is cracked would that be a problem?