#1 backfire

deecha · Posted: August 1, 2008, 5:45 pm Post subject: #1 backfire

I have a 1980 650 and I have the xs performance air filters and stock carbs. I got the bike to run and the right side seems to be running fairly well but the left side keeps back firing and popping so any suggestions or help would greatly be appreciated.

xsjohn · Posted: August 1, 2008, 6:09 pm Post subject: Re: #1 backfire

Have to clean the pilot circuit........Carefully remove the mixture screw and there is a washer and a tiny and tiny o-ring below it.....real easy to loose them for sure....o-ring first them washer....bent over paper clip will let you fish them out.......to putting them back after cleaning ...place them on the mixture screw with the carb upward and they will go in the correct position without having to drop them in there and hope..........

Spray brake cleaner or carb cleaner in the mixture screw hole and hold your finger around the spray nozel to force the spray into the pilot circuit.......a small guitar string to probe the three tiny holes behind the carb throttle plate......has to come out freely or pilot curcuit won't work properly or at all..........another free finger can cover the mixture hole in the throat to be certian the three holes are clear..........been there and done that......and will again........

And when you are all done you still have a epa nightmare........Ha..........

xsjohn

deecha · Posted: August 1, 2008, 7:17 pm Post subject: Re: #1 backfire

thanks a lot xs john I will do that and let you know the results of my work.

xsjohn · Posted: August 1, 2008, 8:58 pm Post subject: Re: #1 backfire

Get it runnig consistant with no raises or lowering at idol and a decent exceleration and then I can help with the rest........spray the throttle shafts on both sides of each carbs......if it changes much the seals are bad on the throttle shaft....always oiled those places while it was running and made carbs last till last week....59 thou....changed them both out with the spares and glad to see the old ones gone.....not much into changing throttle shaft seals and both were geting bad....will make low speed mixes a pain for sure.......

xsjohn

deecha · Posted: August 10, 2008, 11:21 pm Post subject: Re: #1 backfire

I cleaned the carb and I got the bike running but still will not idle. It seemed like the #1 cylinder was not firing each time so I swapped the plugs and the #2 cylinder started doing the same thing. There is no more backfiring or fire coming from the pipe so that at least is a good thing.

deecha · Posted: August 10, 2008, 11:24 pm Post subject: Re: #1 backfire

Another thing I forgot to mention that the left side mixture screw had the washer and the o-ring but the right side only had the spring, no o-ring or washer. How much of a difference does that make?

tweedy64 · Posted: August 11, 2008, 9:11 am Post subject: Re: #1 backfire

A lot i'm afraid me ol fruit. cheers tweedy

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Take a paper clip and make a tiny fishhook out of it - odds are the washer and O ring are stuck at the bottom of the shaft where the idle mix screw goes in. Order and replace both O rings (Mikesxs.com) (make sure your aren't stacking them on the right side - get the old ones out.

To answer you question - the O rings make a big difference.

If the problem travels with the plugs you have bad spark plugs. I have had bad ones new out of the box.

Also check the resitance of the plug caps (on the wires) they should be 4 K if they are more replace them.

deecha · Posted: August 11, 2008, 3:44 pm Post subject: Re: #1 backfire

Thanks a lot guys I will get the parts and let ya'll know what's going on.

deecha · Posted: August 20, 2008, 6:56 pm Post subject: Re: #1 backfire

Just wanted to let everyone know I got the bike running today and it is running good, still some minor tuning. I installed new mixture screws along with new spark plugs and spark plug caps and it fires right up. I can't tell ya'll how much I appreciate ya'll helping me out thanks a lot guys keep up the good work.

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