'81 Backfire and sputter

cfinn1 · Posted: July 31, 2007, 1:59 pm Post subject: '81 Backfire and sputter

Rode my 1981 XS650 into work this morning (70 degrees out) and it was running GREAT. Rode the bike to the gym over lunch (83 degrees out) and it ran GREAT. Came out 11/2 hours later and started it up and it was popping/sputtering unless I pulled the choke out. Never really seemed to get better even after it warmup up.
I know this vintage tends to run lean and I believe this bike is running on the lean side but this definately CHANGED at a snap of the fingers. Any ideas to what might have happened and what my next steps should be?
Got a trip planned in a 10 days and I need to get this resolved.

xsjohn · Posted: July 31, 2007, 2:36 pm Post subject: Re: '81 Backfire and sputter

Sounds like some junk found it way int the pilot jets......Fuel filter will help...Have you cleand the tank out......Is there junk in the fuel system.....If that thing is lean I cringe to think about a trip.......

John

cfinn1 · Posted: July 31, 2007, 2:47 pm Post subject: Re: '81 Backfire and sputter

Tank interior is clean as a whistle, looks like new. I've put 12000 miles on the bike with current jetting. It doesn't show signs of running lean from a performance stand point but the plugs are nice and clean and definately doesn't look to be running rich. As stated on this board this vinage XS650 runs on the lean side of things. I was thinking about richening it up based on the postings you have made on this forum.

Do you think a little seafoam or other cleaner in the gas tank would be worthwhile? I'll take a look at the fuel filter and maybe change that out. I'm wondering if I somehow developed an air leak, screw fell out etc...

By the way XSjohn I'm fasinated by your posts regarding what you have done with this bike. Definately is very helpful to us general hacks out here just trying the enjoys these great bikes.

KYLEPRESTON · Posted: July 31, 2007, 2:55 pm Post subject: Re: '81 Backfire and sputter

I DONT SEE HOW A HOLE WOULD DEVELOP LIKE THAT BUT YOU COULD CHECK THE CARB DIAPHRAGMS FOR PIN HOLE LEAKS THEY COULD HAVE DRIED OUT. ARE YOU LEAKING ANYTHING?

cfinn1 · Posted: July 31, 2007, 3:04 pm Post subject: Re: '81 Backfire and sputter

Didn't see any evidence of any thing leaking. I was wondering if I develop an air leak in the carb mount or something of that nature.

xsjohn · Posted: July 31, 2007, 3:44 pm Post subject: Re: '81 Backfire and sputter

cfinn1..If you could get the bowls off easily like I showed it would be 10 minutes to check ...Maybe the junk was alrerady surounding the pilot jets and just moved to the tiny opening and closed off the fuel.....You guys aren't hacks......The best person to tune the bike is the owner......he is the one that rides it and hears it a bunch...

John

cfinn1 · Posted: August 1, 2007, 8:42 am Post subject: Re: '81 Backfire and sputter

I had a little more time to "listen" to the bike on the ride home after work. The popping is occuring around 2500 rpm and only on the right side. I figured this eliminated the fuel filter since that feeds both sides. I took the carbs off and disassembled the right carb. I blew everything out and pulled the jets out and didn't see ant problems. Put the carbs back on and it ran like a CHAMP!!! I wish I new exactly what I did to fix it, figuring it was some crud in there somewhere. Glad it's running good again, nice ride in to work this morning Smile

xsjohn - ok, hacks might be too strong of a word, how about the "newbies in training"

Thanks for the help guys.
Happy riding.....

xsjohn · Posted: August 1, 2007, 8:56 am Post subject: Re: '81 Backfire and sputter

The ole hidden piece of junk syndrome......How about work in progress....Remember they do run good lean...that's the beauty of water cooled engines.....not good for air cooled ones though...Best to play with it to learn the boundries if you enjoy that kind of stuf.....If you don't weigh a bunch some taller gears makes longer rides easier to deal with.........

John

cfinn1 · Posted: August 1, 2007, 10:08 am Post subject: Re: '81 Backfire and sputter

I order some jets this morning from MIKES to fatten up the mixture, ounce of prevention...........

xsjohn · Last edited by xsjohn on August 2, 2007, 4:28 am; edited 1 time in total

Good......You can play with the needle position at your leasure....Once you find the sweet spot you will be amazed what one or two thousands does when you venture from that spot...Final determination is always made at full running temperatures....Just got off the expressway and had to remind myself.....Before dicking with them..one exit was a hair raising experience....now I can ride till I need a proctologist.......Too much information I know.......

Canadian needles might be fun to play with..................

John

cfinn1 · Posted: August 1, 2007, 3:36 pm Post subject: Re: '81 Backfire and sputter

By the way I'm also picking up the laser thermometer today so I can check out the temps before I put in the new jets, way cool stuff and looking forward to it.

xsjohn · Posted: August 1, 2007, 4:48 pm Post subject: Re: '81 Backfire and sputter

Great......It takes them at least 10-15 miles to get completely warmed up....good to pick a day in the high 80's.......

John

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