Problem with my bike 1982 Yamaha Maxim xj 650 NEW TO SITE!!!

Hello everyone! I just purchased an 1982 Yamaha Maxim XJ 650 last week. It has a stage three dynojet kit (rebuilt in November cleaned and all etc.), a rebuilt motor (rebuilt in November), carb with 4 individual air filters, and a moded exhaust with headers and half cherry bombs on each side, has almost 20k miles, and has seca forks in the front.

It turns on immediatly, and I am on my way. I cruised around for 45 minutes yesterday with no problem. Takes a while to warm up, with some backfiring. Once warmed up, it ran great. Took it out again that night, while ridin started spitting and sputtering,a dn cut out in the middle of the road. I waddled to the side, restarted after several tries, made it to a parking lot and died again. I killed the battery trying to start it, so had to run it up the hill multiple times and ride down trying to pop the clutch; didnt work. My friend came and jumped me. I road for a bit, then cutout again. This happened 4 times; longest 2 miles of my life!! I would get goin, hard to accelerate, backfiring and all, and I had to keep it reved high, and even so it was hard cause I would sometimes push the clutch in to chaneg gears and the bike would just shut off and I would glide (lights still on and all).

I have been readin different posts and decided to start with changing the battery today, and put fresh gas in. I originally ran it with gas that had sat in it since January. Went for a test ride, still back firing, hesitating acceleration, but once it gets goin flies like hell. The horn also doesnt work, but I havent investigated that yet. I just want to get it running right and dont want to cut out again in the middle of the road! Also, I have to keep the choke on to keep it idling higher, cause with teh choke all the way off, it idles really low and wants to cut out.

The bike still starts up immediatly though, one push on the starter and its on like a charm.
I am thinkin it is too lean since the backfiring and needeing to keep the choke on, needs more fuel. I dont get it though because itw as running awesome earlier in the day, and the couple times I saw the bike and test road it before I bought it.

PLEASE HELP!!!!! (I attached some pics of the bike so you see what exactly it is)

Thanks
Dan

Anyone near Buffalo, NY

 

Make sure those mixture screws are 2.5 turns out at least. When I first got mine maxim the PO had them turned way in, and it would run fine, but eventually would die, and be a pain to get back running. Also you might want to clean the tank out, and run some seafoam through the carbs

 

Re: Problem with my bike 1982 Yamaha Maxim xj 650 NEW TO SIT

thanks for the fast response! I did not run seafoam, but I fully drained the tank today and put in fresh gas. The filter is clean and all, and now had fresh gas.

 

I dont see pics. That old gas may have slightly clogged the petcock?

 

make sure there isn't any leaks in the exhaust system allowing fresh air to get in... somehow or another that leads to backfiring (i forget why). also i'd say check your valve tolerances... if your backfiring that could possibly be a floating exhaust valve... farting out the carbs is a sign of a floating intake valve.... many helpful links available in my signature for all the FAQ's and How-to's and Walk-throughs of these wonderful XJbikes.com patrons.... best of luck to ya!

 

So I checked the spark plugs and a rich black deposit was on each one. I cleaned them up, started the bike, no backfiring or nothing, no popping or anything. Took it for a ride. I dont get a mile or two down the rode and startes running crappy again. It died, took forever to start, finally got it rode a mile and half and pushed the other half mile home.
Carb adjustment? running way to rich right? I put on a new battery and drained the gas and put fresh gas in.

 

How about a timing light to tell if you got spark, when it's acting up?
You could have an Ignitor box with an intermittent short, or a coil going out. To verify, you swap with a known good one.

 

Sounds like you are running a size or two too big of jet. I'm not a carb expert, but experience from the past says that your idle mixture is fine, but your running mixture isn't. Clean the plugs and do a chop test to see if the carbon buildup was from a rich condition or from running poorly. I'd do that before switching out electrical components.

 

Not having any history with the bike makes it tough to diagnose. The PO got rid of it for a reason. I think we might now know why. Consider this your rite of passage.

"It's the carbs, it's always the carbs." Truer words were never spoken. My first impression is that your float levels are set too high. With the aged gas in the tank, it's very possible you've also got crud in the carbs, too. I would recommend that you:

• add an inline fuel filter.
• replace the fuse box (if it hasn't been done).
• check your float levels.
• remove the carbs and clean them.
• replace your spark plugs as they're probably fuel-fouled.
• bench synch your carbs.
• reinstall and synch your carbs with a manometer or equivalent.
• colortune then fine tune the carbs.

This should get your bike running in top form and make you an ace XJ mechanic. Also, once you get the carbs apart, seek advice on the jet sizes installed (they should have numbers stamped on them) for your configuration and location (altitude). You may be under- or over-jetted.

 

Re: Problem with my bike 1982 Yamaha Maxim xj 650 NEW TO SIT

I cleaned out the carbs today. ALready looked extremelky clean but did it again anyways. The guy I bought it from went through the whole bike last year. He is actually helping me to get it running right; weird cause it was running great for him and once I got it went down the tube haha, but he is helping me to get it back in shape ( friend of mine; he bought a new bike so was gettin rid of his old one. I have seen it around for a whole and always seemed to run good. I watched the rebuild happen!)New CDI box and fuses etc., new piston rings, all new gaskets and seals, modified high flow exaust with half cherry bombs, and the stage 3 dynojet kit, and 4 individual air filters. Just put a new battery in, will get new spark plugs, even though I just cleaned them up and look great today. After reading what it says on the dyno jet box, it seems as though the stage 3 dynojet kit is the perfect match for the bike. Everything looks great inside the carbs. COuld this be out of aadjustment because the bike was redone during the winter time?
I cleaned the inline filter (looked great already), all fuses are in good condition. Bike will start up fine (just one click and its runnin) but after a mile or so down the road it will start sputtering. I am going to put the carbs back on today, hook everything back up and use the vacuum tester for the carbs.

 

Re: Problem with my bike 1982 Yamaha Maxim xj 650 NEW TO SIT

This may sound stupid, but check the vent in the gas cap. You take it apart, clean it, and put it back on in 15minutes. I had a similar problem with my cb350. The vent was stuck, so as fuel was coming out of the tank, a vaccuum was being created. I could fix the problem by leaving the cap open and never experience a problem, if I closed it, a mile or two later, it would sputter and bog down eventually stalling.

Its likely not the problem, but it is a quick check.

Stephen