New 650 owner!

jerseyjew · Full Member Joined: Mar 28, 2008 Posts: 48

Hello all! As the username suggests I am a jersey guy, although I currently live in DE. I picked up a 1978 XS 650 Special from a local guy last summer. According to him the bike has 116k miles on it which seems little insane to me, but who knows. The bike ran decently when I purchased it, but the charging system immediately took a dump so I replaced just about everything. It ran fine and was fun to ride but the suspension was on the outs as well. I just recently rebuilt the front forks while replacing the rear shocks as well as the front and rear sprockets and chain. I love how tight the bike feels now. My only problem left is a pesky clutch a slight miss/hesitation when going full throttle above 5k or so. I have already gotten some great advice from this site and hope I can contribute something back! Thanks for reading

-Joe

Retiredgentleman · Posted: March 30, 2008, 7:56 pm Post subject: Re: New 650 owner!

I've got one of those 78SE's myself. They are a good year, got the 35 mm forks/cast wheels/disc brakes..........don't have the electronic ignition, but learn how to set-up the points, clean the carbs really well and check all electrical connections and all is well.

jerseyjew · Full Member Joined: Mar 28, 2008 Posts: 48

The points I am still trying to figure out, hahah. The guy that had it before me pretty much rebuilt the whole harness so the electrics haven't given me too much trouble!

jayel · Posted: March 31, 2008, 8:32 am Post subject: Re: New 650 owner!

"a slight miss/hesitation when going full throttle above 5k or so" you might just be experiancing CV carb lag cracking open the throttle doesn't open the slide like a cable controlled slide the engine vaccum has to raise the slide, what you're running for air filters/air boxes can effect this, so can the needle jet setting if you have the adjustable needles raise them one notch

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

If the bike has some mods like air filters or freer flowing exhaust, you may need to go up one size on your main jets as well. Above 5K is mostly main jet territory.

jerseyjew · Full Member Joined: Mar 28, 2008 Posts: 48

Ok thanks for the tips once again. I believe the exhaust on the bike is stock but it does have the stock filter boxes removed and is currently running foam filters directly off of the carbs. I wonder what size jet I would need to run as the main jet. I am almost positive the jets in the carb are factory.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

First you'll need to determine if the carbs are the originals. Then you'll need to check what size is in there now. These bikes are so old that many times jets, even whole carb sets, have been swapped. There's a chart I drew up at the bottom of this thread that lists all the stock jetting specs for the various years .....

xs650temp.proboards29....1188079591

If your carbs are original, stock main would be a #127.5. They increase in 2.5 number increments so you'd want a #130.

jerseyjew · Full Member Joined: Mar 28, 2008 Posts: 48

Holy smokes that is an informative post! I can't believe it took such an involved write up on some carbs developed in the 1970's. Props to you 5twins. I am under the impression that the carbs are still stock, but I will actually check on the bike to make sure. I guess I will start by pulling the carbs off and then we will go from there!

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Well, even though this was just a "650 Yamaha" to most folks from '70 to '83, there were many little changes and upgrades during the production run (especially the carbs). This is what makes this bike so cool in my opinion. There's lots to learn about it and you can really get into the developmental saga of the model line - if you care to. If not, then take it to a shop, pay them hundreds of dollars for a simple fix you could have done yourself (and they probably screwed up) and live with the results. Old bikes aren't for sissies. They take a real commitment on your part. If you're willing to lay your hands on the wrenches, I for one, am willing to tell you when, where, and how much to turn them Neutral

jerseyjew · Full Member Joined: Mar 28, 2008 Posts: 48

Sweet! I am definitely ready for the challenge. I am mechanically inclined, so I don't think its going to be too terrible.

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