Performance primer

scotts · Posted: April 7, 2007, 7:53 pm Post subject: Performance primer

Let's say you have a stock 650 in good tune. What are the best bang for the buck upgrades? What would you spend your dough on first, then next, etc.
I'm told to get the Boyer Ignition before an exhaust. Are there any cheaper mods? Air filters? Etc.
Give me a run-down from low-buck bolt ons all the way to big bore, re-phased motors. Edumacate me!

xsjohn · Posted: April 7, 2007, 8:33 pm Post subject: Re: Performance primer

I make a kit for the 80-84 now that kicks ass............

John Underwood

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

I usually start with better air filters and exhaust, and some carb re-jetting. I do this on pretty much any bike I get, not just 650s. On the 650, the next thing that usually needs attention is the suspension and handling. New swingarm bushings and steering head bearings are usually needed along with fork springs and better rear shocks.

Apparently, one of the weak points in the motor is the ports. They're very rough with lots of casting flaws from the factory. Some porting work is said to be one of the best things you can do. You'll probably be into your top end within a few seasons as most of these bikes seem to need some cam chain, cam chain guide, or tensioner work so you'll get your chance at the ports.

The Boyer is a nice unit but rather spendy. For that $249, you can do all this other stuff and more. Besides, what good is a nice running bike that wobbles around corners? From what I've read, the stock ignition is fine for stock or mildly modded 650s. I'm perfectly satified with the points set-up on my bike. If you go big bore, hot cam, etc., etc., then yes, I could justify it then.

As John said, get it in a good state of tune, everything set exactly to spec, and this is a nice running bike. Easy starting, nice running, adequate performance - it's just a great all around machine. For an around town, local ride, I think it's one of the best bikes out there.

scotts · Posted: April 8, 2007, 11:46 am Post subject: Re: Performance primer

5twins, that's exactly the type info I'm looking for. The bike will be getting a good tune-up right off the bat, including a valve adjustment and a cam chain adjustment. Don't know if I'll get a chance to polish up the heads though.
I'll probably change out the homemade header for a stock type exhaust; probably the Commando unit.
Good airfilters...recommendations? K&N? Uni-filters? etc?
What do you recommend for rear shocks, because I feel like mine will need replacing soon.

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

That new Commando system Mike's has is supposed to be very nice. I've already replaced my headpipes so I'm thinking of getting just the Commando mufflers.

The UNIs are the cheapest good air filters but I hear they deteriorate after several years and can start falling apart. I use K&Ns. If you take care of them and don't inadvertantly poke holes in them or anything, they'll last you a lifetime. I got the pod version because they were cheaper than the airbox replacements and my airboxes were just a mess (from battery acid) when I got the bike. If you go with K&N pods, you'll want the RU-0981s if you have BS34 carbs and the RU-1820s if you have the BS38s. Same filter body, just different mounting flange I.D.s. Here's about the best place to get them. Good price and free shipping .....

www.ajusa.com/cgi-bin/...ory_lookup

Some report the replacement shocks from Mike's are pretty good but I'd rather put that $79 towards a nice set of used Konis. They're my favorites and you can rebuild them if need be.

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