Newbie project questions

natemeins · Posted: March 10, 2007, 12:55 am Post subject: Newbie project questions

Hey folks,
New to the 650 scene, still trying to decipher all the different models/engines etc.! My experience is mostly with old VeeDubs. Really excited about doing this project. Have a '75 650 that looks like it has been used as a trail bike. Plan to build a budget-minded cafe racer. Initial plans are 34mm mikuni carbs upgrade and performance cam/valve springs from Mikesxs. Engine seems to have very good compression now, turns over good (doesn't run right now) so should I worry about getting a cylinder rebuild kit or going oversize? Can I get away with just changing the piston rings for the same size that's in it now? Is that overkill at this point? Wanting something reliable but fun for around town. Any help or opinions about these ideas would be greatly appreciated. Have lots of other questions as well concerning suspension and such but I'll save that for another forum. Thanks!

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

If it has good compression run it or if you just wanna freshen it up some than go for it but check the condition of the cylinder walls and have the block liners checked for taper.

The carburators are an excellent choice but why would you want to slap a performance camshaft in without addressing the real breathing issues that restricts the XSs performance potential. The head is the heart and soul of any motor not a camshaft, I'd suggest you work on that first,then if you feel the itch to upgrade the power band,then slap a camshaft in.............Jack

royfisk · Posted: March 10, 2007, 8:46 am Post subject: Re: Newbie project questions

exactly jack, I think personally that I would also do the cam chain, adjuster shoe and follower shoe. These seam to be high wear items on these old machines, or just dry rotted out. But I would do all 4 , carbs, head, cam, and chain adjusters. Now you would have a decent streetrod. As for the pistons do a compression test, adjust the valves and do it again. Is it within spec? If not try to get it running and run it awhile, do it again is it within spec? If so run it, if not rebuild it. At that point you need to decide what you want! Mayby a 750 kit?

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

Hmmmm.....reliable and fun around town. Hmmmm...budget minded.

Well, what I would do assuming your cylinders are in good shape is as follows; hone cylinders, stock ring replacement, mill 30-40 thousandths off the top of the cylinders (or copper head gasket instead), valve springs (no cam), 36mm carbs, 17 tooth front sprocket, 36 tooth rear. This should provide you with mucho in town fun. Just don't plug it up with stuffy exhaust pipes or late 70's or early 80's xs headers. Maybe use Mac instead.

You're looking at around 500 bucks or so with those mods. You could just skip the rings entirely if it has good compression. I recommend 36mm carbs for all your FUTURE performance needs to be covered in one purchase. I guarantee you if you perform these mods that you will be extremely satisfied with in-town performance. It will not be comfortable on the freeway for more than 20 minutes though. Vibrates your balls off. But man will it rock and roll off the line. Good luck bro.

natemeins · Posted: March 10, 2007, 9:40 am Post subject: Re: Newbie project questions

This is excellent advice, thanks guys!! You're right about the head, and the cam chain/follower for sure. Forgot about them. I was just trying to think of things I could get done now while I have the engine out and torn down so I don't have to take it out again, at least for a while. I tackled that last night...that is a heavy and awkward mutha! it's hard not to scratch the frame trying to get that thing out. So maybe a good honing, (after inspection) replacement ring as a precautionary, a bit of head work, cam chain/follower parts, carbs and a decent exhaust. Sounds pretty good to me. Big help to me thanks again!

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

No problem. Yeah definitely wanna cover those cam chain follower parts. Don't forget to put a new camchain in. I mean BRAND NEW as well. I helped a friend do just what I suggested to you and I broke the camchain (old). It doesn't pay to save a buck when building power. The buck saving was at someone elses suggestion. We were lucky it was at slow speed so it didn't fling through the engine casing. It chewed the cam sprocket off of the crank so a new crank was recently installed.

signed, the maniac

natemeins · Posted: March 10, 2007, 9:52 am Post subject: Re: Newbie project questions

Geez that sucks about the cam. Duely noted. For lack of experience in head jobs (in my Vee Dubs I just bolted new heads on) what kind of work am I looking at and who if anyone should I get in contact with? Are we talking new valves/guides or just reseating them? Porting? Or just a good cleaning out? As far as ignition I've heard the stock points system barely makes a spark to run it, so is it worth going to the electronic conversion? Will I need to re-jet the carbs to make up for the burning effeciency?

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

I would ask around to get a good machine shop recommendation. I'm sure there are many in your area. New valves wouldn't be a bad idea but isn't necessarily needed. The points system is excellent. The Boyer electronic is good to but not as good as the price implies. If you want spark get Dyna coils. I believe we used 3 ohm models. They throw a hot spark. You should be able to get a set for about 150 bucks. Look untill you find them at this price. You will need to fabricate mounts. You may have to run an automotive ballast resistor in order to make the ohmage correct. 10 bucks at auto part store.
Depending on where you get the carbs you will need to play with jets (a pain in the ass). Everyone is saying avoid SFL. I always say PRO-FLO or speedmotoco. Speedmotoco jets em for you. 320 bucks per pair with linkage, manifolds, proper jetting for your setup, etc, etc. This price is well worth it. Although I wanna try flatslides one of these days. Yeah man, points and 36mm mikunis is the ticket in my book. Don't worry about valves and guides unless you are paranoid or you have a problem there already. Just mill tops of cylinders and get a good 3 angle valve job. You could clean up any casting flaws in the head and GO!

natemeins · Posted: March 10, 2007, 1:19 pm Post subject: Re: Newbie project questions

Thanksa bunch maniac. Going to get some stuff ordered and get dirty!

RainLand · Posted: March 10, 2007, 2:34 pm Post subject: Re: Newbie project questions

There's a really good section here on the site about porting these guys.
It's complete with photos and tips. It's a very simple head, and you
could probably just make it look like the pictures and get a good result.
These heads are pretty sad with casting imperfections and such. I've
seen three of them now, and they're all different in the throats.

I've checked the valve springs on all three, and they were all fine.
I bought new valves as cheap insurance, but you don't have to. The
guides were good, and you could probably get away with just changing
the seals. Your VW spring compresor won't work, though - there's not
enough room to get clear under it. Gotta get a short one.

royfisk · Posted: March 11, 2007, 10:17 am Post subject: Re: Newbie project questions

Points do work great but the real downfall to all of these stock ignitions is the 30+ year old coils. I have a hard time with dyna ignitions products due to back in the harley days of my life see these coils and ignition systems bad. Theres other coil manufacturers that make good coils, also cheaper. I have used excel coils with good results. But on the other hand many people have had good luck with dyna products . But I also think that alot of coils get changed unnessasaraly. Do a complete tune-up includeing points and condensors before you change coils.

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

My experience with dyna was pricey and pleasant. They worked good. But roy is right...always check points and condensors before throwing away a perfectly usable part!

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