Any good machine shop should be able to do it. Price wise Im not sure. I think you will notice a reduction in vibration at any RPM under 3-3500 but it will be the same as stock once it goes over that. Ive heard most machine shops wont spin the crank higher than 3500 unless its one of those specialized machine shops. I think you might get better results if you send your head to Jack(hes a member on here) he can port and polish the heck out of it and make some good power.
it's not about power.i got a 72',there is a lead counterweight,it fell out,got destroyed. i thought,i'll give it to a balancer guy,and he can take care of it,since i don't know,was that thing original,how heavy was it.
I picked up two XS2 about 18 months ago to rebuild. One had a locked up engine which turned out to be the weight problem you just described. The other had a chewed up fly wheel and the weight was also loose. Here's what I did. I picked up a newer crank from a 78, which does not have any weights Sourced out NOS rods for the 72 and had Falicon replace the 78 rods with the 72 rods along with all new bearings. They also balanced and trued the crank. The rods are shorter on all 650's after 73. Also the crank sprocket has 18 teeth rather than 17 which means you need to do something with the cam sprocket which has 34 teeth on the 72 and 36 teeth on the 78. To correct this I got an adjustable sprocket from Mega cycle cams which allowed me to run the 72 cam with a 36 tooth sprocket and also allowed me to time the cam closer than the stock unit could achieve. You also need to use the cam chain and adjuster from the 78 or later years. In the end you still have the personality of the 72 motor with updated cam chain parts and a motor which should run smoother from the balancing and the ability to time the cam to close tolerances.
thanks for your reply.that sounds pretty costly.how much was it?! at least now we know,that 72'(and probably earlier ones)have this issue.i heard that from the rd350 as well. any cheaper way to do it?! again,how much was it?!
The truing and balancing was not that bad, about 350 I think. However it was all the bearings,rods that add up. You can send your cam into Mega Cycle and they will do the sprocket for about 100.You can get a crank cheap on e-bay,along with the other cam adjuster parts. It does add up quickly. depending on what you need. I decided to do it this way because I wanted to keep the characteristics of the 72 motor and it is a complete rebuild. It will look great when it's done.Also you get a little more torque from the longer rod with less side to side wear. However you need to watch your RPM's with the long rod . It uses a larger piston pin on the small end. There's pro's and cons to either way. If you can reuse your old rods that would help.
Some people use a 74 or later crank , rods, pistons and camshaft. You can use your 72 cam by pressing off the sprocket and pressing on a 74 or later sprocket. This leaves the engine looking like a 72 motor with the later insides. Using the later inside parts is a good option because the older style parts are getting harder to find. Careful shopping and you can do the whole thing for a few hundred bucks.
75 XS650B with 79 forks and dual disc, braided lines, disc brake on back, Pamco ignition, Pamcopete's reg/rec mods, kill switch relay, home made harness, all LED turn, brake and tail lights, tapered head bearings, bronze bushes in swing arm, soon to get shock and fork upgrades
xsleo,you don't have that old crank anymore?! okay,you are saying i can use a later crank,use my 72 camshaft,put a 74later sprocket on the camshaft.., so basically i need a crank+ sprocket of a cam, 74later?! that's it?! do i need to balance it?!
..wait a sec,you said "pistons". what about,taking the flywheel of a 74later,since they have the same partnumber,and put it on?!i would have a machineshop have to do it,pressing off and on,right?!is it possible anyway,would have to be pretty exact?!just an idea and this balancing,would i have to balance it?! i don't want to spend 400$ for balancing.or just a get a whole new motor instead,i don't mind having a later model engine in. it's all about the $,can't afford a lot right now
If you go with the late model crank you will need pistons for that crank, cam chain,late model adjuster,and camshaft sprocket or late model cam. I would keep your cam because it has worn into to rockers already. You can not use early pistons
Do I understand you to advise this fellow to rebuild his motor using all those old parts? You reckon that's good advice for a going-on-40-year-old motor with a failed crankshaft? False economy I'd say.
Spent 400 on the balancing thing about 7 years ago....Falicon.......they take it apart and put dumb weights on it big ends and spun it at 500 rpm....don't know who would spin it faster without a special cage to hold it properly.....an atom bomb if it came apart is what I was told.......it did idol smoother but was still a rat on the express..........much prefer the 8-1 compression set up for lower rpms with tall gears and the timing to retarded some to support all that ..........and when it finally gave out 15 thou later it was at .016 thou runout.........didn't have them weld it....should have I guess...and never mistreated it by over reving or such...........
Might as well tell you guys this.........years ago I had another XS and I thought in my infinite wisdom I was going to balance it myself......being the cheap bastard that I was......... And going on some bad advice I removed a bit of weight from the big end side............got worse............dismantle and took a bit more off the big end side........got even worse again..............long story short and from just from a plain good ole guess is the backside is where I should have been removing weight from........ Oh well....and that might be easy to prove by adding some weight to the front side.......maybe maybe not.........
Post by dps650rider on Jun 15, 2009 20:15:21 GMT -5
I keep wondering about the balance factor on these and have a theory. Maybe Yamaha deliberately set the balance factor on the high side of optimal so that if/when larger and heaver pistons were put into the engine it didn't put the balance factor too low.
edwarddav: Hello Anybgody
Nov 20, 2013 3:04:13 GMT -5
edwarddav: I have a 72 Xs, The Carb. Boots are gone, How do I make them or can you Buy them somewhere, Everywhere I look Out of stock,
Nov 20, 2013 3:10:28 GMT -5
Slimbob: Did you try Mike's XS or 650 Central? They usually have them.
Dec 6, 2013 14:29:26 GMT -5
joshelrich: Hey guys. new guy here. Where is the map and where does one introduce himself to the group? I've got a pretty cool project in the works. Trying to relive my youth. Ha ha. 80 frame, 71 engine case with 650 central long rod, big pin 750 kit. Shell 1 cam.
Dec 19, 2013 21:02:48 GMT -5
mwb122: Another newbie here. I appreciate the page and being accepted. Just brought home a 78 xs650 special. She is running good after a little TLC. So far I have cleaned the carbs, battery, fixed leaking clutch push rod oil seal. Now what to do with her.
Jan 3, 2014 8:50:55 GMT -5
mwb122: Bought a 79 special in 79. Was a great bike then and it is great to see they have such a large following!!!
Jan 3, 2014 10:30:04 GMT -5
oldcodgerhenry: Gooday ,all .new Pamco basic ign replacement arrived yesterday ,But the coil wires are different color ,to the trigger wires ,don't want to fry new one.
Jan 29, 2014 15:41:34 GMT -5
floris: at this moment, my XS is with Jerry v.d. Heiden, a well known XS tuner in the Netherlands.
Feb 4, 2014 16:28:08 GMT -5
floris: The engine become's a rephased 270 crank.
Feb 4, 2014 16:28:37 GMT -5
floris: Also a bigbore cilinder set of 890 cc.
Feb 4, 2014 16:29:10 GMT -5
floris: Also a long stroke is gona be applied, what makes the total about approx. 1000cc.
Feb 4, 2014 16:30:12 GMT -5
floris: 965 cc to be exact.
Feb 4, 2014 16:30:35 GMT -5
mahanlee: need help identifying a gas tank i bought on Ebay for my 79 xs. it has a tall neck and the new mikesxs cap i ordered will not work on it. any suggestions?
Apr 10, 2014 13:43:49 GMT -5
mahanlee: Need help identifying this part. It came in a box from the previous owner. I have searched Google and Ebay and haven't found something similar. It has a short bolt with a flat side. The only place I figure it goes is underneath the battery box.
Apr 23, 2014 8:14:07 GMT -5
djonesxs650: Batteryless setup for '78 XS650 with points ignition....I need a wiring schematic, simple as possible...does anyone know of any posts that can help?
Jun 28, 2014 16:02:09 GMT -5
gwc1147: I snapped the outer push rod for the clutch while removing front sprocket. I want to change to the longer rod. 77 650d I would also like to replace the seal and front bushing. How do I remove the broken rod? Any help please.
Aug 10, 2014 20:29:00 GMT -5
boxertwin1: I have a 76' XS and need petcocks for the tank. I don't want to rebuild, I want new ones. Weird, but you can only seem to buy right-sided ones. Any source for both sides?
Aug 21, 2014 14:56:18 GMT -5