The problem may be incomplete engagement due to misadjustment of the gear selector claw on the right-side end of the shift shaft. Instructions for adjustment are in the Clymer manual, but if you don't have that they're also in the factory service manual accessible and printable free at www.biker.net . You'll need to remove the clutch basket for inspection; examine the primary gear on it for slop, making sure the damping springs are in good shape. The eccentric screw that centers the claw turns very hard; a square-shank screwdriver turned with a wrench works well. If that doesn't help you'll need to split the cases to examine shift forks, shift cam, and dogs on the 1st gear pair.
Thanks grizld1: I tried adjusting the gear shift mechanism ( i have a chiltons book, and I looked up the biker.net site that you suggested). They both say to equalize the play on both sides of the of the adjusting gear. I tried that. I found it very hard to get a wrench on the lock nut( there were spring ends in the way), when I finally did, I found it very hard to turn the adjusting screw. I made the mistake of having the bike in neutral when I adjusted it. It took a lot of turns. I think it should have been in gear. I may have adjusted it wrong. I also had a problem tightening the lock nut. Neither Chiltons or the Yamaha manual describe the adjustment in detail (for amateures like me). I am trying not to have to split the cases, any advice would be greatly appreciated. P.S. I did all this last week before I posted the problem.
It's best to center the claw in 3rd. I can't advise you on the locknut--never had a problem getting on it with an open-end wrench. I have a feeling that if moving the eccentric made no difference, you're probably in for a split job. You might try this. With the clutch cover off and the bike on the center stand, dry-shift to 1st, using the shift lever. Then see if rotating the star-shaped plate in the shift assembly by hand gives you deeper engagement (you'll feel it if it does). If that happens, centering the claw may deal with the problem. If it doesn't happen, I think you're in for a split job. The only good news I can offer is that the case lower half can be removed without a top-end teardown. I invert the engine on the bench with the head hanging over the edge, supported on stacked (and padded) concrete blocks, but there are many other ways to skin that cat.
Post by yamacette on Sept 10, 2009 16:34:19 GMT -5
Thanks Grizld1: I pulled the right side off again and adjusted it as you recommended. I found that it was much easier to make the adjustment by making small movements of the adjusting screw and then checking the gear selection by moving the star selector with a philips head screw driver. when I got it moving into first gear cleanly I then tried it with the gear change lever. I put it all back together and tested it. It still had the stutter in 1st gear. Before I split the cases. can you think of anything else that would cause this stuttering? I have a big bore kit on the bike with VM 34s. It runs great with the exception of fisrt gear. Any help or suggestions would be appreciated.
So far I've been assuming (maybe wrongly) that you have a powertrain issue. Can you provide some detail describing the "stutter?" For example, does it seem to be at all related to how much throttle you apply, does the engine itself seem to be missing or surging, is there any mechanical noise associated with it, etc.?
Post by yamacette on Sept 11, 2009 15:55:28 GMT -5
I have read the carb guide at least a hundred times. I have 3 Mikuni manuals. I have started with the recommended jet settings and tried every combination of settings I can think of. I thought it was a carb problem because most of the manuals describe missing while accelerating as a problem. I have a friend who has been a Honda Mechanic for 20 years, he rode it and said that it ran great, and that the fact that you could not replicate the missing or stutering while starting in 2nd proved that it was a drive train related problem. Do you agree with this or do you think it is a fuel related problem? As for your questions describing the miss. There is no sound or clunk. From a dead stop it accelerates about 100 " misses , cathches again and goes another 100" and If I don't shift into 2nd it will do it a third time until until its reving too high. If I start off in second there is no missing or stumbling. I would appreciate your opinion and suggestions. I realize this is a problem that others have described on the web site, When you have recommended that they go back to the guide and read some more. I have tried that and found that no matter what I do the problem is constant.
I didn't think it was a fuel issue; right, that would show up in any gear you selected. I have to agree with your friend the Honda wrench; the regular "cycling" of the malfunction and the fact that it happens at all rpm's and throttle openings in only one gear says tranny to me as well; just wanted to be sure not to send you on a wild goose chase into the gearbox. Servicing the tranny on one of these is pretty simple compared to most machines, but it's still a time-consuming job. Please accept my sympathies!
Post by yamacette on Sept 29, 2009 11:51:09 GMT -5
I have split the cases and found my problem , wear and damage of the 1st ,4th gear and a shift fork. my problem now is where to get the parts. I am trying to get OEM parts rather than used parts. So far my search of the internet has been unsuccessful. Does any one have any suggestions about where I can get the parts?
You probably will have to use used parts. Ebay has whole trannys. Shift forks, the whole deal.
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
Just a thought, but could this be a vibration related short, say perhaps in the side-stand switch? It seems electrical to me. a gear box problem would not make the engine "miss."
Harmonic frequencies can cause odd things and it sounds like something loose is harmonizing at on particular spot that only happens in 1st gear.
A diagnostic might be to run a lead from the hot side of the coil to a instrument bulb. The bulb should glow whenever the coil is getting power. If it "blinks" at the magic moment don't split the cases, chase down the short.
Well, I guess I should read the whole thread before I share my brillient insights. Still, as one who has written and debugged a fair amount of code in my day I remind all that "A" problem is not always "THE" problem.
Anyway, no loss, you found damaged tranny parts and had to go in there sometime anyway.
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