Cy Welch

Drewpy was that the 79 or 80 model? The 79 should have the II and the 80 would have the III.

I don't think things will be right without clamps either as you really need an airtight seal which I don't think you can get without the clamps.

I'd love to find a good manual on them, but so far I have not found anything in my travels. My understanding is that the OEM Mikunis (which these are) were deliberately not publically documented to keep you from working on them yourself. Kinda sucks don't it?

The III's are on pretty much everything US delivered from 1980 - ???. Each model of bike got different jetting, but the base carb model was the same. 650's 750's 1100's and 400's for sure, I'm not sure how many of the others got the same carbs as well.

Look at the side cover by the shifter and it will show how many gears you have. Neutral is generally a half click. If you do a full up, folllow by another you may be shifting to 3rd when your going for second. Just a theory to check out.

For a firewall you might consider Comodo as IMNSHO it's better than zone alarm and free also. I find that at least for me it takes up less system resources and still works as well. For outlook, check where your personal folders are stored. It will be a PST file usually in your user folders. Just copy that to the new machine and you have all your stuff. Outlook express I think you MIGHT be out of luck with although what I did was create some folders in my hotmail account and copied all my stuff to hotmail and then it was there on my new computer. Just copied them back to local folders and everything was good.

I'm of the opinion that any yamaha is worth keeping

First, put an inline filter between the tank and the carbs. Second make sure it's really clean, needing part choke to keep running means it's not really clean yet. Remember to clean the main jets you need to remove the vaccum slides and diaphrams and then loosen and remove the jets through the top. Also make sure you clean the idle jets which are under the rubber plugs in the bowl. If you get it all clean it should run good, although you MIGHT need to drill out the mixture screw plugs and replace the o-rings on the idle mixture screws (they get eaten up by modern gas) if their bad as it won't idle well without good o-rings. Then start at about 2 1/2 turns out on the idle screws and then (I feel this is REALLY important) adjust the mixture with the engine running, and adjust them out for highest idle and then back in just slightly. You may find a world of difference after doing that, I sure did. The BS34 III's like you have (yamaha seems to have used them on almost EVERYTHING for a few years starting with 1980) have very little adjustment so cleaning is very important as it float level.

Don't hold it at max height, but make sure that the little button on the bottom of the needle valve is not comressed at all. Generally if you just let them hang by their own weight when upside down that will get you the right measure. Yes, those are III's and as far as I know they will run fine as long as you adjust them like you would a 1980 since the jetting and all are different.

I would start out by adjusting the idle speed down and see what happens. It could be as simple as setting the idle speed and having things be fine. I have not heard of the carbs getting out of sync to much unless they are taken apart from each other.

Try MikeXS.com for XS650 parts. They I believe support all years of them. They have a great many parts for them that cannot be gotten anywhere else.

The bs34 III's are 1980 models and unless the jets have been changed the float height would be 1.1 inches rather than 1.26 like on model II's.

Quick question, are you counting gears by counting the acceration periods (starting with the first gear start) or by counting upshifts? If you count the number of upshifts you will be one short. 6 speeds means 5 upshifts. That's one down, 5 up. Just making sure you don't think it's 5 when it's actually 6 gears.

The main circuits don't really fully kick in when out of gear. I would still guess either the main jets are having trouble, or the vaccum slides are not working properly.

Darn!! I just got rid of a pair of BS34 II's I hadn't really worked on them enough to know for sure but the slides were not moving but I think with a little soaking they would have freed up. Unfortunately their gone now.

Assuming good compression and spark, make sure that the carbs are clean (sounds like dirty main jets to me) and that the float levels are correct. If those things are right, it should run good in all gears.

It could be. It also could be the carbs being out of adjustment with the one side richer than the other. Make sure the carbs are properly cleaned and adjusted and balance them. This of course is assuming that the compression is in spec on both sides.

Actually the 79 model year shouldn't have the plug like that but rather a screw with a limit cap on it. The plugged one would be a 1980 or later US model with the BS34 III rather than the BS34 II on the 79's. I haven't seen one from that age range that didn't need drilled out and adjusted, and you may need to replace the o-rings on the adjuster to get it working well. As for the rubber plug, that covers the idle jet in the model III carb. I would not think you would get good result mixing the two carb models as according to the book they are jetted differently. You should probably make sure you have matching model number carbs.

It will leak/drip oil out when the alternator cover is off. I will pour out if it's on the side stand. Except for setting timing etc, keep that cover on.

I don't know about the gearing on your model, but mine in 6th gear does about 5500 at 55, by 70 it's doing about 6500. I often think I am in 5th when I'm in 6th (if I don't carefully count the gears I get lost). If I pay close attention I realize when I'm in 6th, and it's always sooner than I thought. Also remember that 1st is one down, then it's 5 up as you work up to 6th.

The originality of a bike is to be different than all the others of the same model. The manufacturer turns them out by the 100's or more exactly alike. Originality is making them different than all the others. Mine is mostly original in look, but painted a colour that never came from the factory (colour changing paint, purple to green and several other colours in between). Does that look bad? No, most everyone who has seen it comments on how they like the paint job and how original it looks. I could have gone for a very different look from original (I have seen several of the same model as mine heavily modified that looked quite good) but I choose to go with original looking, and so far I have not gone for the "new" look, but rather just decent condition old bike (it's 28 years old now). I plan in a year or so to do a frame up restoration, and I plan on doing the engine bits as high polished aluminum, rather than the dull silver paint as stock. Will it look stock? yes to a large extent, but parts of the appearance will be very different from stock. That will be an original look, keeping it exactly like it came from the factory is not bad, but it's NOT originality, it being part of the flock, like all the guys on their harleys.

Also the model year starts well before the calendar year. IIRC my 80 was manufactured in late 79. Cars are the same way, but most of them don't show the manufacturing date.

Well, my 80 XS400G (a special) gets about 42 MPG which runs about 106-119 before reserve. When I used to get about 50 I got about 135 miles before reserve. I'm guessing that that's just about what these bikes get these days. I just can't seem to get it better than that, and it's running pretty good now so I think it's about what it's going to get on todays gas (the added ethenol lowers the milage you get).

This also means that your needle valves in the carb(s) are not sealing. Get a good rebuild kit (one that comes with new needle valves and seats) and get this puppies sealing and you should see a world of difference, and besides you won't be filling the crankcase with gas anymore. When mine did that I decided to actually idle it for about 10 minutes with the gas in there before draining and changing the oil and filter. I know I don't have any gunk built up in the engine now!!! I know there are safer things to use but since the gas was already in there I figured I would take advantage of it (and it worked out fine).

I believe through at least 83 Yamaha used Mikuni BS34 III's which have the idle adjust screw under a plug on top of the carb between the main body and the carb mount. You have to drill and pull the plug to get to them and often the o-rings on the screws are pretty much gone and it is almost impossible to get a good idle without them. If they are the same carbs, Mikes XS has kits with the mixture screw spring, washer and o-ring and the plug for when your done adjusting. They were pretty cheap too. High idle usually is lean mix though, at least if it's the hanging kind that comes down after a while.