Cy Welch

Not sure about the size on them, but you should be able to take them out and soak them in carb cleaner to get them clean. I actually have used a straw from a broom to clean orifices out without damaging them as the straw is tough enough to help clean the stuff out but soft enough not to damage the brass.

I wouldn't get your hopes up. Get the BS34 carb kits from MikesXS as every carb I have seen for the 1980 has had the o-rings for the carb needle valves worn to the point that they leak gas around them. Also remember these bikes were tuned LEAN for 1980 gas, so with the addition of 10-20% alcohol in the U.S. they are REALLY lean. MikesXS has a kit to replace the idle mix screws which includes the plugs that are needed over them so you can adjust the mix for good idle. I haven't done this yet, but plan on doing it in the next month or so. I also have found that mine at least runs far better on 91 octane as the manual says it needs. If I put that 87 octane crap in it I have trouble with starting and idling just for starters. I don't know what type of gas they have across the pond, but I suspect it's better than the crap they sell us here.

I would have to say I experience better performance and such on warmer days. IIRC, while air fuel mixture doesn't change based on temp, the ideal does. 1980 XS400's come extremely lean from the factory, and the needle is NOT adjustable (idle mix is not adjustable either). Every time I check my plugs they show lean (and always have). BTW, it's 100% stock, stock air filters, plugs and exhaust are all stock. I found I was able to compensate by raising the fuel level in the carbs slightly, which made off idle circuit running much better, but idle is still way picky. I'm planning on getting the idle jet kit from MikesXS so I can adjust the idle properly and replug the jets.

I know 1980's and later are lean, but I think that 77's were not.

Have you replaced the needle valve seats? On mine I found that the seats thenselves were actually ok, but that the o-rings were shot, and I couldn't find ones that fit, so I got replacements as part of a rebuilt kit from mikes-xs and even if I leave it on prime there's no leakage. Now that said, I don't leave it on prime normally anyways. If you rebuilt the petcock and it still leaks there is either sometihng wrong with the assembly or something wrong with the kit you got to rebuild it. Properly rebuild and assembled the petcock should work well for years to come. The primary problem I have read about with them is that under heavy load (going up a steep grade two up) fuel flow can shut off. While posting this I took a quick look, maybe this will work. Try this alternate site that carries XS400 stuff https://www.partsnmore.com/cat_index.php?mo...p;category=carb They have a universal and an adapter plate, I'm going to measure my spare tank mounting holes to see if this will fit, if it does I just may order it.

I have to agree. I have never had a problem with my petcock at all. When the engine runs fuel gets to the carbs, when the engine stops, the fuel does. That said, if I could find a conversion kit that didn't cost nearly as much as the bike is worth, I would probably change over.

From what I have been able to discover they are NOT the same. That said I'm not sure that one of the kits from Mikes XS won't work. Also some other things that will work are carb kits, vacumm slide kits (the BS34 ones) and the handlebar control pods (which are also the same). I got the carb kits and they worked well and had most of the parts I needed (I'm going to replace the idle screws as well but the're a seperate kit).

I don't know what pics or vids you have looked at but there are LOTS of twisties over here. We especially have some great twisties in REAL mountains over here, although at the moment they are all under significant snow. Frankly the only long straight roads I have seen in this country are all in the midwest, where there is nothing but long long long long long stretches of prairie with nothing but flat land as far as you can see. Here is CA most of the riding is twisties, and generally not flat either.

The problems described sound like a charging problem. Check voltage with the bike running (hold the RPMs up a ways to insure max voltage from the charging system) and you should get around 14.2-14.5 volts at the battery (this is pretty much universal of all lead acid battery systems) if it's working properly. If it's not, you will need either a shop manual or schematics to be able to fix it yourself. Also you should NOT be getting a drain from the charging system, that right there says there is a problem, very likely the rectifier.

Lets not jump to conclusions here guys. The starting and then reaching the point where it won't even turn over sounds like the battery/charging system. Could be a bad earth (ground on this side of the pond) connection, but I would check the charging system first as it sounds like a charging problem (which I admit an earthing problem could cause). If the charging system goes out it doesn't take very long at all for the battery to run down at all, and that fits the symptoms the most closely in my experience. Your milage may vary, but I would check the charging system first since part of that check requires insuring all the electrical connections are good and solid.

California has garbage gas. They put stuff in it that eats the fuel delivery system. When I put it back together the carbs were it pretty good shape at first, as I had prepped them before storing it. Then I checked them and put fuel in the tank (after getting everything else ready first) and started her up (started on the third try cranking her) and everything ran fine. Things rapidly went downhill, and I pulled the carbs to check things out and found that the pilot plugs (idle pilots on the 80's have a rubber plug in the bowl and pull fuel around another way) and the plugs were gone. A bit later (after I jury rigged some plugs) it started flooding and pulled them apart again and the o-rings on the needle valve seats were basically GONE! Turns out the stupid CA gas dissolved them. I got carb kits from Mikes-XS (plugs and all) which are designed for the modern gas and now it runs quite nice although it's still lean and I haven't drilled out the plugs to adjust the mixture yet (but it's running pretty much like it did new so I can't complain to much). I'm guessing you guys don't have that stupid MTBE in your gas, and that stuff make the gas milage go WAY down (about 25% on my Camaro) and is pretty caustic. Of course I plan on getting new Star 1300 next year, but I'm not getting rid of the XS, I'll just go through and do a proper full restoral so it looks like a new bike. That should be quite fun I'm thinking.

All I can say on that is that it wasn't me who did that. <g> I respect the all the good advice that you give on here to the other vintage riders. Slightly off topic (before starting a new thread) I just discovered I didn't dodge the fork seal bullet (hoping that my seals hadn't gone south while the bike was stored), anybody have the easiest procedure for changing them on a 1980 XS400? I know I have to do it (started leaking on my first sustained high speed ride since putting it back on the road) and I know I can get them on ebay for a decent price, but I have heard horror stories about changing them (while I'm at it I may well attack the upper engine seals as well.) Any help here? PS: Yes the bike in question is the one in my avatar.

Yep, clutches designed for synthetic have rougher friction material than the older bikes used. I'm sure that even they don't grip as well either since synthetic is so much better at reducing friction than conventional.

Well I still have the original sticker under the seat on mine and it states 91 octane minimum. Being as the spark advance is not computer controlled I would suggest that 91 be the minimum used. I personally run the highest I can find and I CAN hear and see/feel the difference. I get some pinging on anything less and gas milage is better with 91 than 87. Oh, it states leaded regular also, but I have been told that the valve seats are hardened so it can handle unleaded just fine.

If you put the castrol synthetic or semi-synthetic in there you may need both a different oil AND new clutch plates. AFAIK wet clutch plates must be designed for synthetic or you need synthetic designed for motorcycles which is not as slick as normal synthetic. This is unless you have aftermarket plates that are made for synthetic which I'm not sure area available for XS400's. You might be able to get away with just changing back to normal dino oil if you put synthetic in there and it hasn't been there too long though. This is of course all based on my understanding of how theses things work, as modern oils just barely let my clutch lock up as it is, without putting synthetic in there. (BTW I have 43000 miles on mine).

For 1980 carbs you can also get kits from MikesXS which come with new seats. What I found on mine (gettitng the same overflowing gas problem) was that the O rings on the seats (1980's us a push in seat) had been eaten by modern gas (along with ALL other rubber parts in the bowls). The kit from Mikes comes with the plugs (required in 1980 carbs) floats, needles and gaskets, with these my carbs have been working pretty flawlessly. I still need to get the replacement blind plugs and idle mix screws and drill the originals out and retune the idle, but other than it being a bit lean at idle (and non-adjustable without some drilling) it's running pretty good now. I don't know about the earlier models, but the 1980 has a relay in the headlight circuit. There are two things that can go wrong with it, one is the relay can go out, and the other is the diode that activates the relay burns out (often when the relay went). I have had both go wrong with mine and it's not too hard to fix if you can get the relay (you can order the OEM part from bike bandit) and the relay can be found on ebay most of the time. You can see an earlier pic of my bike in my avatar, but the paint job has changed. I'll be changing my pic as soon as the weather allows me to get a good pic of the new paint job, which IMHO looks awsome.

My first bike was a 76 Honda CL360 which I quite enjoyed but I sold that when I got out of the army in 82. My second (and current) is my 80 Yamaha XS400G which I have just got done restoring (not a like new restoration but a "well cared for old bike" restoration). It's been stolen and stripped twice since I got it (from the first owner) and this last time I just finally got it pretty much back to where it was before the first kidnapping (yes this is my baby). Stupic California Gas ate the internal rubber parts out of the carbs, so I had to get new parts for them but everything is good now. I just like the way it looks, and for it's age and size it performs better than most bikes in the same size class from the same timeframe (at least in my experience). I'll be updating my avatar soon (it's a picture of said bike as you can see) showing the new colour changing paint job (looks really good even if it's not "factory"). That said, I just can't make myself look at most of the other makes, as I just like my Yamaha better than I did my Honda and I can't quite make myself consider a Harley, so I guess my next will likely be a Star since I want a cruiser or street bike (no crotch rocket for me) and it seems like from Yamaha its either the crotch rocket or the cruiser (Star).

Is your XS400 a G or SG? If so the choke should be a pull button with 2 stops assmuming that you have the right carbs for the year. I start mine on full choke and like Drewpy change to 1/2 choke after a short time but I find that I have to feather the throttle for a little before it will hold at idle. I generally (in the current cold weather) leave it on half choke for about 2 blocks and then turn the choke off. I do have to blip the gas at lights at least until the day is warmer and/or the engine gets fully warmed up. I worry about the excessive RPMs from full choke (like 4000) so I fight with it at half choke as soon as it starts as I can keep it under there. I wish it didn't have the stops as it seems to be best just a little off the full choke, but not quite to the half setting.

Good luck with it. I just spent about 7 months reconditioning my old XS400G and still have work to do on the carbs and found an electrical problem this morning. Should be done before the end of the week though and I'll update my avatar with the new photo (repainted with color (colour for those on the other side of the pond) changing paint, it looks really cool) when I can get the light right to really show the paint off.

If it's the same size as an XS400G and and RD400 it's like 6.?? inches. It's like an odd in-between size slightly larger than the small auto headlights and a bit smaller than the 7" lights on larger bikes. I had a really hard time finding one as they have special fitments on the back to fit into the headlight enclosure properly.

I would stick with the electronic as I have found the 1980 system to be pretty reliable as long as you have good connection. I did have to replace my fuse box as it was no longer making good enough contact. I replaced it with a unit I found on ebay that uses blade fuses (more reliable) and so far things have been just fine. Having had both points and electronic on a bike, I prefer the electronic hands down. Except for the fuse box, my bike sat for 13 years and when I replace the fuse box and prepped it (you know, fresh oil, filter, gas plugs etc) it actually started right up (no I didn't even have to clean the carbs since I made sure everything was drain before it sat). I did have to replace the vacuum pistons thought, as they had pinholes in them. My bike has 42000 miles on it (I'm the second owner) and while I have had to do a bit of restorall work, it's getting to the point of being nice again. The drum brakes are sure hard to find shoes for though. The rear is still stocked by yamaha, but the front isn't any more. If you find parts that are consumables on these bikes make sure to get extras if possible.

Unless you have other than 1980 carbs, the idle mix screws are on top of the carbs under brass plugs as they were designed to not be adjustable. Not idling could of course be many things, but start by making sure there are no vacuum leaks. Unless they have been replaced, check the vacuum piston diaphrams, as they wear out and leak. You can get them on ebay or you can get the piston and diaphragm from mikesxs.com (the later xs650's use the same bs34 carb as the 1980 xs400). Also check the carb holders as they tend to crack and leak also.

Do you mean that the carbs are overflowing fuel or that they are getting no fuel? I have gone through mine several times and have found them pretty easy to work on, I have however found that if you let the bowls get dry that the float tends to stick down and not shut off fuel flow. I just rap on the side of the carb with the wooden handle of my hammer and it's fine again for a while. The stock petcock should shut off as long as you don't leave it on prime, as it's vacuum operated.

Up through about 1/4 throttle the bike is running on the idle circuit. If it's running rich you need to adjust the idle mixture screw to adjust the mixture. At least your the idle mixture it easily adjustable unlike my 1980 which requires almost major surgery to get to the mixture screws. Mine also is rather lean, which as I understand is pretty normal for stock carbs on a 1980.

I have found 00 steel wool to work pretty well in most cases if you don't get to rough with it. I've also used a fine brass wire wheel in my drill for faster work on larger areas. Just make sure you don't spend too much time in one spot and only press lightly or it can eat right through the chrome.