OllieB

Like I said, mine also came with the 100/90 and I have put about 700 miles on the bike. Handling seems fine. I agree with the previous post about choices in the 90/90 size - not available in the couple different makes of tires I am considering. Don't think we really need to change out rims.

I'm curious about this also. Have read previous posts regarding tire size. When i purchased my 1980 XS400 a couple months ago, it was fitted with a 100/90 front tire. My rim is the same size as yours and is a cast rim, not wire spokes. The tire looks proper as it is installed on the rim and is listed in sources as the modern equiv. for the 300/18. My plan is to replace both tires this Winter and I was going with 100/90 for the front.

Your bike has electronic ignition, not points. Intensity of spark will be ok unless coils are weak. I would go with the stock setup: 5K ohm caps and NGK non-resistor plugs. Original caps were 10 ohm resistance but the 5Ks do just fine. Just my personal opinion but I don't care for Iridium, etc. plugs on these older bikes. Iridium is less conductive and used in plugs mainly to extend service life of modern cars because Iridium electrodes erode at a slower rate. Modern engines produce a much hotter spark and can handle the lower conductivity of Iridium metal. I have used Nology Silver (silver electrode) plugs in them because silver has one of the best conductive rates but they are kinda pricey. Stick with NGKs for your setup. I buy my NGK scoot and cycle plugs at Advance Auto. They might not have them in stock but can get them from the warehouse in a day or two.

Yep, had that happen to a motor scooter I owned. Disconnected the alarm/remote start as I didn't really need it for my location and style of riding. Usually comes with the territory of having more than one bike to ride. We should probably wire up a Battery Tender Jr on our bikes!!

From the pics, your bike doesn't look all that bad. Same color as mine! Many bikes of this age will be a rust bucket. Cleaning and polishing will do wonders. The exhaust system looks pretty sound - as far as can be seen. Not unusual for the paint to be faded some even if the bike wasn't kept outdoors all the time. Yes, you should concentrate on removing the carbs, replacing the intake manifolds rubbers, vacuum hose, fuel hose, tank cleaning and fuel tap rebuild. Also, order a set of ignition wires and caps from MikesXS. If yours are original - and they probably are - they are too old and need replacement. Cheap stuff. New plugs if they weren't recently replaced. Forgot if you mentioned that. Yep, the RTV was/is used to try to patch bad intake rubbers. Of course, if you disassemble the carbs, you will need new gaskets. My intake rubbers were bought from ebay and are new O.E.M. aftermarket parts of good quality from Japan or Taiwan - I forget which. There is some pretty crappy stuff coming from China. No, you can't get the fuel tap parts at a hardware store or the like. You need the specific kit for that tap from a place that offers Yamaha parts. With the fuel tap working properly, you can remove that extra shutoff valve. If the in-take (part of fuel tap) gas filter is in good condition, you really don't need the extra in-line filter but some use them anyway - your choice. The issues you describe may completely disappear after you do the above things. Sounds like it is not running all that bad anyway. There are a couple of other external carb seals that can leak vacuum that you might replace while doing the work - the o-ring seals on the idle mixture screws accessed from the tops of the carbs and the butterfly shaft seals. On some bikes never modified, there are plugs in the holes over the idle mix screws to keep us peons from changing the too lean factory setting of about 1.5 turns from seated. Most are recommending 2.5-3 turns out from seat. When checking, don't turn the mix screw downward with too much force as you can damage the seat and mix screw. You'll find other posts about that here. The butterfly shaft seals = 2 on each carb. The butterfly shaft seals can be purchased separately from MikesXS (34 mm Mikuni carb). The idle mix o-rings come in a set of o-ring, washer and new blind plug, IIRC. You can probably get just the o-rings from other sources but you do need o-rings that can resist gas/oil damage. BTW, for this engine, I like regular diesel grade (not synthetic) oil in 15W40 weight. You can buy any name brand - such as Shell, Mobil, Valvoline, etc. Not only is this type oil good for diesel engines but is also specified for hard working older gas engines. I use it in my 1990 and 1977 Mercedes gassers, too. Wix brand oil filters are some of the best and the Wix Co. makes the filters for NAPA. New o-ring gaskets are included with the filter.

@ollie: sorry, I am not good with the 'lingo' but where the carb connects to the engine, the large opening that connects to the black hose, right where it connects on the left one at the bottom there is a bit of wetness there, however, the hose is repaired with RTV, so it may just be that causing the issue, and it running down underside of hose. Also, the engine and entire bike actually run really well as it is, nice and peppy, idles smooth, just a few small things I would like to correct, mainly smell, electric starter, and all around cleanliness. I think it did sit for a decade or more, but my father in law got it for free from a long time friend and he worked on fixing it and getting it going in no time. I don't think i will overhaul the engine, but a good carb dismantling and cleaning can't hurt, i just won't move jets or adjust floats since everything seems to work well. I am going to try to find a shop here in San Antonio with an Ultrasonic cleaner to clean it. Perchance, anyone have a guide to getting JUST the plastic parts needing removal out for cleaning, so I don't have to dismantle every little thing? I read over it in my haynes, and the book is clear on how to do it (though some weird terms i don't knw what they mean here and there), but it is hard to tell whats plastic and what isn't from pics. I may also call the Advance Auto Parts where i found the battery in stock (and only 41, less than some web sites..lol) if they trickle charged it. I know they had to fill it themselves, as it was stored dry, the guy on the phone said they have the battery/acid kit. Anyways, they fixed it up for me for free... Thanks for the help so far all!!! I am going to wait to order gas cap seal until i get carb off and can find true problem, incase i need some new rubber parts or seals or something and get it all in one order. Sounds like you are describing what is called the intake manifold(s). There are round black rubber (metal under the rubber) parts. The hose which connects to the bottom hose bib on the left manifold is a vacuum hose. The other end connects to the top of the vacuum fuel tap. It is hidden by the gas tank. There should be a clamp on the hose where it attaches to the manifold. That hose and the one from the bottom of the fuel tap to the left carb should both be replaced. Most likely they are original and have hardened which sometimes means they don't seal well. It is not unusual for a little gas to dribble down into the vacuum hose so if the hose is not fitting tightly some of that gas could leak out. Hopefully, the rubber intake manifold is not leaking where it attached to the head. After adding acid to a dry battery, the battery must be charged. If the battery is a 12 amp hour battery and is charged, say, by a 2 amp float charger, the charger should be left on for 6 hours. You can see how the charging math works. It is best to charge these small batteries with low amp output chargers - such as a 1 or 2 amp float charger. A float charger will shut off the charge when the battery is fully charged so the battery is not overcharged, boiling out the acid and damaging the battery. Your Advance Auto store may or may not have charged the battery fully/properly. The best type of battery to use in cycles and scoots is an AGM sealed/maintenance free battery. These loose their charge much more slowly on standing, are more resistant to vibration damage and can take lower outside temps w/less risk of freeze damage. They are a little more expensive than the standard wet cell battery. Both types take acid but the AGM battery absorbs the acid into a glass mat so it really can't spill out. You can't ship a wet cell battery w/acid in it but you can ship an AGM battery w/the acid in it.

You can renew your tags at a drive up window here at our DMV. I pulled up to the end of a 4 car line and put the kickstand down. Didn't notice the black top was broken up at that very spot. As I was digging out my papers, the kick stand twisted back up and the bike went down on it's left side on my leg. No great damage, just a couple of scratches, large bruise on leg and deflated ego. Worst part was that it happened right in front of the Motor Vehicle office and a guy on the sidewalk was taking it all in. If you haven't had something funny happen you are either VERY lucky, don't ride enough or lie a lot!! =:-)

johnsnownw, Thanks for your heads up on the gas cap gasket from MikesXS. I was not trying to knock them just that I hadn't seen one of theirs. I have purchased several things for my bike from MikesXS and have been pleased with most of the products and their service. I had already ordered the gasket from BikeBandit before I found the listing at MikesXS. compCoder, These bikes are a little funny when it comes to the battery. If the battery is low, they exhibit symptoms similar to a weak starter motor problem. It can fool you in that the bike will start and run fine with the kick start. A good, fully charged battery eliminates that. Many folks don't understand that these bikes have a charging system which is basically a trickle charging system in that they may put out full volts but not many amps as compared with car alternators. A rundown battery won't get recharged quickly unless you go for an all-day ride - maybe a little exaggerated but you get the idea. You mention "new" battery. Did you just buy it? Did you fully charge it before installing? Was the battery newly purchased by your father-in-law, with not much run time on it but maybe plus or minus a year old? If so, that new battery could be going bad. Batteries don't like to sit around unused for months at a time. They will chemically deteriorate and not be able to hold a depth of charge. By that, I mean the battery may show full voltage when tested but not have enough amps to properly turn over and start your engine. The air filters are a dilemma with these bikes. I was lucky to have a pair of O.E. filters in good condition. You can find, with a search, info on how others have rebuilt the filters using foam to wrap around the housing. Do you really think you need a whole engine rebuild on a bike with only 10K miles? If it has been properly serviced and not abused, the engine should be good-to-go for many miles yet.

Yes, from BikeBandit. Looks like the one from MikesXS will be the same design since both the XS400s and XS650s used the same gas cap. I just can't speak for the quality of the repro one from MikesXS. When you say"main port that points to the front" do you mean the fitting where the gas hose attaches? If so, this fitting is called a "Banjo" fitting and is held on by the one bolt you see. If your fuel tap is working properly, gas SHOULD NOT drain from the tank when the engine is shut down since the fuel tap is operated (opened) by engine vacuum created when the engine is running. If you pull the hose from this fitting and gas runs out of the hose, your fuel tap is not working properly. Is the gas hose in good condition or is it leaking where it attaches to the banjo fitting? If the hose is good and is tight on the fitting, maybe the banjo fitting is leaking. You could check the tightness of the bolt on the banjo fitting but don't tighten too much or you might damage threads in the carb. You could also remove the banjo fitting to make certain it is in good shape. There should be a washer (gasket) on each side of the fitting. Hopefully, the float valve in the left carb is working and keeping gas from flooding the carb. Might just be one of these simple things. There are kits available for refreshing your fuel tap, such as the one here: http://www.oldbikebarn.com/Kawasaki-KZ650-1000-Yamaha-XS400-850-Petcock-Rebuild-Kit My preference is to keep things stock. When you do so, you don't need to change jets and mess around with carb settings, etc. When things are right, these bikes run well and have reasonable power. Many consider them a good "starter" bike to learn on but I have never really wanted a large, big engined bike. My rides are for fun on the back roads in my area - plenty of back roads in West Virginia - and this bike suits my needs just fine. I don't do all day runs or high speed Interstate runs. Hope this helps.

Picked up mine in mid June. Yes, the gas cap gasket listed will fit - I know because I bought one. It is a little pricey!! They are a little unusual in their design. Soak the three screws on the bottom side with some good penetrating oil as they will have to come out for gasket replacement. Another option is to purchase a repro one from MikesXS.com. It is listed there for an XS650 but the gas cap is the same on both bikes. See link below. Much cheaper but can't speak to quality as compared with O.E. version. A couple of other repro rubber parts I have purchased were not as heavy duty as the original. http://www.mikesxs.net/products-34.html#products

Beautiful work. Thanks for sharing!!

Same caliper that's on my '80 XS400 Special and original to the bike. When I viewed the edge of the pads I thought I needed new ones because the lining looked thin. Bought a new set and when I looked at the new pads saw that the lining was wedge shaped. Never seen this design before.

Only weenies shut down the engine!!

Great! Glad to help.

Yep, wires are just screwed into caps. Twist cap counter-clockwise to unscrew and reverse direction to install new caps. Recently replaced my originals (showed no resistance and open circuit) with the same caps. Are the ignition wires new? If they are old and/or of uncertain age, replace those also. Mikesxs.com offers a pair for a few dollars that are the correct 7mm size with copper wire cores. Other than racing application, it is very difficult to find 7mm metal core wires.

This is a timely thread since I was just wondering about the advisability of adding an in-line filter. My concern was also fuel starvation, especially with two carbs that need to be fed. I guess the key is a large enough filter and/or one not too restrictive. All my scoots have had in-line filters but they only have one carb and the largest has only had a 300 cc engine. None already had filters in the tank. Theoretically, a good tank filter should be enough protection but you can only know that after pulling the petcock.

Thanks Drewp. Already have an inquiry in with Speed & Sport. Waiting for a response. They are located a little N. of me. Was also recommended by my local Yamaha dealer - who has been real knowledgeable and helpful in locating a few hard to find items.

Thanks Drewp. My version has the raised gold emblems on the side panels and that is what I was hoping to find. Neither place offers those. Guess I'll just have to keep an eye on ebay. Also have a couple of inquiries into two other possible sources.

spacemanps, thanks!

Anyone know of a source for new side cover emblems for the XS400 bikes? I ordered a set of new tank emblems from Mikes XS and they are great but, of course, he only lists side cover emblems for the XS650 series. The package for the tank emblems says "Made in Taiwan" so I thought perhaps these are being reproduced and someone else might carry the emblems for the 400 series. These are listed as "Obsolete" in the Yamaha parts list. My bike is an '80 and needs the gold emblems for "Special 400". Thanks!!

Looks great!!

Thanks much!!

Thinking about renewing the handlebar damper mounts on my '80 XS400 and saw the ones listed on Mikes XS for the XS650 at a much cheaper price. Anyone know if they are the same? Thanks!!

Yep, and cars had what some called a "breather cap" on top of a metal tube coming up from the crankcase. That was before we decided to "recycle" the crankcase gases. Al Gore probably claims to have invented that too!

Well, I suppose they could get into trouble on an old system with sediment or something messing up the caliper but it seems like a pretty lame excuse to me. This is pretty standard stuff that even a shade tree mech like me can perform. Of course there was the time with the master cylinder on my '90 benz ......... LOL