gazampa

I detached everything and polished with steel wool. Took it all off, battery box included and cleaned everything. Now, the regulator test, the battery is reading 13.8 at idle and 14.2 V under 4000rpm. And, the voltage isnt going any higher. The clicking is mostly gone except for a slight one by the left hand side panel when the ignition key is turned. I put inline blades instead of the original fuse box, bit of a clunky fit, thanks to my wiring expertise not being so great. Removed the headlight and looked at the wires and connections but didnt find anything exposed or blackened even. Im going drive around and use the left turn signal repeatedly to see if anything happens again.

Hi there, My bikes a 1977 Yamaha XS 400 2E - 2G5 series frame number. trying to do two things, 1 ) fix an electrical / charging problem 2 ) understand the electrics better I was out for a ride the other day, bout 60 miles / 2 hours, temperature low 80's, left turn signal pilot went solid after about an hour and a half, small while later the signal fuse melted ( pilots went out ), after about 30 mins, bike running badly - stutters, backfires, power decrease on hills - then stalls. Starts but only goes for about a mile. Checked the battery voltage, 12.4V under 0 RPM and 5000rpm. I have had the headlight off recently when putting on on a new tachometer. What my Bike Looks like. Alternator - There's two branches coming out of the alternator, one ending in a female connector containing three white wires and one yellowishy white wire and one ending in a male connector with a black, green, yellow and light blue wire. Rectifier - On the bottom of the battery. Black grid shaped thing, white wires going in, black wire and red wire coming out. well they look like they are all just going in...or coming out. Regulator - Its that black rectangular thing at the back of the battery and underneath the fusebox. That looks old. like something off a really old telephone. Initially I did have it confised with the turn relay, a cylinder shaped silver item with a three prong connector from nippondenso which has, ND FN 257E / 12.8 V 85cm / 27W x 2 + 3.4W / NIPPONDENSO / 061300 3572 printed on the side. Heres what it looks like on paper. XS 400 2E Wiring Diagram So, Im checking the alternator by the haynes manual method and trying to understand the wiring diagrams, found some colorful ones referenced in other threads. Alternator Test : ( Using actron CP7665 Multimeter from autozone for all tests ) Checking resistance of each of the three white against the yellow. Checking the resistance across the green and black wires. Resistance Readings ( at 80 F - multimeter set at 200Ohms scale ) : White wires : .7, .6 , .5, Green and Black : 4.3. White wires - field coil - ( coming out of alternator ending in a female connector ) - three carrying current from the windings go to rectifier, the last one goes to the turn relay - is this to eventually connect to the ground the turn relay is connected to ? multi colored wires - rotor - ( coming out of alternator ending in a male connector ) - yellow, light blue, going to pilot box. green going to regulator, black going to left handlebar switches, why is that going there ? Green going to regulator, Is this the actual voltage being generated input for the regulator. Also, Is a current from the baterry passed through a winding on the rotar to begin with to induce a field which afterwards is fed by the alternator itself. Or are there permanent magnets. Rectifier Test. : checking resistance of the red wire and the black wire across the three white wires. I get no readings going one way and when I reverse the probes while I do get a brief resistance reading, it flashes up on the meter, then returns to the default value of 1 ( which is the value when theres nothing connected to the probes ) I did the test with the diode check function of the meter, I got constant readings of 625 one way and the other way it just stayed at the default reading of one ( when theres nothing connected to the probes ). Is this rectifier ok ? whats with the resistance reading not being constant ? Regulator Test : I need to charge the battery up now and do the haynes test for the regulator. Also, theres a clicking noise when I turn the key in the ignition coming from the battery section, is this indicative of a grounding problem, if so, how do you test the grounds ? With Thanks. Adventures in Electrical Systems...Bzzzzzt Ouuuchh !

oops, this got double posted

Thanks Tony, appreciate it. Ordered off the internet and part arrived yesterday and fits into place perfectly. Cost $1.40 .It was described as a 'Pin, Special Shape'. And the part was listed in the 'Stand - Footrest - Brake Pedal' Schematic, # 42, in the 'Control and Brake' Category, I had been looking at and listed earlier in the post was in the 'Wheels - Tires - Final Drive' category as the 'Rear Wheel' Diagram. http://www.bikebandit.com/houseofmotorcycles/yamaha-motorcycle-xs400-2e-1978/o/m8253#sch214797 Thanks Again, Gazampa

Thanks for the part number, thats what I really need, hopefully can reorder it.

Sea, Tuiguim. Is iomi shli much a mharu, seachas a machadh le t-im ach B'fhearr liom an phairt o OEM. Beadh sin a bfhad nios fearr.

Could be, im using bolt as a generic term, dont really know what its proper name is.

Hi There, I had a back wheel off for maintenance and when putting it back on found im missing the bolt that the brake rod goes through securing it to the actuating lever. I uploaded a picture, its not numbered but its that cylindrical bolt with the hole in it between the digits 27 & 28. Any Ideas on where to get a proper replacement, I figure on going to a hardware store and browsing for something that will fit. The Bikes a 1978 Yam XS400. With Thanks,

Ive been riding each weekend now since the one before labor day and using it during the week for short trips. It could still do with a bit of polishing but for now its running well. I've put about 800 miles on it and that includes one ride of a little over six hours last weekend on a medium hot day of about 70-80F which it handled well with no complaints. Its got something to say pretty much throughout the rpm range and pulls well from mid to high. The acceleration is not comparable to anything modern I imagine which is great from a safety point of view. I understand leaning out the mix can give it a bit more burst but at the cost of higher engine temperatures. Its hard to beat the sound that it makes, its very throaty. The gear box is a little tight sometimes going from second to third, could just be this bikes gear box, and it slips out of fifth into neutral sometimes which is not cool. My tachomoter is not smooth when its warmed up, it bounces around, it can jiggle around a range of about +-250 rpm. carbs probably need better balancing im guessing. The right side was always complaining, i found that the exhaust engine port was loose on that side ( it fell out, whoops ), but after getting it back in, there was a great improvement vis a vis starting. The o-rings on the idle screws helped big time. It was starting to get there and the o-rings pretty much got it there. On early rides, the sparks carboned up a bit and made starting very hard but after a little sanding and just riding the rpm a little higher, they cleaned up and are tanned. From a starting point of view, its starting really well without any problem at all. The temperatures have been a little chilly lately but it hasnt been having a problem. The current list of fix mes runs as follows. 1 ) Forks weeping on left side. 2 ) new brake pads. 3 ) new Front Tire. 4 ) vacuum balance carbs. Idle still needs a little nursing. Outside of that, a deep off frame clean and a frame repaint would go most of the rest of the way to a full restore. If I find a place for winter where I can work I might give it a try, falling short of that I'll just store it. The pipes are pitted from standing and should be replaced going the full restore route but they are not bad for general use and in good working condition. I might just take care of the fix mes and then maybe sell it on later, hopefully to someone who will take it the full way. As of now though I would call this xs400 resurrected. I wouldnt call it fully restored but its certainly up and about. Heres a quick vid, ill maybe post a better one in a bit, just noticed the kick was a bunny ho, not really for public consumption but there it is. Video

just to drop back and finish off this thread. I had a problem with the drop level using the plastic floats. The drop tang that hits off the post was too small. They could be rigged but ultimately, I bought a couple of stock brass floats from the dealer at an extra 20 bucks a pop. Small price to pay for peace of mind whilst driving around to not be thinking that a rigged tang on the float was going to somehow come asunder inside the carb. The high rpm was down to the throttle screw position.

put 50 miles on it over the weekend. Took it out for two runs of about 25 miles each. I may have missed the airshow ( through my own inexperience, not the bikes fault ) but I can still give it a ride downtown along michigan avenue amidst the skyscrapers and all that, along lower wacker to get the full amphitheater effect of the pipes and up along the north shore for a hint of the cafe racer feeling. Vrooom, Vrooom. The idles not perfect but it is a work in progress, its a little on the high side about 1400, Im new to this but i think im getting the hang of tuning it in and am working on getting it down to 1200.

been working on a similiar project over the summer and have just got a 78 xs400 in running around condition. Its been sitting for five years, theres a thread about it on the forum. Cost wise : new battery - 44.95 ( local dealer ) carb cleaner - 4.95 ( local dealer ) Depening on the condition of your carbs. new floats - 42.95 each ( local dealer ) carb kits - 35 each ( www.siriussonic.com ) Theres also brake pads and tires to consider, havent had to get into those yet. Bought a couple of new tools but didnt need much outside of a standard ratchet set, did buy a multimeter for $20 at autozone, would like to buy more stuff but so far havent gotten to it. The carbs soaked up virtually all of my time. Its my first time, someone more experienced would probably have done it over a saturday afternoon. Get stock parts as much as possible, dont try and pinch pennies on cheaper alternatives. This can suck up time. Overall, its worth it, Im having a good time with it now and still learning. I found the work enjoyable and though frustrating at times, its definitely satisfying to get it out on the road.

Oh, you mean the big screw, the really big one...the biggest one on the whole carb. Christ, I am such an amateur...Yeah, gave that a couple of turns and down came the RPM. What can I say, I like to think it was the fumes. Man, did that feel good though. Still have to tune it in properly but just to not have a screaming idle is really really satisfying right now. Jesus, it feels good. Thank You for that. I wish i could buy you a beer. And that goes to everyone who has helped so far. How does that screw work though, I saw that it pushes open the throttle valves, does that create greater vacuum to suck up more fuel from the bowl. And how come opening up the valves via the throttle on the handlebars increases the rpm. Whats goin on there, I can read up on the internet I suppose. Thanks, will do.

Am completely stuck. I cant get the engine to idle. Is there a secret handshake involved, then again this is my first time tuning carbs, I say that to myself to stay calm but I am going #$%# banannas throwing myself against this. Utter frustration. 1 ) 2 New carb kits from sirius. Able to spray air through the passageways. Two new Idle screws. 2 ) 2 New floats ( genuine yamaha brass float for this model ). Fuel Level set about 5 mm below the lip, thats as good as I could do, I could get higher by taking out the washer in the fuel valve assembly. 3 ) 2 new air filters. Genuine yamaha parts for this model. 4 ) Sprayed WD40 around the boots and no change in anything, sprayed it around carb and no change in anything ( the engine was on ) 5) Before I set the fuel level in the bowls, I was getting backfires on deceleration and shutoff. Now, thats cleared up. Started with the idle screws fully screwed in and backed them off, I did start to get backfires in the left exhaust. But with the screws full out there was an idle of 5k, i think that was just the engine getting fully warmed up though and the idle rising with it. Any ideas, Are these carbs just garbage ? Are there specific settings for the pilot air and fuel jets ? Mine are in all way, thats the way they were when I got them, should they be turned out a little or seated firmly. Is the choke circuit toast ? When I pull the choke out, rpm increases. I figured that was normal for a choke, I dont understand why enriching the mixture didnt slow it down. Is the hgh rpm due to a too rich mixture. Ive been assuming its lean as evidenced by the lean backfiring earlier. Do the idle screws need o-rings, mine dont have any ? Im very grateful for any contributions.

Project is moving along, after replacing punctured floats im working on high idle with a warm engine, i understand its a lean mixture problem most likely caused by too low a fuel level in the bowl, its about 8mm under the lip. Im going to reset float heights and am using a fuel level gauge. So far adjusting the idle screws is not affecting it. I posted a seperate thread about the float work. First of all the floats were stuck, then punctured, now too low. Grrrr, floats. And the new floats fall so low in the bowl allowing the needle to fall out low enough to jam them. The tang on the back that hits off the post is not big enough. I am walking in the shoes of Torakusu Yamaha as he endeavored to tune his first reed organ. The air show came to town, I pedal powered over on my bicycle. Ive got enough progress to be reasonably content with but its not air show quality just yet. The idle is very high and in a crowded area with a fairly rusty driver, it would not be very cool. Getting the carbs right is taking me some time, a rebuild from the sirius kit with new floats was in order from the outset. Here a couple of photos from the papers, i dont think any of these guys would drive a bike with high idle and who knows what else just yet. ( At least thats one thing i might have in common with them ) I have used it to jet down to the store though and the circumference around my appartment which I am driving is increasing. Im not flooding the engine anymore but its very dry. photo1 photo 2

ok, what I have found out. Having the right parts is wonderful. Having nearly right parts - not so good. These floats need a lot of coaxing into place and even then its hard to get the needle to not fall down and jam open. If the jam is not too stong when theres fuel in them, a little tap on the side of the bowl will unjam them. Fill the bowls and make sure there are no stuck floats before putting them back on the bike. Fuel Valve Assembly. - The VM26 valve assembly above doesnt fit, its a tiny bit too small so it wont screw in. You can wrap it in sealing tape and push it in to work as a stop gap. - Also, the above is a 1.8 and the specs on an xs400 call for a 2.0 which i managed to change before they were shipped, plus there is nowhere to attach a filter. It takes way too much time futzing about with stuff, GET THE KITS FIRST THING, dont mess about, its sucks up way too much time. So, back to my particular case, the gas fills up the bowl more than it did before, before it only half filled, maybe a cm above the main jet judging by the gauge level i set up and thats also where the green coloring stops. I have increased the fuel level, it falls a bit shorter than the 2mm below the lip, more like 8-10mms. Anything more and the needle jam becomes difficult to resolve. But, now i have an idle of 5k, ive read about this on the forums in places, and my idle screws have little affect. Screwing them in all the way increases the idle by about 500-1000rpm and unscrewing them all the way does nothing. Any ideas on whats going on, i thought increasing the fuel level in the bowl would enrich the mixture but the forum seems to be saying that this is a lean idle problem ? I have looked through the forum and the solutions revolve around the idle screws which ive tried.

They can move about in the bowl without restriction. However, the pins that came with the float were a tiny bit smaller and slipped out fairly easily, Im using the old ones. Also the tang that restricts how low the floats fall when right side up, not the tang that touches the needle but the one that touches the arm, needed a little bending to get it to come in contact with the arm. It was falling so low that the needle would come close to falling out when the floats fell down and would then stick in that position. Had I put them back on, they would have remained fully open. Thanks, didnt know that, i guess the carbs on the 650 could be a different model carb altogether. I found upon testing to see that the floats closed off fuel flow that one of my needle valve assemblies is leaking. Its a drop every three to five seconds. I switched needles to see if it was the needle but it wasnt. Does anyone know a good rebuild kit for a 1978 Yamaha 400xs . Ive been looking on the web for one but its hard to come by. I did find the needle assembly for some jet skis looks similiar here. link . Its used in the VM 26. Im going to order it and try it out if i cant find a kit.

how strange the change from brass floats to plastic Im changing out the brass floats from my 78 Yamaha XS 400's Mikuni BS 34 carbs to plastic floats purchased from www.mikesxs.net.( $12 each versus $50 for the brass through the local shop ). I figure they should be interchangeable, These plastics are used on later 650 models which switched to the 34's from the 38. I saw some brass on the site but for the 38 and the bowls looked differently shaped. I notice the float heights for brass are 27mm and for plastic its 22mm. Is the height different for the 400 model mikuni 34's or do they just drop in at the correct height. Anybody ever done this, it would seem a pretty common procedure as the brass ones degrade with time, it must have been done many times before. Do the plastics last longer, is that why manufacturers changed or are the plastic just less expensive and easier to come by. Also, anyone know what the 34mm referenced in the name of the carb is, is that the length of the jet ? Ive been around the board and gotten valuable info, but i had the questions above if anyones inclined.

The Face of Progress. Back from the mechanic - statically timed ignitinon. Overall, the bike is starting and stays running with the choke fully in. The throttle is a little heavier than before and ive got the revs drifting up issue. I took a movie. start is on full choke, put the choke in, ghost revs up to to about 4000+, falls back to idle around 1300-1400, then gave it some higher revs, a little unevenly perhaps, looking for responsiveness, of course. start and throttle Havent goten out for a run yet as the right air box started leaking fuel again, not like before though, its a drip now, not a flow, I had noticed a little gas in the floats previously, tried a solder job but i guess it didnt take and there's also a lot of solder already on them... So Ive got some plastics on order and will try them out. Before, the floats were jammed, now i guess its punctures causing them to lose buoyancy and fail to close the flow causing overflow into the air filters. I think i will post another thread about changing over from brass to plastic for the mikuni bs34, could be useful.

( came across this conceptual explanation video of the ignition system on youtube, its for an old four cylinder vw car but its seems fairly transferable, particularly in concept, there are also related videos on valve clearances, and some other stuff, plus dig the groovey music ) ok, so ive half and halfed it. I read and read and read, removed the cover plate, then looked and looked and looked, referencing what I could see to what I had read up on but the condition of the right cylinder wasnt improving on reading and looking alone, So, I poked at it with a screwdriver ! The guy I know who has a garage and an oil pan is not around this weekend so I did a bit of a hack, I got a feeler gauge, picked it up for $1.99, and turned the engine over incrementally with the kick starter until the gaps looked all the way open and measured the gap. sure enough, there was a big gap on the right cylinder's contacts so i loosened up the breaker assembly, just a bit, and then nudged it over, just a bit, until it seemed about right with the feeler gauges.( .3mm-.4mm gap ) Presto. Well, Progress at least, and ill take that. Still a bit huffy, certainly still barking on the right especially when throttling down, but its firing significantly better. After going for a spin around the block, I had two warm pipes and a few suspicious neighbours. So, still backfiring but its changed for the better after the poke with a stick. I took it around the block a couple more times. Its rough, but one thing is that it is starting significantly better and that especially feels like progress to me. Such is the progress in fact that I've dropped it in to a shop, HaHa ! To get it done properly, dynamically, at least I hope it will be. I also want to get an overall safety done for peace of mind as much as anything as well as a little stock taking done of things that need attention as Im begining to think in the back of my mind of getting the paperwork done on it with the great state of illinois and the no less humble city of chicago. Cant hurt to use this trip to the shop to gauge how close ( or indeed perhaps far ) it is to being on the road. My sense is that to do the whole ignition timing properly, well statically anyway : alternator plate off, cranking till correct firing position, setting the gap is doable for a relative novice particularly if you have had the chance to see it done a couple of times. If I had set the dwell completely myself, Id be saving a bit of money that I could put towards stuff thats really worth paying for, it bites a little to have to spend but hopefully im not very far off having it on the road. And after all, no man is an island however pennisular at times I at least may be. So, I was able to drive it to the shop. And after talking about the problems and history was able to start it up on the first kick and demonstrate. Very Nice, it was seized up and covered in rust and dust not four weeks ago. Indeed, they waived the $200 they demand on older bikes, that was nice of them, maybe i looked just needy enough. In fact, After driving it to the shop, talking about it, seeing that it is in pretty good condition, i did think, Gahh, It probably just needs to be ridden in, but as its a first time project, I like the idea of having someone go over it at this point as fingers crossed it might not be too far from getting it out on the road. My goal is to be able to get it out for the Chicago Air and Water Show in mid August. One big thing about this project to date is that I wish had taken photographs from the very begining to document everything. So, im quietly confident in getting out on the road soon, its not until mid week that I hear back from the shop. Plus, im pretty sure that I have electrical work looming as the battery charges down over time. Also, the fuses are pretty loose and I noticed today that they have a tendancy to come loose and stop everything, but at least the fuse fix should be pretty straightforward. The shop is not a megastore but it doesnt feel entirely like a local mechanic either. If anyone has any local mechanics they can recommend on Chicagos North West side, please let me know, it may be that these guys are ok too, you know, but you can never know or have too many contacts. Big Thanks for all the help from the Forum so far, particularly, JimR and Drewpy, folly and DT. I may not be on the main roads yet but I graduated out of the alleyways today and onto the back streets. Fingers Crossed, I can make it out for the Air and Water Show.

In the immortal words of manuel from Fawlty Towers...Que ! ( Fawlty Towers = Old British Sit Com ) Im sensing that im a bit out of my depth here being new to the electrical system, even after reading up on it in the Haynes and online, Im a bit sheepish about getting crazy with the cheese whiz. Is this type of testing that someone with a good hold on basic phyiscs from school and a multimeter could approach. Is it the kind of thing that a decent electrical guy in a shop could do pretty fast ? id like to get the learnin from doin it but dont want to stretch too far.

Ok, battery charged up and it started, however this time on one cylinder only, the left. The right fires intermittantly, makes a crack and puffs out some smoke every couple of seconds or so. Yesterday, there was smoke coming out both so I will get into the haynes and start error testing along the right circuit. If the battery drained down to 9.4, is it likely there is an underlying problem in the electrical. Thanks DT, will keep that handy. All in all, after putting a bit of work in, the bike is showing some signs of life, If I can get the right cylinder firing reliably I can start to get a bit more feedback off the bike as to what needs to be done.

Ahhhhhhhh. ... Cant get it started again, noticed the neutral and oil lights were dimmed so took a reading of the battery, 9.4 V. Its a new battery, purchased on 2/7 . Maybe its a dead cell, how would this affect the ability of the bike to start from kicking, and jumping isnt giving any better result ? I retested the sparks and wasnt getting anything from the right plug. Im recharging to try and get it back around 12.6. Im heartened by the fact that it did spring to life but its possible that there might be some electrical work ahead. Back into the Haynes, Whats the best place to start with this work. Could it be that I didnt clean the carbs thoroughly enough ?

Thanks for the tip Drewpy, I'll use that the next time.

Started on first kick ( only lasted about 60 seconds - all glory is fleeting ) Kicked it and it caught, revved it up to about 6 thousand revs pretty smoothly, lots of smoke, vroooooom, excellent. Good Idle, got in first and drove up alley pretty slowly on half clutch, let clutch out all the way and it coughed and died. Hopefully its my rusty driving skills that killed it. Im letting it sit before trying again, only left it on prime for about a minute after the earler incident so perhaps the carbs have not fully filled. The Carbs. 1 ) One of the main jets was completetly blocked. 2 ) The other was partially but open. 3 ) Nethier of the pilot jets being removable, they looked a bit blocked, so carb cleaner soaked it and compressed air cleaned with aerosol can air. Best I can do for now, did get air through them before reinstall. 4 ) Both floats were stuck, unstuck and cleaned the filter screens on the needle valve assemblys, both of which were caked over in stuff. 5 ) Cleaned piston and needle until smooth, gave the diaphragm a bit of silicon spray ( dont know if this is completely kosher but hope it keeps the rubber supple. Assembly and Reinstall was straight forward. Reinstall greatly helped by being able to dissassemble the air inlets and get them into position. Unthreading and Rethreading the throttle cable was the biggest pain, which wasnt really all that bad either. After Reinstall : Turned tank to prime and left for only about a minute, was a little sheepish after the earlier incident. Ive read it overflows the gas into the air filter rather than the cyclinder by design, thus avoiding any possible internal damage trying to compress a cyclinder full of liquid. That being the case, turns out to be a good feature though its far from a perfect to have gasoline belching out of air filters. So, cant imagine it wont start again, but will have a better idea latter about how well it runs, but since it started, i figured that was worth a post.