Ebola Monkey

Thanks for the replies guys. The supplemental from Yamaha does have 120/90 listed for the rear. It doesn't list the rim size for front or rear though.

Anyone?

FOR PART # 278-18101-01-00 XS400D 1977 XS400E 1978 XS4002E 1978 XS400F 1979 XS4002F 1979 XS400G 1980 XS400SG 1980 XS400H 1981 XS400SH 1981 XS400SJ 1982 So basically every non seca/maxim xs400 from 77-82. Along with: R5 - 1970 R5B - 1971 R5C - 1972 RD350 - 1973 RD350A - 1974 RD350B - 1975 RD250 - 1973 RD250A - 1974 RD250B - 1975 RD400C - 1976 RD400D - 1977 RD400E - 1978 XS360_2D - 1977 XS360C - 1976 XS360D - 1977 DS7 - 1972 TD3 - 1972 TR3 - 1972 TZ250 - 1973 TZ350 - 1974 EDIT: Here's one on ebay $20 + free shipping

The current tires are Front: Nankang 3.00-18 Rear Cheng Shin MS90-16 (4.60-16) From what I can find online Front 3.00-18 is closest to a 90/90. Is this correct? I haven't found an MS90 on any of the conversion charts. But going by the 4.60 size I'm thinking 120/90. Is this correct? What are the actual rim sizes for an 82 XS400SJ? With this I can probably figure out what tires are safe for the rim size, and go from there. Thanks In Advance!

SOLVED!! After taking the generator apart last week I decided I would keep the current one instead of replacing it. I had a new resistor cap on order because one was "leaking", and would shock the hell out of me any time I got near it. I also doubled up my battery ground, as I had a spare ground cable. So now 1 ground to the engine, and 1 to the frame right next to the battery. Charged the battery, and let her rip. 12.3v @ idle A few revs, and 14.5-14.6V @ >2000rpms I don't know if the cap helped or not, but I'm guessing the second ground the big fix. I checked for voltage drop on the original cable, and it was good. Maybe there's a crack thats screwing up the ground with engine vibrations, or something. That could help explain the erratic charging. All that matters is that it seems to be working now. Thanks Again to speedshop, and Drewpy for all your help!

Right on. Aftermarket parts are so readily available, and vary so much they could actually hurt resale. Personally I want to buy a used, unmolested, totally stock bike. Then have my own way with it. My strategy is this... Put on what I want, but save all the stock parts. That way when I sell it I can either sell it with the stock parts OR put the stock parts back on, and sell the aftermarket parts separately.

Ditto on eBay. You can probably find a used gearbox for next to nothing (comparably). Might also ask your mechanic if you can source the parts yourself, because they are available separately (cmsnl.com).

If the new ones are less restrictive you might have to re-jet. That's about the worst. I don't know if the 650's had the same diameter headers, but even if they're different mikes sells the adapters.

I just went through this with my wifes bike a few weeks ago. We did a basic carb clean, new plugs, etc. We got it to run, but only fired on 1 cylinder. Then it ran OK, then only 1 cylinder again. It was fouling plugs after only about 2 minutes also. You need Spark/Air/Fuel to run. I'm assuming air is covered. Do you have spark on that side? Pull the plug, put the wire on it, hold the threads against the case and push the starter button. You should see a spark jumping the gap. If not, try a good plug. If you still don't have spark we'll move on, but I think it's going to be a carb problem since you already mentioned the main jet being clogged. Also, Drewpy is right. You need to do a thorough carb cleaning before you do anything else, and you need a fuel filter. You'll clog up the carbs over and over again if you don't because you're churning up whatever is in the tank, and you probably already have crap in the carbs. When we did the basic cleaning we thought it was good, but when I tore into it again I did everything. I found the needle jet was all gummed up with crap. It looked like seaweed in there, and the rest of the carb was nowhere near that bad. Download This Guide, it's the most thorough guide to your carbs out there. I knew how to clean the carbs, but still learned from it. Once you have spark, do a good carb cleaning, and add a fuel filter you should be good. You should be able to do a complete tear down, and cleaning in about an hour. Then you know you have a good starting point. Just made sure to put a filter on so you don't get more crap in there, and have to do it again.

You're absolutely right. I had a brainfart, and was thinking about the one for the clutch .

There should be screws in there. They are the spots that drewpy pointed out, but if they are untouched they will be plugged with a brass plug. The plugs are pretty thick, and you have to drill a hole in them then use a screw, or something to pull them out. You have to be very careful though because the mixture screws are very close. If you get goofy with the drill you can mess up the mixture screws. If the plugs have been removed the mixture screws are recessed pretty far. Have you actually removed the carbs, and looked?? You can't see the screws without removing them. If you have a flathead screwdriver that will fit in there you should be able to feel them, and adjust. It's a pain in the ass though. They are in the spots with the arrows.

If there's any question on whether something will work or not, go here http://www.cmsnl.com/yamaha-xs400_model16837/ and compare the different models for carb parts. They aren't all the same, and when the maxim, and seca came out they were jetted different than the regular XS400's. I want to say the seca/maxim were jetted richer. Also, is the Canadian sister site to MikesXS.

It's SO low at the moment because I had been tinkering around with it so much after I pulled the generator. Now I'm delayed for a few days waiting on the new gasket to come in. I should have the new gasket Monday, at which point I'm going to reinstall the old generator (with some heat shrink around the chafed area), add a second ground strap to the chassis (for good luck), replace the faulty plug cap (assuming it comes in), charge up the battery, and cross my fingers.

Take the left rear cover off (where the shift lever goes through). There's a spring loaded return in there. I would guess that something is broken, or stuck.

That's what I was getting at speedshop. Trying to bypass regulator to eliminate it as the problem. Here's what I'm getting with the field coil connected, and ignition on (still disassembled so not grounded via the case right?). 11.87V across battery 11.87V between GREEN from Coil, and Battery negative with the regulator disconnected. 2.50V between GREEN from Coil, and Battery negative with the regulator connected. 11.87V between BLACK from Coil, and Battery negative with the regulator disconnected.(same readings between the ignition, signal, and headlight fuses and battery neg, as they all tie into the same brown wire) 11.07v between BLACK from Coil, and Battery negative with the regulator connected.(same readings between the ignition, signal, and headlight fuses and battery neg, as they all tie into the same brown wire)

I've been fighting through this charging system problem on my wife's bike, and it's driving me nuts. I found on some 650 forums that you can bypass the voltage regulator to find out if it's the problem. Is there a way to do this on the 400's? I've tried 2 different voltage regulators, 2 different rectifiers, and am ready to try different armatures, and field coils.

I tore the generator apart today. The cloth wrap on 1 wire from the generator was worn, but the plastic insulation was fine. Other than that, everything looks to be in great shape. There are no visibly damaged areas on the wire sleeve, and nothing looks pinched. I also cleaned up the other used regulator I have. It has 1 wire worn through the insulation in the same spot, but it's down to the wire, and someone had done a really bad tape job on it. It also has a couple area where the wire sleeving is cracked. Now, with my meter both armatures OHM out to the exact same numbers (1 - 1.1ohms), and both field coils OHM out to the exact same numbers (3.4ohms). Considering my current wiring is in better shape, should I even bother replacing them? I destroyed the gasket in the process of getting the armature, and coil out so now I'm waiting until Monday at the very least for that to come in. I don't know what else to do. I can't start buying "know good" parts for this thing. They're too damn expensive, but with used parts I don't know what I'm getting because everybody says "the bike ran perfectly before were tore it apart". I think we all know that's BS. Battery - Known good Stator - Have 2 both test out identical Field coil - Have 2 both test out identical Regulator - Have 2 both test out almost identical Rectifier - have 2 both test out almost identical It's getting to the point where I want to put it back together and sell it.

Diode under the seat is part of the headlight circuit. It's Fresh.

I do have a solid state regulator, and have tried another one. I've also recently replaced many of the connectors including the ones to the generator, regulator, and field coil, so I know they are good. I haven't dug in to see where the wires go into the case yet, but that will probably be the next step. Hopefully someone else remembers if it's going to be filled with oil before I dig in. Hopefully someone else remembers if I'm in for an oily mess or not.

Drewpy, Isn't the mixture screw blocked by a brass cap on the 81? I know it is on the 82.

Petcock: PRI: Prime, not vacuum operated, just OPEN On: Vacuum operated. Only lets fuel through when engine is running, if petcock is good. RES: Reserve, also vacuum operated, same as above, when you hit the reserve level go get gas. As far as the revving, check for air leaks in the carb holders. Also what choke setting do you have it on. Mine I start on full choke, then turn down to half for a few minutes, then off. If I leave it on half it will rev up to around 3000, and stay there after a while.

O-rings: (for 4 carbs, but it's cheap, leaving you extras) You want the kit for mikuni BS carbs 80-84 Most everything else: http://www.mikesxs.net rebuild kit (needle, seat, gasket, and pilot jet plug) is out of stock I got my needle and gasket here: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=200474693262 I did have a problem though. With the clip that attaches the needle to the float they would not seal. They are just a hair too short. I removed the clip, and they worked fine. I didn't use the gaskets yet, as mine still seal very well.

Yeah, did replace the diode. I load tested it today, and got no load with the key off, and 4.25V with the key on. Now for the voltage readings: Idle: Battery: 12.25V Generator: ~10.6V on all 3 legs Field Coil: 10.35V <<seem odd? 2,000 RPMs: Battery: ~13.5V Generator: ~12.5V on all 3 legs Field Coil: 12.25V <<seem odd? 2,500 RPMs: Battery: 13.5-14V Generator: ~13V on all 3 legs Field Coil: 8.8V <<seem odd? All of the voltage readings fluctuate a bit, and will vary because I would do 1 @ all RPM ranges, then the next. I never got above 14.15V or so, and it would fall below 14 if I stayed above 2500RPMs or so. It seems to be keeping up (not great) as long as I don't turn on the blinkers, or brake lights while idling. When I do it drops voltage, and can't seem to catch up. I have another field coil, but it's well used, and ohms out almost identical to the one that's on the bike now. My replacement plug caps will hopefully be in by Friday. The service manual isn't very explicit about replacing the stator, and field coil. Is that area filled with oil? Do I need to replace gaskets if I open it? Thanks Again For The Help

The front brake switch is in the brake lever perch. 2 going in, brown, and green/yellow. You could disconnect the rear switch, should have bullet connectors on it. If the lights still on, probably the front switch. Thenn try unplugging the front switch. I believe the plug is in the headlight bucket.

Thanks for the reply. The field coil should be 4Ω ±15% Mine is at 3.4Ω which is right at the bottom end. I have (2) regulators that both ohmed out the same, (2) rectifiers that both ohmed out the same, (2) stators that both ohmed out the same, and (2) field coils that both ohmed out the same. These are all used. The extra rectifier was on the bike, the regulator I bought off ebay (stock regulator was already replaced), and the stator, and coil were a surprise in a parts lot I bought. I think the previous owner was trying to track down this problem, and failed. Like I mentioned the Regulator, and Rectifier were already replaced. The headlight was also on a switch when I bout it. I assumed it was because the diode on the headlight circuit had shorted out, and previous owner hadn't found it. May have been been, but may have also been because it was a drain on the system. The only other thing that I've noticed on the bike that is not right is 1 resister cap is leaking. It tests out at 10kΩ, but if I touch it with the bike running I'll get a shock. I verified it is the problem by switching the ccap to the other cylinder, and got the same result. This couldn't effect the charging system could it? The other cap ohms out at like 3MΩ. My meter is a Fluke 83 III, so not a cheap meter, but never been calibrated. Ive had it for years, but looks like new. I take good care of it. Will look into getting it calibrated though.