gdarrell

Exhaust stud that is! Ok, well maybe not what you thought Thanks to all for the help getting my old XS400 S going!! Couldn't have done it without some really smart guys out there with good advice and trouble shooting tips. My current puzzle is that one of the exhaust studs (inside stud on left cylinder) is gone. The threads are gone as well and it appears to have been either reamed out or wallowed out. That is, the hole is no longer round, no threads, and its larger than the stud signficantly. Been this way since I got it. It doesn't "leak" too bad, but I don't know if this will cause me to burn a valve or something over time (leak is noticeable, especially during cold start). I have found a replacement stud from a hardware store that matches the thread pattern on the studs that are still there (these studs are no longer available from Yamaha). My question is how to fix it? Can you JB weld it in place? Or, fill up the hole with JB weld and then try and tap threads into the patched hole (can that be done)? Do I need to be able to remove the stud later or make this a one time "permanent" fix? I am sure I am not the first to see this problem, so would appreciate any creative solutions (that is, ones that don't involve replacing or removing the head)

I replaced my wires with wires from AutoZone (got them cheaper) and reused the caps. This may not be advisable, so I would let some of the other guys here weigh in on that. It worked for me, but the wire size is one smaller than the original.... Check the wires with a timing light to see that you are still getting spark to the plugs. If tank is really bad, might consider getting one that is in better shape off ebay. Mine was not bad. I have seen some tanks with the internal coating applied, but the ones I have seen are peeling on the inside. Doesn't give me a lot of confidence. could have been a bad application, though, or maybe just age. If you haven't cleaned the carbs, then I would disconnect the fuel line until you do. No point in putting more junk in there or through the cylinder heads.

what do you guys think?

just thought of something else.... if battery is dead, then you won't be able to keep enough voltage for the electronic ignition to work. others have posted on that issue, so if you can get it running with jumper cables, you may not be able to keep it running once you pull them off and battery voltage decays below around 11v.

sure... I have the same problem. got an extra but still haven't been able to get the snap ring out to release the piston - its stuck in there.... let me know how much for yours. how does the replacement work and how much did it set you back? might be worth checking into...

assuming the obvious that the tank has gas in it, then try setting the petcock position to "prime" which should cause gas to flow directly to the carbs from the tank. if that works, could be a problem with the petcock vacuum. I have problems not getting enough fuel sometimes and can switch to prime and it works ok. I don't think thats a good long term solution, but it helps troubleshoot.

Hi guys, anyone know where you can find a new plastic reservoir to replace the ones on the late 70s early 80s XS 400s? Mine is old and leaking around the bottom. I have taken it apart and cleaned it thoroughly, but it now leaks past the large O-ring that is supposed to seal the reservoir to the aluminum master cylinder. I either need to get a replacement (with O-ring) or find someway to seal it that won't break down from the brake fluid. Brakes work ok, but I don't want to grab a handful of brakes one day and get nothing but air

I am convinced that my problem is the "starter clutch." I am now able to get it kicked and running pretty much on first or second kick now. After I finally got the carbs really really clean and solved the TCI ignition problem, she started firing. for the first several times, it took starting fluid, but it seems to be happy now and starts easily on middle choke position and good strong kick. Let me know how that job goes. I have been reluctant to tear into it because I wanted to get it running and make sure it was otherwise mechanically sound. I have put on a 100 miles, so I think it is.... But, I don't really know what is involved with the starter clutch replacement. If anyone does or has done it, a post on that would be great!!

I did finally get the old girl running. I was able to check for a spark by hooking up my timing light, turning on the ignition, kill switch set to "run", and giving it a kick. The light would strobe well on one side but not at all on the other. That convince me that I wasn't getting fire on one side. Swapped coils from one side to the other with no effect which told me my coils weren't the issue (shame I had already bought an extra set off ebay!). Did a little research and got lucky with a random hit on a google search that led me to believe the TCI box was bad. Apparently, there is a failure mode where one of the wires inside the box comes loose from vibration (and old age) and while the box is "good", its only sending out a signal on one side (spark on one side). The website talked about opening up the box and finding this connection and resoldering. Easy fix and there was also a link to a guy that could rebuild them. this was for some XS 600s I think and that was all he worked on. Apparently there is no test for the box - you can replace with a known good one, but who has those laying around? Anyway, I ended up and got lucky and found a box for less that $30 bucks, so I bought it. Plugged it in and bike was now getting fire on both sides - success!! Well, not so quick. I was finally able to get it fired up after a little shot of starting fluid (ether). Its running good, still needs carb synch, but I have put a few miles on it (maybe 100 or so) in the last month. I didn't open up my old box yet to check for the loose wires, but its on my list of things to do to check the solder connections. If you have checked coil resistance, plugs, and plug wires, then you might consider opening up the box to look for a loose solder joint. I will also say that when every one on the forum talks about voltage, they are correct. It just won't work without about 11 volts min to the ignition circuit, so you should check that as well. Good Luck and let me know how it comes out!! Painted the bike this week and will post some pics soon. Big change since she was under the apple tree

You can check out this site also: Candlepower Motorcycle Headlights they make replacement lens/bulb combinations for motorcycles in several sizes. Recommend you pull your lens, draw a circle around it, and measure across to get the diameter if you do a replacement to make sure it fits. I had good luck with their 6-3/8 inch for my 82 KZ440 that came with a multibracket (headlight adjustment bracket to fit several japanese style bikes that had the adjuster bracket mounted on the lens itself). Of course, it may mean an entire changeout to lens/bulb combo, but after that, they use standard H4 bulbs that you can buy anywhere, including any autoparts store.

Ok, here's an update. Changed plugs, rechecked wire connections, fuses, etc. Still no luck.... I have convinced myself that if the TCI were shot, I wouldn't get any fire at all (can anyone confirm that? will it fire on only one side or fail altogether?) At any rate, tired of kicking with no luck and finally decided to tear the carbs down again Turns out my "good cleaning" wasn't as good as I thought it was. As soon as I opened them up, they were still really sticky on the inside with more traces of varnish. One of the floats was stuck (left side - coincidence??) So, today I took them completely apart and gave them a really good chemical soak. This time, they almost sparkle - sort of... Mostly back together, still need to set the floats. Stay tuned, if it doesn't start tomorrow, then I am out of ideas

If its the 6-3/8 size that was used back then (not sure about Yamaha, but both Honda and Kawasaki used this size), then I found a source from Candlepower in the US that makes a nice replacement refletor with replaceable H4 bulb. The kit comes with the reflector and bulb and can be ordered here: Candlepower Replacement Motorcycle Headlights They also have other sizes available as well. I took my lens out of the brackets and drew a circle around it, then measured the diameter to confirm the size. It was 6-3/8. I ordered one for an 82 KZ 440 and it worked great. The dealer wanted something like $65 for a sealed beam that has poor light quality to begin with. This replacement is very bright and was $48. The lens also has the adjustment screw bracket on the back of it (although I did have to tweak it some to fit in my bucket). Now, I only have to replace the bulb (around $10), not the whole unit.

Thats certainly worth trying as well as swapping plug wires. will try that tonight.

its the smooth cover - so its TCI. At the risk of sounding ignorant (not hard for me), how do I check for the 12V at the coil? I checked the resistance on both coils and the output of the pickup (from the smooth box) and all the values were spot on with the book values (3 ohms for primary, 8.5Kohms for secondary, etc). So, that would suggest coils are good, but doesn't tell me if they are getting juice which is a really good question. I hooked up the DVM to the coil lead wires (not plug wire) and only get a few hundred mV. I rotated the engine slowly through the timing points but did not see a change. Obviously, I don't know what I am doing

You can get a copy of the XS360 - XS400 shop manual here: XS400 shop manual wiring diagrams are in the back by model no. See pg 1291