grusvag

Ok, will do. Thanks.

Had a weird electrical situation that left me stranded last fall and want to test the electrical system on my 1980 XS400SG. I got as far as checking the output(?) at the battery while the engine is running at or above 2,000 rpm. The Haynes book says it should be at least 14.5v but mine was only reading about 11.3v. Am I correct to assume that the alternator isn't putting out what it's supposed to? Should I do some further testing on the alternator? Battery was somewhat recently charged. (should I first charge up the battery then do the output test?) Thoughts?

The guy I went to actually enjoyed working on the old lock, something different for him. A change of pace for him and he nearly thanked me for getting to work on it!

Yamaha Dealer tried making new keys from the code on the cylinder - no luck. Locksmith B was able to pick it and cut new keys for a quite reasonable $35US. Ok, now to see how the beast is running this year!

Thanks for the offer Ttaskmaster but I think the airfare would kill me! I tried fiddling around with a screwdriver and pick and didn't have any luck. The other key I have won't even go in so I called a few places: Locksmith A wanted $75US to pick it and cut a new key. Locksmith B said they could do it for $25 - $40US. Then I called a Yamaha Dealer. $18.52. They cut a new key from the code I provide them and presto! (I hope.) Will go up there hopefully on Friday and see how they do. Will let you know it works out. Thanks for the suggestions!

That's not a bad idea. Take the tank off and take it to a locksmith. I like it. No destruction, no buying new parts (I hope)... Will pursue that idea and report back. Thanks.

I seem to have lost the key for my locking gas cap. Any thoughts on how to get it open? I'm guessing I'll have to drill it out and then replace it. 1979 XS400SG

Can anyone recommend a headlight upgrade for a 79 XS400? Mine sucks.

Just wanted to let everyone know that I finally go the old cow running properly! Didn't really need to blow out any passages in the carbs although I did, after thoroughly stripping them, soak the carb bodies in carb cleaner, spray them down with brake-clean and then dry them off with compressed air. Put all the bits back in and after some trial and error with setting the float heights got it running better than it has ever before (for me anyway). Starts on the first kick (still need to replace the starter motor) and runs beautifully. Smooth, powerful and the mileage, upon first check, is above 50mpg. That's for a lot of stop and go city riding and some fiddling around with the idle speed. Thanks so much for everyone's help! Looking forward to putting many miles on this bike. My wife has even signed up for the Motorcycle Safety Foundation Course to get her license. Ciao.

Well, hallelujah. Finally got the damm thing running properly. I lost count of how many times I took the carbs off, changed the float heights and put them back on. What finally worked for me is setting the height at exactly 1" (when upside down, on the bench)(distance from edge of carb body to uppermost edge of float. I tried them at 1.07" and it ran like crap. I tried it at 1.15" and it ran like crap. I tried it at 1.0" and it runs beautifully! I gave up trying to measure them by tilting the carb and blowing air through the fuel supply inlet because a. I would have to have made some kind of rig to hold them steady while I adjusted the float heights and b. it simply wasn't very repeatable. There didn't seem to be a point where the air (fuel) would abruptly stop. Instead it would gradually taper off so it was hard to tell at what point to take the measurement. I even tried a neat suggestion found elsewhere about running fuel into the carb (while on the bench) and then measuring the actual fuel level in the bowls by running a clear vinyl tube from the fuel drain at the bottom of the bowl up alongside the bowl so you can see exactly where the fuel level is. (Setting Float Heights) That sort of got messy because I had bad connections with my bench hoses. So in desperation I resorted to trial and error and getting it in 3 tries eventually. Ugh! Still pops a little at idle so I may try to tweak it a tiny bit, but man does it run a whole heck of a lot better now! It's like a different bike! Tons more power and response. Starts easily and idles much better. This has the BS34IIIs on it so I can't adjust the idle mixture. I think all I have to do now is synchronize the two carbs and I'll be on to other chores on the bike.

So do you think these specs would be good for my 1980 BS34 III carbs?

Awesome, thanks. Is this for the model II or model III BS34?

I've been struggling to clean and rebuild the carbs from my 79 XS400SG and aren't too impressed with the Haynes Manual. Does anyone know if there's a good manual for these carburetors out there? I found something at Lambretta Works's website http://www.lambretta.net/shop/shopexd.asp?id=3996 but it doesn't include those models. I'm new to carburetors and am eager to learn about how these things work and exactly how to work on them.

Now I'm really confused! 1. I thought the floats shut the fuel flow off when they were bottomed out as in the pictures (or raised when in their proper orientation when mounted on the bike). When the floats rise, they push the needle valve assembly up so that the rubber cone seats and closes off fuel flow, right? 2. I'll reset float height to 1.1" while holding the float at it's maximum height (while upside down on the bench). 3. I was told that they're BS34 IIIs from a 1980 and later US vintage because the idle mixture screw is capped off as show in this picture:

So I guess I'm bending the right thing to adjust the float height? And is it ok to use the BS34 IIIs on my 1979 bike?

Just want to make sure I'm doing this right. To raise the float height and shut the fuel flow off sooner I should bend the "tongue" of the float: So that this distance measures 1.26" (according to the Haynes manual): And just to be clear, this is done when the carbs are off the bike, and upside down. Do I have this right? It's a big change from where it was.

I knew enough to take them apart and clean them but most of the inner workings are still a mystery to me. I'm guessing that when fuel fills the float bowl it raises the floats which then make the needle valve assembly close off the flow of fuel into the float bowl. Do I have this right? That would make sense because the floats were way beyond spec - they were too high - when I put the carbs back together. Shortening this distance would make the needle valve close off the fuel flow sooner, right?

Just rebuilt a pair of carbs of the BS34III vintage, put them back on the bike, set the petcock to Prime and not long afterwards a lot of fuel came pouring out the right-hand carburetor. I had the air cleaners off and the fuel was coming out the back of carb and would have gone right into the air cleaner so it appears to be an internal leak. Before I pull them back off the bike and start breaking them down again, does anyone know where the leak might be coming from and where I should be looking in order to fix this problem?

I'm an idiot. The two BS34IIIs are fine. They match and I'm just going to rebuild them. Hopefully they won't be too problematic to get running properly. Thanks for everyone's help. I'll let you know how I make out.

Would it be normal for only one of the MS34III carbs to have this plug in it? It's twin did have the mixture screw in it. So it sounds like you'd recommend I use the original BS34II that came on the bike, is that true?. I'll need to find another rebuildable candidate in that case. My original has a broken body. Anyone want to trade a freshly cleaned and stripped BS34III body for a BS34II body?

Cool. Just the answer I was hoping for! Don't know why this bike would have had euro-spec carbs on it. I'll have to ask the previous owner(s) if they know why. Want to keep my variables to a minimum as I'm not sure this bike has ever run perfectly in my possession. One last thing I have to adjust! Thanks.

Ok, I'm working on rebuilding the carbs from my 79 XS400SG, and had to buy a spare set for parts. I'm cleaning both of them thoroughly and will choose the best parts from each to rebuild a "new" pair. Problem is that I've discovered that one carb seems to have a post plugged by the factory while it's duplicate has a jet screwed into that same place. Question: Why is one plugged like this? And is it ok to use this plugged one in place of the one that came off the bike that had a jet screwed in there? (Unfortunately, I can't use the one that came off the bike because part of the housing is broken.) This carb came off the bike: There is normally a jet screwed in this hole. It's off right now being cleaned. This is the carb that I would like to replace it with: Why is this plugged? And can I still use it in place of the one above? Same model stamped on both sets:

I've got a shop compressor and can dial in a specific pressure. Can I use that instead of a bicycle pump? Sounds like I shouldn't use high pressure.

After riding it a bit these past few days I've come to believe that one of the jets (main?) is clogged for the following reasons: 1. Still needed to spray starting fluid in the carbs to get it started this morning. 2. Simply feels "flat", and although the engine runs ok, it just doesn't have the power it should. I can barely go up hills full throttle. 3. It sometimes backfires when it's shut off leading me to believe it's running lean. 4. It sometimes surges like the blockage temporarily clears but only very briefly. I may remove the carbs on the bike and try to figure out exactly where all the jets are and try to blow or clean them out and then just put it back on the bike to see if that makes a difference. I still want to completely clean and rebuild the spare carbs but want to see if cleaning the jets out is what the problem is. Thanks for the advice about the floats, I'll make sure they're as they're supposed to be.