Carburetor Problems

[kevingkruse]

Hello everyone, I recently purchased a 1980 xs400 special and after only needing a battery got it going. I've been having problems with my carb tho, I've cleaned it a couple times, everything looks ok, the boots were cracked up so I sealed them with SealAll and sprayed them down, didn't hear it rev up, so I'm guessing they are good. When I cleaned it the first time, it started up good and idled fine but I would have hanging rpms from around 5K down, sometimes when it hits 3K coming down I would hear a click coming from somewhere and the rpm would go down, but only randomly. I've messed with the air screws and they didn't do anything, and I would have some hesitation on the throttle. The next time I cleaned it, it wouldn't started for good amount of kicks (starter is bad) but it would start, and now it will idle but dies on throttle. I didn't mess anything up, that I know of... I noticed that before, there was no fuel in the vacuum line but now there is. And now the choke doesn't work as good, it only makes the rpms go up about 500. I'm just confused on how all this happened when just recleaning my carb. I tried syncing my carb but I'm not quite sure on how to do it right,and I've been searching all around, I've found some things but they didn't really help. Any other suggestions? Thanks for reading, I'm just itching to get this thing going good.

 

[New guy]

Hi. I just went through a carb clean for the first time. Take a look at my thread and check out all the tips from everyone. Have mine back and working now. Bcware's carb vid is awesome. Good luck.

http://www.xs400.com/forum/showthread.php?t=8064

I forgot. Go buy a new throttle cable. Just do it. Even if you think its working OK its probably not. $20 and worth every penny.

 

[kevingkruse]

Well I will look over that thread, but as for now, I was able to mess with the tuning and got rid of the hesitation, and the rpms go down a lot better, could be a tad better, and it was able to start easy, while it was warm... the next day I tried starting it and on the first kick it started with a kick of the rpms and went down to a stall, now it just won't start anymore. My plugs read lean, and there's fuel in my vac line again, after the tuning yesterday there wasn't any... I'm thinking I might just have to buy new boots but I don't hear any rpm change with WD40.

 

[kevingkruse]

Ok well after another deep carb cleaning I found a little gunk that came out of one of the circuits and was able to start again, although, after tuning around a lot, I can only manage to get it to idle very low so I can throttle it niceley and the rpms drop nicely, if I try and raise the idle screw or the sync screw, the rpms drop slowly, I tried messing with the a/f screws also and couldn't make it any better. Upon reassembling the carb, I noticed I don't have any o rings for my a/f screws, but I was able to find them which came along with other goodies with the purchase of my bike. Would those not being there make a problem like I'm having? I also ordered some new carb boots so maybe that will fix some things. As for the a/f screws o rings, how do they go on the screw, I have the o ring and washer, in which order do they go on? Thank you for your paintence with my noobiness...

 

[DanMach]

Missing o rings on a carb is always ba.d I'd replace that asap.

It should be washer -> oring to squish that oring in.

Good on you for keeping at it though. Make sure you have a filter for the fuel because these things can be VERY touchy to particles.

 

[kevingkruse]

Thanks for your reply, and I have definitely been keeping at it, to the point where my girlfriend gets mad... But she will be happy when she's ridin on the back with me

I'm also going to change the points since I've got new ones laying around, maybe that will help with starting a little easier? And probly good to check and adjust the valves, I've read around and I think I get how to adjust them, but for the nut to loosen the valves to adjust them, is it the middle one that is showing right then I take the alternator plate off? I thought I would have to take the head off to adjust them but I don't really know anything about 4 strokes.