Strange coughing sound and centrestand

Eduard

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Hello everyone,
I recently got my hands on yamaha xs400 from 79 as my first ever motorcycle. It is in a good state so I am not planning any rebuild, I like it the way it is.

I am a beginner so pardon me for asking those probably simple questions:

1) When I start the motorbike and let it warm up a bit, after a minute or so there starts to be a strange coughing sound from the exhaust. It is not continuous, happens just from time to time (maybe after 10-20 seconds). After I ride the motorbike a bit the sound disappear although I had a feeling that I heard the sound few times during the ride (but not sure). Please what could be causing this sound?

2) am still figuring out how to put the bike on the centrelstand the easiest way. Are there any tricks? I tried to do it while sitting on the bike, first I pushed the bike little bit forward while holding the front brake then swung the bike backward and pushed with my left leg on centrestand. However this technique was quite exhausting. I am relatively small person so maybe my bodyweight could not do enough force on the centrestand. I suppose the best way would be to do it while standing next to the bike?

Thank you very much and happy riding
Ed
 
Hi Eduard welcome to the forum.

The exhaust noise could be any number of things.
Think of the engine as a system that breathes air, drinks fuel, has a spark, explodes, pushes you forward and shoots exhaust out. There are many variables that could cause a coughing/popping noise here. Some of the most common things to check would be the fuel supply, the air supply, the carbs, the spark, and then the actual exhaust system.

Starting with the fuel supply. Check your gas tank. Then look at the petcock (the fuel on/off switch, mounted to the bottom of the tank). Then check the fuel line. That flows into the carb. Also going into the carb (directly under your seat) is the air filter.

For spark, check the spark plugs.
As for the exhaust, it's likely fine if it hasn't been modified.

Your motor will make different sounds at start up, choke open idle, choke closed idle, once it is warmed up, and once you're driving. If you can post more detailed pictures/videos (or sound clips) that will help members check out your potential issues a little easier.

My guess is that the settings on your carb aren't quite right. This means that the jets in the carb need to be adjusted, or potentially changed. WIth the limited information in your post, I can't really say. It might be a small backfire, it might be a crackle, I'm not sure.


As for the center stand, my best advice is to do that when you are standing beside the bike. Stand on the left side of the bike, with both of your hands on the handlebars. Then, keep your left hand on the handlebar, and take your right hand and move it towards the back of the seat. Then step on the center stand footpeg, and press it into the ground. The center stand works by lifting the bike upwards, and backwards towards the rear tire. So by sitting on the bike and doing this, you're not only lifting the weight of the bike, but also lifting your own weight. By standing off to the side, you can use your right hand to guide the bike backwards and upwards, which takes stress off the foot peg that you are standing on. There are lots of good videos on youtube for that.

To take the bike off the center stand, I just straddle the bike, and push forwards on the handlebars and the bike falls off the stand and the stands retracts into the storage position.

Goodluck and post pics of the bike when you get a chance!
 
Hello Addison and thank you very much for the reply.
Pardon me for responding so late, but I was traveling.

Unfortunately I don't own a garage so until I find a better solution, the bike is for the winter in my living room :).
Which means that I can't run it inside, so I am waiting for some sunny and not freezing day to take it out again.
I will make the videos of the issue and post it here.

I got the bike from a gentleman, who told me that he cleaned and set the carbs, put in new air filters etc.
The petcock was at ON position during my testing last week.

I have an idea: is it possible that during the transport of the bike some fuel got somewhere it should't? So then when I started it, it made some of those coughing sounds?

About my second question about the central stand - it was really simple in the end. Thank you!

I will make and post the videos as soon as I can.
Thank you and have a nice christmas time!

With kind regards
Eduard


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glad to hear some of the issues are sorted!
and WOW that is a great looking bike, enjoy!
I'm not sure about the gas issue. Entirely possible, but someone with a SOHC would be better suited to answer that (mine is DOHC).
I have the same rims as you, on my second bike.
Love the sparkly paint. Very nice.
Enjoy your Christmas as well and please send more photos when you have a chance, I do wish I was able to put the bike in my living room as well, would make working on it easy! For now, the garage will do.
Addison
 
It sounds like you got the center stand use figured out. I just want to add that when you put your foot on the stand and your hand on the frame by the seat, you push down with your foot at the same time as you lift with your hand works well. Trying to do it with just the lift with your hand or the push with the foot is much harder than doing them both together.
There are things you can do to make the center stand easier to use. One is greasing the pivots of the stand. One way to do this is to pull the mount bolts out. Clan and coat with grease. Another is to remove the stand and add grease fittings to the stand so you can add grease easily. Doing this once ever year or so should be plenty. Probably hasn't been done in years.
I keep a few pieces of 2x6 lumber about a foot long around. When you want to use the center stand run the rear tire up on one of these pieces of lumber. This lifts the bike up so you don't have to lift it as high to get it on the stand.
Leo
 
Hello everyone,

thank you all for your replies.

I changed the oil filter and poured in some new oil and finaly ( last week ) took my bike out for a ride. The weird sound is not there anymore, so the problem is solved! I noticed that the oil level was alarmingly low so I suppose the coughing was caused by that ( so the main issue is my inexperience :) ) .

Here are some more pics of the bike, if you are interested.

Have a nice ride!
Ed
 

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