Smoke from engine

[Taras]

Hey guys,
First of all, I am a total novice on bike mechanics but with an incredible urge to learn everything there is about this cute little thing. Something tells me either that or lay of half of my salary to pay off a mechanic

I've had some problems starting my bike lately so after alot of research on this excellent forum and troubleshooting I came to these 2 conclusions:

1. Faulty petcock, no fuel is reaching the carbs. If i turn it to prime the fuel flows but not on reserve or on. I ordered petcock rebuild kit, replaced the o-ring and the rubber diapragm, assembled everything back but it leaks like hell from a small hole on the side of the square plastic gasket. Also, the fuel is flowing constantly, doesnt matter if it is on prime or on. Could I have assembled it incorrect?

2. The fuel was overflowing and leaking out of my air filter box. I removed the carburators, took them apart and the float was stuck. While I was at it I cleaned out all the jets and sprayed everything out with compressed air. Everything seems to be fine now.

Put everything together, after a while the engine started but after a couple of seconds some smoke came from the right side, I couldn't really see exactly where it came from. Then the engine died. Also, the right exhaust was very hot compared to the left one.

What could that be?

Appreciate the answers!

 

[hmusket]

What year bike do you have? Has it ever ran consistently? When you bought it what work did you do on it. ie. spark plugs, wires and caps, points and timing if 79 or older?
If you have the proper petcock rebuild kit it shouldn't be leaking. You may want to take it apart again, check for tears in the diaphragm, or proper assemblly, or get a manual petcock as discussed in an earlier thread. Your left cylinder probably isn't firing.
Download the manual from the tech section. Start there.

 

[networkguy]

Hey I'm a newb but :

It sounds to me like your petcock was working fine to begin with. Fuel should only flow freely on "prime" setting. Both other settings use the engines vacuum to open the petcock and let fuel through. Hence no fuel should come out on these settings with engine off.

 

[isigt]

Just a quick thought about the smoke, did you clean the engine with wd-40 or something similiar?
That could cause a bit of smoke until it burns off.

 

[Taras]

1. Its a -82 SE, it ran fine when I purchased it but shortly after there was a fault in the ignition which I had exchanged. Since that I have changed the plugs, air filters, oil and battery.
I removed the protection lid on the contact breaker yesterday and measured the gap, it was about 0.3 as the manual says.

2. Yes but the fuel did not flow when i sucked on the vacuum hose to open fuel flow on reserve and on
I have inspected the rubber diapragm and all looks good, i tried every possible way to get it back together but it still leaks and doesnt function properly. See attached pic.


3. Well, i used some WD-40 on the inlet rubber to get the carbs in a bit easily, but it was barely anything.

There is spark on the right cylinder and when i put my thumb over the hole the compression is strong enought to lift it up. If the cylinder wasn't firing there shouldnt be any exhaust coming out from the right pipe, right?

And why is the right exhaust so much hotter, could it be that it is running way to lean? Right carb not doing its job? Retarded ignition timing?

 

[hmusket]

When you reassembled your petcock, was the diaphragm on both sides of the gray plastic? I've also heard of people getting the wrong replacement parts, plunger of stopper on the diaphragm that goes into the petcock main body, being to long or too short.

By ignition, you switched out the TCI or CDI? There was recently a thread who replaced his with one that ended up being defective.

Double check your carbs, clean passages, float levels, etc.

If you spray water or spit on the left exhaust, does it steam?

Just thought of another question: Where was the smoke coming from, around the engine? from the muffler?

 

[Taras]

Yup I have the plastic piece in the middle of the rubber diapraghm, is that wrong?
The spare one seemed to be identical with the old one.

I actually don't know what they did to the ignition, a workshop did that. But it ran fine after that.

It seemed that smoke came from the engine area and not the exhaust.

Man, if I just could get that petcock to work so I could exclude the fuel issue.

 

[hmusket]

I have a few yamaha vacuum petcocks, they don't look like your's. On the bottom where your fuel hose comes out there's a screw on mine, I suppose to empty the fuel tank. Just a guess though. If thats the case someone may have modified yours, so originally,before your rebuild, the only way gas would come out is when prime is on. Is there another fitting or hole on the side of the body of the petcock that may have been plugged?

But then again maybe yamaha made a change, I wouldn't know, I don't have anything newer than 1981,LOL. Perhaps someone with an '82 can give some insight.

Also, maybe the smoke is from the gas from the leaking petcock hitting the engine.

 

[Taras]

Progress! I got it to run again, strange thing is, it starts better without choke than with, could that be because my idle mixture screws are to closed?

No more smoke and both exhaust pipes are equally hot. Took it for a spin actually, wonderful feeling after countless hours of fiddling around with it!

The petcock is still weird though, it drips from reserve and on but the flow increases when diaphragm is open. Found a replacement on a scrapyard not so far, gonna go there tomorrow and get a new one.

 

[akronevan2]

Good luck with everything!

 

[hmusket]

Sounds like your getting things sorted out. Good deal.

 

[isigt]

Good to hear it's working out for you!

Också kul med en till svensk på forumet.
Släng gärna upp en bild på hojen vetja!

Everyone here like pics.

 

[Taras]

Thanks!

Still got the issue with the choke though, bike starts without without choke, I pull out the choke and the engine dies. The choke is limiting the air right? So perhaps my idle screws are to far out and giving it to much fuel while choke increases it even more?

Ja svenskarna är överrepresenterade på detta forum verkar det som

A pic of the bike is coming soon!

(Btw, got my motorcycle driving licence test tomorrow, wish me luck )

/T

 

[HoughMade]

In these bikes, the choke adds fuel. Actually, it's not a choke at all. It's an enrichener circuit. If the weather is particularly warm, you may not need the enrichener. If it is not, your idle mixture is probably a little rich.

 

[lhaolpa]

Looks to me that the white block where you show that it's leaking is backward.The hole shown should face outward to displace the air when vacuum is applied. lha

 

[Taras]

Hey guys!

Passed the licence test today, finally I can ride (legally)

Took the bike out for a little longer ride, still some issues.
It goes like a rocket on mid and high rpm, but as soon i release the throttle it sounds like the revs are way to high. Also, when I stop at first the idle is low but then it picks up. Cant tell you what the revs are ( dont have a counter ) but I can hear it is too high.

I've got 2 rotations out on the idle mixture screws. Wont start at all with choke out.
How should I adjust the idle?

Any thoughts?

P.S, petcock replaced and is working fine.

 

[lhaolpa]

You need to fix your idling problem before you ride much,as being able to idle at a consistent speed is important.When you want to slow down,the engine helps do that.You probably have some trash in the carbs,and need to be cleaned.also try to adjust the idle mixture screws by starting the motor,turn to 1-1/2 turns out,then try to set the idle slow while turning out on the screws,then the speed,back and forth until youhave it as you like it.Adjust a little at a time,like 1/8 turn. lha

 

[Taras]

How should the speed scew be positioned when I adjust idle mixture?

 

[lhaolpa]

The speed screw,or throttle stop should be adjusted for a smooth idle,about 1000-1200rpms.That is when you play with the mixture screws,little by little to achieve the best idle,which is usually the fastest idle,then you adjust again with the throttle stop for a smooth 1000-1200rpms idle speed. You may have to turn them 3-3-1/2 turns out. lha

 

[Taras]

Alright, i'm out 2.5 turns now, bike started easy. Adjusted the speed idle, it was idling nice for a couple of minutes so I took it for a short ride.

First couple of minutes all seemed good, then when I released the throttle the revs obviously went down but it still sounded high (as I said before, I don't have any revcounter). As soon as I engaged second or first gear the revs dropped, put in neutral and it idled fine.

So It seemed kind of stuck on high revs for a while until lower gears were involved. That doesn't sound like it is idle mixture screws does it?