START UP AND IDLE PROBLEMS!!

[Roykimsw]

Hello everyone, this is my second time to upload a post. Before start to write sorry for my English. Its my second language.
I have a 1980 xs400G. Last time I posted about electricity problem. I have been working on that. Hopefully I will fix that soon or later. However, I found two serious problems that I'm assuming engine part or carburetor.

1. When I started my motorcycle, smoke comes out from left exhaust.

2. I just changed oil last week but oil light come on when I turn the engine off and on which is red light. During a ride, it came off. I think problem 1 and 2 are relative. Because I looked up the previous post about smoke come out from exhaust they mentioned oil leaked from some where in engine. Also as I mentioned I just changed the oil but when I checked oil level today. It was really low. (I checked from oil sight window)

3. This problem is my biggest concern. My start is bad. I have to crank the engine so long time or during the start I have to give some throttles. Also when I started engine, always I have to open full choke otherwise it won't be working. Even when I had a long ride after its same situation. I don't open the choke it doesn't start. This is main part!!!!! When bike was stop for signal. I was holding clutch and gear was first gear, rev started slow down and killed engine off...if I made neutral position or I gave some throttle in 1th gear then it's okay. But I assume if you are holding clutch all the way in 1th gear or other situation if you held a clutch it won't turn off the engine. Idle rev is really unstable I tried adjust idle screw but same happen again, its only worked when bike in neutral position then I can see the idle rev is adjusted.

Please guys give me idea, what I have to look for these problem. I assume all the problem are connected. Really hard to start up and hold idle position...

Thanks guys!!

 

[danalpatt]

Ok so as for the 1st one what color smoke white or black
2nd is the oil light on well idleing at 1100-1200 rpm
3rd is the carb clean?

trouble shooting
1st start bike and figure out what color the smoke to much fuel is usualy blackish oil leak is usualy whitish grey allso if ur still not sure try and smell the smoke a little bit does it smell like unburnt fuel or does it smell like oil if it smells like fuel i would try new spark plugs

2nd one could be sensor or oil pump

3rd if new plugs dont help i would compression test if compression test is good (see manual for psi rating)
then i would take carbs off and clean them real good then see if that helps another thing check to see that petcock is working if you have a res/off/on on petcock just pull fuel line that goes to carbs turn petcock to on for half a second and see if fuel pisses every were then it is probly good
if u have petcock that has res/prime/on and it is a vacuume petcock you can test it by pulling fuel line to carb turning to prime and if fuel pisses every were you are semi good you can then with vacuume line still on bike turn petcock to on and start the bike for a sec and if fuel pisses then petcock is good turn bike off and fuel shoud stop after you try this let us know

 

[arfstrom]

I agree with Danalpatt, That first bit of troubleshooting will hopefully clear up everything from Rings (worse case) to valves, Then if only one piston is firing, you might smell unburnt fuel in the exhaust. So good tip

Carb, yup, everything with idle comes down to Carb and how clean it is. any flaw's in your cleaning process will be noted on the various running issues. (dies at stop light, have to hold the throttle higher RPM so it doesn't stop. There is a adj for idle speed you can adj while its running, (wear gloves as its next to the Head, slightly hot) If your Tach is working, Idle should be set about 900 RPM, I know i have mine set for 1,100 RPM. I have not felt the need to adj it this year.
Only thing I haven't seen is air leak? Make sure you don't have an air leak on the carb boots. An air leak will not give you a nice working bike. (I use to forget to plug the petcock to the intake brass tube.)
Good luck

 

[danalpatt]

LOL arfstrom i did the same thing with the brass fitting forgot to plug it once and she ran all kinds of screwed up lol and you are right i forgot to mention to check carb boots and if they look fine use some wd40 or starter fluid and spay some at the boots it will tell u if u have a hair line crack that u cannot see if idle changes well spraying u have a leak

 

[arfstrom]

I like think we all have done something like that, at least once in our lives

 

[danalpatt]

yea once or twice or allmost every time i pull the tank off