Bike wont idle

hey guys,

i have a 1982 yamaha maxim 650. I have had it for 7 years and my cousin had it before me. It has never idled properly. If you set the idle to 1100 then it is a dog when your driving it and the revs take forever to drop down when you let off the gas. If i set it up so it wont idle at all...ie it dies then the revs are up and down really quick...which is how i like to ride it.|
He messed around with it and had a small engine guy work on it and they could not get it to idle. I had a small engine guy shim the valves, clean the carbs and sync everything and they could not get it to idle either. everyone said that they figured that pilot jets were reamed out with a torch cleaner causing the idle problem...so this spring i ordered replacement pilot jets...I just fired it up tonight and the same thing. there is no difference between these jets and the ones that were in it. I just wont idle or if you get it set to idle...it slowly drops and stalls out in a matter of 30 seconds to 1 minute...and if you have it set then get on the throttle it burp and wants to die.

what could be causing this? I put the baffles back in and it made it a little bit better...but still..shittly throttle response if it will idle.

I was going to sync the carbs this weekend and then go from there...but i really have no idea what the issue is...oh, what rpm should i set the idle at to sync the carbs?

any help is much appreciated.

thanks

 

One guess is a vacuum leak. Run an unlit propane torch around the throttle shafts on the carbs and the intake boots. If the idle changes, you found your leak.

Other potential issue could be fuel delivery. Check your petcock and fuel cap vent. Verify that you are getting good gas flow from the tank.

Couple of starting points. Let us know what you find.

 

Have you changed the air filter?

 

I will pick up a torch this weekend and give it a try. The boots are in awesome shape so i cannot see this as being the problem.

But I do have a fuel issue. My reserve does not work. i was told the petcock was likley seized or the inntake straw broke off.. this was a few years back. But when i had the tank off for paint, i played around with the petcock...if i suck on the vent line...the petcock works as intended...so i was thinking it could be a vaccum issue at the one carb where the vent comes off.

i will check this weekend anyways.

Another thing i thaught of is that my throttle cable is not set right..ie, i need to tighten up the cable and then try fine tuning the idle.

 

Hmmm. Mixture screws maybe?? Set em all out to 2.5?
Idle is supposed to be 1050 btw.
-SLK

 

Ok, So I have been super busy. I finally got the whole bike back together this weekend....I had been playing with the idle screw and once i got the baffles back in the bike and the exhaust sealed up. It was idling smoother then it has even idled before. I never did get a chance to check for vaccuum leaks...but one of these days I will.

So yesterday i put plates on it and took it for a ride...With the new pilots, it starts up now without choke. It idles around 1000-1100 really well so thats where i have it set...according to the bike tac, which could be out. Anways, took it for a rip and got 1 really long block away and as i was sitting at the lights idling it started sputtering and stalled...I got it going and the throttle response was crappy, i had to feather it to keep it goin until i got to speed...so i figured...i am out of gas...So fueled it up and still, same thing...could hardly keep it going...so i started home and 1/2 block from the house it died and i tried for 10 minutes to get it to start and nothing. it was as if there was no spark for fuel...so i pushed it home, pulled the fuel line and there was fuel in the line to the carb, but still no start...so i put a clear line on and it moves fuel in the primary position where i was riding.... So i pulled the plugs one at a time and all 4 were sparking but they looked like they had a heavy film of black soot on them, except 1 which i assumed was the last to fire.

What could be the cause of this I picked up a couple new plugs today..they didnt have 4 so i was going to try a maiden voyage tonight again.

also, does anyone have a diagram showing where the fuel air mixure screw is...i think it may be idling too rich and maybe even running to rich causing the plugs to foul.

oh also, the oil level is supose to be centered on the eyesight...is this when the bike is on the center stand or the side stand...i cannot find my manual. thanks

 

I think that sounds like either a petcock issue, or a Vac Leak issue. Could be because the Vac hose going from your intake manifold to your petcock. Did you pull the plugs after it died on you? If they're wet that'll tell you if you're fouling them. Oily plugs mean a busted piston ring btw.
The Idle Mixture Adjustment Screws are located on the "back" of the carbs. Closer to the airbox. Its on the top, and its a standard head screw. Very small. Do you still have the silver caps on yours?
-SLK

 

not to steal the threed , but mine does the same thing if i turn up the idle screw the rpms hang for a long time , i dont have any hesitation on starting out though and response is very good , i just cant get it to idle , ive tried the propane trick and nothing, and my inline fuel filter seems to always be full so its not starving for fuel, this the only thing i cant seem to figure out, what im missing!

 

Your initial problem with bad idle and oscillating rpm's was definitely caused by clogged pilot jets. As for your current crappy throttle response, not sure. Black plugs means you're running way rich - usually this happens when people run the bike with the choke open or have their mixture way off. I'm sure in your case it was due to the choke since the bike would not run without it.

Oil should be checked with the bike on the center stand. If the oil level is near the middle or top half of the sight glass you're good - if it's above it you got a bit too much and if it's below it, you need more.

 

My Bike has hesitation from Idle when I come to a stop light. After I've been riding a bit you know?
But its beause of my #40 pilot jets I'm sure. I've got my stock 35.6 jets on the carbs 1 and 2 and 3 and 4 have #40s in them.
So its trying to burn more gas coming from a standstill.
Maybe your jets then?

 

Nope, not wet. Not oily...just really black and sooty.

Ya, I think i still have the silver caps on mine then...do i take them off or just leave them be.

 

Perhaps i miss explained myself initially...I never had a problem with oscillating idle...I had the exact symptoms as pictishusa. I could only get it to idle at higher then 1050 and but smoothe...but when i set them this way, then they would hang when i was riding it...so i would set it so it would not idle and then the rpms would not hang.

Fuzzy, i know my choke was not on, i manually make sure it is off at the carbs because it does stick just ever so slightly. As i mentioned, my ride on tuesday everything was running beautifully until i got and actually took it for the ride...

I have been starting it a couple times a day since tuesday..it seems to be hard to start again and sure smells rich once i get it running.

 

OK,
So here is the latest status...so hopefully someone can help me out.

As mentioned, i changed my pilots and cleaned the carbs. It idled well...i went for a ride and then it died and i could not get it going and the plugs looked pretty black.

So I bought a couple new plugs...they only had 2 where i went...and installed them. Got it running again and indling nice. Over night i noticed fuel/oil mixture leaking out of my lower aluminum cover...perhaps this is the stator cover? Anyways, I left the petcock in the wrong position and i assume that one of the needles didnt seat right and it overflowed...but it was odd that it came out of that cover...to me anyways.

So I went for a ride tonight...it idled smooth, never hung up while riding...about 5 minutes into my ride i noticed that it was stumbling off the line...it seemed like i needed to keep the revs up when engaging the clutch or it would try and stall out...on the way back from Wallyworld, it was the same story except if felt as if it had no power under about 4 or 5000 rpm.

When I pulled the new plugs...they were as black as the ace of spades. My bike has to be running super rich right...which is why i has no power at the bottom end.

So, as mentioned above...i tried to find the air/fuel mixture...but I cannot find anything that even remotely looks like an adjustment screw or a cap that is covering one...does someone have a picture of what and where this thing is?

Also, I was reading a bit here and there was mention of measuring the depth of the pilot screws...was I suppose to take a measurement before replacing the pilot jets...if so, perhaps thats where my problem lies...I installed them and screwed them until they were all seated firmly...but not crazy firm.

any help would be greatly appreciated!!!

thanks

 

First if you have fuel/oil mixture leaking out, your oil is shot don't run the bike until you drain it and put fresh crude in the motor.
It might not be leaking from the cover but from above/behind it.

I suspect it is stumbling because you arer running super rich and fouling the plugs at low rpm's.
When you pulled the carbs to replace the pilots you should have done the complete carb clean.
*Including the enrichment ciurcit.*
If you look at the motor side of the carbs to the left of the plunger that is actuated by the choke.
You will see iether a hole with a screw in the bottom or a brass cap.
This is the mixture screw, it should of come out and the passage seriously cleaned and Orings replaced.
I suspect this is were your problem lies.

 

Pull the carbs, remove the caps and cleant the mix circut very well, it took me 4 times to get it clean, I was in to big of a hurry to do it right the first time. I boiled mine and blew a lot of copmpressed air till all of the crud came out of all 3 holes, make sure it comes out of all 3,

 

I found the mixture screws...mine had little rubber plugs not brass plugs. I cleaned that carbs like I normally do...never have cleaned the enrichment circuit before and never had any enrichment problems. The only issue i had with the bike, and it has always been like this before i even got it, was that it would not idle and several bike mechanics said it was because the pilots have been reamed out with torch cleaning tips...so I put new ones in and since putting the new ones in...it has been running super rich.

I will give it a good cleaning this week...hopefully that cures all problems...and before taking the mixture screws out I will make sure i mark down how far they are turned out.

 

Ok, so a few things to this point.

I have the bottom half all torn apart and the bowls are soaking in carb cleaner/seafoam along with the jets and fuel related parts for the bottom half...everything thus far was squeaky clean as i had cleaned these before.

I did notice that 1 emulsion tube may be partially plugged.

I also noticed that during teardown that at least 1 and maybe 2 intake boot clamps didnt get tightened down...perhaps a vaccuum leak but I am not sure how that would cause it to run rich.

On the top end, i have only taken apart he enrichment circuit...rod, forks, dust caps and the enrichment valves...the valves seemed to move smoothe although there is signs of some varnish and a bit of gummy crap.

I also checked the pilot adjustment screw...all of them were roughly 2.4-2.5 turns from seated and moved very nicely...actually everything so far has come apart with no difficulty...exept i have one drain screw thats stuck and 1 hat screw that needs to be replaced.

So far...it has been pretty easy. The 19 page guide i found on here is intimidating due to the length...but really its not that bad...gonna make this full teardown a part of my regular routine from now on.

 

ok..so exactly how much force should i be using when bottoming the pilot screws? I am using 3 fingers..but my fingers are strong...

Also, how should one go about getting a stuck "O" ring out of the bottom of the pilot hole...i had one fold on me and get jammed down the bottom of the pilot screw hole.

I assume chacal is the guy to order new "O" rings from?

 

ITS ALIVE!!!!

IT IDLES LIKE IT NEVER HAS BEFORE...I DID NOT SYNC THE CARBS AS THEY WERE DONE A FEW YEARS BACK AND FROM INSPECTION STILL LOOKED PRETTY GOOD...ONCE I GET A PORT PLUGGING TOOL MADE THEN I WILL VACCUUM SYNC THEM.

I STILL NEED TO PLAY WITH THE IDLE MIXTURE SCREWS A BIT MORE...HOWEVER I THINK I HAVE THEM PRETTY GOOD...I WENT FOR A RIDE TONIGHT AND HAD A FEW OLD BIKE ENTHUSIASTS LISTEN TO THEM AND THEY FIGURED THEY SOUND PRETTY GOOD AND WHEN I PULLED THE PLUGS THEY LOOKED ABOUT RIGHT. NOT BAD FOR FIRST TIMER LUCK I GUESS!!!

THE ONLY QUESTION I HAVE LEFT IS WHAT PLUGS SHOULD I RUN...THESE GUYS ARE TELLING ME TO RUN 8'S BECAUSE THEY ARE A LITTLE BIT COOLER AND THE BIKE WILL RUN BETTER...BUT ALL I HAVE EVER RUN WERE THE 7'S. ANY RECCOMMENDATIONS?

 

It will run cooler with 8's but, you don't have an overheating issue.
I would run 7's as called for in the manual.