1985 XT600 Idling Issues, Please Help?
 

Hello;
I have a 1985 XT600N (North American Version) with Idling Issues.
Things I have done so far...
Pulled the carbs, cleaned out Most of the Carb But not all of it. I removed and cleaned all the Jets, Replaced the Rubber Coasting Enricher Diaphragm
(I originally thought this was a accelerator pump), removed the float cover and cleaned all that area - the float seemed to be moving up and down normally so just replaced the float back in its place after cleaning all that area out.
(At the time I had the Carbs Apart I was not able to figure out where the: Needle Valve & Valve Seat were located, was planning to replace them with New ones I received in a Rebuild Kit)
Did NOT replace the Needle Valve
Did NOT replace the Valve Seat
Did NOT remove & inspect the Jet NEEDLE - was sliding up and down smoothly though
Replaced ALL the Fuel Lines.
Reinstalled the Carburetors Properly.

ISSUE:
Kick Starts with the choke ON, let engine Idle at 2000rpm for about 30 seconds then slowly put the choke back to OFF position - Idle did not really change at all after turning choke OFF... blipped the throttle a couple times and the rpm's went to 5000rpm's and stayed there, after about 20 seconds I blipped the throttle twice, rpms's stayed at 5000rpm, blipped the throttle two more times and the Idle Stayed at 5000rpms, then shortly thereafter I shut the engine Off.
When throttle is Blipped the Carburetor Throttle returning back to Idle Position as it is Supposed to, Throttle Cables are NOT Sticking.
Air/Fuel Mixture Screw is set @ 21/2 turns OUT from Bottomed Out (turned all the way In)

I could not find any Past Troubleshooting info on this site regarding my particular Idling Issue.

"I would really Appreciate any ideas of what my Idling Issue could be".
Thank You

UPDATE:
After studying the Repair Manual some more and looking over the Carburetor again, I decided to check the Throttle Stop Adjuster (I'm guessing this is what it is called, my Repair Manual does Not give a name for it).
It is the Knob that hangs down from the Carb that can be turned by fingers, from the Right Side of the bike, to adjust it.
I discovered that I was able to turn the Knob Out/Counter Clockwise a full 10 turns before the Throttle Stopped Moving down to its full stop position (Closed/Idle Position). I am going to Guess that this may have been at least Part of my Idle Issue.
I suspect something may be Sticking though to cause the Idle to stay at 5000rpm after Blipping the Throttle?
Could it be the: Needle Valve & Valve Seat being the problem and need to be replaced?

Yamaha XT
 

I am no expert, and I'm sure others with similar experiences will pop up, but I experienced a similar problem two years ago. Ultimately it was the Intake Manifolds. I tried to go "Cheap Charlie" and use gasket seal, but that only did the job for some weeks. Ordered new ones, problem solved, and they were not too pricey. The O rings were shot on the old ones (even though they looked good) and the rubber/plastic coating around the outside was broken in several places.


My 2 cents worth, and just an opinion given all the sorting out you've done. My XT had about 100,000 ks on it.


Regards,


Dr. G
Chief of the World Adventure Affairs Desk, CITY BIKE
Sole Sensual Survivor: http://www.greataroundtheworldmotorc...nturerally.com

yep, most likely an "air leak" from a dry manifold.


With the engine running, spray WD40 where leaks can occur. If the idle speed changes when you do this then you have a leak.

I appreciate the feedback!
I am leaning towards the Rubber Manifolds as well after reading some more on line about Idle Changing on its own.
I Have found the Manifolds on eBay, Very Inexpensive, I will add the link... (see below)Do these look correct? They look just like the Higher Priced ones that are also on eBay.
https://www.ebay.com/itm/Pair-Carbur...S/323457565769

These Manifolds Look Correct for 1985 XT600 ?
Thank You

UPDATE:
Removed the Intake Boots, they look Good. Tried flexing them by hand working my way all the way around each one, no cracking or separating of any kind that I can see.
(is it possible that there is some kind of crack or something in one of them that I Cant See?
One thing of Note..... The Left Rubber Intake Boot that has the Nipple protruding Upwards out of it has a Rubber Cap on it. That Rubber Cap has a Clamp Holding it in Place BUT, the Cap Spins Very Easily while mounted onto the Nipple and that is with the Hose Clamp on it. I am guessing that this Could be an Issue and be letting outside air in, under the clamped Cap?

I removed the Old Clamp that was attached to that Nipple Cap and replaced it with (2) New Aftermarket Hose Clamps and the Cap is now on the Nipple very firmly, does NOT Spin at all by hand, I am hoping this may have been at least part of my Idle Issue.
(I will add pictures later this eve)

*With the Carb removed but the Throttle Cables still attached... I watched into both the Intake and Outtake sides of the Carb while turning the Throttle.
**The Main Carb - The Slide & Needle move up and down Freely and Butterfly at the Outake end opens and closes as it is supposed to.
**The Secondary Carb - The Slide does Not move But, the Butterfly Starts to Open Up at about Half Throttle and at Full Throttle the Secondary Butterfly stops at at Full Open Slightly Past the Level" Position, I believe that is the position it is supposed to stop at?
(More will be revealed)

pity you didnt try the wd40 trick, would tell you right away... it could be a leak at the manifold joint to head too. smear some sealant there. the little cap gets sucked shut by the motor, hard to believe it is it. run the motor and press on it :)

I Started the bike this afternoon

1) First start - with choke on - Started up and had a low idle but kept engine running with the handle bar throttle - turned Choke OFF, No Change in idle speed But, kept my hand on the Throttle so it would stay running.

2) Second kick start with Choke OFF - Low Idle, kept running with handlebar Throttle - "I then began turning the Throttle Stop/Idle Adjuster (picture added) , kept turning it and at about 6 full turns the engine would just stay running, let off on throttle, turned the Throttle Adjuster about 1 More full turn which raised the Idle Slightly, Blipped the throttle and the Idle stuck at 3000rpms, while at 3000rpms I backed off the Throttle Adjuster 1 full turn and the Idle Dropped back down to where it was, I had to work the throttle opened by hand to keep engine running.

3) While I was holding the Throttle at a Steady RPM, I sprayed Carb Cleaner all around the Two Intake Boots, the Idle did not seem to change at all.

4) While engine is Running, the Carb seems to be Sputtering/Choking, like it is not getting enough fuel and also backfiring while running.

Would a Choke Problem be the Cause of my Idling Issue along with the "Sticking on High Idle" when the Throttle Adjuster is moved to a certain point?

I am determined to fix this so Please keep the Suggestions Coming!!

Also, the Engine Sounds Really Good, no odd noises, I am really happy about that!! :thumbup1:

(I have come to the conclusion that I need to pull the carburetor "Again", and work in that area behind the Choke Rod on Inside of Carb. The Choke did not seem to do anything to the idle speed when I pulled it In or Out with the engine Running)

*Update with the Idle Issues on my 1985 XT600N.....

I left the carb on the bike (this time) and started making Adjustments with the Air/Fuel Screw and the Idle Knob while engine is Running.

1) First... the Choke does not seem to do what it is supposed to do until the engine is about half way warmed up, once its half way warmed up the Choke will Raise the Idles as I apply it - I assume the choke area of the carb needs cleaned and parts replaced.

2) So... with the Choke OFF & the Key OFF, I have discovered that it is Best if I Manually (with my hand) push the Kick Started down numerous times until the engine has done about 3 Complete Revolutions. Turn the Key ON, manually get the engine to the spot where I cant hardly turn it over, and Kick Start it with my foot, it usually starts within 2 - 5 Kicks.

3) once running, I keep the engine running with the Hand Throttle until it is about half warmed up, start moving the Choke Lever to the Left until the engine stays Idling at around 2000rpm. Once the engine gets warmed up... the Idle starts slowly Climbing and that is when I start turning the manual Choke back Off.

4) (Engine Running) While I had the Choke on... I started Turning the Air/Fuel mixture screw until the idle started changing. Then with the Choke OFF I started backing off the A/F mixture screw until it almost dies, then turn it back Out until the Idle comes back to 1400rpm.

5) End Result for my bike when Idling...
Air Fuel mixture screw is "Out 4.5 turns" from turned all the way in/bottomed out. If I turn the A/F screw a 1/4 turn IN (lean) from the 4.5 Turns Out Position, the engine begins to sputter/die,
Also... I've got the "Idle Knob" adjusted to where the RPM is @ 1400rpm

5) Where I have the Carb Adjustments at this time... the Engine Idles Perfectly, doesn't try to die (after it is warmed up) No Popping, No carb choking No backfiring.

I know the Choke area of this carb needs some work But, it is running good enough for me Right Now.
I will update again once I ride the bike. The front tire is currently flat cause I rolled it over one of my pointed tools and somehow that point poked all the into the tire and it went flat. I will take that front wheel/tire in for repair shortly and then go for a ride and report back on how the bike runs On The Road. :thumbup1:

Your not getting good fuel flow at idle from the carb into the motor . For your choke issue take the float bowl off and look into it . There is a couple small holes that go into passages on the side . One goes to the choke tube where the choke gets it's fuel from . I'll bet that hole is plugged thus your choke isn't supplying fuel or very little when the chamber is sucked empty and will then suck air . You'll need to spray cleaner in that choke tube (the brass tube that stick down from the bottom of carb when you take the bowl off) and make sure the cleaner comes out in the choke plunger port. There also must be an o-ring around that brass tube when the bowl is on , you'll see the groove for the o-ring in the bowl .

Also you'll need to make sure all the o-rings are good and present on the choke plunger , mostly around the tip as it will suck air otherwise even if choke isn't pulled out . Take care of that and you'll likely get rid of the hanging idle . May need to properly jet it once all sealed up and working correct . If your choke is working right it should shut the motor down from flooding out when motor is warmed up and cold the motor should drop way down on idle when it's shut off . There is an area where it'll run either way but not a real long time before the motor is too warm for the added fuel .

I put a std o-ring in the intake boots where it bolts to the head . I can't remember which dash# but it's a little thicker than the metric one so seals better once tight . No need for RVT .

.