[SteveXS850]

Hey yall! I need some help with my restoration project BIKE: 1981 Yamaha XS850
<<<this bike is a Three cylinder(3 carbs for fuel system) with a kick-starter AND electronic Ignition>>>

Bought from a friend who neglected it in the last year, i am very familiar with it however because he and i used to work on it together...

SO bike was in 100% pristine OEM working condition a year ago and then my friend tried to turn it into a cafe but stopped midway and left it looking like GARBAGE.

THE BAD------Here is what he did(lots of unfinished work)READ BELOW

-he left handlebar controls on and kept the SPEEDO and IGNITION SWITCH but ripped off all the other gauges, lights and electronics including(headlight, brakelight, all 4 blinkers, tachometer)---also he did not remove excess/unused wiring and just left everything open and did not shrink wrap/close up or protect the ends of each individual wire so they are all hanging there unprotected

-after doing this he left the bike sitting under a bike cover in his driveway WITH A FULL TANK OF GAS for about a year without starting it up, and there were definitely times when the wind and rain ripped off the cover so it has had plenty of exposure to water i think.

-ever since he messed with all the wiring the only way we used to start the bike was with the Kickstart(ran well and no issues kicking it only 1-4 times usually started right up if it was warm) or bump start(running it down the hill and dropping from neutral to 2nd gear it would start up).

........OK, thats what he did wrong, so i tried to start it and begin the restore process but it wont start, when kicking it i had no luck, i could feel the kickstart working correctly and catching and turning but engine was not turning over not even a sputter or two. And when i tried screw driver to the solenoid it would turn over but not start---so then i pushed(in neutral) down an incline until i got about 10 mph speed(guessing)and dropped it from neutral to first and it tried to go but back tire locked and didnt work....so then i did neutral dropping it into 2nd gear and it would run for about 3-5 seconds then die(i did this about 5-7 times same result every time) even when i was FULL OPEN THROTTLE. adjusting the throttle did not change the time it took to cut off either, it didnt stay on longer or rev up any more with the throttle open

ALSO when in gear and i pull in the clutch it wont roll freely( it has resistance as if the clutch was not even pulled in at all)

SO HERE IS WHAT I HAVE DONE SO FAR

All parts i use are correct OEM and i am using the maintenance manual for reference to everything!

--i only want to have Speedo, headlight, taillight for minimalist look(have replacement OEM taillight, headlight ready to be installed)

-have not touched an wiring yet---all fuses in tact EXCEPT THE MAIN FUSE is blown and immediately blows new fuse if i put new one in.

- CONFIRMED that the bike has compression when i took out the plugs and stuck my thumb over all three holes and used screw driver to start.
-ALL NEW battery, ignition coils, spark plugs and tested the connection is good but not getting spark when i ground a plug to the side of the engine
-REPLACED and readjusted clutch cable to the correct tightness and still having issue with it
-REPLACED throttle cable, have not adjusted it. was waiting to get it running first, but its connected properly and i put some wd40 on the mechanism on the carb that the cable connects to and it twists well
-inspected the carbs they look fine, no issue because they are relatively new and have been cleaned before

-we emptied all the old gas from tank and carb and replaced all fuel lines and petcock is in working order then put in fresh gas--however i don't know if there is soiled gas in the cylinders or not, could it be that due to being rained on and sitting so long that the fuel is either too old to ignite or too much water mixed in? if so how can i get the bad fuel out of the cylinders so new can flow in

-also i don't know what a kickstart has to have to turn on a bike(does it need a battery and ignition system to work properly?
-in regards to the clutch not working properly could the clutch plates just be stuck together from length of time sitting? if so, would getting it running(ie bump start it) allow them to become unstuck.

-whats the deal with the main fuse? and do i need this fuse in order to bump start or kickstart

-when i bump start it and run it down an incline and pop it into 2nd gear why would it come on for only a few seconds and then cut off even when i had new gas in the tank and it was flowing well into the carbs???

-and FINALLY what am i missing- i bet that i am overlooking a small detail, i am not a mechanic but have spent a few years working on and learning about this exact bike


any help would be appreciated!

-Steve

 

[Critter]

I would start with finding out why the main fuse blows the second you replace it.

 

[cmonSTART]

SO bike was in 100% pristine OEM working condition a year ago and then my friend tried to turn it into a cafe but stopped midway and left it looking like GARBAGE.

:sigh:

 

[SteveXS850]

:sigh:

I am just as frustrated as you.....

 

[SteveXS850]

I would start with finding out why the main fuse blows the second you replace it.

read up on my wiring diagram and the ignition switch is not getting power from blown fuse so thats why no spark...

blown fuse is because of headlight wires not connected properly and they keep shorting.

 

[Critter]

Okay Steve, then that is the first thing you have to fix and work from there.

 

[SteveXS850]

Update on bike

OK SO GOOD NEWS IS BIKE IS RUNNING.

bike win run and rough idle, found out that cylinder 1 is not firing. cylinder 2 and 3 running well as i can see.

replaced spark plug wire to cylinder 1 and am feeling warmth on spark plug and continuity is good, its not grounding to the frame by accident and not shorting.

exhaust for cylinder #1 is a 1 to 1 and exhaust for cylinder #2 and #3 is a 2 to 1. exhaust for #2 and #3 has proper fumes flow through and it gets hot to the touch(like normal). exhaust for #1 has air flow through and its warm but NO fumes from combustion.(not normal)

also noting that the bike will idle roughly but it takes starter fluid to get the bike to start initially. trying to use starter fluid very sparingly.

here is pic 1...when bike runs with cylinder #2 and #3 the brass things circled here that coincides with #2 and #3 do not move unless holding down on the throttle, and they dont move much.(seems to be normal)
BUT the brass thing i circled in this picture that matches up with Cylinder #1 rattles and vibrates quite rapidly. im assuming it is supposed to act like the other two

pic 2...only took of this cap and examined the inside, there was a spring and everything seemed to be in tact. put spring back and reassembled(coincides with cylinder #1 )

pic 3....we took all float bowls off and cleaned them, this float bowl was sticky, unstuck it and reassembled

after bike is shut off, small amounts of white smoke flow out of the end of the exposed carbs...perhaps excess gas that is not evaporating?, is this a carb issue, and gas not getting to cylinder 1? that would explain why the spark plug is warm and trying to ignite, and air is flowing through the exhaust but doesnt look or smell like exhaust fumes. it just seems like there is no combustion coming from cylinder one. and i think i have compression and spark, but no sign of gas there..what is my next step.


i have more questions after this also..bike bump starts(with screw driver to starter) but replaced and confirmed start button working and in tact and button still does nothing, and sometimes i hear a weird clicking noise when bump starting, could it be the starter relay? that is not allowing the button to take action? im also seeing VERY hot wires next to rectifier regulator. jsut ordered replacement for rectifier regulator and starter relay as those were pretty cheap.

 

[SteveXS850]

also adding more details here

also wanted to add this, so to clarify

-when running the bike on two cylinders, the throttle valve that coincides with cylinder #1 (that is not running) vibrates rapidly and is visibly more open than the other two throttle valves--(((could the diaphragm on top of throttle valve not be sealed properly? or perhaps spring is out of place?)))

i believe now that cylinder #1 is way too lean to even run, that's why white gas fumes come from the back of the carbs after shut off(basically indicating gas is going in but too much air is not allowing for combustion, since the spark plug for cylinder #1 is dry after every test

i can also see that the butterfly valve that coincides with cylinder #1 is also slightly more open than the other two, i guess i need to adjust everything enough to get it to idle and then tune and sync left and right carb with the center carb??


i am examining the carbs tonight will update asap!

 

[Unkle Krusty]

They look like diaphragm carbs to me. Open the top and check the diaphragms for any tiny holes, and that they are seated correctly. Also check the needles for straightness. And check that the pistons slide up and down smoothly.
With previously owned bikes, anything is possible.

UK

 

[SteveXS850]

i am taking a look at the carbs tonight. if you take them apart do the seals have to be replaced? and any tips on how to reassemble properly after i check it out?

 

[SteveXS850]

Mikuni mic kugyo

They look like diaphragm carbs to me. Open the top and check the diaphragms for any tiny holes, and that they are seated correctly. Also check the needles for straightness. And check that the pistons slide up and down smoothly.
With previously owned bikes, anything is possible.

UK

not sure what mikuni carbs they are but i think they are mark twos.

i have taken them apart. it looked like there was an issue with one of the diaphragms not sealing properly because when the slide would go up and down i could tell a difference....after adjusting i see a difference, will know more when i put them on the bike on Wednesday..

what is this screw for, fuel and air adjustment for what? for the choke? the small pinhole and the other larger angled hole, when pulling the choke i can see holes align in the larger angled hole. the screw has a needle that fits down into the pinhole, and in my carbs the needle was broken off and lodged deep into each pinhole. have to find replacement screws for this because they are all broken off. what is this?

 

[SemiFast]

Didn't have time to read the whole thread but I did see your last question........

"what is this screw for, fuel and air adjustment for what? for the choke? the small pinhole and the other larger angled hole, when pulling the choke i can see holes align in the larger angled hole. the screw has a needle that fits down into the pinhole, and in my carbs the needle was broken off and lodged deep into each pinhole. have to find replacement screws for this because they are all broken off. what is this?"

It's the fuel mixture screw for idle and slow speed running.
Turn In for leaner mixture. (Less fuel).
Turn out for richer mixture. (More fuel).

Don't know what the "starting point" would be for that year model.
In the early days the starting point was usually about 1 and 1/2 turns out from lightly seated.
Later years, about 3 ~ 4 turns out.

 

[SteveXS850]

Didn't have time to read the whole thread but I did see your last question........

"what is this screw for, fuel and air adjustment for what? for the choke? the small pinhole and the other larger angled hole, when pulling the choke i can see holes align in the larger angled hole. the screw has a needle that fits down into the pinhole, and in my carbs the needle was broken off and lodged deep into each pinhole. have to find replacement screws for this because they are all broken off. what is this?"

It's the fuel mixture screw for idle and slow speed running.
Turn In for leaner mixture. (Less fuel).
Turn out for richer mixture. (More fuel).

Don't know what the "starting point" would be for that year model.
In the early days the starting point was usually about 1 and 1/2 turns out from lightly seated.
Later years, about 3 ~ 4 turns out.

great thanks! so previous owner must have jammed the screws in too tight because the needle at the end of the screws were broken off and lodged into the hole, also making the pin hole slightly larger. does this completely destroy the carbs or can i just buy new mixture screws and still have a proper seal?

 

[SemiFast]

Yes, you can just replace the mixture screws and use the same carbs but....
The damaged port (outlet hole) will change tuning a little as in the correct amount of turns out will probably end up being a little less than it would be with an undamaged port.
But it should work just fine after adjusted.

 

[SteveXS850]

OK SO I FIXED CARB ISSUE--

so i synced up the carbs and did a pretty decent job with a rebuild kit. made sure to cross my T's and dot my I's twice being extra careful!


ISSUE I AM HAVING---

come to find out that im still having bad luck with cylinder one. it turns out to be the spark issue again that i thought was resolved but turns out im still not getting any spark. i am getting correct readings from the ignition coil(i use the OEM service and repair manual for everything troubleshooting based)

basically everything from ignition coil-spark plug wire-plug cap- and the plug itself IS ALL WORKING FINE. i checked to make sure it has the proper connection. so i went to the next thing behind the ignition coil.

----

here is where i am confused: so on both WORKING ignition coil there is a two pin connector with black and red wire-this connects to the wiring harness. There is the same two pin connector with black and red wires on the NON WORKING coil as well. so when i use my multi meter to check the wires and connection this is what i found--

we are working with the female side of the two pin connector(((((the side that is connected to the bike and wiring harness)))))

working coils/wires-

Test A: Red (multimeter pin) to red(bike wire), and black(multimeter pin) to black(bike wire)---------------------------- READS ROUGHLY 20 ohms.
Test B: Red (multimeter pin) to black(bike wire), and black(multimeter pin) to red(bike wire)---------------------------- reads NOTHING....does not read 0, DOES NOT JUMP OR MOVE THE NEEDLE at all
this was all consistent for both working cylinders and their coinciding coils/wires.

so i did the test on the suspect wire......

not working coil/wires-

Test A: same test, same result.-------------------------- reads roughly 20 ohms
Test B: same test, DIFFERENT RESULT-------------------also reads roughly 20 ohms?????


so i think i found the issue but problem is, i have no idea what this means. im assuming there is something wrong with the connection/wire.




so what is my best course of action now?

thanks guys!