Jump to content

xvs 125-starting /running problem


jimmythemoonlight
This post is 4215 days old and we'd rather you create a new post instead of adding to this one. You can't reply in this post.

Recommended Posts

Do you want an ad-free experience? Join today and help support the Yamaha Owners Club.
  • Replies 53
  • Created
  • Last Reply

Top Posters In This Topic

whilst it would be wise to look at the valves (since your piston ring wasnt up to scratch your valves might not be either) b4 you take the covers off try this (i wrote it a min ago b4 the last post) .

its sounding like a timing problem (spark timing) or a problem with the air fuel mix ........any chance you can take a video of you trying to start the bike so we can hear what the engine sounds like?

also see how the spark plugs "spark" with relation to the engine, 4 strokes should only spark 1 every 2 tdc (each cylender) im gonna type it out cause i cant quite remember

1.tdc=exhaust closed inlet open

2.bdc=inlet close (compression starts)

3.tdc= spark

4.bdc=end of pop (exhaust valve opens)

so the 2nd cylender should go

3.tdc=spark

4.bdc=end of pop

1.tdc=exhaust close inlet open

2.bdc=inlet close (compression)

so the sparks should be intermittant. as to the carb its a dismantle and have a look thing. il go onto that if u want to.

hey there, thanks for that , top one ref the oil in pot tip,. yes i see what you mean with this however in all honesty i think it will take me a while to process this info... i agree with the hunch on the timing thats what my gut instinct was tellin me ...i am sure that the fuel mix is not correct however even at its worse would i be right to assume the motor would run ..if not really badly as opposed to this case not at all,,,,i am going to look at the valves at some point next but i have taken on board the spark sequence.. in relation to the video footage i will have a go but i am even worse with computers than i am at bike engines .. thanks .. with a bit of luck i can get something uploaded...can i do this through photo bucket ??
Link to comment
Share on other sites

yeah i used photobucket no probs,

i found that these engines are temperamental when it comes to the air fuel mix. and it wont run if its off.

i found that you needed the black pipe that connects the air filter to the carb to get the right pressure so anything to do with the carb if not on properly could stop the engine from working. plus is the engine up straight? and not leaning back? sometimes if its on a bench it leans back also the carb could do with a clean if its been sat around for a few weeks (if you havent done so already) and its quite simple to sort in 30 min

Link to comment
Share on other sites

sound as , thats what i would call a pearl of wisdom...i think it would be best for me to have a good look at the carb as if i am honest i did nothing to it other than stick it on my new lump... i did notice that when air box and stuff was off that i had fuel mist squirting out of it..but connecting the dots with what youve said i think i would be write in assuming that thats the pressure for the black tube in the wrong place ?? i ahvent a clue how to ste the mix and i cant make head nor tail of the manuel .. could i be rude and pester you for a basic run down please..??

Link to comment
Share on other sites

sound as , thats what i would call a pearl of wisdom...i think it would be best for me to have a good look at the carb as if i am honest i did nothing to it other than stick it on my new lump... i did notice that when air box and stuff was off that i had fuel mist squirting out of it..but connecting the dots with what youve said i think i would be write in assuming that thats the pressure for the black tube in the wrong place ?? i ahvent a clue how to ste the mix and i cant make head nor tail of the manuel .. could i be rude and pester you for a basic run down please..??

Ok, so its prob a good idea to check valve clearences, just to be on the safe side,,,,least youll know thats done for the future.

If the timing cant be adjusted,,,,and engine was running before you got it,,,,,and you didnt do anything to heads, timing chain, adjuster, or drop the engine on the floor or anything like that,,,,,, then i think messing with the timing will do no good. Fair enough, if you can check timing marks or something and make sure they all line up, then thats what i would do.

If your carb settings arent set right then this is almost the same as if the engine timing was off.

Look in your manual, find where it says "Air Screw Turnouts" or mixture screw.

Find this screw on both your carbs,,,,set it to what the manual says for now. What you do is turn it in untill it lightly seats (gets tight) then what manual says to turn it out by then this is what to set it at. Make sure you turn the screw full turns and not half turns like some people think.

The lads are right, saying that things should be conected up, all the bits have a job to do so if not conected then your missing valuable components. Even the exhaust do a job of helping sucking out gasses and pulling through fuel, this more for a 2 stroke but is also the case for a 4 stroke.

So id start at the start again going through things till everything checks out. Slow job but a well !

These are good wee engines,,,,,,,, this will keep yur spirits up !

Link to comment
Share on other sites

quick rundown of the carb (for reference)

top of carb = inlet

bottom = outlet

there are 2 covers (with 4 screws to hold them in place) either side,

one side is round, it has a spring in it , and also a rubber boot which holds the "jet needle", if you take the rubber bit out the needle will follow, with pointy end down, look on the top you will see a screw head, undo it (its got a spring on it) , with that undone push the pointy end and take the needle out. the needle (pointy end down) will have 3 notches (or more) and a clip. for a basic setup the clip should be smack bang in the middle. put it all back together and turn the carb to the opposite side. (dont forget to put the spring back in)

this side will have a bit sticking out (with a hole/pipe facing down) and a screw just above or on it. this is the "drain tap" put the hole/pipe over something and undo the screw, the spare fuel will drain from the carb. do the screw back up again.

undo the 4 screws that hold the cover on.

take the cover off, you will see a piece of plastic called a "float bowl" which acts like the system on your toilet, it lets fuel in at a certain level then stops when its reached that level. there will be a small spring attached to it with a little piston thing (not sure what its called). this piston thing stops fuel coming into the carb when its full. you will see the "float bowl" pivots on a little metal bar, slide the bar out and take the float bowl out (with the spring piston thing) and put to one side.

look in the carb you will see some brass pipes. the big one in the middle is your "main jet" undo the top bit with a flat head screwdriver, this is the main jet that lets fuel in when you open the throttle, there is a hole in the middle, blow through it! as crud gets in there. put it back on the brass pipe.

to the bottom left (or right) is another brass tube with a flathead screwdriver head. undo that. its your "pilot jet" this one controls the fuel at startup. should be a tube that goes smaller with holes round the outside and a hole in the middle. blow through that one aswell to get rid of any crud. put it back in then put your float bowl back on (dont forget the little piston thing and spring!) then put the cover on (do up the screws diagonally .....top right 1st then bottom left 2nd then top left 3rd then bottom right last ect.) then adjust the "mixture screw" a brass screw on the outside of the carb. just screw it all the way in then turn it out by how many turns the manual sais (think its 3 full turns)

and thats it the carb has had a "quick" clean. it will need adjusting when you get the engine running but we can sort that out when we get to it. to properly clean it you would squirt carb cleaner in all th holes and soak the jets in fuel but unless when you open it up and loads of bits of crud comes out a quick blow should sort any blockage.

Link to comment
Share on other sites

ahh thanks fellas,, i am stoked by all the effort you have put in on these replys i was at a point of allmost giving up, i was unable to get any footage today because for some reason it wouldn't parrp, spent all afternoon getting the soddin tappet covers off as they where so tight it was beyond a joke in particular the one at the back over the rear cylinder it rounded on me ...oh fun and games...i got the bugger though and as i have the old lump its a sweet swap with a gooden, i am going to revise with great vigour the instructions that have been put out for me ...thanks fellers...you guys know who you are...i have to dash but i will be sure to keep you posted...once again thanks..

Link to comment
Share on other sites

.....the story so far.......i had a look at the tappets this mornin(took another day off)....looking at my manuel ref I mark on generator(for rear cyl) and i mark on sprocket it had become apparent that the marks did not line up regardless to how many times i rotated the crank...possible ureka moment ?? well see ................................ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

Link to comment
Share on other sites

just to update ...i have just crawlled out the garage after an intense couple of days, i have learned a lot about this bike...ref tdc and tappets ......i thought the line on the timing chain sprocket was meant to line up with the dot that is cast into the housing of the timing sprocket,,,,oh how wrong i was after struggling like a bugger trying to line everything up to this point i cranked the engine by hand to discover it wasnt prepared to do a full revolution (even in the manual it has an arrow pointing to it) then whilst scratching my now balding head i saw a faint line on the face of the housing...this faint line was the same on the rear housing too so i lined up my sprockets with this both front and rear and making note of the "t" and"i"marks on the generator side, ,,,sorted i got it lined up and good to go....i think they where already like that i was just looking at the wrong point ..this was complemented with the standard poor luck of dropping the chain down the gap so i had to take the clutch housing off to retrieve it and so on ..this exersise took a good few hours but at least i know i got it right. cranks easly and smoothly in the correct anticlockwise direction, so new oil, batt charged,plugs clean, airbox/filter on, carb serviced no air leaks,, all connections sound,tappets set,........have a cup of tea and a fag to celebrate .........hit the start button....she cranks over (startermotor good)...still cranking .....puff of smoke out the front cyl....puff of smoke out the rear cyl .......i can feel her trying......... and thats as far as its willin to go... almost at the same point now as i was 2 days ago......keepin it as positive as possibe......is there anythig here i have overlooked?? any ideas fella's ?????????????????????????

Link to comment
Share on other sites

If it's got air, fuel, compression, a spark, correct valve timing and oil, it HAS to run.

Have you checked through the carb? Made sure that it's pulling fuel, that the choke and throttle are all as they should be, and the air filter etc. are good? Idle and main jets good?

You've established that the valve timing is fine, so it's not that.

It's sparking fine.

Compression is obviously fine because that's down to the valve timings and opening and closing properly, and it sounds like it ignited something at least if there was a puff of smoke

I'd say by process of elimination that it must be fuel. Sounds like it's not getting enough.

Link to comment
Share on other sites

ok

so the cam, valves and timing are fine.

the carb is clean (and set to a basic setup)

the black inlet manifold is on properly

compression is good

the air box (black tube going to filter) is attached and not leaking.

the filter is on with no leaks

the sparkplugs are ok

the wiring is sorted

the exhaust is on

the emergency stop switch is turned off (would cause a puff of smoke or a backfire if on)

the fuel tap is on prime

the choke is half way.

how old is the fuel in the tank? (might be worth using fresh fuel) and what color are your spark plugs...are they soaked in fuel after starting? and your sure the ecu is fine?

try starting the bike without choke and half throttle (or blip the throttle) as it could be over fueling with the choke on

my next thought would be to put the bike together and bump start it. (get a m8 to push down a hill or on a flat road, with you on it, in 2nd gear with clutch in then let go of the clutch and keep pushing while you blip the throttle)

im only sugesting the bump start as the last thing to try as it should force the engine to fire/ start (the oil in the cylender trick prooves that the piston rings are worn) but the bump start should get it going.

Link to comment
Share on other sites

yes i believe i have ticked those box's ....however i put my rear swing arm on today and the wheel so i could put it in the garden.....i had it on blocks(level) at first, as a result of this i had the bike on its stand....and it still tried to crank over...is this wrong ? i thought there was a safety non start incorporated with the stand ref the switch,....and besides this i remember the being a problem with the rear cylinder on the original engine..i dont know if this is a fluke or some kind of pointer to the fact that it is the electrics...is there a chance that the ht lead and coil is not doing its job...also i had porposfully wired the ht/coil s up the wrong way..front to back and i still get the same reaction off the engine.. front cylinder tries a number of dull to run...the poping has returned regardless to which way i wire this the same reaction,,,, i am at the point of giving up...on the brink i am,,,,,, what do you reckon of those symptoms ?

Link to comment
Share on other sites

the stand switch acts like the switch on the right controls, when its on it stops the spark signal, so the bike will try to start but nothing will spark so the engine wont run.

the symptoms your saying sound like its a spark problem. look in the manual it will tell you how to check the coils.

and dont give up! just think what you know now that you didnt know when you started! :) you started out not knowing what the problem was or where it was coming from and now you have narrowed it down to just a few components :)

since you have taken it apart and inspected the majority of the engine id put it down to a spark problem as the engine and carb is fine.

its just a case of finding exactly where it is

things i would check:-

spark on sparkplugs. take the plugs out, put the ht plug on the sparkplug, with some insulated pliers hold the sparkplug so the bottom is touching an earth point (a bolt or similar) then press the starter button. (should be a nice blue spark)

next id check the coils, ht leads and caps (mainly the bolts that hold the coils on as its a main earth point)

if that dont sort the problem then next up would be the wiring

then the ecu and battery.

Link to comment
Share on other sites

  • Moderator

Where are you in the world, one of us may be near enough for a hands on lookie see.

Link to comment
Share on other sites

fair one thanks mr paulwhite..i have tried the spark plug thing and to be fair it has a reasonable spark...i have done all that was suggested to me so far exept one thing that i have over looked reference your earlier post and that is the fact i havent put the exhaust on , i have not had anything that felt positive enough from both pistons during the attempts to start that would make it worthwhile....in the mind set that i would have to take it off again anyway..also my old origional standard pipes where rotted to death ....i have got a highway hawk straight through system to put on...i unknowingly thought that they wouldnt offer a great deal in the way of back pressure anyway ( to display my total lack of knowledge) does it work on back pressure????? i am thinking that i have a prob with the electrics for sure maybe not just the one either ... along with other issues ...i have a mate who has a lot more experiance than me willin to have a look ....i am just in the process of coaxin him round .... what lovely weather we are having perfect if the bike worked ......i guess .....here's hoping...

Link to comment
Share on other sites

But you still havent set the carb's up propperly,,,,,,,, air/fuel mixture,,,,,,how many turnouts !!!

If you have spark on boath plugs,,,,,,why do you think you have a problem here.

Did both cylinders not let out a couple of bands/pops,,,,,,,,, this is the engine combustion working and firing

Is the engine turning fast enough with your battery for the bike to start ???????????????

U-Tube whats happening if ya can so we can here the think trying !

Link to comment
Share on other sites

  • 2 weeks later...

just to update .....................................i have somewhere to hang my overalls in the garage....my xvs 125......best lookin and most expensive hanger i ever did have ...quite funky really , and to think people pay a fortune to have a table made of an old plane wing to be oober funky and futuristic,i am well ahead of that.

Link to comment
Share on other sites

probs the best thing to do would be to write a list of everything you tried / checked and put the project on hold, one day you will get the motivation back then at least you know / can remember what you have done and what needs doing. sometimes the best thing to do is walk away then come back at a later date.

to be honest i do this all the time il strip my bike down to bare frame with the intention of completely restoring it from the paint up. then when i get part way through i loose all interest and put it on the back bench till i get the motivation to get it sorted.

im sorry to hear you havent managed to get the engine started but hopefully you will do one day :)

Link to comment
Share on other sites

the stand switch acts like the switch on the right controls, when its on it stops the spark signal, so the bike will try to start but nothing will spark so the engine wont run..

the bike will start while on the stand, it will cut out if you put it in gear while the stand is down

Link to comment
Share on other sites


×
×
  • Create New...