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xvs 125-starting /running problem


jimmythemoonlight
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hi folks, this is one for you ...i have recently had my xvs 125 stripped down and powder coated etc, i had bought a 2nd hand engine which was complete apart from the shiney crank case and chrome bits the engine was from a fella down south who had the bike vandlised for whatever reason but it was a cherrished and loved bike,when i first got the bike i had a look at the plugs these where very tidy showing sign of use but no coke etc, and the oil was nice and clean which backs up the claims of its cherrished history i stuck a new clutch in new oil and all the rest of the basic maintenence things, i put the carb off the old engine straight on it, and slotted it into the frame, this is where the fun ends for me....i fitted my pick up from old lump..i put my starter motor on from old lump and eventually after getting it to work in the right direction i too off the plug leads and turned the engine as i was thinking it would get me some oil around it prior to a good start, so i then hook up a tempory fuel line as the tank is in for spray..plug the res fuel line and feed the primary, i check all my connections on the wireing loom and choke on hit the start button,during the crank i was getting a popping noise from the front cylinder sounding like a cork popping on a wine bottle this is a regular noise then after about 6or7 pops from the front the rear cylinder sounds like it wants to fire properly lets out a puff of smoke and all stops, it seams like the front cylinder is running backwards and the back one forwards but intermittently......i have faith in the new engine and as i am a novice i believe that this is something i have done/failed to do. if i rigourously twist the throttle the engine will pop on the front cylinder as if it thinks its running but the popping noise seams to be more into the engine rather than out the exhaust this continues till the rear cylinder kicks in 5 10 seconds later and stops all, plugs are good, fuel is good, no air leaks can any one shed some light... i looked in my manuel and it says that the ignition timing cannot be adjusted....is there something i have done to make the timing for want of a better word 180deg out ??

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Thats clearer, are you sure the fuel is getting through from your temporary supply? From that disc i'd be looking more fuel starvation.

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thanks sorry, i forgot to mention i had swapped the plug leads round to all the configurations and tried a start to no avail , i then put the wires for the plugs in the correct format reference the manuel, i am gratefull for any suggestions as i am truly baffled...and i am far from an expert..

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the "popping" is sounding like a timing problem look in the manual to see how to check it........the only way it can be out is if someone has taken the heads off.

are the coils in the right plugs?

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thanks paul, as far as i am aware the fella that sold me the engine did not tamper with the heads and it was runing prior to me having it delivered, i have done every permutation possible with the leads/plugs and had no joy, i reverted back to my manual for the correct wiring format, i dont know much but is it possible to mess the timing up by rotating the middle of the pick up by hand when the covers where off ??

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Are the plugs wet with fuel?Confirm plugs sparking

Have you primed the fuel supply?

Checked the valve clearances?

Black rubber manifold to the carb sealed properly?

Air filter in (clean one)

no i havent checked the valve clearance but i did all the other checks, however how do you prime the fuel ?
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, i dont know much but is it possible to mess the timing up by rotating the middle of the pick up by hand when the covers where off ??

only if the cam chains were loose but unless you undid the tentioner they would stay tight.

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yeah ....sleep on it and try again with a fresh head. just go over everything to do with ignition, so ecu to coils to plugs, then the engine. check everything is on properly then turn the engine without the HT leads connected to the plugs, it should sound normal then try with the plugs connected.

my only other thought is the piston rings are letting the fuel air mix into the case under compression. open the oil plug and take a whiff if it stinks of fuel then it could be the rings.(but dont quote me on that)

im not sure how to sort it but i heard if you put a teaspoon of oil in the sparkplug holes then with the plugs out turn the engine over it should fire up when you put the plugs back in.

anyone want to clarify on this?

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hey paul thanks for that ...i will have another go and take it from the top in the mornin, i cant thank you enough for your posts , this site is really the only source of info for me, the type of info that aint in any book ,,,,, have a cyber pint on me ..cheers. i will keep my progress logged.

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no i havent checked the valve clearance but i did all the other checks, however how do you prime the fuel ?

I meant that the fuel cock has to be in the "prime" position. There should be a little arrow on the handle, the arrow needs to point to the right as you look at it. Thats the prime position.

Valve clearance procedure is on pages 3.6 to 3.9 in the service manual. If youve got the tank off, it would pay to check them, and as youll be looking at the timing marks, it may/may not show somethin not quite right timing wise.

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If the engine was running before you got it then i wouldnt be worrieng about timing or valves.

The most likely cause of your probs is your carbs from your own engine. Set these to what the manual says.

Popping out the exhaust is a sign of over-fuling,,,, too much fuel,,,,,again carb settings.

Taking carbs off one engine and onto another does not mean that they are set up propperly for the new engine,,,,,every engine has its slight differences.

Have you a good earth connection,,,,, engine and frame,

Try new plugs,,,,, sometimes plugs dont spark when there under pressure,,,,, specially if they've been lying arround for a while.

Is the choke working propperly

You may also need to clean the jets in the carbs if not done allready.

You said there was an occaisional fire ball out of the carb,,,,,,,,what do you mean by this ??? Have you not got the airfilter in.

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hello mr two wheels...thanks for your reply, ref the fire ball out the carb.. i had the air box and filter etc set up on the initial start attempt but as i was having no luck i turned it over with it off at which point i saw the fire ball , after putting it all back together for more start attemps i could see the air filter box was jerking agressively with a silenced /dulled pop from within it ...if you get me, i have followed mr whites(avatar of eyeball and razor) advice ref the teaspoon of oil in the piston pot and it deffo worked for the front, it now fires up and runs...not well but it works, i am thoroughly gratefull for advise and look at this site with anticipation of a reply,..................however the rear cylinder is not firing at all ....taking on board what was said ref spark plugs i swapped them over knowing the front one worked, i put a drop of oil in the rear cylinder but that never worked..bearing in mind i have the exhausts off out of the rear pot i am getting a random blue flame ...so i would think it safe to assume i am getting fuel and a spark ( fuel all be it a wrong mixture).. however when ignition has taken place some times the front cylinder will run faster and faster louder and so on in a steady incline, , , i let it pick up pace hoping for the back pot to kick in ..but nothing just more blue flames..

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hello mr two wheels...thanks for your reply, ref the fire ball out the carb.. i had the air box and filter etc set up on the initial start attempt but as i was having no luck i turned it over with it off at which point i saw the fire ball , after putting it all back together for more start attemps i could see the air filter box was jerking agressively with a silenced /dulled pop from within it ...if you get me, i have followed mr whites(avatar of eyeball and razor) advice ref the teaspoon of oil in the piston pot and it deffo worked for the front, it now fires up and runs...not well but it works, i am thoroughly gratefull for advise and look at this site with anticipation of a reply,..................however the rear cylinder is not firing at all ....taking on board what was said ref spark plugs i swapped them over knowing the front one worked, i put a drop of oil in the rear cylinder but that never worked..bearing in mind i have the exhausts off out of the rear pot i am getting a random blue flame ...so i would think it safe to assume i am getting fuel and a spark ( fuel all be it a wrong mixture).. however when ignition has taken place some times the front cylinder will run faster and faster louder and so on in a steady incline, , , i let it pick up pace hoping for the back pot to kick in ..but nothing just more blue flames..

Id say if you got flames at the rear cyl, then its actually firing

Air filter box jerking, could that be back pressure from one or both cyls ie valves not seated.?

I still say while youve got the tank off, check the timing and check/adjust the valve clearances before you take the carb off, its not difficult to follow in the service manual.

Process of elimination, make sure the mechanicals are working correclty first

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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.

would explain why your getting blue flame from the cylender when the other one is fireing.

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