XR125 - Acceleration problem
 

Hi, my wife has a xr125 which she is using to get her confidence up before going for her big bike license.

2 weeks back I was informed that the bike was going like a dog.....it would start but was behaving peculiarly when accelerating - it appeared the choke was on.
A week later it appears that the bike is behaving in a similar fashion (x1000), but the choke isnt on this time.

- The bike starts fine.
- The bike revs fine in neutral.
- In gear, the bike will not accelerate beyond a dawdle before wanting to stall, followed by stalling if you deccelerate immediately - it has the same feel as driving with the choke on but exaggerated.

Any advice would be appreciated, Id like to try fix this myself so may ask plenty more questions.

Thanks

Gotta check fuel flow - disconnect pipe from tap - and run into a jar to see is flowing nice for at least 10 secs +, & check filler cap breather hole by undoing cap whilst draining fuel into jar (does it flow quicker with cap off?) .

If OK - drain carb and check for shite :(

Is air filter clear ????

Take plug out & check colour (post photo if not sure wot you're looking at.

:thumbup1:

Awesome, sorry for delayed replying.

I will give this a go this evening, wanting to pick up some carb cleaner and a new plug.

The exhaust is blowing a bit and has gotten a bit worse - could this be the problem ?

A leaking exhaust will effect the running - but probably only marginally :eek3:

Pigford......I think I need help.

1. I disconnected fuel line between tap and carb, fuel flowed well.
2. Opened petrol tank cap and fuel flow did not alter - no blockages.
3. Carb...well, that is now in my kitchen. Removed Float chamber and there appears to be some (tiny amount) fine black powdery stuff at the bottom. I have drained this.
4. Air filter...looks a mess to me (as attached). Was planning to get a new one tomorrow and fit. Is it ok to use clean engine oil on the filter ?
5. Spark plug....another mess...as attached (Black, powdery, gungy..not wet).
6. I didnt check compression, but replaced the plug and shocked myself while testing....wow, the current can jump to earth itself:clap:.



A few question to questions....
1. Can one use a general degreaser to clean the carb, in addition to carb cleaner ? (how would one clean a carb?) - I read one can boil a carb in lemon juice (dont laugh). Why should one not use water to clean a carb, assuming it is dry before refitting ?
2. How do I remove the throttle valve slider from the bike ? - Do I need to take the entire throttle cable off ?
3. I notice on the choke there are 3 settings...the butterfly is full open, partially open...and closed ??
4. The obvious question....what next to get the bike run ?

PLENTY more questions to come.....hope that is ok.

Im going to nose around a bit and check of the jets are clear....

Thanks for the help.

That plug is BLACK.. Althogh , with a filter that old and clogged, im not surprised lol..

It could also be that black from the choke sticking or you're burning oil. Checked the level ??

Anyway, while the carb is in pieces, make sure the float bowl valve doesnt have a fine filter hiding under it. These often get wet.

It's a shame you took the carb off before checking the fuel flows from the carb drain freely too.

Anyway. Dont use degreaser on your carb. It leaves a residue. You can use petrol, or carb/parts/brake cleaner.

Blow out ALL the jets while your in there.

Take the top of the carb off and check there are no holes in the diaphram. Thats how you get the slider out too. BE VERY CAREFUL not to lose any parts and be very systematic taking it apart. Keep things in order.

The choke has three settings. Its nothing complicated or fragile. You will be able to see it open and close now the carb is off.

haha yeah......the seller prob though I was a sucker (which I may have been......but this can be my motorcycle-101 class :smartass:....all good. Hopefully the only real expense will be to fix exhaust holes (fingers crossed!)

OK.....
- I havent checked the oil level as yet....will do during daylight hrs. The bike doesnt leave smoke trails behind it..tbh I will need to be more observant though, my wife has been riding this one so I have been out the loop until this issue.

- Float bowl jet ?...Im flummoxed. Is this the Primary (Needle) jet, Primary Pilot jet, Pilot screw...or something with the overflow ? - I didnt see any filter hiding around any of these....what do you mean "These often get wet" ? - water ??

- Carb drain.....I took the carb off the bike and then initially emptied using the carb drain before just pouring out the float chamber. The drain appeared ok. Why do you ask ?

- Thanks for the degreaser warning....I was about to soak in "muc-off", the label makes it sound good for all jobs :biggrin3:. Anyways.....filled a tub with petrol and got cleaning. Also used some Brake/ Clutch cleaner.

- Blasted a shot of cleaner through the jets.....took a peak though em and they clean as a whistle. Tightened all the jets back in place. Only the Pilot screw was 1.75 full turns off tight (as before I dismantled) - sound correct ?

- Diaphram....I unscrewed the top of the slider and took the slider out. I saw a spring but no diaphram....does the 125cc have one ? The slider is still attached to the bike which is why I asked if it is possible to remove this without disconnecting the entire throttle cable. Do I need to clean the slider ?

- At the risk of asking the obvious....having the choke fully closed, is this for the same reason as having a petrol tap....to switch off when not in use ? ...or once one has flooded the carb ?

Thanks for the help.....

[quote=Trichelia;297944]haha yeah......the seller prob though I was a sucker (which I may have been......but this can be my motorcycle-101 class :smartass:....all good. Hopefully the only real expense will be to fix exhaust holes (fingers crossed!)

OK.....
- I havent checked the oil level as yet....will do during daylight hrs. The bike doesnt leave smoke trails behind it..tbh I will need to be more observant though, my wife has been riding this one so I have been out the loop until this issue.

- Float bowl jet ?...Im flummoxed. Is this the Primary (Needle) jet, Primary Pilot jet, Pilot screw...or something with the overflow ? - I didnt see any filter hiding around any of these....what do you mean "These often get wet" ? - water ??

Sorry, I meant float VALVE.... Its what opens and closes when the float bowl is full so the carb doesnt flood. Sometimes there is a fine mesh filter under it which is easily gummed up. These filters can also hide under the main jets etc. You really need to take the jets out of the carb. Check it properly.

- Carb drain.....I took the carb off the bike and then initially emptied using the carb drain before just pouring out the float chamber. The drain appeared ok. Why do you ask ?

See above. If this is clogged or not working properly, the carb wont have sufficient fuel to run when you open the throttle.

- Thanks for the degreaser warning....I was about to soak in "muc-off", the label makes it sound good for all jobs :biggrin3:. Anyways.....filled a tub with petrol and got cleaning. Also used some Brake/ Clutch cleaner.

- Blasted a shot of cleaner through the jets.....took a peak though em and they clean as a whistle. Tightened all the jets back in place. Only the Pilot screw was 1.75 full turns off tight (as before I dismantled) - sound correct ?

If the bike idled ok with it at 1.75, leave it alone !

- Diaphram....I unscrewed the top of the slider and took the slider out. I saw a spring but no diaphram....does the 125cc have one ? The slider is still attached to the bike which is why I asked if it is possible to remove this without disconnecting the entire throttle cable. Do I need to clean the slider ?

Im really not sure if it has one. I don't know the bike first hand..

- At the risk of asking the obvious....having the choke fully closed, is this for the same reason as having a petrol tap....to switch off when not in use ? ...or once one has flooded the carb ?

Nope.. The choke when fully on will close off the air supply to the engine.. This makes the air/ful mix much richer (more petrol), which is what a cold engine likes.

If you look into the carb, the butterfly in there just restricts air flow depending on its setting.

That looks like a paper air filter. You're not supposed to oil those, just use them as they are. Oiling a paper filter will clog up the pores in the paper, restricting the air flow and causing the problems you've mentioned.

Only use oil if the filter is made of foam. The holes are much larger so the walls can be coated in oil and still allow air to pass through.

Thanks guys…..
I left home this morning with the carb in a Tupperware in the kitchen and the house smelling of petrol…wifes loving me !! :D


Backofbeyond….Air filter makes sense, thanks before I create my next problem J

I presume the float valve is under the float pin or there about….I didn’t seen any filters, Ill take a closer look. If I find one Ill give it a clean and Ill blast a shot of cleaner through the value anyway.

Found this site – looks like there may not be a filter.
http://www.google.co.uk/imgres?imgurl=http://www.dansmc.com/carbs/japanese_carbs/suzy_re5_carb.jpg&imgrefurl=http://www.dansmc.com/carbs/japanese_carbs/carb_pics.htm&usg=__vYxHYn_Xyr7XOV7XJmyNl65HUHU=&h =555&w=750&sz=55&hl=en&start=20&tbnid=junylZL4_PQT cM:&tbnh=104&tbnw=141&prev=/images%3Fq%3Dmotorcycle%2Bcarburetor%26um%3D1%26hl %3Den%26sa%3DN%26tbs%3Disch:1&um=1&itbs=1


Im still not too sure whether the slider and pin should still be attached to the throttle cable on the bike or I should remove this along with the carb ??

We’ll, short of checking for this elusive Float valve filter, I think the carb is almost ready to be reattached – and the pilot screw (air/ fuel mix?) and throttle adjustment screw (idling?) tweeked if necessary.


A few silly questions…..
- Within the lead to the spark plug (not sure what its called), is there no + and – cable ?- is that why I got a shock when testing the plug…..the power cable being the positive and bike being the negative ? Does one just touch the plug to the bike to prevent the earthing taking place though me ?:stormy:

- How tight to torque the spark plug without torque wrench ? – Is there a rule of thumb on this ? I thought I heard finger tight and then half a turn tighter, something like that. (else I can grab a socket on the way home to fit my torque wrench)

- Should one torque set the carb bolts on the float bowl ?


Ill buy an air filter this afternoon and fit it this evening, I have replaced the plug, cleaned the carb, checked the petrol tank breather pipe for blockages, the carb breather pipe, the fuel line from tank to carb using On and Reserve settings, cleaned the petcock filter......Assuming there the bike is still kaput….what next ? - burn it :taz:

Thanks

Unless you really need to remove the needle and piston for some reason, i'd leave it on the cable and just give it a bit of a clean with carb cleaner and a cloth (carefully).
I serviced a customer's XT 125 like yours a couple of months ago and as far as i remember the only fuel filter fitted is in the fuel tap, there isn't one behind the float valve. You'd need to drain the fuel tank and remove the tap body to get to the filter but as you've already found the flow to be OK then i'd say this isn't your problem...anyway it seems you have a very RICH mixture problem and blocked fuel filter would cause the opposite.
If you're happy that the carb is nice and clean, refit it and the air filter and see how things are. A good rule of thumb when fixing problems is to do ONE THING at a time so when the problem goes away you'll know exactly what the hell was laughing at you!
Check the air intake snorkel into the airbox hasn't been blocked with something, it's under the seat. Another customer's bike had similar over-rich running a couple of years ago and the cause was a rag that he kept under the seat which had been sucked into the intake!
Another cause could also be the exhaust baffles coming loose and blocking the system up.....sometimes you can check this by taking off the exhaust system and shaking it to see if it rattles.

The metal of the engine is the return path for the spark. Bear in mind that in order to complete the circuit the electricity has to jump across the gap at the end of the plug. That requires loads of volts, just like :stormy:. Electricity is lazy though and if an easier option presents itself that doesn't involve jumping it'll take it. That would be through you if you're holding the wire or the cap - even if the plug is earthed against the engine. You can avoid the taser experience if you close the plug gap down to nothing but that tends to knock the performance of the bike down a bit :smartass::confused1:

How tight to torque the plug? Finger tight plus half a turn? Sometimes!

Let's assume you're putting in a new plug. Screw it into the hole and tighten it gently until the threads bottom. Easiest way to do this bit is to use a socket but turn it with your fingers. At this point you need to tighten it up so put the ratchet or whatever on the socket and turn it. New plugs have a crushable washer fitted and that's where the half turn bit comes in. They will screw down about a further half turn before they go solid.

A used plug ( = any plug that's been tightened once) has already crushed the washer down and needs very little actual turning, just tightening. If you try to force a used plug the extra half turn you'll damage something - probably the threads in the cylinder head and that's an expensive fix. If you've got a torque wrench that's a good start. Look up NGK's (or whatever make of plug you've used) web site to give you a tightening figure but in rough terms it's just a bit tighter than the force needed to crush the sealing washer in a new plug.

Right then - after all that good advice - now just whack it all together & see if it runs OK :thumbup1:

Hope this is now sorted, the easiest thing to do to check a sick engine is take the filter out and see how it runs, if it runs ok you've got a blocked filter if it runs worse its running weak-fuelling/carb. Then check plug/s; dark=rich, pale=weak, they should be a "biscuit" colour (I always go for cardboard box brown). Its good you now know the innards of your carb. cleaning it out can't hurt and sorting leaking exhaust should help smooth running.
A friend had a CG 125 and the choke was travelling beyond off to being partially on over centre(does that make sense?) causing the bike to hold back.
P.S. always get someone else to hold the HT lead

And another thought.....If the airfilter's in that state it could be well worth your while doing an oil and filter change, check brakes, chain and sprocket etc. etc. Its good to do a full service on a bike that's new to you, then you have peace of mind that everything is as it should be and good to go many more miles

Guys......I was chomping at the bit all the way to the shops to fetch my air filter only to find out that they didnt have any - practically reduced me to tears.
Hopped online and bought one last night, received the email earlier today saying its been dispatched....praying it arrives tomorrow !

This evening Im going to fit the carb, tighen up the plug.....check the air snorkel for rags etc, then wait out the delivery :frown:.

Are there any tips how best to get the air out of the fuel line when reconnecting the carb ? - or do I just fit, open the fuel tap and choke...and hope gravity does the rest ?

In addition....Oothef, haha....are you kidding ? (or not? :eek3:)

Seems a good way to lose friends...:laugh:

Also....even though the air filter housing has a mesh over the pipe to the carb intake port....is it safe to run the bike without the filter (even to check its working?) - Id need to ride the bike as that is where I was experiencing the problems (only once gears engaged and me pulling off)

Lastly, great idea.....once the bike is up and purring.....Ill work my way around and give it a service.....loving this, learning plenty!

Will be back with an update once the filter arrives......fingers crossed !!
Thanks for all the help..!!

Good luck

You guys are LEGENDS !!:D

It works !

I have worked it out - the hole(s) in the exhaust are blowing directly into the air filter snorkel.....need I say more :thumbdown:.

I fitted the carb, I wedged some cloth between the exhaust holes and the snorkel.....the bike started 1st time, I rode 40 meters.....bike pulled fine :clap:.

Hoping the filter arrives today so I can fit it, and gonna make a plan to get a exhaust system replaced before we ride ANYWHERE.

Guys, thanks a bunch, I really enjoyed this !

PS - Was going to take the bike to the garage to get the exhaust replaced...or should/ can I do it myself ?

:mchappy:

You've got this far......The worst thing about exhausts is that the nuts have a tendency to seize on the studs in the cylinder head, if you are going to have a go, get some quality penetrating oil and give them a good dose, leave to soak then give em some more and maybe some more! Use a good socket/ring spanner, preferably 6 point and see if they crack. Sometimes it helps to tighten them a fraction to break the corrosion, if they don't slacken easily watch it as the studs can sheer, sometimes running the engine to get them v. hot may help but watch it cos the exhaust will take your skin off! Having said all that they may come off no bother......
Make sure you get a new gasket with the exhaust and when refitting don't tighten tight until everything is nicely aligned so as not to stress anything.
You can do it.

Just seen the "loosing friends"
friends as well as spark plugs have to be tested, after the shock you can usually run faster and further than they can, so long as you are not laughing too hard to concentrate on your evasion techniques.
My first encounter with high tension voltage was as a kid, I started one of my dads lawn mowers and it went on to full bore and I could not stop it! I pulled the HT lead off and was possessed by an evil indescribable power until the effer finally stopped and I walked away with a nonchalance I didn't really feel.
Cartoons have it off to a tee

Thanks Oothef...will be sure to pick one of my tubbier mates ! - haha

Been at the bike again....and got a few thoughts

- To check compression without a gauge......at the risk of embarrassing myself. I hear placing your thumb over the plug hole and pressing the starter, the compression should blow your thumb off the hole. I presume this is because the stater motor turns the engine, causing the piston to move resulting in the desired compression one is checking for ?
Also....the piston would only create increased pressure around the plug and never a vacuum (across the 4-strokes) ? - ie: your thumb would not get pulled ? and this is because when the engine is on top dead center on the exhaust stroke, both the inlet and exhaust values are open simultaneously for a moment...so no vacuum (and stroke 2, top dead center on compression....is obviously "compression" ?:blushing: - apologies for the ignorance.

- When one checks this....what is done with the HT lead (?) and spark plug ? - is this left with the plug attached and resting against the bike ? - or plug removed ?

- 3rdly.....Seriously !! - How do you check the plug for a spark...without me getting a shock or offending a mate ?

Thanks for the info on removing the exhaust system. All went ok, took a bit of heave-ho but the header holts came lose. The big problem I had was trying to seperate the header from the muffler (to remove the system from the bike chassis)....which I couldnt do, so I had to take the neanderthal approach of breaking off the muffler at the weakest, most rusted point and sliding it all though...it worked.

XR125 exhaust systems also appear fairly scarse online. Ive ordered one through Honda (will be about GBP180) with a few bits and pieces....gaskets, clamps..)...seems ok to me ?

Odd question....I could not find the header gasket on the exhaust Ive removed ?? Could it be that the gasket has COMPLETELY changed shape and is almost "merged" with the exhaust port vent ? - Will it require some muscle and screwdriver to remove ?

Hoping to receive all the bits and pieces end of this week so I can get into part 2 of my Mr Fix-it course :smartass:.

Yet again.......thanks all for all the help !!

I don't know that the thumb compression test really tells you much as low compression will still push your thumb off, but try it.
If you leave the plug in the cap put it out of the way, or rest the threads on the engine where you can see it and you can watch for the spark, a strong one is fat and blue.
Is there a lot of carbon in the exhaust port? try scraping it off carefully with a small screwdriver or similar. Gaskets tend to be compressed in, but you can see the joint with careful inspection, they often take some persuading out.
A thought... Keep it clean, whether just the plug out or a full strip down don't let muck enter as it will lead to wear.
When replacing the exhaust use anti-seize/copperslip on threads and joints, it'll make it easier next time(maybe new nuts?).
If you're going to get into spannering on your own bike/s get a manual, they can save a lot of blood, sweat and tears and have all spec. for servicing(and everything else). Valve clearances need checking.
I've used David Silver for Honda spares, always been good for me.
(not recommending, but I've started bikes up with no exhausts on, just for the terror of it! just start, rev rev n stop brill!)

Hey guys, Im back.

Took a while to get all the bits....but now fitted and running !

If I give the throttle a burst from idle, the revs hesitates as if it may want to stall...but then climbs perfectly. This didnt happen pervious to the exhaust replacement, new airfilter etc..

Could this mean the pilot screw needs an adjustment ?

I will take it for a ride tomorrow to give it a bit of a stretch.
Cheers

The slight hesitation is not uncommon on some older carb bikes - they were set a bit lean for emissions :(

Get the bike well & truely warmed up and then try - and if it still stumbles on initial pickup, play with the pilot screw.

If the range of 0 - 4 turns doesn't cure it, you may need to go up a size on the pilot jet :confused1:

This problem can be more pronounced on the bigger singles which seem to hesitate/stall due to their size & flow characteristics :thumbdown: like my XL500R.

Pigford.....took the bike for a quick spin, did a few blocks and the bike appeared fine, no hesitation at all. Perhaps it just needed a good rev....hadnt ridden it for 3 weeks.:thumbup1:

Im off to Cornwall this week on my xt600, gonna give the panniers, tent etc a bit of a shake.....once Im back I will continue on the 125cc service....oil change, brakes etc..cant wait, this is like a drug !

Thanks for all the help....chat soon :mchappy:

PS - Im amazed that we got the bike to start, let alone run properly.....once the carb was in my kitchen in a bowl of petrol, I thought that it was all over...never to start again....haha, what fun !!

Pleased you're up and running again, it's great when it all works, the real test is when it doesn't..........How I set carbs (on singles) get it warm, set tick-over then screw mixture screw in and out slowly, find fastest tick-over point, re-set tick-over and try again. If it's already running O.K. note how many turns out the mixture screw is before you start then you can always revert back to that if there's no improvement.
Have a good shakedown in Cornwall, always liked Crantock just outside Newquay, dunes, beach, river...Enjoy