pit bike 125 problems.

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locko90

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hey, I have a crossfire cf125 pit bike.
am having trouble with carby, bike was dying when opening throttle, I cleaned carby (was filthy) pilot jet was blocked. Now bike does not die as bad as before but its still doing it a bit. Also when bike is idleing if i put the choke on it wont just gain higher revs it just dies and stalls. Could this mean i need to clean carby more thoughrly or could it be something eles ? Any help would be great!
 
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my67xr

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Welcome to Miniriders,

Where the pilot jet screw's into the base of the carby, at the end of the threads you should be able to see light though into the main bore of the carby



And did you clean the hole's that run across the pilot jet ?
 

locko90

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Thanks mate.
Yes can see light through the pilot jet from bore and yeah cleaned all the holes in the pilot jet.
Why would it be dying when I put choke on? Could it be running to rich or lean?
and my mistake its a crossfire cf125*
 
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my67xr

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You might need to check the pilot circuit is clean too.
Blow compressed air into the 2 or 3 holes in the air filter side of the carby and check you can feel it coming out under the carby base through the jet holes.
Also have you cleaned it with the mixture screw out?
Do you have a foam air filter on it, and do you have filter oil on it?
 
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locko90

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ok tomorrow ill give it a blow out with the compressor.
no haven't cleaned it with the mixture screw out, not sure where it is?, am thinking its the one on the bottom as the one on the side increases revs and decreases revs with turns.
am I right here ? the carby is a mikuni pz26.
yes its a foam filter on it and no filter oil, will be getting some on Tuesday. (bought this bike a week ago and that's how it came no oil on it)

just another thing to add the engine oil is really dirty and has watery consistency as when I wipe the dip stick on a rag it soaks it up instantly, and the oil smells at bit like petrol.
was wondering if this could mean anything? is my engine supposed to have really thin oil like this?
probably shouldn't be riding it until I get the oil changed right?
 
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my67xr

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Yeah it will take a couple of flushes to get the black out of it.
Sounds like you need to take the kick start and r/h cover off the engine and clean the oil strainer too.
Thin oil is a sign it's been running really rich.

Take note of what jets are in the carby too, if it's a mikuni copy 22/26mm then it should have a 15 pilot and a 95 main.
Most of them i have tuned have needed a 20 pilot jet to get them to run sweet.

How many turns out is the mixture screw set at atm?
Try it at about 1.5 full turns out, then tune it from there.
you could try the needle clipp on the second slot down too.

Running it with no filter oil will be making it run too lean as well.
 

locko90

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ok hopefully ill be able to get a oil change done and clean the oil strainer tomorrow.

how do I tell what size the jets are?

not sure on how many turns out the mixture screw is, ill find out tomorrow and try tune it from 1.5 turns.

not really sure what you mean by having the needle clip on the second slot down??
also what will having the needle clip lower do ?
 

my67xr

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The jet's have number's stamped into them, main jet will be on the top, pilot jet will be stamped on the side


The needle is located in the slide.
To remove it you need to compress the spring toward's the cap, and feed the cable through the bottom slot of the slide and out the side.
Then you remove the spring clip that hold's the needle into the slide.
Having the needle clip on the second notch down is a touch leaner than the standard setting, (centre notch)
The pic below shows a needle with the clip on the fourth notch down, slightly richer than standard

jet_needle1.jpg
 

locko90

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cool I understand how to do the clip now, although I think the bikes running to rich atm, wouldn't I wana raise the clip to make it more lean ?

can u plz explain why I would wana drop the needle clip bit confused :s

hang on does having the needle clip one lower make it more leaner?? so confused
 
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loace

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Hi mate if ur bike is warm and u put the choke on it won't necessarily run , it will be too rich for it to keep running
If it's bogging 3/8 to mid throttle like u are saying I would lower the needle to the Bottom clip P4
This will richen it ,
also make sure u don't have a manifold leak spray some carb cleaner or brake cleaner around the joints and make sure the revs don't change if they change in either way fast or slow u have a manifold leak which can hamper tuning
And one other thing is make sure ur valves aren't tight and are set at the right specs
 

criggs

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If the carb was dirty enough, it's also possible that it still has some varnish or deposits that aren't quite letting enough fuel flow through. First find a video or diagram showing how to fully dismantle your carb. Then, pick up a tin of carburetor dip (it's not expensive, Chem-Dip is a good one, runs 10 bucks for a gallon-ish), take all of the jets, screws, and rubber gaskets out of the carb, and soak the bare carb body and both jets in the cleaner for an hour or so, then afterwards give it one more go over with carb cleaner and compressed air to get all of the cleaner and remaining debris out. Put the jets in just tight enough, too tight can damage them. Put the air screw in all of the way, and back it out 1 and 1/2 turns. Check that the needle jet moves freely and doesn't get stuck, and check your float level (I just try to make it parallel to the carb body while it is upside down, a quick google search can help you with this). Then, lastly, check your spark plug and wire.

I just recently went through a no-start issue with my SSR 125, and the chem-dip really got my carb a lot cleaner than just using the carb/choke spray. Once I was done, she fired right up and doesn't bog. This may not 100% fix your issue, but you can't really move further until you are 100% sure that carb is as clean as possible.
 

locko90

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thanks alot for the info on the bike! been so much help! here's a basic run down on what I did, I played around with the carb yesterday blew it out with the compressor, found out that the mixture screw was about 3 turns out! so turned it in to around 1.5 it didn't run right so I went in a bit more about (1.3-1.2) didn't start, so I went out to just a bit past 1.5 turns (by this time I was getting pissed of taking the carb on and off to tune) once again it didn't start, put the choke on kicked it over and it started, gave it some revs and lowered the choke, realized then I needed less airflow so cupped the air filter side with my hand and it ran like a champ! pump to wot and no bog!! :D so whacked the air filter (no oil) back on ran like sh*t again (no filter oil yet) so I put a cut out water bottle slpash protector over the carb and running awesome now. was boosting around the track all yesterday! ill be out there again today might chuck a few pick up tomorrow :)

oh and also when I changed the oil (20w-50 4 stroke oil not sure if its the exact right oil) when I first kicked it over I couldn't believe it, felt like the spark plug was out literally was like the weight of my leg kicked it over!! haha unreal!
like you said the jets are 95 main and 15 pilot. I should probably get the 20 jet like u said but its running so good now probably wont need to. I can hav it in 4th at about 10ks and punch it to wot and not the slightest bog just pulls.

but all in all bike it going great now. and I have learnt so much about getting these engines going right. thanks alot for the help guys awesome help!!!
 

loace

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Sounds like ur on the right track,
Filter oil will richen it a little , I tried going bigger on the pilot myself and found it too rich ,I had the best result lowering my needle clip to the very bottom
 

my67xr

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Having the needle clip on the bottom notch is the richest setting.The best position for the Idle mixture screw is somewhere between 1.5 - 2 full turn's out.
Anything either side of this the pilot need's rejetting, so if it runs sweet at 2.5 full turn's out, you need a bigger pilot.
The #20 would be perfect and let you turn the mixture screw back to 1.5 turns out.


The 20w50 oil will be fine, as long as it is a motorcycle specific oil,
And that it is safe for use with wet clutches.

With it being really easy to kick over/start, it sound's like you need your valve's adjusted.
you will need to adjust the valve/rocker clearances to .003" for the inlet and, .004" for the exhaust

Watch this video it explains the best way to do it.

[video=youtube;QJciyJRJh8Q]https://www.youtube.com/watch?v=QJciyJRJh8Q[/video]
 

locko90

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that looks a bit technical with adjusting the valve clearance, I think ill have a mechanic do it :s don't know where id get the paper to measure valves to start with.

yesterday the bike ran so good I went out today and bought some things for it including higher handle bars (they where a waste of money) they made the bike feel weird put the old one back on. I was thinking it would be better because when I stand up the bars are to low, oh well lesson learnt there :(.

so I got some air filter oil on the air filter and it seemed to bring back the bog! I thought I might need to get it warm and it will run better which it did, took the misses out to the track so she could have a bit of a run out there, was showing her the track (going slow through the scrub) and it died I was like ****!! and noticed there was fuel pissing out the carby and air filter, turned the fuel off after about a min she started back up and got us home, I let the carb bowl run dry and gave it a tap trying to free the float put the fuel on and it didn't seem to over flow. so went for a quick ride and it started over flowing again!

the china let me down today :(

so I was thinking I should open the carby up and adjust the float up ? or clean the carby filter as I think its the vacuum that's causing this?

any ideas guys ?
 

my67xr

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feeler gauges can be bought at hardware shops or any auto parts shops

thickness_gauge.jpg


I would recommend fitting a #20 pilot jet if it has A Mikuni 22/26 copy.
With the flooding the needle and seat has something stuck in it. and is not letting it close.
Or the float arms have been bent, and has changed the float level
 

locko90

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oh sweet ill have to get a set of feeler gauges, :thumbup: ill grab a larger pilot jet for it tomorrow if I get around to it. will the bike shop want me to take the carb into the shop to fit the right jet?

ill take the carby apart for the 15th time :( and take the needle and seat out and have a look. hopefully this fixes it.
don't think it got anything to do with the air filter? just because the carb was not leaking while not running as soon as I started up and went down the road she started again.

thanks man, sorry to be a pain.
 
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my67xr

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This is the carby you have ?

$_3.JPG


Motorcycle-font-b-Mikuni-b-font-font-b-Carb-b-font-VM22-26mm-Carburetor-Carby-For.jpg


MIKUNI-Carburetor-VM22-26mm-PZ26-Air-Filter-Visble-Throttle-Settle-Cable-Fit-125cc-140cc-GPX-KAYO.jpg



If it is, the pilot jet is the same as a Mikuni VM28/486
The one on the far left

Mikuni_pilots.jpg
 

locko90

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yep thats the one! thanks bro! :D
 
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