94 yz 125 questions NEW TO FORUM

[Drennan yz]

Q.1 .I bought a 94 yz 125 its in great shape but the guy i bought it from hasnt takin the bike out in 2 years. theres nothing wrong with it but i was wondering after sitting so long is there anything i should do besides change the spark plug...

Q.2 . i want to put some mods on the bike just to bring it up to date it is a 94 after all what are some good cheaper mods to start off with.... thanks Drennan

 

[2stroker144]

i would start by going through the engine just to make sure everything is in spec.

 

[flyingfuzzball]

give the carb a good cleaning. chances are its gummed up from sitting. also i would get rid of the gas in it.

and the cheapest mod you can do (that i know of) is get it jetted correctly. besides that (not so cheap) get the suspension redone.

 

[Drennan yz]

k thanks im not worried about the suspension its got machine racing suspension works great just motor wise im looking to upgrade just dont know what to go for

 

[m4i2k2e2]

give the carb a good cleaning. chances are its gummed up from sitting. also i would get rid of the gas in it.

and the cheapest mod you can do (that i know of) is get it jetted correctly. besides that (not so cheap) get the suspension redone.

yea, when you sit on it it might seem fine. when you start riding it in different terrain and jumping it it may be weak. if it still seems fine adjust it to yourself. set the sag and so fourth.

-mike.

 

[skos]

change all the fluids. It is a cheap change that could say you big $$

 

[Drennan yz]

how do you jet the bike correctly do you mean the right size of jet???

 

[rmc_olderthandirt]

Is this your first bike?

If you are new to dirt bikes I would try just riding it and see how it runs. There is a good chance that the carburetor needs cleaning but I would at least give it a try before I started tearing it apart. If it runs OK then ride it. If it bogs, won't idle or runs poorly then clean the carburetor.

To correctly jet the carburetor requires a bit of work. There is no "right size" jet, but there will be jets and needle positions that are better for how your bike is equipped, the altitude you are riding at and your riding style. Again, if you are new to dirt bikes and it runs reasonably well as it is then I would leave it alone until your skills improved.

Once your riding ability improves and you start pushing the bike for performance then it would be time to rebuild the top end. The engines on these high performance bikes require frequent top end rebuilds (piston & ring) and if you don't do it you will eventually have a major failure that will cost a lot more $$ to fix. 20 to 30 hours on a top end it pushing it. If you don't know the history of the engine then you should plan on a rebuild before you start asking a lot from the motor.

As for modifications: Get your skill up and figure out what your riding style and type of riding is. A modification that can help in one situation will hurt in another. A great example is the pipe. You can change the pipe for one that provides more power at high RPM or you could put on a pipe that provides a bit more torque at low RPM. Which is better for you could depend on if you ride track or trail.

As mentioned before the overall best thing you can do is get the carburetor jetted properly. Note that changing the pipe will probably require a change in the carburetor jetting as well.

Rod

 

[Drennan yz]

im not new to dirtbikes i had a yz before but it didnt sit that long. . . i didnt have it that long so i never spent any time in the engine... iv had this bike out a couple times now i have sense changed all the fluids an SP and it runs good has trouble at idle when warmed up i can tell it needs to be re jetted big time im going to clean the carb for all i know theres a birds nest in it... i know how to ride but when it comes to pulling the motor apart im dead in the water ... i have another question if you dont mind i like speed i do have a heavy wrist whats the best type of jet to go for a 125 i have a track near by i will be on it from time to time so power is important ... might as well go big? what about the best pipe for the track? its the get up and go im looking for nothing like a holeshot!

 

[Drennan yz]

so i took the bike out and it was running strong then it quit took out the plug it was fouled i carry an extra so i put it in started riding and it quit again luckly i was with a couple friends with there bike and got a tow back i think the jets are set wrong.. is this the problem? im going to get a jet kit an reeds is there anything else i should be checking ??? or doing

 

[julien_d]

Is it smoking a lot? could be a bad crank seal on the right hand side sucking tranny oil into the crankcase and fouling the plug. What mix ratio were you running? Fresh gas I assume?

 

[rmc_olderthandirt]

Jetting for sure, and you might want to go hotter on the plug.

If you are heavy on the throttle then I highly recommend that you get the top end rebuilt ASAP.

Rod

 

[Drennan yz]

yz 125 motor seized and then unseized an now runs fine???

so i just put a new spark plug in my bike started it up took off and hit 2nd gear powerband and the bike shut off and the tire locked up... i took the plug out it was fine put it back in and kicked it an it was seized wouldnt budge i pushed the bike backwords in gear to try an get it un-seized and it did finally... started it up an it ran fine...WHAT THE HELL JUST HAPPEND???

 

[Drennan yz]

BUT now when i hit the powerband the motor chugs an it wont go threw it i have to shift or the bike fouls the plug

 

[2strokesrock]

When was the last time you put a new topend in it?

 

[Drennan yz]

i never did i bought the bike a couple years ago and didnt ride it that much i took it out for the first time in 2 years the other day an it ran ... "OK" had some trouble fouling the plugs an then this happind....... what does a top end rebuild consist of??? i was just going to get a jet kit and new reeds but something is wrong if the powerband wants to kill the motor and foul the plug as soon as it hits???

 

[oldguy]

The more you run it before pulling the top off and seeing what happened the more expensive the repairs are going to be. Without looking inside we would all be guessing what happened and you only risk more damage by running it

 

[Drennan yz]

yea im pulling the whole motor apart tomorrow looking over everything i dont want to take the chance but thats not normal at all... i want to get in the bottom end to see if theres pieces down there might as well to be safe cant have the tire lock up like that at high speeds if that happins i might not be replying anymore