Gpx 125cc problems

[dirtyboy1994]

Hi everyone and thanks for reading my post. I have a problem with my motor it is a GPX 125CC. I bought the bike and brought it back home I got maybe 15 minutes of time out of it and then they croaked.topped in 4th gear was going about 50 to 55 miles an hour I get back into my buddies driveway and there's oil all over the back end of the motor and the back wheel. The kid I bought the bike off of claims it was built properly. I have no idea what I'm dealing with here and I need your guy's help I'm wondering if this is going to be a new motor fix or if it's something I can fix myself quickly and efficiently. Thank you guys

 

[my67xr]

Welcome to Minirider's,
the engine may have been over filled with oil.
Or maybe it has worn ring's and piston

I would drain the oil out of the engine and measure how much was in there, post up how many ml's you got out of it

 

[dirtyboy1994]

Ok I will do that today. Also on another note when I rode it the first time it was sputtering a little bit. So I pulled out the spark plug and the guy before me stripped the threads from the head and basically put some tape around the threads and placed the spark plug back in. Now it's just spinning freely... Is there any way to fix it without buying a new head? Also back to the oil when I check the oil after it all spilled out there was still a decent amount in the motor.

 

[my67xr]

The head will need to come off to have the spark plug thread repaired, either a Helicoil, or a Threadsert will fix the threads

 

[mikkh]

Larger size thread can be made to fit larger thread spark plug. When I get home I will specify the larger thread spark plug.

 

[dirtyboy1994]

well at this point I want to get another motor.

where can I find another motor like mine for a cheaper price?

I was told that lifan motors are great. but I would like to stick to a GPX.

if you guys can drop some links to some cheaper more reliable websites please do

 

[gottagetacheaperhobby]

Dhz sell the hi comp gpx 125 for 440 i believe. What about simply sourcing a new top end, head included?

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[dirtyboy1994]

unfortunately DHZ doesn't ship to the united states.....I looked for them. they are about $300...a new motor seems to run about $400-475. I feel like I should just replace the whole thing.

 

[gottagetacheaperhobby]

Ahhh ok sorry mate. Try tbolt maybe? They seem to have a larger range than many others...

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[my67xr]

Maybe talk to TBolt about this top end for your's
GPX & YX 140cc Top End KIT - WHS-1353 - GPX YX 124 & 140 Parts and Kits - Pit Bike Engine Parts - TBolt USA, LLC
Or this will take it out to a 146cc
TB 146cc Bore kit and YX 140 Big Valve Head Kit - TBW9066-0492 - GPX YX 124 & 140 Parts and Kits - Pit Bike Engine Parts - TBolt USA, LLC
I think both kit's above would need a cam and spring upgrade as a minimum too if you want to rev it out anything like the 125HP engine


Then you have the TB V2 race head 146cc top end kit for around $579
TBParts - Roller Rocker Race Head V2 146cc Big Bore Kit China 124cc & 140cc engines - TBW9126 - GPX YX 124 & 140 Parts and Kits - Pit Bike Engine Parts - TBolt USA, LLC

 

[dirtyboy1994]

what do you guys think about this?

Lifan 125cc Motor Dirt Pit Bike Engine 4 UP!! 125M-SET

seems to be the cheapest solution.
anyone know anything about this motor?
anybody ever use this website? or heard about them?

Thanks guys!

 

[gottagetacheaperhobby]

I can say a lifan 125 will be a big disapointment powerwise compared to a gpx 125...

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[dirtyboy1994]

Really? Some people say that lifan is much better than gpx. Care to shed some light?

 

[motodevo]

The lifan 125 is a good motor but as said, power wise it has nothing on the GPX. The GPX has much higher compression and a much livlier cam. Not to mention the lifan has the clutch mounted on the crank (ie if you're holding the motor at 12000 rpm, the clutch is spinning at 12000rpm) where the gpx has a secondary clutch (spins at a fraction of the rpm of the crank), if the lifan was making the same sort of power as the gpx, the clutch would try to make an exit through the cover (and possibly into your shin) in no time flat. The gpx is more comparable to a 150cc motor powerwise. The lifan 125 is a good mix of power AND reliability. I have a few of them and they are good motors but definitely no powerhouse of a motor.
With your GPX did it hole the cases and leak or just blow a lot of oil out of the breather near the back engine mount? It sounds like you were revving the crap out of it for a prolonged period of time, if so its not that unusual to blow oil out of the breather. They are not really designed to be held wide open constantly for prolonged periods. Think of how long you can hold it wide open on a track, even on a long straight you are only going to be at max revs for 10 secs tops before you have to shut it down for a corner. Also make sure your breather isn't blocked, if it is it will pressurise the cases and push oil past seals that it shouldn't.

 

[gottagetacheaperhobby]

^^^what he said. A gpx will make close to 14hp, with a 13000 rpm limit. A lifan 125 is around 7 or 8 hp, and would be lucky to rev to 10 000 rpm. I found my old gpx 125 to be very reliable, especially when you look at the power it puts out and how hard it can rev. Gpx also has a servicable oil filter, same as the 160hos etc..

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[dirtyboy1994]

i checked the whole motor and there was absolutely no where that oil could have came out of at that rate besides the breather. i was revving the hell out of it. i just bought it and wanted to top it off at full speed i hit about 60mph and then oil started coming out. but my threads in the head for the spark plug are stripped. what would be a cheap fix?