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Need Help Identifing Dirt Bike

4K views 24 replies 4 participants last post by  MrKitty 
#1 ·
Hey everyone I just bought this smaller dirt bike, but I am not able to figure out the type of engine that is on it without taking it apart.


If anyone has experience with these types that would be much appreciated!


Thank you in advance!
 

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#3 ·
That bike has many names and numbers, QC 50 mini dirt bike is one. It's a 49cc reed port 2 stroke clone copy of a Blata 2.6 mini moto engine, 44mm bore & 32mm stroke. Can you find any numbers on the frame?? I have many bikes with that engine. To find parts on eBay, search,

49cc two stroke mini dirt bike parts, and see what shows up. There are also online stores that sell parts, pocketbikeparts and scooterparts4less on the .com
 
#4 ·
Great! Thank you for the quick response!:tango_face_grin:


I will try to clean up and look tomorrow.


From what I'm seeing from googling you are exactly right! According to a website it says mixture 25:1. I may be wrong but I thought most of these used the 50:1 ratio?


After cleanup I will see if I can provide more information and photos!
 
#6 · (Edited)
Here are the only numbers/symbols I could find on the whole frame/engine.

*I tried to add photos but they are not showing up when I add them even though they are smaller than 512KB

I also cleaned the carb and put in fresh gas and it starting and reved up but the clutch was not engaging. I took that apart and the clutch pads/shoes were smooth and I read a post where CAM2 said to sand them down to be rough with 80 git sandpaper. Would that help?
 
#7 ·
You need to make sure the arms swing free and snap back quick....

Deglazing the clutchpads isn't a bad idea just make sure the clutch is pressed on the crank tightly and if it has a reduction transmission make sure it's operating correctly by spinning the bell and seeing if the output reacts...

GOOD LUCK
 
#8 ·
The bell isn't with any damage and no scoring inside, nice and smooth. My clutch is a 3-shoe clutch. I'm guessing if I do replace it would it have to be another 3-shoe or could it be a 2-shoe?

Also is there a thread I can read that shows how to adjust the arms properly?

Thanks!
 
#9 · (Edited)
Are you sure the clutch is pressed onto the crank good...Theres clutches without a keyway slot and you can have that clutch and it could be loose....

Theres no dedicated thread on the clutches..Theyre kinda melded into threads

The rule of thumb is to take a screwdriver and try to pry the arms outwards then see if they snap back quickly..

The Dis-similar metals between the steel shoulder bolts aswell as the aluminum and magnesium cause alot of oxidation between the two...

Remove all the arms..throw away the 3 wavy washers,,clean up the shoulder bolts of any rust aswell as deoxidize the arm pivot holes then use a lil antisieze compound on the screws whenyou reassemble......

Also make sure the clutch arma are on the right way....Its easy to put the arms on wrong............

Posting pics of what youre working with tells alot more than you know........
 
#11 · (Edited)
Thanks for posting the pics.....


You have the 7:1 reduction transmission....Try taking the cover off to see of the chain is still hooked up to the chain gears and that the chain or gears arent busted

As far as the clutch it looks like you may have a sticking clutch arm issue....

The clutch itself looks like its got a huge abundance of epoxy holding it to the crank so its safe to say its not loose.........

Remove the 3 springs and the 3 screws,,clean up the shoulder bolts and the holes,,use a lil antiseize and chuck the wavy washers in the trashbin.....

On your question on whether you can use a 2 shoe clutch...You can if you buy the right one....

Good Luck
 
#12 ·
With all that epoxy on there your going to want to use the proper puller if your going to remove the clutch arm mount off the crank you can get a new clutch and just replace the arms but that clutch has some good life in it still

The 2 shoe raceing clutch is a short life clutch just so you know

Like CAM2 is saying the arms are more then likely stuck take the springs off and work the arms if they feal at all sticky do what CAM2 has posted
 
#13 ·
I would take the arms off just to check everything. If and when you do remove the whole clutch look for a key slot in the crank where the clutch goes, and if so buy a slotted clutch and woodruff key.
 
#17 ·
Nah its not a bother for reassembly....The clutch you have has plenty of pad to it...

When you tighten the screws and before you add the springs make sure the arms swing freely.......If they dont use a file to finetune the mount width,,,,,,,,

remember to throw the wavy washers in the trash,,,Theyre more trouble than help....

Good luck
 
#20 ·
Leave that epoxy piece on, don't think it is going to spin on the crank. When you buy a new clutch take the arms off the new one and put it on the piece that's there. Look on ebay for racing springs: 49cc 2 stroke mini dirt bike parts. The come in 8, 9 & 10 gauge wire. The 10s work better on steel arm clutches, 8 and 9 for alum clutches.
 
#23 ·
When I did mine, I drilled one 1/4" ( 6mm ) where the two are and one 3/16" hole in the middle of the thin lower arm. Just a few grams makes a big difference. I also weigh and match weight of the arms. Match the heavier arms to the lightest one, then you can drill more holes to lighten the whole clutch more. Every time I have done this, all the arms weight were different.
 
#24 ·
I do a whole bunch of different sizes which are dependent on the type of rpm grab im looking for....I pretty much have the hole size to arm weight and spring choice to rpm ratio formulas from all the different ways Ive prepared them all.................

Everything chinese made will all have different weights no matter if they look the same....I once took 5 clutches and 5 44mm pistons and weighed the arms individually and out of 15 arms not one arm weighed the same...LOL...Out of 5 pistons not a weight match either...LOL
 
#25 ·
It all depends on how heavy you are the size of your tires and the way it's geared where your engin makes power start small and work your way up the bigger the holes the higher the rpm engagement

Once you find the sweet spot you will know it on the azz dyno

Once your clutch hits full lock keep it locked don't back off the throttle to where it unlocks and has to slip again

Keep extra springs on you for extended rides

Good luck 🙂
 
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