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Discussion Starter · #1 ·
Hey guys! I have a mototec demon 50cc 2-stroke mini dirt bike, I've been ordering a few mods for it, so far I picked up a HD clutch and fiberglass reeds, and I'd like to get a high performance carburetor...would that be a worthwhile mod and could anyone reccomend a size/model carburetor? There are plenty for sale on ebay, I want to make sure that I order the correct one. Thanks for your help!
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Discussion Starter · #5 ·
Hey guys! I ran into some issues with the stock carb, gas started leaking from the overflow line pretty bad, I tried fixing it with no luck. I get a bit nervous about working on carbs because Im not very experienced at it, so I figured I was taking the safe route by ordering an 11mm replacement (that'sthe size it came with) ($15). Installation was easy, and it doesn't leak, but here's the issue...the bike has less power...I can hold the throttle wide open and it struggles to take off with me on it (I weigh 147 lbs), and once it gets rolling, it's still very sluggish, and it starts harder as well. With the old carb, one pull and it fired up...now its 5 or 6 pulls. I installed carbon fiber reeds while I had the carb off..I didn't expect major power gains but I didn't expect a loss of power, either. Im wondering if this is a jet issue? These carbs are so cheap Im tempted to order one of those Dell'orto sha 14mm copies instead of messing around with this one. I just want the bike to be drivable. Thanks for your advice.
 

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Discussion Starter · #9 ·
Hey guys, new to the site. I bought the same bike you have. Where are you ordering these parts from???
Hey guys, new to the site. I bought the same bike you have. Where are you ordering these parts from???
Welcome! I've bought just about everything from Amazon &Ebay. Have fun with your bike!
 

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Welcome! I've bought just about everything from Amazon &Ebay. Have fun with your bike!
Hi, new to the forum. Bought one of these for my son for his birthday and I'm looking to upgrade the carb as well. Stock carb boggs down or shuts off at full throttle and immediately starts pouring fuel out of the overflow when it sits. I've tried adjusting the idle screw but I either can't find the sweet spot or thats not the problem. I tried ordering one that came up in the search results in Amazon, but it didn't fit. It's pretty tight space wise for the carb, so I assume I'll need some sort of flange to turn it and get any bigger carb or filter in, but i just don't know enough about dirt bikes in general to make any sort of informed decision on what to buy. Any way you could drop links to ebay/Amazon or wherever of exactly what I need to complete this? Carb, flange, filter, etc. If for some reason thats not allowed, just size of each?
I really appreciate it, hoping working on and modding this bike will be a good learning experience for me and my son. Anything to get him out of the house.
 

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If it bogs down wants to die at wide open throttle then it's setup to lean and the needle needs to be raised up if fuel dumps out the over flow then the float hight needs to be adjusted by carefully bending the tang.

They are never properly setup from the factory the adjustments are part of dealership prep if you did not buy from a dealer then you have to adjust the carby yourself
 

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If it bogs down wants to die at wide open throttle then it's setup to lean and the needle needs to be raised up if fuel dumps out the over flow then the float hight needs to be adjusted by carefully bending the tang.

They are never properly setup from the factory the adjustments are part of dealership prep if you did not buy from a dealer then you have to adjust the carby yourself
Great, ill give those a try. If I can get that going would you recommend just sticking with the stock carb or upgrading?
 

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I recommend the pumper carburetor retrofit kit if it's not to long and can fit in your frame the nice thing is it has no float so it doesn't leak gas and can be adjusted by turning the screw instead of having to replace jets you need the intake manifold and air filter with the choke to make it work.

The stock carburetor is honestly the best carburetor after modifications the petcock delete is the best mod for it

 

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For the taper bore, some people use a dremel, others a taper bore bit for a drill. Can be had at Harbor Freight or a hardware store. The trick is to not get all the way in the middle. Only the outside.
For the petcock mod, will use a drill bit but before that we use JB weld to fill the inside. Then drill a hole straight through.
 

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Unless it's a real SHA the clones you get on eBay are junk. Just type in pocket bike carb and look for a primer bulb for generic pumper carb, super easy to tune if you're not mechanical for around $20 with manifold filter etc.


If you want to spend about $50-60 on the real deal pick one of these
  • Walbro HDA48 15mm
  • Walbro WT603 16mm (Might need bracket)
  • Walbro WT813 16mm w/ acell pump (better than WT603)
  • Walbro HDA48D 16mm (no return line)
 

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Unless it's a real SHA the clones you get on eBay are junk. Just type in pocket bike carb and look for a primer bulb for generic pumper carb, super easy to tune if you're not mechanical for around $20 with manifold filter etc.


If you want to spend about $50-60 on the real deal pick one of these
  • Walbro HDA48 15mm
  • Walbro WT603 16mm (Might need bracket)
  • Walbro WT813 16mm w/ acell pump (better than WT603)
  • Walbro HDA48D 16mm (no return line)
I have heard the wt603 and 668 do tend to lag on throttle, also wt 990 is exactly as 813 but without accel pump, i was told better max speed vs accel ( accel pump)
 
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