Difference in carbs

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seacamper

Banned
#1
#1
Whats the difference in carbs between 24mm
97cc Carburetor with 24 mm Air Intake for Baja Blitz, Dirt Bug, Doodle Bug, & Racer Mini Bikes (Standard of Japan)
and 19mm
97cc Carburetor with 19 mm Intake for Baja Blitz, Dirt Bug, Doodle Bug, & Racer Mini Bikes (Huayi)

I just sent for a kit from Dudleydoright (Thanks DDR for spending the extra time getting me set up) because my carb is bogging down on a brand new old style DB. I was wondering if the 24mm would give me a performance upgrade if I had a 19mm on it now.
Tom
 
vette66_00

vette66_00

Active Member
#2
#2
If you figure out how much you are going to spend trying to get the stock motor to run right...ie carb kit, new carb, couple of times to church to pray (cause it will need an act of (pick your god) to make it run right consistently) and your time. You will have paid for a 6.5, a clutch, and in your new free time you can fix the world economy.

Don't buy any upgraded carb for the 97cc engine, its not worth the time and even more headaches its going to cause you, having to figure out a new set of jets to get it to run right.
 
S

seacamper

Banned
#3
#3
I agree to a point. I have a 6.5 conversion and it is just an incredible difference. My problem is I do not want to cut my boys loose with it for a couple years. Just yesterday I let the 11 year old use it, and he lost control in a wheelie where he jumped off the bike with his hand on the throttle and the bike did a full circle wheelie with him holding on and it smashed into my other son's bike. I have no problem investing in a jack shaft that can be used when we do the 6.5 conversion and no problem figuring out the jetting issues. My 2 "new style" 97cc DB's are actually very perky and reliable. Their get up and go is more related to the gearing. I just picked up an old style 97cc and it is the one with carb issues. My boys ride with friends so i like to have spares to keep the bickering down. I am hoping to get the carb issue knocked out on that one and put a jack shaft on it and maybe my wife will ride it.
 
D

Dudlydoodleright

New Member
#6
#6
Generaly when a carb is too big one needs to run a lot of fuel at, and just off idle, as there is too little vacumme to draw gas. Then if the carb has no accelorator pump it dies on progression. Some will run still more fuel to help with that-and that is how a motor that is a stage 2 or 3 gets off low rpms and runs at high rpms with a long cam. At lower rpms a carb that is too large when the gas is hit while at too low an RPM it may result in cyclinder overfilling and rebound. Literaly the cylinder fills up too much and before the cam closes the valve the fuel mix flows backwards and the cylinder empties-if this happens and you have the air filter off you can see the fuel mix blow backwards out the carb. Now I don't know if the 19mm carb is too big as I don't know were they get 19mm from--but that would be like a 27mm carb on a 200cc motor--REALLY BIG!!! We all hope you get the carb and tell us it works and kicks butt. We are also thinking that the way they came up with 19mm is not the coventional measure or if it is you may have too big a carb for stock valves, compression and cam---hope you get something that works good and will like to hear what you have to say either way--PS I can't take a picture right now and load it to this post but I have a DB30 carb right here next to my keyboard I'll shot it and post it in a few minutes it's 16mm-I'll put my meteric ruler to it so you can see.
 
S

seacamper

Banned
#7
#7
Dudlydoodleright said:
Generaly when a carb is too big one needs to run a lot of fuel at, and just off idle, as there is too little vacumme to draw gas. Then if the carb has no accelorator pump it dies on progression. Some will run still more fuel to help with that-and that is how a motor that is a stage 2 or 3 gets off low rpms and runs at high rpms with a long cam. At lower rpms a carb that is too large when the gas is hit while at too low an RPM it may result in cyclinder overfilling and rebound. Literaly the cylinder fills up too much and before the cam closes the valve the fuel mix flows backwards and the cylinder empties-if this happens and you have the air filter off you can see the fuel mix blow backwards out the carb. Now I don't know if the 19mm carb is too big as I don't know were they get 19mm from--but that would be like a 27mm carb on a 200cc motor--REALLY BIG!!! We all hope you get the carb and tell us it works and kicks butt. We are also thinking that the way they came up with 19mm is not the coventional measure or if it is you may have too big a carb for stock valves, compression and cam---hope you get something that works good and will like to hear what you have to say either way--PS I can't take a picture right now and load it to this post but I have a DB30 carb right here next to my keyboard I'll shot it and post it in a few minutes it's 16mm-I'll put my meteric ruler to it so you can see.
Click to expand...
I am fine with the stock carb re jetted, I just saw these and said "Hmmmmmmmmm":confused1::confused1::confused1:
 
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Dudlydoodleright

New Member
#8
#8

My calipers put it at just under 16--the port running into the block is 16mm so anything bigger than that will work only to the point were that port loads up-if you grind the insulator to blend from the carb to the block a 19 might help but the larger carb ---I can only hope for those who get one that they can make it work.
 
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supernova

Banned
#10
#10
vette66_00 said:
If you figure out how much you are going to spend trying to get the stock motor to run right...ie carb kit, new carb, couple of times to church to pray (cause it will need an act of (pick your god) to make it run right consistently) and your time. You will have paid for a 6.5, a clutch, and in your new free time you can fix the world economy.

Don't buy any upgraded carb for the 97cc engine, its not worth the time and even more headaches its going to cause you, having to figure out a new set of jets to get it to run right.
Click to expand...
I totally agree. But if you must have a small displacement engine go with the greyhound 2.5ohv, $94 at HF on sale and it looks like a tiny 6.5 and was used on two bikes in the project logs. I asked and he said it ran great, seems like the best alternative to a 6.5 swap unless you count a little briggs. The new style DBs dont look to be as easy as far as a briggs goes, my daughter's old style is a dead reliable runner that I even ride. Yeah trying to get the 2.8 to run right seems like whizzin into the wind to me but an ambitious thing to do!:thumbsup:
 
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