bbk and pipe need some carb help!!

[7m-iata]

It just seems too need more? The listing on Ebay says 23hp but thats obviously a WAY optimistic listing lol compression is 155psi I'm running 32:1 castor synthetic my plug is brand new and perfect coffee color I just cant figure anything else out besides the engine running out of cfm from the carb. You have to remember this isn't a dio so its not the stock honda carb it's the stock chinese mikuni I'm unsure of the size I've read somewhere it is 19mm but I've yet to measure it... I just can't figure anything else out Its got a brand new coil on it also just to get rid of that possibility. Would I benefit from some aftermarket reeds? I don't see anywhere for porting since the reed cage just goes to a big open area and my tranfer ports match perfect to my gasket which matches my bore perfect as well /: just at a wall here and when the engine was stock the takeoff was alot slower but I had a few mph more on the stock setup with just a pipe.

[bakaracer]

What brand bore is it? 23Hp rating puts it in s class with the stage6 r/t LC or polini evo 3 or team mhr

[7m-iata]

Not sure its probably just some offshoot brand. Its stamped 73cc on the bore so its not actually a BBK but rather a stock 73cc cyl for a different engine (probably a zuma or something of that sort). I know it was the more expensive kit but I didn't actually order it I bought it "used" (installed but never ran) off of my friend. He doesn't know much about any mechanical things so he just bought the most expensive one (with in reason) might not be from Ebay. I just did a search for bore kits and can't find one that has the same piston as mine. All the kits on ebay have circular ports in the piston mine has large square/rectangular ports on the piston. looks like this kit but its stamped 73cc not 72cc, the casting looks a little cleaner and the cyl head came with it.
http://www.pccmotor.com/70jogmi1ecyb.html

[bakaracer]

Then its a Chinese bore kit. Your luck if its even 9hp. That exhaust your using, is that a mrp or the one from ebay? The only motor came stock 70 is a eton viper 70 quad. For scooter wise they are either 50cc or 100cc for these horizontal minarelli motors. Zuma only came 50cc in the US. Bws100 is outside the US. 47MM bores for these motors is what they call a 70cc but its actually less than 70cc. More like 69cc.

[7m-iata]

Its not the mrp but its not listed on ebay either... the dimesions of the pipe are pretty good measures exactly the same as the high end pipes at the local scooter shop, just looks to be made of a little cheaper material. it may not have a whole lot of power but it def has wayy more than stock. I'll draw up a port map soon and see how it looks, I've searched a few forums and some people are finding that a select few of the ebay bbk have really nice maps /: who knows?? It's always a mystery when you get things second hand, either way its cutting out at high rpms where it should be pulling at its best... and I LOST mph from stock...

[bakaracer]

Try holding the throttle at 1/2, 3/4 and full throttle see where it starts to cut out.

[7m-iata]

it runs about the same at any throttle but it cuts out at high rpm when I let off to about 7/8-3/4 itll pick up a little then bog a little then when I get back to wot it picks up and bogs out. but if I just gun it from a stand still it carries smooth until it hits 38 40 ish then starts to basically surge just slows down and picks up...

[bakaracer]

Jetting to rich on the main it sounds like. Does the carb burble a lot when getting on the throttle around 1/2 throttle?

[7m-iata]

yeah it does. I had one size smaller jet in it before and it starts popping at high rpm and the plug shows lean.. thats one of the reasons I'm looking at another carb, I've tried one size up from where it is now and one size down, either way it basically won't run. If I run one size down it "chugs" from takeoff kinda burbles as you put it until it hits around 15 then picks up a little then starts to pop and backfire. I just cant seem to win with it and the jets and fuel pin are the only changeable part in the carb.

[bakaracer]

Did you try going more than 2 jet size bigger?

[7m-iata]

no that just seemed WAY too big. I've always heard of going 2-3 sizes maybe 4 when you do a 70 kit and pipe but I'm at just about 7-8 sizes (hard to tell because of how mikuni sizes their jets) from the stock #77 I have a 1.4mm jet in it now which is just about a 107.5 120 keihin I tried a 110 mikuni or 125 keihin jet which seems too big too me , but if I go any smaller it runs lean.

[bakaracer]

Are you running it without the airbox?

[bakaracer]

no that just seemed WAY too big. I've always heard of going 2-3 sizes maybe 4 when you do a 70 kit and pipe but I'm at just about 7-8 sizes (hard to tell because of how mikuni sizes their jets) from the stock #77 I have a 1.4mm jet in it now which is just about a 107.5 120 keihin I tried a 110 mikuni or 125 keihin jet which seems too big too me , but if I go any smaller it runs lean.

I don't know where you heard that but it varies on motor, setup and region. Even though you have a horizontal minarelli, it doesn't mean the same jetting applies. Some minarellis come with a 12mm , 14mm, 17.5mm carb so stock jetting will br different. A zuma and jog has the same size carb but come with different main jet size.

[7m-iata]

I was just going off of what I have been reading mostly on here I know people basically run a 100-110 on 70 kits and have alot of success with that setup. yes no airbox theres literally 1 inch or less between my carb and frame though it does get good airflow there (I didnt have a carb when I mounted the engine /: )I've dealt with ery few 2 stroke things besides weed wackers and go peds but I've never had to screw with jetting besides on a 4 stroke which seems to be waaayyyy more forgiving even with turbo setups if your a little rich its nbd.

[bakaracer]

You can't go by what jets work on a dio motor. The 2 motors flow way different from each other. You neef to find out exactly what carb you have first. Mikuni made a lot of different carbs. The ones that came stock on pretty much all the horizontal minarelli style motors have a removable pilot jet. With no air box on jetting will in crease higher then you think. Keep going up on the main till it starts to 4cycle.once there back off 1 or 2jet sizes. Just because guys on herr use a certain size jet or jets doesn't mean its the same for your application. Never go by that rule of thumb. That is the worst tining way of thinking.