APT Smart Carb Testing today 40mm Billet Sphynx 363

[Jerry Hall]

It's funny you say that because my pilot and needle have always been leaner than what most people say they run or whoever the builder is recommends. I can literally count on my hands the number of pilot jet sizes that match mine that I have seen on the forums over the years. Mine is in the low 40's right now and I still feel it is rich, my needle diameter is about the only difference I see in my needle which also affects what most would call the bottom end.

You probably have a Keihin carb that has a worn out needle jet.  This is a common problem with carbs that have some miles on them.  You need to find someone in your area that has bore guages that can measure holes in the .1000" range and has the accuracy of .0001".  If you cannot find anyone send me the carb and I can measure the needle jet.  

If the needle jet is worn out it is new carburetor time and or you have to keep installing leaner jet needles to try to compensate for the ware in the needle jet.  Keihin does not offer replacement needle jets.  Mikuni does offer needle jets and typically offers about 50 different sizes to fit each of their models to aid in the fine tuning of their carbs.

[RyanWsly]

You probably have a Keihin carb that has a worn out needle jet.  This is a common problem with carbs that have some miles on them.  You need to find someone in your area that has bore guages that can measure holes in the .1000" range and has the accuracy of .0001".  If you cannot find anyone send me the carb and I can measure the needle jet.  

If the needle jet is worn out it is new carburetor time and or you have to keep installing leaner jet needles to try to compensate for the ware in the needle jet.  Keihin does not offer replacement needle jets.  Mikuni does offer needle jets and typically offers about 50 different sizes to fit each of their models to aid in the fine tuning of their carbs.

Ya I thought something that at one time, but after one 36PJ, 38PJ, 38 PWK A/S, a handful of 34 PJ's, one new 36 PWK, a few different bottom ends with and without new cranks bearings and seals, a few different cylinders ranging from 100% stock to a 300 PV, a handful of different reed cages new and used, misc pipes, silences with and without new packing, a few different ignition combos and a partridge in a pear tree I have decided mine is just an anomaly over the years so I just put it were it likes it and find something else to worry about in life.

[Tbone07]

Yep, and he is not kidding. Its like feeding your R a bunch of steroids. You will be surprised how much power is being hidden by your Kiehen carb. You will be asking yourself if someone added 50cc's to your bike.

You might have just made me spend another $400 this offseason, Puma....:disgust:

[j@y]

You might have just made me spend another $400 this offseason, Puma....:disgust:

Don't worry I called APT today and from the conversation that we had you probably won't get the cast smart carb until next season starts lol.

[Jerry Hall]

Ya I thought something that at one time, but after one 36PJ, 38PJ, 38 PWK A/S, a handful of 34 PJ's, one new 36 PWK, a few different bottom ends with and without new cranks bearings and seals, a few different cylinders ranging from 100% stock to a 300 PV, a handful of different reed cages new and used, misc pipes, silences with and without new packing, a few different ignition combos and a partridge in a pear tree I have decided mine is just an anomaly over the years so I just put it were it likes it and find something else to worry about in life.

Are you saying that your pilot jets and needles tend to be leaner than most other guys with similar engine packages regardless of what carburetor you are using?

[trx250scar]

Are you saying that your pilot jets and needles tend to be leaner than most other guys with similar engine packages regardless of what carburetor you are using?

That's What I gather. I Also am confused

[RyanWsly]

Are you saying that your pilot jets and needles tend to be leaner than most other guys with similar engine packages regardless of what carburetor you are using?

Correct, similar location and air intake setups also. I just thought it was odd that Tony said he felt most Keihins were rich on bottom after switching to the smartcarb and mine always tended to want a pilot jet smaller than what most were running or recommended. For Example if you took any of the random combos I listed and put a 50 plus pilot in the thing it would have a very poor idle, have a lag coming off idle-1/4ish throttle area and smoke excessively at idle. I chased this for quite a while always wondering, trying different fuels, air filters, filter oils, all kinds of crazy stuff and finally just rode the thing and quit wondering. Never had a failure or a complaint from anyone who has rode it so I suppose it is must be ok. I just still feel like it could run cleaner on bottom which is why I am interested to see what Kyle thinks of the power delivery because he seems to be pretty anal with his jetting.

[Pumashine]

After working with big bore cylinders for 10 years you will see the Keihins tend to be too rich on the bottom end. The Polonda wanted to be much leaner than I could be comfortable with. The Shearer in-frame Puma pipe took me hours of time to get close. Using leaner needles and adjusting clip position. Always seemed to be too rich or too lean. I melted the strap over the electrode on my spark plug. But I did learn what too lean feels like. Like the spark plug is popping or snapping each revolution. I finally gave up and hung the Shearer in-frame on the garage wall. I was so very disappointed as this pipe had truly amazing power on the top end. I got the LED in-frame Puma pipe and it seemed to work OK on the bottom end. But after installing the SC it went from OK to simply amazing bottom end snap and power. Never too lean, just right I hope and the top end seems a little lean. They are going to have to make some FMR's which will let more gas into the carb at WOT. Whatever Kyle ends up with I want one richer than that.

[udontknowme]

It's funny you say that because my pilot and needle have always been leaner than what most people say they run or whoever the builder is recommends. I can literally count on my hands the number of pilot jet sizes that match mine that I have seen on the forums over the years. Mine is in the low 40's right now and I still feel it is rich, my needle diameter is about the only difference I see in my needle which also affects what most would call the bottom end.

alot of people dont know how to tune a carb. not saying im a expert but some people just really dont have a clue. so if joe blow says he uses 55p, it dont meen sqaut because hes probly got the wrong size in there. there for you cant really gain any perspective from what joe blow says. depending on the circumstances, low 40's pilot isnt uncommon. seems like i got 42p in one of mine bikes. might even have 2 bikes in the low 40's. cant recall off top of my head. youll know when its gets to small. probly start sounding tingy and good chance it wont run with the choke off unless theres a ton of heat in the cylinder, even then it may not run without choke. this is the common pattern ive seen from keihin when pilot is to small

[86-250rbuild]

Don't worry I called APT today and from the conversation that we had you probably won't get the cast smart carb until next season starts lol.

Yea i talked to tom last week about my 38 cast i placed order with on may28. . He said at least 2 more months. But u can spend the 675 and get the billet. Wooooo

[jcs003]

i have a 42 pilot in a ported stroker motor and it runs well from bottom to top.

john

[j@y]

Yea i talked to tom last week about my 38 cast i placed order with on may28. . He said at least 2 more months. But u can spend the 675 and get the billet. Wooooo

how much do you have to put down as deposit on the pre-order? Tom said I could wait until they get them in stock but I get the feeling they're going to sell out fast.

[86-250rbuild]

well i  preorded payed the whole price

[j@y]

Yeah I went on the site and saw you have to pay full purchase price. I may look into a 38mm lectron possibly

[Burns363R]

Did another WOT long pull tonight.  Bike felt great.  I changed the cover on the Go Pro and you can hear it alot better. The Go Pro is mounted to the handle bars, hence the weird angles when I'm doing wheelies.  The pics of the spark plug are from right after killing the throttle when i came back into the garage.  Looks pretty good to me.  sounds like we have a winner.

http://youtu.be/lBFdg-jGZ98?list=UURhJ3oFnLARwWYVG9fDuWKQ