We drag race where to stay in a stock class, the stock carb must be used.

Besides the jet kit has anyone done any mods to the stock carb such as boring - taper - oval?
Or any other good idea's.

Thanks, Oldmanracing

 

I run an open air box for trail riding, K&N w/outerwear - but got a Uni foam carb mount for dunes and drags. The foam Uni won't get smushed by the seat and wear holes through the outerwears.

Dynojet needle will provide much much smoother throttle response - the kit is well worth it. With the air flow increases I've made, I also had to up the pilot jet to 45 from stock 40 - one guy on here said Alba recommends 47.5. Not sure why Dynojet does no research on pilots - really lame.

Remove your needle and look in the bottom of the hole it goes in - it is D-shaped in the bottom. This D ledge causes the needle to sit crooked, and rubs the side of the needle jet as it moves up and down. Sanding a flat on the side of the spacers under the clip will allow them to sit flat, elliminating the rubbing and wear, and hopefully promoting better atomization at the same time. This will cause the needle to sit a bit lower though, about half a groove's distance, so manipulation of spacers may be needed to fine tune needle length somewhere between 3rd and 4th groove.

I run the stock carb, and with open air box I use Dynojet 200 main. Some people think this is rich, but its not - maybe I just happened to get a super clean flowing head or something. Anyway, when I put on the carb mount filter for the first time I should have to jet up, and 210 is the largest jet made for this carb. Knowing this, if I bored the carb or even just ported the head and intake manifold, I would surely be flowing much more air through the stock carb than its capable of delivering fuel for. Get a set of precision # drill bits for making your own jets if you go down this road - they come in increments of .002" and are the only means of precise jet drilling I know of.

 

I have done the same needle jet mods to my stock carb as hightower except the pilot jet and it has made a tremendous difference! Highly recommeded! I run a dj 195 main with carb mount k&n and modified end-cap and it runs very good for a stock machine.

 

I have taken past advice and have modified the washer in bottom of slide for needle.
I have also chamfered the front edge of vacuum slide and opened the 2 vacuum ports.
I had to go to a 50 pilot and 3-4 turns out on screw - When down shfting the slide being more sensitive will be leaner and bark back thru the exhaust.
Still using the stock needle in the 4-5 position depending on using airbox or direct mount filter.
Jetting 175 to 185
I have also advanced the timing 4 1/2 degree's.
I have lowered the float bowl and this helped get more consistant midrange power. Plugs would load up and be running rich no matter what height the needle was.
Throttle response is great.

I am now in search of top end power with stock carb.
Has anyone done any experiments and did they work.
Thanks

 

Have you thought about drilling out the 2 small holes in the slide to a little larger size? This would probably not help top end though.

 

Steve,

The 2 small holes in the slide is what I referenced to as vacuum ports.

 

Yeah, I just figured that out! doh! Oh well, it sounds like you have done a lot of work and research on the stocker! thanks for sharing the info!

 

Is there anyone this evening with suggestions to improve the top end flow of the stock carb?

Any help please

 

Eric,

I just love it when someone gives input that makes me do some serious thinking.

What elevation are you at, average humidity and temperature?

Are you using the stock snorkel?

Are you using the stock tubes?

 

Mr. horsepower, what size endcap hole gave you these results? Whatr does cutting the spring do ? Did you put any extra baffle plates in the stock core to quiet it down ?