Carb slide vent hole size

[Venturous Randy]

It is my understanding that there is a difference between the MKI and MKII on the difference in the diameter of the hole in the slides. I read in another post about using a dinajet kit and it said with the weaker springs, the slide hole needed to be opened up and frankly, that did not make sense to me. I would have thought that weaker springs would require a smaller slide hole as a larger allows more vacuum to pull the slides open quicker as would weaker springs.

What would opening up the hole do on the slide actuation, especially with the washer change and extending the needle out .030 more on an 83 model?

RandyA

[Gearhead]

I dunno about the specifics of any DJ kits for the Venture. In general they supply different slide springs and different needles, and they often recommend drilling out the vent hole. The DJ slide springs aren't necessariy weaker, though - just different; I've noticed in the past different spring wire diameter and different length. Since there's a whole new needle with different taper, all bets are off when trying to make sense of it.

 

That being said, I spoke with somebody, maybe DJ tech support, not sure, who said that enlarging the vent hole in the slide doesn't cause MORE lift of the slide, but rather QUICKER lift of the slide, for supposed quicker throttle response.

 

Jeremy

[Venturous Randy]

That being said, I spoke with somebody, maybe DJ tech support, not sure, who said that enlarging the vent hole in the slide doesn't cause MORE lift of the slide, but rather QUICKER lift of the slide, for supposed quicker throttle response.

 

Jeremy

 

That would be my thinking also. I was wondering if anyone had enlarged their slide holes and if they could tell a difference. Thanks for the response.

RandyA

[pegscraper]

I opened mine up a little bit. I couldn't tell anything, but I stayed pretty conservative with it. I didn't open them up as much as I was told to do. One of these days I'll go back and do them the rest of the way. I know, not a 1st gen, but hey.

[CrazyHorse]

Its my understanding the that the airjet under the diaphram controls how fast the diaphram responds the smaller the faster 1983 was 180 my 1990 is 170. I also put in 83 needle set which have a more aggressive taper at the end my 1990 and multiple notches to raise or lower the needles. The 170 air gave quicker throttle response for me. Squeeze knows alot about this. Maybe he'll chime in. Now with the 83 needles set to the lowest needle point and then lowered again using the 5bikes method i get about 42 mpg plus the nice benefit of better power if I want to crank on the throttle due to the more aggressive needle taper.

[Gearhead]

Hmmm...that jet is called Pilot Air Jet #(1 or 2). It controls the air to the pilot circuit (idle and low throttle) through the coasting enrichers. Not sure how it would affect slide opening rate.

 

Jeremy

[5bikes]

The air jet under the diaphram was filled in with JB Weld (24 hr stuff) and then redrilled out with a #53 drill bit. Was a guess.

And yes I do have slightly better throttle response. Had a hesitation just off idle, now gone.

Was a "Squeeze" idea I modified.