95 Summit 670 HAC

[Coldfinger]

95 Summit 670 HAC gone bad

Can someone tell me how to tell if the HAC is in good condition?

 

[sledsrock]

Many will say there is no way to tell...........but

I have found not only does the HAC compensate for altitude it accounts for temp changes as well. I proved this when I was experiencing a very rich situation. What i found was If you remove the HAC, and measure the pin (needle) protrusion, keeping in mind temperature changes will (should) cause the pin to change the protrusion depth. As the HAC gets colder the pin will drop down in deeper (less protrusion) into the HAC, as the HAC gets warmer the pin will protrude out further. This is true for altitude too, the higher the altitude the pin will protrude out further, and the opposite for the lower the altitude. So, pin moving out will result in a leaner setting, and pin moving in will result in a richer setting. Measure the pin protrusion at room temp, throw it in the freezer for a little bit and measure it again, the pin should have dropped down deeper into the HAC. If there is no pin protrusuion change, then it is bad. A hair dryer will work too.....only opposite. All the HAC is is a sealed aneroid chamber that controls a tappered pin (needle). I hope this helps some.

 

[Coldfinger]

The pin is approx 10 mm from the top at 39 degrees temp. I heated the HAC with a blowdryer and it didn't appear to move the needle.

So if the HAC is bad, as it seems it is, do I just hook it back up and leave it in place (convenient way to plug the airbox hole and hose ends)?

Anyone know for sure what jets to run. I've already dropped the pilot jet from 75 to 65. The mains are now 420 (stock).

Thanks.

Jim

 

[sledsrock]

To remove HAC..........

Use the 95 Formula SS jetting specs and you will be close. You can leave it in place, but need to vent the float bowls to atmosphere.

If the pin did not move, then it's bad. If you wanted to replace it, I have a source - the last one I bought was about 1/2 the price of BRP. Same exact unit.

 

[Coldfinger]

I partially disassembled the HAC tonight. If it's bad what do I have to lose, I figured.
Here is what I found -

That thing is so simple I can't believe they want $350 or so for it. I did find a source for $279 though.

The needle is attached to a diaphram which creates a sealed chamber on the back side where the protrusion goes into the airbox.

The needle is adjustable by removing the nut and dual hose barb. Then remove the center tube with a wrench on the bottom nut. This will expose the needle.

Next, on the backside scrape away the paint that seems to seal the back and you will expose a slotted screw. Remove that screw and o-ring.

Then, grab the needle and pull it up, and, at the same time install the screw with oiled o-ring. This seals the backside chamber and the air pressure inside holds the needle up.

Install the tube, dual barb, nut, and it should be good to go again (at least for a while). If the air leak was thru the o-ring, hopefully this process will help seal the o-ring. If the air leak was thru the diaphram itself, it will no doubt leak again and the unit is shot. I'm not sure what the needle depth should be, but I've heard 3-7mm and mine ended up at 5mm after my experiment so I guess it's better than the previous 10-11mm.

I suppose it may be possible to squirt some liquid electrical tape or something into the backside to try to seal a small leak in the diaphram.

 

[sledsrock]

Now your gettin the idea..............so simple, yet so darn expensive. I actually did a cutaway on my old one. I found a supplier a couple years ago that was getting about $179.00 for the same exact thing, they are (were) the vendor for BRP.