670 High Altitude Compensator HAC Calibration
I know many are in favor of removing the HAC when it fails and jetting like a model with out HAC. That may be the best in most cases, but I wanted to share something here I learned by reading on another Snowmobile forum.
You can indeed actually recalibrate your HAC pod, if the diapram is good, and it is quite simple. First let me back up.
Symptoms:
The sled was super lazy and rich through the entire rpm range. Top rpm we could get was about 7200.
Specs and Jetting:
1996 Ski Doo 670 Summit with fresh top end.
M-10 Suspension
Jaws twin pipes
Air box gutted (shelf completely removed)
Mains: P 370 M 360
#75 pilot jets
Stock 7DPI 1 clip in #3 notch
Altitude and Temps:
Plug reading were taken at 4200 ft. and 12 degrees F and still safely on the rich side a bit.
40 mile test ride after recalibration was from 4000 ft to 6500 ft and temps in the teens F.
So here is what we did.
1: Remove the HAC pod from the air box and take it into a heated area at room temperature (60 ~70* F.) We were at 4200 Ft. Alt.
2: Clean all the blue sealer compleely from the plug (screw) on the back of the pod and remove the screw and the O-ring that seals it. clean and grease the O-ring place it on the screw and set aside.
3: Apply a light suction or light air pressure to the hole to assure the diaphram is good and will hold a vacuum and does not leak.
4: If all is good, I put a few (3~4) drops of "Power Service" diesel fuel conditioner in each side of the diaphram. (both sides, back where plug was removed, and front into the center vacuum tube) This will lubricate things, condition old rubber diaphram a bit, disapate moisture and aid against feezing up.
5: Now apply light air pressure to the back hole where plug was removed. (yeah,, blow on it) If you get fuel conditioner in your mouth spit repeatedly till taste is gone.
6: While applying pressure a small brass pin will slightly protrude through the front center vacuum tube. Get a hold of this brass pin with your fingernail and hold it while you replace the rear plug and greased O-ring.
5: Then carefully loosen the plug, slowly letting air out till you see the brass pin going back into the tube then stop it by screwing in the plug. Now measure from the top of the tube to down in the tube to the tip of the brass pin. When you catch it at 5 mm tighten the screw securely. If you miss it you can have a re-do. Actually all the info we can find says 3mm to 7mm. I chose 5mm because it was center spec. But if you are a little either side I think you would be good to go.
6: If you have time let the pod set over night and re-measure to assure it is not leaking. Or reinstall it and re-measure in a few days just to be sure the pod is air tight inside.
This took our 96 Summit 670 from a lazy fat dog that would only turn 7200 rpm to a screaming machine that easily runs to 8200 rpm in a blink.
We have 50 miles on it now and all is still good. We have only been to 6500 feet Alt. But she ran the same there as she did at 4000.
Hope this helps someone as it did us. Here is a pic of my son and the 670 after recalibration at 6500 feet.
Jeff
I know many are in favor of removing the HAC when it fails and jetting like a model with out HAC. That may be the best in most cases, but I wanted to share something here I learned by reading on another Snowmobile forum.
You can indeed actually recalibrate your HAC pod, if the diapram is good, and it is quite simple. First let me back up.
Symptoms:
The sled was super lazy and rich through the entire rpm range. Top rpm we could get was about 7200.
Specs and Jetting:
1996 Ski Doo 670 Summit with fresh top end.
M-10 Suspension
Jaws twin pipes
Air box gutted (shelf completely removed)
Mains: P 370 M 360
#75 pilot jets
Stock 7DPI 1 clip in #3 notch
Altitude and Temps:
Plug reading were taken at 4200 ft. and 12 degrees F and still safely on the rich side a bit.
40 mile test ride after recalibration was from 4000 ft to 6500 ft and temps in the teens F.
So here is what we did.
1: Remove the HAC pod from the air box and take it into a heated area at room temperature (60 ~70* F.) We were at 4200 Ft. Alt.
2: Clean all the blue sealer compleely from the plug (screw) on the back of the pod and remove the screw and the O-ring that seals it. clean and grease the O-ring place it on the screw and set aside.
3: Apply a light suction or light air pressure to the hole to assure the diaphram is good and will hold a vacuum and does not leak.
4: If all is good, I put a few (3~4) drops of "Power Service" diesel fuel conditioner in each side of the diaphram. (both sides, back where plug was removed, and front into the center vacuum tube) This will lubricate things, condition old rubber diaphram a bit, disapate moisture and aid against feezing up.
5: Now apply light air pressure to the back hole where plug was removed. (yeah,, blow on it) If you get fuel conditioner in your mouth spit repeatedly till taste is gone.
6: While applying pressure a small brass pin will slightly protrude through the front center vacuum tube. Get a hold of this brass pin with your fingernail and hold it while you replace the rear plug and greased O-ring.
5: Then carefully loosen the plug, slowly letting air out till you see the brass pin going back into the tube then stop it by screwing in the plug. Now measure from the top of the tube to down in the tube to the tip of the brass pin. When you catch it at 5 mm tighten the screw securely. If you miss it you can have a re-do. Actually all the info we can find says 3mm to 7mm. I chose 5mm because it was center spec. But if you are a little either side I think you would be good to go.
6: If you have time let the pod set over night and re-measure to assure it is not leaking. Or reinstall it and re-measure in a few days just to be sure the pod is air tight inside.
This took our 96 Summit 670 from a lazy fat dog that would only turn 7200 rpm to a screaming machine that easily runs to 8200 rpm in a blink.
We have 50 miles on it now and all is still good. We have only been to 6500 feet Alt. But she ran the same there as she did at 4000.
Hope this helps someone as it did us. Here is a pic of my son and the 670 after recalibration at 6500 feet.
Jeff
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