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Discussion Starter · #1 ·
Changing jets on my '99 XCR-800 is a PITA. After reading all the posts on Snowest and HCS regarding the Holtzmann Engineering ATACC, I decided to splurge and buy one to see if it could be as their advertising states, "like fuel injection for the carburetted sled", or something like that.

First order of business is to make sure your sled is jetted properly to -20* F. or -28* C. as the unit is set from Holtzmann to that temperature. It is adjustable for other temps.

Next you want to determine where your carbs are vented to: inside airbox, or outside airbox. Inside airbox means your carb vents connect to the airbox in some way. You can see in the following photos, my vent tubes connect to the plastic barbs to vent into the lower half of the airbox.
[attachment=54813]
When your filter is getting clogged with snow, the vacuum in the airbox increases substantially, by venting to this location, the pressure influences float bowl fuel level, allowing slightly less fuel into the system to prevent a rich/choking situation for the engine.

Now determine where you want to place the temperature sensing unit. It should be high above the carbs. From the above photo, you can see I placed it a little below the top of the upper airbox, but higher than the floor of the upper airbox. I also made sure to place it between the two silencer cone inlets so cold air will be constantly circulating around the unit. I did not think it would be the best to place it in an area of relative dead air, like in a corner. Also, everything attached to the temp unit should be placed lower. In this photo, you can see the temp unit from the inside.
[attachment=54814]
Off to the left at 7:30 you see the carb vent line, and the blue line is for the altitude sensing chamber. Just barely visible pointing straight down is the air inlet.

Here is the altitude sensing chamber.
[attachment=54815]

Drill a 9/16" hole so you can insert the temp sensor into an appropriate place in the airbox. Use 1.75" of the 1/2" I.D. plastic tube to connect the unit to the reducer fitting, and secure with the included hose clamp. You must leave at least a 3/8" gap between the reducer and white plastic screw. In the background, you can see I plugged the vent barbs with silicone.
[attachment=54832]

Next, drill a 3/4" hole to place the air inlet. I went straight down into the lower airbox. The air inlet must be in the same location as the original carb vents, so this is where it goes. If you look closely, you can see the end of the cute little filter to place over the end of the inlet.
[attachment=54816]

Drill a 9/32" hole for the new carb vent line, which you can see up above in the first pic. The line must remain clear, so you need everything to be pointed downhill.

Now drill a 15/64" hole into the top of your carb plate, this is called the vacuum source. There are different placements for different carbs, so you have to go to the website to find where you'd place yours. Mine is for the Mikuni TM-38 flatslide. Insert the vacuum source fitting, with a little epoxy.
[attachment=54820]
[attachment=54822]
The instructions state to make sure it will not interfere with carb function, as you can see, it does not protrude from the underside of the plate where I placed it.
The instructions are very clear to leave the 1/4" I.D. line connecting the vacuum source to the reducer between 16" and 24" in length. I telephoned Holtzmann to ask about this: the shorter the line, the leaner the mix. A 16" line will be about 1/10th a jet size smaller than leaving it 24". I left mine 20". Note: the tiny line connecting the temp unit to the altitude sensing unit must not be shortened. It must be left the length it comes to you.
 

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it dont look to bad. if you just took your time and did what the instructions said could a guy do it pretty easy? or did you have to call holtzman alot? keep us updated.

look out phil mickelson. lol
 

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Discussion Starter · #3 ·
It only took me 2 hours, and that is because I am so anal about where everything goes and how it looks. If you look at the first photo, you see the screw to the left of the fuel pump mount? I was going to have the carb vent line come out there, and leave a nice smooth loop inside the airbox. I must have thought about this for 15 minutes: "is there enough of a downhill slope? What if I go nuts and climb a steep hill and get some fuel in the line, will it clear, will I burn my motor"? The result is I went with a less visually appealing solution, but a much more reliably draining line. Sometimes I think I need to see a shrink.

I did call Holtzmann about the line length, I wanted to find out why they are specific lengths on the vacuum source line and the altitude sensing chamber line. I believe it has to deal with the volume of the line and pressure changes.
Ya, and I wanted to buy two more vacuum source fittings to place in the tops of my other two carbs, so everything would look balanced. But the guy I spoke to told me there was no justification for doing so, so I didn't press the issue.

Who is Phil Mickelson?
 

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the tech editor the snow goer.
 

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Discussion Starter · #5 ·
I gave her about 13 pulls and she took off. Sounded very strong. I was kind of worried because it has been so cold, the oil is kinda thick, but with the engine block heater I bought from Hi-Perf the motor is soooo easy to pull over. You really need to get one, it makes starting a cold machine a real easy task...not a chore.
Either way, I let the machine idle for a few minutes then blipped the throttle a couple of times. Instantaneous throttle.
The instructions state the pilot circuit may need to be richened. My sled idled very nice, right at 1,500 rpm even after warming up and blipping the joy lever a few times, dropped right back to idle.
My machine has a 50 pilot jet, 145 pilot air jet, 0.9 air jet, mixture screw at 1 turn out from light seat, needle in the 4rth slot, and 470 mains. I'll take it out tomorrow while light to give it some running room and check plug colors.
 

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sounds good. I have thought about the block heater for a while now. just never got to it.
 

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Phil Mickelson did a whole series of technical videos for Ski-Doo back in the early to mid 80's. If you are wanting to learn the basics backing up most aspects of snowmobile theory (motor, clutch, carbs, suspension) then try to find the tapes, tons of good info.

Be careful about all the vent tubes getting located and cut to the proper length. My Brother in law ran his ultra rmk for a year without any troubles, pulled his motor to replace mounts, forgot the variflow line setup and burned his motor on the first wide open run.
 

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Forgot to mention though that the Holtzman setups work great, just make sure everything is in properly.
 
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