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Question About Jetting 1986 Ski Doo Formula Sp

1735 Views 5 Replies 4 Participants Last post by  billww, 
M
Just was given an either 85 0r 86 ski doo formula sp that has been sitting around a long time. Needed a lot of work but i am done with most of it. However i do have one issue. The carb that was stock with it was completely rotted out from rat pee or something and needed replaced. I bought 2 carbs off ebay that came together supposedly the 34mm mikunis i needed to match the stock one. However once i got them i noticed they were actually 38's as close I can measure (might be 40's) I got two of them so i would have one to replace and one for parts also giving me options for jets. I tried to fit one of them in the carb boot and amazingly it fit ok. So i figured i would give it a shot running with the 4mm larger. My questions are as follows:

1. Is my fuel pump going to be able to supply the fuel this monster needs>?

2. What jets should I start out with to be in the ball park of a smooth running motor? As it is stock i have to choke it halfway to keep it running and even then when i goose it the motor bogs and dies most of the time. (this is with the airbox off)

3. Is it even possible to jet and tune this thing so that it runs right with this configuration? I wasnt sure if the motor would draw enough vacuum to use the larger carb.

4. HOw much more power can i expect from this "high performance" setup :p

Thanks for any suggestions you can give. This site is a great resource already to me just by reading the existing posts. I figured it would be a good place to ask specific information as well.
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B
SEND THEM BACK AND GET RIGHT ONES . I CAN NOT BELEVE HOW MUCH TIME AND MONEY ARE SPENT BUYING CRAP SIGHT PARTS IF YOU GO TO A DEALER YOU GET WHAT YOU WANT WITH A BIG G . YOU ARE ASKING ABOUT ALL THESE THINGS TO FIX YOUR SHIPPER,S WANT TO SELL YOU ALL THE MOD PARTS TO FIX HIS SREW UP . OR BETTER YET LET MET SELL YOU ALL THE PARTS NEEDED TO MAKE YOUR SLED RUN GOOD NOW. IF IT IS NOT STOCK IT WILL NOT RUN RIGHT.:
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M
WOW!!! I can't believe you are so angry that I would ask a non-stock jetting question on this forum. And I can't believe you expect me to drop hundreds of dollars at a dealer to buy a carb for a beaten up sled i got for free. I can see how maybe you don't want to spend the time messing with anything non-stock but I have the time and would like to try. YOU apparently you have a enough time to slam me for asking a simple question that you don't HAVE to respond to. Besides many people buy larger carbs and rejet their sleds for more power so your last statement "IF IT IS NOT STOCK IT WILL NOT RUN RIGHT" holds no water.
I am simply trying to make lemonade out of lemons here because of a shipping error and didnt want to ship this item back to canada and thought it might be fun as a project to tinker with (I have the time for the most part) The sled runs but has a lot of holes in the power and needs the choke on to idle. I know the jetting is off and just wanted a simple place to start as I have never had to do anything but stuff with stock jets.

Really you are unbelievable!

P.S. your caps lock is stuck on..........


Thanks for any responses anyone else can give me.....
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P
now remember hes been working on sleds longer then we've been sitting on the seats of snowmobiles :blahblah: but the carbs you bought would have to be 34mm carbs if they still fit into the original stock boot. but if they are bigger and happened to fit the larger carbs are going to intake alot more air because of the larger opening so you will need a larger jet. Take the old jet out of the bad carb and see what size it is. Then i would try buying a few jets going up in increments of 10 in size from the stock size until you find one that seems to make it run pretty good with no choke. When you need to have the choke on it means your not getting enough fuel in with the air so you have to choke off the air for it to run right. As for the pilot jets and such you may need to change those but i'm not so sure about what you might need as for a size in those. But as far as buying carbs from the deal is outrageous... you could probably buy another used snowmobile for the same price as they want for a carb. dont listen to billww hes a bull####ter.
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WOW!!! I can't believe you are so angry that I would ask a non-stock jetting question on this forum. And I can't believe you expect me to drop hundreds of dollars at a dealer to buy a carb for a beaten up sled i got for free. I can see how maybe you don't want to spend the time messing with anything non-stock but I have the time and would like to try. YOU apparently you have a enough time to slam me for asking a simple question that you don't HAVE to respond to. Besides many people buy larger carbs and rejet their sleds for more power so your last statement "IF IT IS NOT STOCK IT WILL NOT RUN RIGHT" holds no water.
I am simply trying to make lemonade out of lemons here because of a shipping error and didnt want to ship this item back to canada and thought it might be fun as a project to tinker with (I have the time for the most part) The sled runs but has a lot of holes in the power and needs the choke on to idle. I know the jetting is off and just wanted a simple place to start as I have never had to do anything but stuff with stock jets.

Really you are unbelievable!

P.S. your caps lock is stuck on..........
Thanks for any responses anyone else can give me.....[/b]
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Can you get me the model number off the original 34mm Mikuni and I'll look and see if I have a matching carb. I'll need to know what the original main jet and pilot jet was. If I do, you can have it if you pay the shipping.
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B
I beleve that the 85 and 86 may of came with 38s and the 87 and 88 40s then they down sized in 89 They kept getting biger trying to keep up with the 600s but did not need to the 85 th 87s where one of the fastest stock sleds I ever saw 0 to 80. I,am sorry that you think I was saying that to you I was saying that about the parts co . So many times we buy parts and wait and wait to get are sleds on the snow and when the part comes its the wrong one.
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