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Discussion Starter · #1 ·
Iv heard alot of guys say to put 420 main jets in my proX 700. How safe are these. I do not want to melt a piston or get stranded somewhere. And these take the standard mikuni hex style jet?
 

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Discussion Starter · #3 ·
how much of an improvement can i expect to see over stock jetting?
 

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420 mains with a gutted airbox is safe at sealevel down to -5 * and you could still WOT for 1/2 mile ,colder then that or stock air box you will want to have 430's if your going to run it WOT on cold days. Gutted air box makes it act one size richer then stock.

I would never tell any one to jet this close unless your capable of reading plugs ,wash and know that you have 91+ fuel in the tank...... your that close on extream cold days!
 

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to give you an idea, i was with someone that had a completly stock 700 and they ran down to 410's in 0* weather. i would not suggest running that small of jets but if you want the best performance possible and are very good at monitoring what XC Mark mentioned, it can be done. this was in MN also, different barometeric pressure then out east.

430's- way safe, not making all power
420's- still safe to about 0* to -10*, much better performance
410's- doable to about 10* to 0*, very noticable power difference from the 430's, requires constant monitoring of piston wash
 

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if you jet it, be sure to get OEM jets, no aftermarket jets, as the size they come in cant always be trusted.. have learnt this the hard way,

just my 2c
 

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so when you guys say safe till -10* is that -10 c or -10 f just so i know i have 420S in my 600 with a gutted airbox. i live in ont can

thanks
 

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420 mains with a gutted airbox is safe at sealevel down to -5 * and you could still WOT for 1/2 mile ,colder then that or stock air box you will want to have 430's if your going to run it WOT on cold days. Gutted air box makes it act one size richer then stock.

I would never tell any one to jet this close unless your capable of reading plugs ,wash and know that you have 91+ fuel in the tank...... your that close on extream cold days![/b]
So a gutted air box actually loses air flow on those?
 

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So a gutted air box actually loses air flow on those?[/b]

No gutted air box reduces the amount of vacuum in the airbox , the carb vent lines are vented to the airbox there by reducing the vaccuum in the fuel bowles creating more flow of fuel.
 

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i ran 420's on a stock sled with a single pipe and reeds (stock airbox) down to -20... above that I personally believe you can run 410's on a stock motor fairly easily, but you have to pay attention to what your plugs/wash are telling you...
 

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i ran 420's on a stock sled with a single pipe and reeds (stock airbox) down to -20... above that I personally believe you can run 410's on a stock motor fairly easily, but you have to pay attention to what your plugs/wash are telling you...[/b]
This year I am running 420's. seems snappier on a 20F day. Next year 420's with Holzman Varitemp installed
 

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450s are stock right?[/b]
440 is stock... on a stone stock motor/airbox/pipe sled the best bet is to install 420's and a holtzmann tempaflow... it'll run great in any weather that you'll actually WANT to ride in and be safe...
 

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Discussion Starter · #16 ·
440 is stock... on a stone stock motor/airbox/pipe sled the best bet is to install 420's and a holtzmann tempaflow... it'll run great in any weather that you'll actually WANT to ride in and be safe...[/b]

I plan on getting a tempaflow next season. How hard is the install of one of them?
 

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tempaflow is about 1~2 hours to install, its easyier if the box is gutted but not a must. basic hand tools and a drill index and a step drill that will punch up to a 5/8" hole if I recall correctly.
 

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Can any one explain why that tecnology was not purchased by OEM? Seems Team clutch and PERC have been purchased. Also how close is the Holzman to the first gereration Doo carb that regulates for air temp? Do they both regulate by float bowl pressure/vacuum?
 

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Can any one explain why that tecnology was not purchased by OEM? Seems Team clutch and PERC have been purchased. Also how close is the Holzman to the first gereration Doo carb that regulates for air temp? Do they both regulate by float bowl pressure/vacuum?[/b]
imho, with fuel injection coming no-one wanted to bother
 

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imho, with fuel injection coming no-one wanted to bother[/b]
I dont recall seeing any tech info in magazines on how skidoo designed their carb to adjust for air temps? Maybe I read it was "borrowed" from OMC when Doo bought the division? I bet it is based on Float bowl pressure/vacuum.
 
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