91 Polaris efi to carb conversion

[Wormeylevi]

Hello I've done quite a bit of research on this conversion and the average say to go to stock carb ive also came across the use of 46mm carbs,well thats what ihad laying around, to match the boots. I was wondering what jets to use for the indy 500. The stock 38s call for 280 main and 40 for other

 

[pistonbroke800]

I would guess that 46mm carbs are gonna be way to big for your 500. You would probably be better off to go to a sled wrecker and find some 38mm's

 

[Longhairfreak]

You dont like EFI?

 

[Wormeylevi]

The stock efi carb and boots are 46mm and the posts on other sites say there is a dead loss on putting the stock 38s on I also came across a video on YouTube with almost exactly the same as what I'm trying to do and on the video by xx1800 the acceleration is sick. Talked to uncle who ice races dirtbikes and he says it will be a headache to tune them but is possible. And to leave pilot number stock and to upsize main by 25% as a starting point

 

[Wormeylevi]

The machine was from a friend that was given to me as he couldn't get it started. After fighting with it all I could find out is the ecu is bad because it pressures up fuel system, no injector pulse when pulling or cold start pulse, and no trouble codes from ecu when i unplug components. So when I checked into new ecu I found out they don't make part and for used it is 300 w/o chip and the chip is also 300. As I'm on a limited budget I decided to go cheaper route. Yes I also understand this sled is rare as it was a test sled for Polaris and am going to keep efi parts for restoration in possible future.

 

[kovs]

I have a cousins sled with this exact problem. Found a guy with 3 boxes but dunno what he wants for 1 hopefully find out this week. otherwise its scrap heap as im not going to the trouble or project length and detail you are to convert it.

 

[Wormeylevi]

It isn't much to convert. the carbs here, in B.F.E. Alaska,are 75 a peice from scrap yard. Don't know how much for fuel pump can't be more then 50. Carb boots from a 1980 yamaha svx 440 to match stock 38s( that's my big issue is that I'm not totally sure if this boot is correct so I'm trying to stay efi 46mm size) and last but not least is to finish drilling the pulse input through the crank . By my math that places the numbers a lot lower then the cost of ecu or chip. Not to mention a new machine

The stock 38s have a deadloss going from 38-46 so there is a loss of power the pulse input hole on my 91 is under the left cylinder carb boot it has threads but not fully drilled through the block heard the trick to that is putting grease on drill tip and going slow

 

[Wormeylevi]

Got it running and idles awesome so pilot jet of 40 is good. The 320 main is a little big it seems to not be pulling fuel correctly. So I hope to start tomorrow with 300 and have it running good.