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WOT start when warm

G

George Majewski

New Member
Messages
9
Age
56
Location
LaCrosse, WI.
Country
USA
Years Snowmobiling
35
Snowmobile
99 xc 600
I have a 99 xcsp 600 with primer and choke. After riding, I have to WOT for it to fire up. Already gone through carbs. Fuel pump rebuild?
 
Are you sure the chokes are not leaking? How do the reeds look?
 
Choke looks all good. Never pulled out the reeds. Runs excellent when riding. Gonna rebuild fuel pump and go from there. Thanx for the response.
 
To much fuel would be the root cause for needing WOT on start. Pull the impulse line from pump to crankcase. The impulse line should be completely dry inside the line, if not, the diaphragm (in the pump) has a hole in it. That's the only way for fuel to enter the engine directly from the pump. Most likely cause would be the sealing o-ring on the needle & seat assembly in the carb. The only way to know for sure if the sealing o-ring is bad is to pressure test thru the fuel inlet nipple with a low pressure pump and bubble fluid.
 
The Keihin PWKs on that sled didn't have an o-ring on the float, that was the Mikuni design on the later engines. The Keihin float needle is rubber tipped and seated to the carb body itself. Since they are likely original and the rubber was from the pre-ethanol era its a good chance they might be shot.
Here's a exploded view with aftermarket part#'s, see #8 in the diagram. Polaris wants $45 for a replacement fuel needle.
 
1639533071819.png


This is the pump we use in our shop, bubble fluid can be a simple soap and water mix in a spray bottle.
 
850Switchback said:
The Keihin PWKs on that sled didn't have an o-ring on the float, that was the Mikuni design on the later engines. The Keihin float needle is rubber tipped and seated to the carb body itself. Since they are likely original and the rubber was from the pre-ethanol era its a good chance they might be shot.
Here's a exploded view with aftermarket part#'s, see #8 in the diagram. Polaris wants $45 for a replacement fuel needle.
Click to expand...
Your right on, I was thinking later models. You can still test the needle & seat the same way. Or maybe a leaking primer? Pinch the line or try a Mighty Vac.
 
Fuel pump looks good. In process of rebuilding. Any tips on how to get the two round rubber plugs through the hole? DK has a rebuild kit for my carbs for $72.
 
Mike-DRH said:
Your right on, I was thinking later models. You can still test the needle & seat the same way. Or maybe a leaking primer? Pinch the line or try a Mighty Vac.
Click to expand...
I did the same, even wrote a whole response about Cat dealers selling the o-rings separate since Polaris doesn't, before I realized wrong carbs lol
George Majewski said:
Fuel pump looks good. In process of rebuilding. Any tips on how to get the two round rubber plugs through the hole? DK has a rebuild kit for my carbs for $72.
Click to expand...
a very light coat of petroleum jelly and they should pop right in
 
After much frustration, come to find that a drop of Dawn dishwashing liquid with a small allen wrench worked out very well for popping in those pesky rubbers. Gonna buy a carb rebuild kit and do them next year. Thanx to all.
 
Turns out after riding today, after first start up I used a spring steel style paperclip, which didn't totally pinch off the primer line. It however does seem to be the culprit of the matter. Normally started on first or second pull after warmed up. My model has the choke as well. At this point I would think I could simply bypass the primer?
 
I don't see why not, it was just added as a cold start aid. The 97&98's didn't have a primer.
 
Have you tried Hudons in NY or Al's snowmobile in VT? not sure if there are any sled salvage yards closer to you
 
Dennis Kirk has either Parts Unlimited or SPI rebuild kits for those. That SUDCO link I gave you above has individual components available for order.
 
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