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Discussion Starter · #1 ·
My brother in law has a 1979 Citation 4500 and when we run it after it warms up it seems to loose power and not even pull itself. Could the coils be breaking down when hot? After you let it cool down it runs great again till it gets hot again. The fan is working. Thanks Fastrac
 

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I have the exact same problem with my 79 Elan 250. It will not raise in RPM when it does this. I think it is vapor locking. Mine is a tillotson HR, fully rebuilt properly and has points.
 

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Discussion Starter · #6 ·
Elan Rider, Yes the RPM's fall off and yes it is the 377 F/C single mikuni setup. We have not pulled the plugs when it starts to lay down. We put snow down by the fuel pump and after a little bit it will run good. After it lays down you can try to give it full throttle but it will only get a little, tried raising back end up and it wont hardly pull with track off ground. Thanks Fastrac
 

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Fastrac - I think you are already on to it. If you are putting snow on the fuel pump, you could be plugging a leak in the pulse line or the seals in the fuel pump until the melt water evaporates.
You can get a rebuild kit for the fuel pump at a Skidoo dealer or online at MFG supply. You can replace the pulse line with automotive vacuum hose. I suggest doing both.

snow4me - Have you checked your plugs when your Elan is acting up? Does your tilly have the high speed adjustment or just the low speed mixture adjustment? What kind of shape is you pulse line in?
 

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Elan Rider, the plugs look great when it is acting up and the pulse line is new as well as the fuel lines. I don't remember wheather it has the high or low speed adjustment, but it only has one, haven't been serious about it since last year. The fuel lines are running right under the muffler, I was thinking this might be the problem. I bought some expensive heat shield but haven't put it around the fuel lines yet. The fuel pump is built into the carb of course and the sled runs great until it gets warm from running a while. All of a sudden it starts bogging and eventually quits. I do see bubbles in the fuel line when this happens, they are traveling pretty fast. I do not know if the bubbles are there while it's running, only after it quits and I pull the cover to look.

Thanks, Daryl
 

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i used to work as a marine mechanic way back when and the coil failure when warm usually will result in one cylinder cutting out. The reason this happens is the plastic coating on the coil has a crack and the voltage "leaks" out (grounds out).

If you think one cylinder is completely cutting out it could be the coil.

But i would spray some starting fluid down by the crank shaft while it's idleing and see if that effects the idle, you may have worn crank seals.
 

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I checked my crank seals and they were fine. Did the starting fluid trick like you said. I plan on installing a primer bulb so when this happens I can give the bulb a squeeze and see if that perks it back up. Hopefully I can do this next time I'm up.

Daryl
 

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My '80 citation ss did the same thing. (after running for about 20 mins it would slow down soo much that it didnt move the track) We did checks on the internal coils and they all seem fine. Head gaskets look eh, so were changing them. After that we are rebuilding the carbS, Im hoping that its just a carb thing and not a crank seal or anything. Ive been talking to some people and they thing its a pressure thing, and not coils, but others think its coils and not pressure. soo, after i change the head gaskets ill check the pressure and give you an update.
 

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I looked at the fuel lines in my Elan while it was running (I made sure it was good to go in case we actually get snow on Friday). There were lots of bubbles in the return line, and none in the supply line. There is no insulation under the muffler in my Elan, but there appears to be enough of a continueous flow of fuel to prevent vapor locking.

My Citation SS used to vapor lock, but the symptoms were that it wouldn't restart after it got hot. No problems while it was running or on days when the temp were below about 20F. The fuel would boil in the lines after I stopped the motor.

Are you sure there isn't a leak in the supply line? It could be a leak in the pickup hose inside the tank. Does the amount of fuel in the tank make any difference?
 

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I looked at the fuel lines in my Elan while it was running (I made sure it was good to go in case we actually get snow on Friday). There were lots of bubbles in the return line, and none in the supply line. There is no insulation under the muffler in my Elan, but there appears to be enough of a continueous flow of fuel to prevent vapor locking.

My Citation SS used to vapor lock, but the symptoms were that it wouldn't restart after it got hot. No problems while it was running or on days when the temp were below about 20F. The fuel would boil in the lines after I stopped the motor.

Are you sure there isn't a leak in the supply line? It could be a leak in the pickup hose inside the tank. Does the amount of fuel in the tank make any difference?[/b]
Hi elan rider.. I have been having the same problem with my SS """"""My Citation SS used to vapor lock, but the symptoms were that it wouldn't restart after it got hot. No problems while it was running or on days when the temp were below about 20F. The fuel would boil in the lines after I stopped the motor."""

What did you do to correct the problem??
 
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