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Discussion Starter · #1 ·
I rebuilt the carb, set it up, adjusted the idle and high speed adjusting screws. And it had this problem before I started. It will fire right up cold or warm. Sets there and idles good. With the track off the groung, you give it throttle and it runs good to about 1/2 throttle then starts to die out. With the track on the ground, give it throttle and it won't even rev up enough to move the sled. Bogs down and acts like it runs out of fuel. You can see the fuel coming into the carb and flowing out of the return hose. Runs goin downhill but not on the level or uphill. The hose that goes from the engine to the bottom of the carb is vac the operates the pump,RIGHT? Can that vac be bad? I'm sure others had this same problem at one time or another. Hey people, PLEASE HELP.
Thanks for your time,
Bill[:(]
 

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I had the EXACT same problem with my 74 Elan. I found my problem to be a worn out belt. The belt was sitting too low. Changed the belt, and VOILA. Perfect, I had all my power back.
 

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Discussion Starter · #3 ·
I understand about the belt, but when it's up on block and the track off the ground it also acts like it's runnung out of fuel. This starts at half throttle. Starts bogging out.
 

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Discussion Starter · #5 ·
You say jetting problem, but it has the same jets as it alway did. And worked fine before. Think maybe they're dirty?
 

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wow keep us up to date as to what you find. I have a 76 John Deere sitting behind my garage and it does exactly what you r describing. It has sat there for 2 years now. I have a nephew who will be be old enough to start riding soon so if i could get that thing fixed it would be great.

Rich
 

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Check tank fuel inlet screen. High speed fuel passage could be plugged. Fuel inlet lever inside carb may be missadjusted.
 

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I would clean the jets then re set them to the base starting point (1 1/2 turns ?). Also check needle and float to make sure everything is moving freely.
 

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What engine ,and what carb. are on this sled?
 

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Discussion Starter · #10 ·
It's a 72 Panther 399 with a Tillitson HD carb.Where are the jets located on this carb? I rebuilt the carb and didn't see the jet. Needle ans seat were replaced and adjusted. Cause the arm for the needle is to be even with the floor of the pump housing. Like I said, you can see the fuel being pumped and returned to the tank. Checked the high speed adjusting screw, and the opening seems to be open.
Triple6, you stated about cleaning the jets and reseting them to 1 1/2 turns.........are you talking about the idle and high speed adjusting screws? I believe the idle screw is set to 7/8 and high speed to 1 turn. Now that's just a starting point.
Kevin, is there a screen in the tank? GOOD IDEAS GUYS, we'll get it yet. I know there's a screen in the bottom of the carb, and that's clean.
 

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These carbs didn't have jets, they had needles, usually a high speed and low speed. Try messing with those.

You can still buy rebuild carb kits for those.
 

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To answer you original question....there is a diaphram that can be weak inside the carb. Rebuild kit will take care of that. You might also have some crap in with the needle and seat. Just take it all apart and clean thoroughly.
 

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Discussion Starter · #14 ·
Already did get a kit and rebuild the carb, set everything to specs also. did mess with both idle screw and high speed screw. Didn't help. Kevin where is that passage, if you can explain, I'll know where, cause I had the carb apart about 4 times, LOOKING< LOOKING< LOOKING. Found nothing. Also the kit included the pump dia. No dirt in the needle and seat. It makes sense about crap in the jet or passage, but need to find that secret passage.
 

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OK I'm pretty sure the passage goes from the pump chamber into the area between the high speed seat and the spring loaded rubber gasket on the high speed needle. From there when the needle is backed off the seat it goes to the little venturi inside the throat of the carb. I believe that it goes through a little chamber that is normaly covered by a welch plug. Underneath the welch plug will be a pressed in jet that you probably can't remove and probably can't see the orifice as i think it is actually off to the side a little.

BTW Is that a JLO engine with the cooling shroud cast into the heads and barrels? If it is I can tell you from experience that you will have to watch the heat on the down wind cyl. The last one of these engines I had I made a duct to go directly from the fan to the outside of the hood. Also doubled up on the PTO side base gasket to lower the ports and reduce compression and lastly adjusted the points so that PTO cyl was somewhat retarded from recoil cyl.
 

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I guess I meant raise the ports. I wish that the old JLO/Cuyuna came with dual carbs so that you could have run the hot cyl. a little richer. Easy engine to work on and a darn good thing.
 
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