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Hey all, new here. Merry x-mas.
I am helping a friend get his indy 440 with a 500 engine in it going. Its around the mid 90's engine. Not exact on the year. It bogs when coming off idle. Carbs have been cleaned 3 times and replaced pilot and mains with new. running a 35 pilot and 270 mains for now. Needle clip on the #3 slot. New pulse line, floats adjusted. Choke plungers taken out and set up with 1/8 inch slop. the sled will start fine. Will idle great, but when giving it gas it will bog and almost die. If you choke it some, it will come back to life and you can take off with it. Does this cold or hot. Im assuming then its a lean condition. Sprayed starting fluid around PTO side seal, carbs, and base gasket and got nothing. When ridding it has good smooth power with no hesitation as long as you keep it over 3500rpm's. Plugs look nice and tan. Have not dealt with fuel pump yet. It does have a aftermarket fuel filter between tank and pump. Could this be restricting flow? Also tried a # 40 pilot jet and made no difference. Thought maybe clutch related, so took belt off and still ran the same with bog off idle. Will this eliminate a clutch problem or not?
Any ideas, please throw them out here.
Thanks, Dave
 

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Discussion Starter · #2 ·
Need to add that i took exhaust pipe off and blew thru it with an air hose to make sure it was not plugged. It seemed restricted. Is this the norm? Or should the air pass right thru it? With using 80psi it blew out the other end with the same pressure as blowing out your mouth.
 

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Sounds like you have a lean bog off idle. Where is your air screw set? Try one turn out from lightly seated, if it still bogs, go in 1/8 of a turn on each air screw until the bog is gone. If you get the air screw all the way in with no change, and the bigger pilot jet didn't help, suspect a clogged air passage or fuel passage to the pilot jet.
 

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Discussion Starter · #4 ·
Thanks BC Dan. I have done this too. No change. I sprayed carb cleaner thru passages with jets removed and it was fine. I am now going to try and figure out what year this motor is and what size carbs it takes and jetting. Im running br9es plugs but some ran the 8's. If it was a bad seal lets say, would it run well once you get going from say 20 miles an hour up to full throttle? would it sit and idle at 1800rpm with a bad seal? I thought i was a good backyard mechanic with doing all my own maintenance on my own sleds and engines. This has got me baffled to no end.
 

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could very well be a clutch issue! it dles good? pulls in the upper rpm range? just bogs down low like when the clutch engages? clean them up real good, then may also be a soft spring. and this is not the original engine for this sled? is the gearing right for this clutch engine combo?
 

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So I’ve got the same issue on a 96 Classic Touring (500). I’ve completely cleaned the carbs, set them with the 7/32 bit, set the idle with the 1/4 bit (Twice). Verified the pilot jets were both 40’s, set the mix screw at 1.5 turns, tried 1 turn, 3/4 turn. Checked the fuel line in the tank, golden.
Starts and idles great at 1600rpms. When I apply the throttle it boggs and won’t accelerate. If I crack the choke for a second the rpm’s will go up and I can open it up. Once they are at 3k+ she runs like a champ. But from idle to 3k is tough.
I was thinking maybe the fuel pump IDK I’m stumped.
 

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When I inspected the pick up line, it looks like new, no signs of any obstructions or breaking down.
IMO I would think a pick up line issue would have effects on high RPMs versus low as more fuel is needed. Idk, I’m questioning my sanity at this point.
 

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The fuel delivered from idle to about 1/4 throttle is metered by the pilot jet. If you have issues in that throttle range, concentrate on the air and fuel circuits to the pilot jet. Those passages are very small and can easily get clogged with varnish. I have boiled the carb bodies in water with limited success at removing that junk. An ultrasound would probably do the job, as well. I also use the 1 gallon can of Berryman's carb cleaner, but make SURE you don't put any rubber parts in there or they will be destroyed.

When cleaning, did you run a small wire down all the passages? Sometimes that can dislodge any debris, as well.
 

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I soaked them in Gunk carb/parts cleaner. I wasn’t able to reach the opening although it was open. Is it possible it is partially closed?
Also something odd, just before I left this am I started it and it appeared to not bog. Now the only diff was that it had been in my heated garage until last night so it was 10 degrees out this am.
 
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