Im at a total lose for ideas. 89 Indy 500, starts and revs right out, pull the choke and it will idle down but as soon as you throw the choke off revs out again. Carbs are clean and seem to be working. Any ideas would be appreciated.
Need Help 89 Indy
- Thread starter HighmarkMiked
- Start date
Here are some ideas for you. Is a throttle slide hanging up or misadjusted? Did you clean all the jets including the pilot jet? Are the carb boots free of cracks or splits? It could be leaking crank seals. Is this something that has just started to happen or is the sled new to you?
Ive had the sled for years and it was running good when I stored it. I cant see any cracks in the carb boots and the carb slides both look like there coming all the way down. If I had a crank seal gone would it make the machine totally peg out? not just idle a little fast but 5-6 grand fast??
No, I wouldn't think it would idle that fast but who knows. It might be worthwhile checking them by spraying some WD40 or similar down by the seals while it is running anyway to see what that does. If the carb slides are not hanging up it has to be a lean condition making it rev so high.
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Flying Dutchman
Well-known member
I would guess the pilot jet is plugged off. Storage does this to the fuel. how long was it stored??
FYI, the pilot is inside the float bowl. It's the smaller of the 2 jets. Once removed you will see that there are several tiny holes in the pilot. These holes can easily get plugged.
FYI, the pilot is inside the float bowl. It's the smaller of the 2 jets. Once removed you will see that there are several tiny holes in the pilot. These holes can easily get plugged.
The machine has been in warm dry storage for about 5-6 years. Ill check the crank seals with the WD40 trick again, maybe I just didnt get enough in there the first time and Ill pull the carbs again and really go through them. Im leaning towards the carbs having a problem because I just cant see the crank seals causing such a high idle. Any other ideas???
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clutch man
Well-known member
Can you mix up the fuel lines from the pump to the carbs, or does it matter which one goes where?
It doesn't matter.
Just so Im 100% clear on the fuel pump plumbing, the two outlets that are closer together go to each carb, right? and the one outlet that kinda stands alone goes to the crank, right??? Im sure that was the way it was plumbed before I replaced the lines but with my lack of success with all my different attempts to resolve my problem now Im grasping at straws......
I am not sure, did you say you pulled your carbs and cleaned and made sure your pilots and mains were all shiny clear and clean??? your needle and seat could be a bit stuck as well..If you have seen the inside of these carbs after they have sat for even a season with the ethanol laced gas we get these days, you would consider a look see, at least ..but the fact that it runs on choke suggests you are getting fuel...jmho
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Rrrrrrandyw
New member
Sounds like one or both of the slides are hung up, are you sure you have them in the right grooves? You should not be able to get your finger under the slides at idle, or maybe the large slide screws are turned all the way in, Try running the large phillips screws out about 3 turns from all the way in. If neither of these are the problem, have a close look at your throttle cables and make sure they are all tight, no slack in them at idle. Good luck.
I went through the carbs again last night, pulled pilot jet, pilot air feed jet, main jet, blew all orifices with carb cleaner, they were spotless.Reinstalled carbs still the same, super high idle. The slides are moving up and down freely, slide screws are 4 1/4 turns out, all cables are good with no apparent problems. Clutch Man suggested it might be fuel pump so I will try that next. Any other suggestions???
Just curious as to what size of drill bit you can slide under the throttle slide when it is in the idle position.
Pull the airbox so you can se the carb slides, back the idle screws right out, take them out of the carbs if you have to, look and see that the slides are sitting right down. Did you maybe hook or pull on a throttle cable and stretch it out a little? Check the cable adjustments on top of the carbs, an 8mm and a 10mm if I remember, do you need to adjust the cables to let the slides sit down? These are the old 38mm round slide mikunis right? I think the fuel screws are 1 turn out?? anybody know for sure? I've been watching this thread for awhile and retiredpop has been giving you good advice, hang in there you'll figure it out.
Thanks Jay, I run foam air filters and I have them off so I can see right up the carbs. Both slides come right down to the stops. The stops are set at 4 1/4 turns out, thats the way it used to run at. I tried backing out the slide stops and started it up, same super high idle, didnt make a difference. They are 38 mm Mukuni's slide carbs.I dont think its the cables because the slides move and bottom out evenly. Im going to try the fuel pump next but if the pump was pooched would I not get any fuel, starving the motor???
I don't see it being the fuel pump, but never say never. the carb bodies have notches that the slides seat right down into, I'd make sure the slides are going completely down and not sitting on the idle screws at all. If they are and it still revs high you have an air leak somewhere. Retiredpop has a good idea to look for the leak with a can of wd40
Retiredpop and Jay I would say about 3/8 to 1/2 inch gap between slide and bottom of carb. Do you think that is ok or is that too much. I did back the screws out and it didnt make any difference but now Im wondering if I should loosen the cables right off and then back the screws out to make sure its not the cables holding up the slides even though the screws are backed right out. Ive done the WD40 thing twice and had no results and I replaced all gaskets (head, cylinder block) so other than crank seals I cant see where the air would come from. I havent changed out the carb boots but they look ok, how much of a leak would it take to make the engine rev out to 5000+ rpm???
Way to much, cables are definately holding slides up. Pull your idle screws right out then unhook a slide from the throttle cable and just drop it into the carb body and compare it to the other side. retiredpop was probably thinking 1/8" drill bit size gap or something like that. 3/8" or bigger is 1/4 throttle or more.
Thanks Jay and Pop, Ill drop the cable on the one side and see what I get. Ill let you know what I come up with.
