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Discussion Starter #1
I have question for the high performace saavy folks. Will a cold/cool engine (150 degrees) directly affect performance as in taking away? I had a problem a short time ago about my bike falling on it's face when the secondaries kicked in. It would light up and fall off then light up again and so on. I replaced the stock fuel pump with a Holley Red and took her out and Shaazam. It was solved. The other night, above temps, had a mustang try to mess with me and sure enough when I got on the 4 barrel, it coughed and would not hold. Was the temps the prob ya think?

Chris
 

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Chris,

I doubt it. Although temps below 160 may reduce h.p., you shouldn't have fallen on your face because it was cool out. I've run my 502 pretty hard while in the NC mountains and with ambient temps in the 30's and 40's. Not a reason to falter.

Better look elsewhere. As far as where, there's too many possible answers without knowing more specifics. Many components to the fuel picture outside that fuel pump and although not as many, a number of electrical considerations. With the "cough" you reference, I'd be looking at carb/fuel issues first.

A suggestion would be to start with the easiest. Looking at your plugs can be a real good barometer.

Elliot 8)
 

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Don't think so about the temperature causing the problem of going flat unless the engine is super cold. From past experience and also from Marv at Chopper City, is that if you run Nitrous your best performance is at 165 to 170 degrees. I can tell a lot of HP difference between 185 to 190 as compared to 160. I have no flat spots at 130 degrees and above but I have never tried it below 120 degrees.

Adrian
 

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Discussion Starter #4
Quick Disconnect

Well, I'll look into it. I am wondering now if the quick disconnect I am using on the crossover tube does not allow enough fuel through when the secondaries need it. I did not have that installed when it was working good before. I don't have the marine type that was posted but may have to switch to it. I am using a male/female type for hydraulic lines and so forth. It will tolerate the gasoline but wonder it is slowing my fuel down under the demand. I will also make sure the rich/lean is set right. Got to get it right, though. I don't ride like the S Fl boys but when I want to run...I want ro run.
 

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Hi Chris, Winter brings on the winter formulated fuels. This fuel will vapor and percolate in a heart beat. If you were running the bike at a slow pace for a long period of time the fuel in the carburetor gets hot, and when you open the throttle hard it vaporizes instantly. You'll get a big bog. Then once the coool fuel starts flowing it takes off again.

Try riding it again in the same conditions. If it does it again try this. Rev the engine a few times to clear the hot fuel out of the Carb. Then nail it. Mine respond well to this trick. Also check those fuel filters. If the pump has to pull hard for the fuel it will percolate.
 

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Chris,
I agree with Mike that it is fuel related. Sounds like when you hit the secondaries, it's starving for fuel. Like Mike says, check the fuel filters, and don't forget to eyeball the fuel hoses also. Kinks, soft spots etc. I believe there is one inline filter, and a filter in the carb where the fuel line enters. Also, (and this is a pain but........) check the screen on the fuel petcock. I changed my petcock to a petcock with reserve feature. When I pulled out the old petcock, the screen had a lot of debris around it.
I really doubt that the crossover is doing it. Good luck and let us know what you find.
 

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Discussion Starter #7
Testing tomorrow

Thanks for all the tips. It is supposed to be sunny and 50 here tomorrow so I'm planning a test run. I'll double check everything before. The filter in-line is a month old but I haven't looked at the one in the carb. I'll report back what happens.


Chris
 

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Discussion Starter #8
Done good

Well, I took her out for a good ride today and she hooked up every time. Must have been what Carb Mike said. Anyway, thanks again for the tips.


Chris
 

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Discussion Starter #10
Duuuh

Well, it may have been a gremlin but I is a thinking it was lack of fuel as in my pick-up in the tank was sucking air. Went riding today and had the same problem. About a mile later I had to hit the reserve. As soon as that happened, I remembered the other night (first time) and I had to gas up right after that mustang wanted to scare me off. I have the pingle with reserve so I'm thinking that it was at the point where it was almost out but would grab a bit of air here and there. After gasing her up ...shaaazam! Well, third time is a charm so I will reserve my official findings till I can try it one more time with plenty of go go juice , of course.

Chris
 

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Bogging in Secondaries

Secondaries may be opening too quickly. Is the most common cause of bogging at full throttle. See Mike's description about the carb and tighten up those secondaries about 1/8th turn at a time and your problem will be gone.
Joe
 

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Bogging in Secondaries

Secondaries may be opening too quickly. Is the most common cause of bogging at full throttle. See Mike's description about the carb and tighten up those secondaries about 1/8th turn at a time and your problem will be gone.
Joe
 

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Bogging

Chris,
Just curious if you have felt the bogging any more this winter? I have had this same problem with my 502 for the last two winters. It got bad enough that I could be just running up the interstate and she would just cut out on me and then catch again.

I took Carb Mike's advice and looked into the fuel situation due to the winter-formulated gas issue. I now run an octane booster only in the winter time and I have not had a single hesitation/bog. I think Harley is now selling a fuel additive that is marketed to do something similar to this. I can't remember exactly what it said, but it was something like a winter fuel additive that helped with this issue.

Bill Taylor
 

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Discussion Starter #14
Bog

Bill,

I have had the bike out several times since then and I haven't noticed a bog. I think my particular problem was fuel starvation but I am aware of the winter fuels thanks to Mike. I should probably run an octane booster as well. We'll have to hook one of these days around the state line or somewhere for a eat and greet. Take care.


Chris
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Chris,
That would be great. It may work out best to do it once the temps come back up some though. I am a bit of a "zip code rider" when it is cold...35 to 40 degrees outside.

Our Mid-Atlantic Chapter of the BHRA gets together fairly often. Are you interested in getting plugged in to our group? We have 25 members and are always looking for new Boss Owners to ride with us. I send out emails every couple of months to update everyone on Chapter Meetings, rides and shows/events. Send me your email address and will add you to my group email list. [email protected]

Bill Taylor
 

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Chris

Have any of the symptoms come back or do you have it licked?

I've got a similar situation I'm working through.

Added K&N with Extreme lid, Crane Vacuum advance, Quick Disconnect, routed the fuel line around the back of the distributor. Still running stock fuel pump, but hope to change that out this weekend. Have not checked petcock, or adjusted carb any.

When I hit it hard, it'll run strong for about 1 or 2 seconds then bog, take, bog, take etc until I slow it down. Normal rollon is fine.

Kinda dangerous, have no confidence with overtaking, if I need the horses in a hurry.

Aldo
 

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Aldo , that does sound like it's starving for fuel . Could be your carb. inlet filter is partially plugged , fuel pump or maybe even you float level . Should be fairly easy to correct .

Good luck,
Jack
 

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Fuel pressure for sure... Might wanna check that. Wether it be a clogged filter or pump.. fuel pressure/volume is the culprit.
 

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Discussion Starter #19
Don't forget that it could be your upper air valve flopping open and closed. I had the same thing a while back with my Q-jet and could never get it straightened out. I pulled the carb at least a dozen times, changed fuel pumps, cleaned all filters and checked all plug wires. I put the Holley repalcement carb on and that went away. Stock fuel pump does just fine. It could be a lot of things.

Chris
 

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Chris , what would cause your upper air valve to flop open and closed unless you had no tension on the wind up spring ?

Thanks,
Jack
 
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