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Discussion Starter · #1 · (Edited)
Hello, I have 86 nighthawk 450sc i just bought a few months ago and im extremely new to motorcycles and carburetors and just curious if some could tell me if its normal for my bike to have to run/idle for 10+minutes before it will let me drive it. If i attempt to ride it before than it will sputter out and die once i start giving it throttle. Had the carbs cleaned by the local harley shop but issue is still there. Would the canister being hooked up incorrectly cause this? Also should add that after the bike is warmed up it runs completely fine and has no issues at all other than taking what i think is a long to be able to ride, Any help or advice would be greatly appreciated.
 

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Something isn't quite right, they are a bit cold blooded but rideable within the first 3-5 minutes. I would start by verifying that the ignition is correct, there's a sticky in the Electrical section on diagnosing the ignition system. Once that's confirmed/repaired then check the sync, check that the accelerator pump is working, set the mixtures.
I don't know much about the canister system other than what I've read in the FSM, every bike that should have it that I've dealt with has been missing it or it was disconnected.
 

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Discussion Starter · #3 ·
Awesome thank you longdistancerider! Not to be a complete pain in the butt how do i search for this sticky? Completely new to this website haha! Sorry! haha
 

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Awesome thank you longdistancerider! Not to be a complete pain in the butt how do i search for this sticky? Completely new to this website haha! Sorry! haha
Stickies are the blue threads at the top of each section, when you click the Electrical section it brings up the page and they are always the first threads, it's the way specific topics are held to be found easily.
 

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Discussion Starter · #6 ·
Thank you very much for all your help! I'll have a look at that now, also curious if there's any way for me to check the sync on the carbs myself? I tried searching online but couldn't find anything. Turns out my buddy at the Harley shop just took the carbs off and spray carb cleaner in there not sure if that's how they should be cleaned or not. Thanks again I'm advance sorry for being such a rookie haha!
 

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Everyone's a rookie at some point in time, we'll help you along.
Rather than going thru the process of actually cleaning and rebuilding the carbs, no your friend didn't really clean them other than remove external crud, I'd suggest adding Berryman's B12 or Sea Foam to the fuel, following the instructions on the can, and ride it for a couple of tanks. There's a sticky in this section on rebuilding these carbs, it's time consuming and if you follow the instructions you'll only need to do it once. Short cuts mean you get the pleasure of repeating it at least once more.
There are 2 vacuum port plugs on the head, Philips screws, above the carb insulators. Those come out to install vacuum fittings temporarily, they have to be plugged when done. That's where the hoses for a vacuum type sync, manometer are connected. I use a Edelbrock Uni-Syn for my stuff which requires removing the air box boots instead of dealing with the vacuum fittings.
To check the accelerator pump the air box boots have to be removed to watch the little nozzle at the bottom of the choke plate to see if it squirts when the throttle is twisted fast.
Hand Fashion accessory
 

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Discussion Starter · #8 ·
Update on bike I went over the lines and realized I had the vacuum line that goes to carb not Hooked up correctly so when i got that straightened out the bike started right up and was good to go after a few mins of getting to temp, it still has some slight lag when I throttle it takes it a minute to go so I'm assuming that's carbs, what do you guys think?
 

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Discussion Starter · #10 ·
Okay thank you very much again for the advice ill get some tomorrow. In your opinion which is better? My local walmart has Seafoam sf-16 motor treatment but if thats not right i can check around for berrymans.
 

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Discussion Starter · #12 ·
Thank you sir, I added some berrymans when i filled up yesterday, very hopeful this will fix it, other than the initial start up/warm up this bike has been amazing to learn on and ride, Next just gotta get to painting it and find something to remove some of the surface rust on it to make it look good now. Have you ever heard of anyone using acid to do this? My buddy mentioned but figured id ask the experts before i thought about it haha.
 

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Discussion Starter · #14 ·
Update I added the berrymens and it seems to have fixed the issue completely! Thank you so much for al your help! It runs amazing now and I'm able to right away if I ride with the choke on for the first few minutes! Now I can paint it and add a led/day maker headlight and she will be gorgeous! Thanks again!!'
 

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Good deal, a lot of times the carb problems are just due to old fuel deposits on the jets and passages and the additives clean those out nicely.
 

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Discussion Starter · #16 ·
Yeah it runs beautifuly now!! Thanks again! Do you have any experience with either straight piping this bike or removing the baffles? My buddy said it will make it sound better and run better if that is done but couldn't find anything about it with a quick google. He wanted me to just buy straight pipes from a hardware store and for them to the headers and call that good. What do you think?
 

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If you really want to go backwards and have problems then by all means remove the baffles. Seriously, the engine and exhaust system are designed to work together with some back pressure. No baffles or straight pipes will not improve anything about the performance and probably degrade it. You can change the mufflers w/o any issues. I'd suggest looking for some take off HD Sportster mufflers, commonly found in a pile of old parts at your local HD dealer or a HD shop. This gives a louder and deeper sound, not obnoxious.
 

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Discussion Starter · #18 ·
Okay gotcha thank you for the advice, I'll see if I can come across some hd mufflers and see how that sounds, appreciate it once more! I figured I'd check with you since you seem to know everything about these bikes. Haha. Thanks!!
 

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I bought an 86 450sc a few years ago.. It was on the road with no problems for the first year I had it. it's been off since I started working on it. However, prior to me taking it off the road, I had NO trouble at all. I could walk out in early/mid November (in Virginia), and start it cold.. and ride away immediately without any issues. Full disclosure, I just read your first post cause it caught my eye.. and immediately replied. I have yet to read through the whole thread. Just thought my personal experience might shed some might on your situation.
 

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Discussion Starter · #20 ·
Update bike has been running like a dream, can?t thank you enough for all your help! Silly question have you heard of changing the speedo and tachometers with the digital ones? Also do you think installing a fuel gauge would be useful other than those things the bike is perfect!!
 
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