How to Use Seafoam on a Motorcycle with Carbs – Honda Nighthawk 450

How to Use Seafoam on a Motorcycle with Carbs – Honda Nighthawk 450


Hey how’s it going people BrownBrady here And in this episode I’m just gonna show you How I used Seafoam to treat My 1983 Honda Nighthawk 450 Also known as the CB450SC As you saw in my previous video I was experiencing some hesitation and backfiring Especially during low speeds So somebody over at the Facebook group Honda
Nighthawk Owners Suggested that I try to see if I can address
the issue Using Seafoam before I start taking apart
the carbs So yeah it makes sense I mean this is My first carbed bike I went ahead with that So I’m gonna try to keep this video under
5 minutes So the first thing I did was I started the
engine And warmed it up After it was warmed up I drained the gas that was inside the bowls In the carbs And after I did that I used a couple of beer bottles To measure how much gas was inside And then using the empty bottle I created a 50/50 mix of Seafoam and fuel And then I disconnected the fuel line from
the gas tank And I filled it up with the 50/50 mix I had to make my own funnel because The funnel that I bought had too big of a
hole So after doing that I restarted the engine And I let it idle until it consumed all of
the fuel In the bowls One mistake I made there was I should have warmed up the engine longer So that way I could rev the engine But I wasn’t able to do that because Every time I revved the engine it would stall So I suspect that it was fouling the spark
plugs After the bike consumed all of the fuel I refilled it back with 100 per cent Seafoam And I let it sit there overnight And then the following day I drained all of the Seafoam from the bowls I reconnected the fuel line to the tank And then I put 8 to 9 capfuls of Seafoam into
the gas tank And then I turned it on I revved it up And I noticed that some white smoke was coming
out And it did it felt like anyway anecdotally It felt like there was an improvement When I revved the engine slowly Whereas in the past whenever I did that I would feel some hesitation Between 1,000 to 3,000 RPM’s If I’m gonna quantify it I would say that There’s about a 50 per cent improvement However there was still some backfiring I would say that the Seafoam treatment did
help I suspect that there is another issue Anyway that was what I did to treat my bike
using Seafoam The next step for me I think would be To check for any vacuum leaks I’m gonna check around the intake boots In my next video I’m gonna show you that If you have any comments or any helpful hints To diagnose what the problem the backfiring
could be Please let me know in the comments section If you liked this video please hit the like
button Or better yet hit that subscribe button And I’ll see you in my next video As always ride safe and thanks for watching You look like a bobble head

72 comments

  1. Vacuum leak or just being too rich.  Usually backfire popping is running rich.  Do you get that muscle car gassy exhaust smell and how do the pipes look? Sooty at all?

  2. Hey nice video glad the foam helped, I recently bought a 2013 CBR 250r similar to yours but all black. I have a an issue with the bike though, I cant seem to get it over 60 mph. Is this common? Is it because the engine size?

  3. @BrownBrady Great video. I always wondered if the sea foam works. I should have used it on my old 1998 Suzuki LS650, before I got rid of it, due to some head gasket problems, front fork seal, and oil leaking out of the exhaust pipe. You can see how bad it was by checking out my old motorcycle vlogs playlist on my channel. I even had problems with it not getting good fuel efficiency. The bike I have now, is great. It is a 2014 Honda CTX 1300 Deluxe, with ABS and Traction Control and Bluetooth.

  4. What do your plugs look like?  You can tell a lot about your mix from their condition.  I also found putting iridium plugs in my '81 xs1100 fixed some of the popping/backfiring issues I was having.

  5. Hi…good post….I'm a motorcycle collector and the older 450s are one of my favorite vehicles.   Light, powerful, and so much fun.   My mainstay are Harleys but I love my Hondas too.   Presently I have a 1986 Nighthawk 450SC and previously I owned an older 450 Nighthawk….both with fuel problems from rusty tanks.   I can say from personal experience that taking the carbs apart is  no fun, but were loading up and with CA smog equipment, fuel was also loading in the air box…very dangerous.   I found the floats to be out of adjustment and dumping a rich mixture and raw fuel exploding in the tail pipes.   I also  noticed the petcock was loading the smog lines with fuel because of a defective and frozen vacuum unit  on the petcock, also dumping fuel into the air box. The filter on the bottom of the carbs is near worthless and  recommend an inline filter directly out of the petcock for any debris  matter from the tank.   After I super cleaned the tank, completely took apart the carbs and cleaned all needle valves, the mid range lag you are talking about is no longer a problem, no loading and no backfiring.   Hope this helps…..Like you, I didn't want to tear into the carbs, but finally caved and tore them  completely apart and cleaned….old, varnished, bowl full of debris, and marginal needle valve operation.     All is good now.

  6. Dooood nice video. Sweet vintage Honda. My Harley (1985 Sportster with Super E carb) had occasional backfiring and hesitation as well. It ended up being two problems: fuel line restriction caused inadequate fuel to be delivered and the main jet was clogged. I don't know if my symptoms were the same as yours, but I would suggest you take out the jets and blow them out with compressed air. You should be able to access the jets just by pulling the bowl (you might not have to completely remove the carb). When you get them out look through the hole into a light (the sky or something) to make sure you can see clearly through the jet. After that just put it back together and tune the carburetor properly. Rich or lean could cause problems, including rough running and backfiring. Do you have a factory service manual?

  7. Disable your AIS, (Air Induction System) Your bike will run 100% better overall, and is the main reason your getting that annoying back fire in low RPMs. Burning leftover fuel.

  8. lol why didn't you just mix it directly into fuel instead of having to go through the whole process of draining funnelling etc

  9. hmmm i ride a sport bike but it is still carburated….i dump a whole bottle of seafoam in and get on the high way and open her up….granted my bike is shit under 4k because it was made for racing but it does still help….but you also might want to buy a carb sync tool and sync them….only takes about 20 minutes to do and boy your bike will feel like an entirely NEW machine

  10. Got over 26K on my 2009 Vstar without it. Runs like a bat outa hell! You don't know what your talking bout Cuz.

  11. My bike had a rough idle and given any throttle it would stall. After using Seafoam, bike doesn't even crank to idle anymore 🙁

  12. Probably not a problem anymore but I've read that backfiring and hesitation can be due to a head gasket leak.

  13. Get yourself some Marine outboard TCW3 rated oil and add it at 1 oz per 5 gallons of gas. Add it every time you get gas. Most large parts store sell it. That bike will purr.

  14. I have a 04 kawasaki vulcan 750 and someone recommended I use this. My baby isn't turning over. I attempted to jump start it, thinking it was the battery, and it backfired and later turned off on her own. Any recommendations on what I should do?

  15. hey nice bike! i have an 85 cb45sc. been watching dawino6260's videos for years. recently moved to FL, and decided to visit the guy. he is the guru of all bikes like ours. mine would pop and backfire occasionally on letting off throttle too suddenly. he pointed to a "air pump diaphragm" on the side near the fuel inlet. said that it was just now beginning to fail. try looking him up. real nice old hippy. hhh cycles in Venice fl. anyways I thoroughly enjoyed your documentary! I used to wash mine as a kid and dad used to say maybe he would give it to me one day. he finally did. it sat for a while so I've already been through all the tricks to remedy symptoms of sitting. one of the worst things were the switches. i tried all sorts of contact cleaners and had to work them back and forth for a while. i hit them with a spritz of wd 40 occasionally. the ignition switch had to be taken apart and the little contacts cleaned. theres a guy polecat or something, has great videos on the same family of bikes like the 400t hawk. anyways happy riding, and we totally love your videos!

  16. I have recently purchased a 2000 Honda Valkyrie. Previous owner said sea foam would damage, corrupt carbs. I've heard to use an ounce per gallon of gas. Is this ok? What about using non ethanol gas with carbed bike? Thanks.

  17. Back firing is often something to do with the ignition timing. That is the timing is out to the point where the ignition occurs while the exhaust valve is open a little when it should be closed. But I imagine that these bike had CDI by the time this one was made. However, if it doesn't have the standard mufflers then they may not create the amount of back pressure needed to to prevent unburnt fuel, igniting inside the exhaust. If you have constant velocity carbs and you have mufflers other than stock mufflers it could be running too rich. Anyway the valve clearances are something else to check, so I would check the valve clearances and if this one has shims for adjustment I would get someone to do the shims for you. But if you can adjust the tappets yourself check you manual to see how to do it. Have fun.

  18. When my bikes start running bad from clogged pilot jets I use Seafoam but it sometimes take quite a bit and quite awhile to dissolve the crap, but it always works.

  19. About to do the same thing with my V Star 1100. Hoping it will fix the odd idle. This is the best video I've seen on using Seafoam in a bike.

  20. same thing i did except all sea foam in thr fuel line no mix. draining tomorrow and will see if it stops my leak or i have to clean carb

  21. For the backfiring, drain the floatbowls and fill them with acetone and leave it in for a half hour. This will remove any varnish on the jets or needles and increase you F:A ratio. Tony Surridge, I too have a cb450sc.

  22. This maybe a stupid question but why didn't you just put equal measures of Seafoam and fuel on a low tank (with say 1L of fuel or less) and just run that mixture through until you needed to fill up the tank?

    Surely that would have been much easier with no tools required!!

  23. This is the best method of Seafoaming if you want to let it sit in the carbs overnight. Your method is the simplest and requires only a beer bottle and a funnel. Great camera work, no bullshit title cards or bad music, or shameless self promotion. Great.

  24. 💀yoo just put it on the tank the more you add the better it cleans it legit fixed my carb problem on my yzf 450 I got a 1.1 gallon tank I put 2 cans of sea foam in my tank and half in my old it works way better

  25. And look up sea foams YouTube they will tell you that the more you add the better it cleans and it won't hurt your motor in any way shape or form and it won't fuck with ur spark plugs

  26. I thought backfiring was a bad thing too, but I talked to a mechanic and it also depends on how you a shift, if you down shift alot instead of braking it will backfire too, they sell exhausts that are meant to have that backfire sound cuz it some people's personal preference to sound like firecrackers when your ridin…ride safe bro

  27. Can anybody tell me how long does it take for gas to gum up. I just bought a bike Suzuki Boulevard s40 and it only runs when the choke is out. Bike sat for 2 years outside under a m/c cover. I'm thinking of trying Seafoam.

  28. DO NOT USE SEAFOAM. That shit don't work as well as B12.
    Use Berryman B-12 Chemtool Carburetor Cleaner
    and pour about 2 oz per gallon.

    Edit: Pour it directly into the fuel tank. Don't need to take out the fuel line lol.

  29. Seafoam does work but it has its good points and its bad points.!! It's over 40 year old technology it was invented for two stroke outboard boat motors that had a lot of carbon and oil build up on the Pistons and combustion Chambers !!!!!

  30. If you still facing problem with miss fire while reducing the throttle at comparatively higher speed, it may be due to air ingress in exhaust pipe (silencer), check for it and try to fix it, it may solve your problem.
    Only intake manifold air leaking will also disturb your bike idling.
    Happy thumping and sage drive,,

  31. the directions for the use of seafoam, is 1 ounce of seafoam per 1 gallon of gas, ride the bike with that mix in the gas tank, in other words, seafoam is more like a fuel additive, and using it this way, my bike is idling smoother, and running with 100% improvement. I recently bought this 03 honda shadow, that was previously owned by a cancer victim who no longer could ride and had the bike sitting in his garage without ever being started up.. It had a rough idle and backfiring, not anymore though.

  32. Dont be afraid of the seafoam.
    I run a 40/60 mix In the gas tank ('09 ninja 250 w/ 30k miles) to every 1k miles and shoot a 12 oz. can through the air intake (after removing the air filter) 500 miles later to clean up the double.carbs.
    Still running great on oem carbs w/o a rebuild and tons of hard riding.
    I've heard it can be used in engine oil too but havent looked into how.

  33. Check for vacuum leaks by spraying some brake cleaner around the boots. It will surge if there is a leak, replace the boots if necessary. Next, check your valve clearances. Plenty of videos on how to do it. You look like you are able to turn a wrench so have at it. Finally, pull the carbs off, remove the bowls, clean them up nice and remove the two jets in each and spray with care cleaner followed by compressed air. Reassemble, and finally, you should get the carbs synced. Replace the plugs and you should be good to go. Always run a bit of Seafoam in the tank. It helps to prevent varnish in the carbs.

  34. Backfiring is usually a bike running to lean. Pull carbs off and actually clean the bowls and jets/ passages. Seafoam is good but its a additive not a fix all by any means. Check the airfilter and clean or replace that. If its a aftermarket airfilter that is the problem causing it to run too lean. Replace with factory air filter or get you some new jets for the carbs to make more gas. Carbs may need tuned as well. Also if exaghts was.modified that will lean carbs out. When i moded my bike(less resistance exaghts and high intake air filter i rejetted carbs. No more bike farting and more peep on throttle. Good luck

  35. Your Hesitation is likely that Fuel filter …… Your running Gravity feed. That filter maybe restricting fuel flow.
    there are clear filters so you can see what is going on .
    I'd find one of those.
    Also if you suspect Plug Fouling Change Them !
    New plugs are Dirt cheap .

  36. Granted this video is old… I was having an occasional leak of fuel from the float bowls overflow on my 2005 Katana 750. I tried a half bottle of Berrymans B12 with a tank of gas and nothing changed too much. I was still getting the occasional dripping which would cause the bike to idle rough while it did it. While riding the bike ran fine once moving along….few weeks later I decided to dump an Entire can of Seafoam in my tank with a full 5 gallons of gas. Over the course of the tank my bike would do the white smoke deal. The bike began to run smoother throughout the whole RPM range and it has idled just fine and so far…no more floats dripping. Fingers crossed doing this just cleared up my carbs and possibly freed up a stuck float.

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