bpw

I doing a bit of a custom build, and Im trying to run basically straight pipes. Bike wont run worth a **** lol... Yes I know why and yes I know about back pressure.

So, Ive put a baffle in them still wont run. It'll start run for a few seconds then die. I put a more restrictive baffle in, same thing. So next Im thinking the solution may be with a bigger main jets.

Id like to know what size stock is and also if anyone can pint me to a place I can buy just the jets that would be great I dont want a "Kit"

I know the bike isnt gonna run at its peak like this but its more of a ratrod and I just need it to run well. Any help is appreciated.

-Brian

7moore7

What color is your bike? This is important... if it's not yellow there's no point...

But in actuality, do you know what the jet settings are now? While it won't run great with strait pipes, it should still run, even with stock jets (at least mine does with stock headers and no slip ons). Stock is 175f/178r for the mains, and 45 pilots in the US. The jets are all "Keihin series 21" and can be bought at places like ronayers.com/bikebandit.com or most local motorsports shops.

I think you should see where they're at now, as there may be more at issue than just a mains adjustment. If if won't idle, it's not a mains issue...

smokinjoe73

Wow, this bike with straight pipes wont just be loud, they will hurt people's feelings.

Have you run it with pipes to know your baseline? Meaning was it running fine with pipes but not without?

Are you gonna paint a name on it like skycrusher, ballstomper, or something similar?

bpw

Currently the bike is red, and flat black... and gloss black.... and blue.... oh and white


I posted a pic awhile back its not for everyone (that was apparent lol) but yes it did run with the stock header and aftermarket cans. After I put the "baffle" in its alot quieter when it does idle for 25-30 seconds but still wont stay running. My theory was because there is much less back pressure a bigger main jet would kinda sort things out and get me running at least as a starting point.

But yes its loud (when it runs for a few seconds),yes its ugly (right now) but its coooool, any way any help is right on and thanks 7Mo

7moore7

One thing you may want to keep track of during this project is those exhaust valves. I had a my headers loosen up from improper install (ahem...can't believe the idiots I let work on my things!). My exhaust valves kept creeping out of spec and I could not for the life of me figure out why. Eventually I replaced the heads to just be rid of the problem once and for all and that's when I found the loose headers. Anyway, turns out I was burning them up, and from further reading I am 95% certain it was due to long term leaks at the header mount.

Now, I'm not sure this will be an issue in your case. From my understanding if you have long enough pipes that the intermittent reverse flow from the valve movement doesn't expose said valves to the atmosphere (containing caustic oxygen), you should be fine. Plenty of other motorcycles do it!

smokinjoe73

So it idles long with cans but short without? Thats odd. Sounds like fuel starvation. Is there any chance its a fuel flow issue? Vacuum line hooked up right?

7moore7

I'm with Joe, I wouldn't limit your troubleshooting to just jets... there may be other players in the game...

jerryh

Running out out of gas of course wow. Easy for me to say

bpw

At first I had the vaccume line backwards.... At least I think good idea though. I always get those screwed up. Have a hard time remembering which goes where.

captainchaos

I've run several superhawks for a short time with open midpipes just messing around and besides the fact that everyone's ears were bleeding the bikes still ran fine . Your problem lies elsewhere and it's not running like **** because of the exhaust. Besides the vacuum lines what kind of shape are the carbs in and have you considered cleaning and rebuilding them? Or if you're lazy like me the last superhawk I bought and resold I just bought a clean set for cheap off a freshly parted bike, swapped them out and the bike ran perfect.

8541Hawk

+1 I've never had an issue with the bike running with the cans removed.... other then sounding like you are at the pits of a NASCAR race....

bpw

Now that you guys got me thinking (thanks), the problem could be all sorts of things.

Basically I took a perfectly good running motorcycle and proceeded to dismantle it then put it back together using all sorts of different parts and now Im perplexed as to why it wont run lol. Dumb dumb dumb...

Ive been working on it for about 6 months now, I rode it home so I KNOW it ran fine. But you guys make some good points. Im pretty sure the vac lines were correct (tank is off right now) I put a CBR tail on it and maybe in the process didnt remount a sensor right? If theres a tip over sensor maybe I screwed that up?

Another thing the Captain Of Chaos got me thinking about is, the bike sat for months I tried to empty the carbs but maybe the Ethanol in this new fuel gummed them up? IDK any ideas will get followed up on and I appreciate your brains.

captainchaos

Yeah haha they definitely do sound like stock cars once you wind it up past 3 or 4k rpm. Mmmmm think I'll go take my mufflers off

captainchaos

Yeah as I'm sure you're already aware of ethanol sucks the big one, at least in that it goes to hell faster than gas used to. Last time one of my superhawks sat a couple months without starbrite in the gas it puked foul fuel all over the floor when I went to start it and had a stuck float.

jerryh

Hey I went from RS3s to stockers with bafflectomy after hearing sorneys. Total revving stock car moan. A sound I missed til now. My father and I went often but I stopped going when he passed in '95

bpw

I had a sticky float in a gxsr and a ktm do the same thing.

smokinjoe73

when you say nascar, I assume you mean motogp.

Kurt999

Pull the plugs, are they fouling or are they dry? If they're fouled make sure the rubber vent pipes (that come one from each carb and route through the side plates to the gap between the carbs) aren't pinched or blocked. If the plugs are dry then check the fuel tap, vac line to the tap and floats and float valves in the carbs. Run a remote tank or stick a funnel in each fuel pipe and CAREFULLY fill with fuel and run the bike to eliminate anything in the fuel tank. Have you had the carbs apart? If so have you wound the fuel screws out to their original position? Are they clean inside?

With open pipes on the bike will still run, don't start changing more stuff because you'll just get confused and end up chasing your tail