Fuel economy and float questions

Jonj57

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Jul 16, 2016
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133
Hey all, been having a strange issue and I think it has to do with either my ignition, fuel lines, or float height or even all 3. I havent been able to tell yet by pulling off the bowl but I think my engine is consuming more fuel than my lines have been able to pull from the tank and it suddenly dies and needs around 10 minutes to start again. My thoughts so far are that its a combo of too small fuel lines/and a weak spark causing poor combustion/fuel economy. The float height might be a problem but I haven't messed with that or opened the bowl in a while for it to suddenly act up like this. It's also been smoking a lot more than usual and extremely hard to start.

Going to replace the stock ignition with a gas bike super charge, too broke for a jag but from my understanding it should still provide a much stronger spark than before an take away my possible weak spark issue. Already modified my woodruff key to put the timing more in line for higher RPM and cleaned the carb out completely. Next stop is finding out the correct float height for a dellorto 14mm sha and adjusting from there. Bought a new plug as well just in case, never hurts to start fresh!
 


Steve Best

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Sep 22, 2012
Messages
1,236
Whoa! just go simple first.
You diagnosis sounds pretty good, so check it out.
Pull the fuel line off the carb. Does fuel pour out or just trickle and drip?
If it pours out the tank filter is good, try removing the float bowl (carb in place). Trickle or pour?
If it trickles the needle valve is plugged. clean it with air, carb cleaner or a fine copper wire.

Get it fixed before you put the new ignition on.
Nothing like having a stack of mods on an engine and not knowing which one is screwing it up.

Steve
 

Jonj57

Active Member
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Jul 16, 2016
Messages
133
I wanted to replace the ignition anyways, but you're right one step at a time. I'll put the new system in once I've sorted out the rest of the issue. I'll probably end up removing the tank filter as I run a paper one already mid line and don't really need it. I don't think it's the problem but it can't hurt and is one less thing to worry about, then next step is to check flow in the lines like you said, then check flow to the bowl. God I hate opening carbs up....
 

Steve Best

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Sep 22, 2012
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1,236
Fear not Jon, the little Dellorto carb is a no brainer. Just don't lose any parts.
Do it over a concrete floor or someplace you can find the needle valve if you drop it.
Somewhere in the grass beside my garage there are many small lost parts...

Steve
 

Jonj57

Active Member
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Jul 16, 2016
Messages
133
Fear not Jon, the little Dellorto carb is a no brainer. Just don't lose any parts.
Do it over a concrete floor or someplace you can find the needle valve if you drop it.
Somewhere in the grass beside my garage there are many small lost parts...

Steve
Haha I've take these small carbs apart far too many times is the problem... New filter? Rejet. New exhaust? Rejet. Clog? Disassemble clean rebuild. Haha I dread the day my Seca 650Rj needs another cleaning, I hate CV inline 4 carbs haha
 

crassius

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Jul 23, 2012
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4,575
these things use so little fuel that almost any amount of flow that can be seen is enough to run it

excess vibration can cause fuel to foam in the carb and cause surging, but if it goes totally dead, then I'd be looking for something heat related
 

Jonj57

Active Member
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Jul 16, 2016
Messages
133
Carb cleaned and found a fuel clog in the small casting hole that flows fuel from the fuel line wheel and the float needle, just blew it out and cleaned everything else while I was in there. Runs and starts a lot smoother but still has the same problem with dying without reason. So I fixed one issue and now need to solve the other, I checked the engine while it was hot and can't find anything that seems out of norm, and on top of that it's around 10-30 degrees most of the time and has even died in freezing rain in the exact same way so I don't think it heat. Maybe the CDI is going bad and once it warms up it starts to go haywire? If that's the case I should have a new CDI/Coil in the mailbox today anyways so we'll see. Any other suggestions in case I'm wrong?
 

KCvale

Motorized Bicycle Vendor
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Apr 18, 2010
Messages
3,518
You running a stock spark plug?
If so replace it with an NGK 5944 (BPR7HIX) Iridium spark plug before you start 'fixing it'.

And while the plug is out pedal the bike up and down the street with the clutch out to blow any puddled fuel out of the crank case.

I am still amazed what those 2 things fix ;-}
 

Jonj57

Active Member
Joined
Jul 16, 2016
Messages
133
Oh god no! NKG plug was purchased before the kit even got to my door! And I've tried that but will do it again anyways, can't hurt to be a little extra clean
 

KCvale

Motorized Bicycle Vendor
Joined
Apr 18, 2010
Messages
3,518
Oh god no!
NKG plug was purchased before the kit even got to my door!
And I've tried that but will do it again anyways, can't hurt to be a little extra clean
Hehehe, good early call ;-}
 
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