400f cuts out up rough hills
Posted January 11, 2013 - 01:27 PM
I finally found a good jetting combination But now that I have been on a few off-road rides have found the odd problem that if I hit big whooped sections or rough steep uphill the bike dies for a second and then goes again. I mean completely cuts instantly then comes back a second later.
I assume it's a fuel level problem in the bowl but is it floats or float valve causing it? on the flat ground it is flawless.
Posted January 11, 2013 - 01:29 PM
Posted January 11, 2013 - 02:07 PM
I took all vents off carb.
Posted January 12, 2013 - 06:17 AM
Posted January 12, 2013 - 01:26 PM
I do still think its fuel related because I can chug slowly up until a certain angle and it will stop and go and stop and go again it does give a bit of a pop as it dies while I'm on the gas.
If I go full WOT I can keep it going up a hill but it cuts out worse at mid.
Problem is that I can't tell if it is flooding or starving.
Posted January 12, 2013 - 02:07 PM
Posted January 12, 2013 - 07:24 PM
I'll bet we can figure this out...
Posted January 12, 2013 - 08:46 PM
I would say for sure that is starvation.
I would raise your float level 5mm (or just properly set it to factory specs),and look at the main jet to see if it has the anit-surge plastic funnel.
You can get the bike running and tilt the crap out of it to replicate the gas position in the bowl....
If it does not drool gas out of the overflow when you tilt the bike over 20 degrees, then the float level is too low.....
Edited by Krannie, January 12, 2013 - 08:47 PM.
Posted January 12, 2013 - 11:21 PM
I'll give it a go.
This is the last issue to fix in what started out as a totally screwed up carb.
Posted January 27, 2013 - 09:57 PM
So the only thing I can think of is my float needle is dodgy. I think the little spring loaded piston on he back might be dead or it's jamming open on rough stuff.
Going to order a new float needle. I'd get the seat too except I don't think I could get the old one out. It looks like it's pressed in.
Any other ideas greatly appreciated as its getting a bit frustrating now.
Posted January 28, 2013 - 07:03 AM
Posted January 28, 2013 - 04:17 PM
When the bike is stationary it seals correctly and no problems.
But when on rough or steep ground (up or down) I think you are spot on about the main getting swamped. I can JUST keep the bike running if I go FULL THROTTLE which must be just enough to keep the fuel level down a bit but if I back off it bogs then goes then bogs then goes.
I have ordered a new float needle, so HOPEFULLY it will end my frustration.
In other breaking news, I have been running a #45 pilot with NO MAJ as an experiment and it has worked brilliantly to solve my Hot starting issues. I have just received a #40 pilot so I will put my #75 PAJ back in and hopefully get better response from the fuel screw as I'm only at 1/2 turn out right now.
It's getting so close to being a good bike I can taste it.
I'm still baffled about how much I have leaned it out to make it run well......
1st clip OBEKP needle
Could the float needle have been causing my extremely rich conditions all along ?? Because that means my jetting will need doing again....
I guess I'll find out when I get the new Float needle.
Posted January 29, 2013 - 04:12 AM
On the bright side of things, just look at how much knowledge you've gained from all of this jetting run around!!!
Posted January 29, 2013 - 02:45 PM
I can now strip out and rebuild a carby in about 10 mins.
It's always the simplest things that trip you up.... in hindsight I should have replaced the float needle at the start, because it did initially leak but then seemmed ok after I fiddled a bit.
Big thanks to William, Krannie and Maniac for expert guidance through the dark arts of carb tuning.
Hopefully by next week my troubles will just be my riding skill instead of the bike
Edited by Thommo_400f, January 29, 2013 - 02:45 PM.
Posted January 30, 2013 - 03:59 AM
Posted March 16, 2013 - 08:49 PM
If I nail it from standstill it pulls hard all the way. No off idle bog at all.
If I chug in 2nd and pop a low speed wheelie it bogs/coughs at the top which causes wheel to come down and then all is good again. Same if I hill climb. Coughs on steep rough stuff. It does cough on really steep down as well but less noticeable since I'm not on the gas.
I have tried the float at 9mm and it wouldn't even go up a smooth hill.
I've got it at about 12mm now and it helps but is still bad.
The one thing I am not sure about is how deep the seat should sit in the carb body. Should the hex nut section of the seat be flush with the edge of yhe orifice? Wondering if the seat could possibly be pushed too deep?
Posted March 17, 2013 - 02:28 AM
Posted March 17, 2013 - 01:16 PM
From memory there is a retaining screw for my seat so I doubt it could be the wrong height....:/
Are there any air passages that lead down into the bowl that could be getting partially blocked by fuel splashing?