Need help- 300ec not right!

[ucrtwf]

Hi Guys,
I've looked and looked through all the float adjustment posts, lean conditions, etc. I can't find one that matches my bike. ('10 ec300, with pwk carb) It did this before and after the RB carb mods.

Here's the issue-
When I'm going up a steep hill, my bike fluctuates in RPM with constant throttle input. It would also leak out the overflow sometimes just over the kickstand angle. I figured I would adjust the float height and be done with it. The 14-16mm dimension does not apply to my bike. I took it apart, measured 17mm, if I get it any lower than this- it won't compress the spring on the needle. I put it at 18mm just for a change, since I thought the fuel level was too high (puking out the overflow at shallow lean angles). The pictures found on the forum showing the float height don't look like my float. The ones in the picture look much more low profile than mine.
I took it for a ride, ran well- then I pulled a wheelie- not super long (200 yards), and it started cutting out (just like it would on a hill). All my other bikes have been able to sustain fuel for very large hills, and wheelies as long as I wanted.
I'm going riding tomorrow- any thoughts would be VERY appreciated.
Tim

 

[Jakobi]

Hi Guys,
I've looked and looked through all the float adjustment posts, lean conditions, etc. I can't find one that matches my bike. ('10 ec300, with pwk carb) It did this before and after the RB carb mods.

Here's the issue-
When I'm going up a steep hill, my bike fluctuates in RPM with constant throttle input. It would also leak out the overflow sometimes just over the kickstand angle. I figured I would adjust the float height and be done with it. The 14-16mm dimension does not apply to my bike. I took it apart, measured 17mm, if I get it any lower than this- it won't compress the spring on the needle. I put it at 18mm just for a change, since I thought the fuel level was too high (puking out the overflow at shallow lean angles). The pictures found on the forum showing the float height don't look like my float. The ones in the picture look much more low profile than mine.
I took it for a ride, ran well- then I pulled a wheelie- not super long (200 yards), and it started cutting out (just like it would on a hill). All my other bikes have been able to sustain fuel for very large hills, and wheelies as long as I wanted.
I'm going riding tomorrow- any thoughts would be VERY appreciated.
Tim

It sounds like its running out of fuel - float level too low. Usually the opposite happens when going down hill and the float level is too high. Too much fuel pushed in by gravity causing a rich condition/stalling.

Have you tried setting the bike up on a stand to run it and see at what angle it cuts out? or is it under load that its running short on fuel. Is it lean condition ie cuts out and gets herky jerky, or rich and blubbery?

Have you asked RB? Considering he knows stuff and things and you've spent money with him, and he's worked on and set up the carb, it'd be a good place to start!

 

[hannesd]

maybe a leaking needle?
if it doesn't close well enough, fuel keeps comming down...logically...

 

[gasser]

Also check your radiators. An overheating condition can cause varying rpm.

 

[ucrtwf]

UPDATE-
I went riding for a bit yesterday. The bike ran lean. I had the air screw ALL the way in, still at sustained throttle (half throttle or more), it would lean out. Also a new observation- a couple times when I would go over a mild jump, it would bog for 5-10 seconds after landing. Strange. I took it apart at lunch, one of the reeds had some very mild fraying at the corner, maybe .020-.050 from the edge. Anyone thing that could be an issue?
Overheating- not a factor. I've got a temp gauge on it, and it never runs over 200 deg F, and down in the 150-160 range when I've got some air going through the radiators. It's not a condition that builds.... it's there from the start (when cold of course it's worse).
Thanks again for any thoughts. I'll send Ron from RB an email to see if he has anything to say.

 

[GMP]

Split your vent lines up and run two high, two low, with the overflow also low. Also, the 16mm float height does not apply to the new carbs.

 

[ucrtwf]

Thanks Glenn,
Just to be clear, there are four hoses coming out of the carb. Two point up, two point out to the sides. Right now I've got the two pointing up- going up and over the slide cap and down. The two going out to the sides just come out and down. Do you mean route the hoses up instead of letting those hang?
Thanks again,
Tim

 

[GMP]

Yes, terminate them up high with no loop down, preferably with a small filter. The idea is to always have a free vent path. If they are all terminated down, the carb will not vent during a water crossing and will draw water into the bowl. This will also allow fuel that may enter the vent passages to escape easy. From what you describe you most certainly have a fuel level/vent problem, independent of jetting. I'd go back and check the float level and general assembly of the carb.

Edit:

Not the carb, but also make sure your gas cap check ball is free and the cap is properly venting. Cut the rubber gasket away from the vent holes in the center. The tiny holes can swell shut and you loose venting. Happened to me.

 

[Jakobi]

Yes, terminate them up high with no loop down, preferably with a small filter. The idea is to always have a free vent path. If they are all terminated down, the carb will not vent during a water crossing and will draw water into the bowl. This will also allow fuel that may enter the vent passages to escape easy. From what you describe you most certainly have a fuel level/vent problem, independent of jetting. I'd go back and check the float level and general assembly of the carb.

Edit:

Not the carb, but also make sure your gas cap check ball is free and the cap is properly venting. Cut the rubber gasket away from the vent holes in the center. The tiny holes can swell shut and you loose venting. Happened to me.

+1

The two lines that run up and over are the ones you want to reroute to the airbox. Some people will put a T joint in them at the top and run an extra length up to the airbox, but I simply ran them to the air box instead of down.

Good call on the gas cap Glenn! This ones always overlooked and such a simple thing can cause so many issues.

With the carb, I'm not sure which one came on your 2010. Mine has the shallow bowl, 17mm drain bolt, and a flat metal top retained by 2 phillips head bolts. The float level on these are around 7mm. I actually set mine up so that it is just off level. Its not a bad idea to connect the fuel up to the carb while you have it on the bench with the bowl off. You can then hold it level and modulate the floats to visually see when they start to flow and ensure you get a good flow of fuel.