Setting up the bike properly.... finally

[JezZedexE1]

Just thought it would be a good thing to do, seeing as the bike was running but not quite properly.

Idling is a bit erratic, the fast-idle does not make any difference and overall a bit off. I also feel as though the engine temp seemed a bit higher the my other bikes.

Step one is to get the bike on the bench, replace fuel filter and get fresh petrol & new plugs.

Checked the TPS and the readings are within spec.

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Is there any recommended maximum height for the petrol tank? Is this too high?

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Out with the carbtune kit next.

[Streetfighterkz]

Is there any recommended maximum height for the petrol tank? Is this too high?

My thought is that the higher the tank, the richer you’ll be on your fuel. The return is further from the regulator and therefore the pressure loss is higher as the fuel needs to be “pushed” up into the tank which sort of causes a restriction. This restriction causes more back pressure and therefore more flow through the injectors. Again, I have no proof. I’m just trying to think back 12-15 years to my fluid dynamics class in college.

Later, Doug

[JezZedexE1]

That does make sense, I had thought the return could cause a problem. Thanks Doug.

I will lower the support frame so it is to one side of the bike but at much the same height as if it was on the frame. That way the return line will be closer to stock spec. (specifically the pressure) just a bit longer probably.

[Turboblew2]

My thought is that the higher the tank, the richer you’ll be on your fuel. The return is further from the regulator and therefore the pressure loss is higher as the fuel needs to be “pushed” up into the tank which sort of causes a restriction. This restriction causes more back pressure and therefore more flow through the injectors. Again, I have no proof. I’m just trying to think back 12-15 years to my fluid dynamics class in college.

Later, Doug

huh?? the return line could be 100' long & you wont notice any change in pressure to the injectors... thats what the regulator does.
Ive seen where the tank return bung gets plugged and the bike still ran.
It would be really simple to test... simply cap the tank return and pump the bled off fuel into a jug.
Also your premise would really look silly on a fuel system that doesnt have a return line... ala dead head.

The whole premise of using the tank is utter amateur anyways. The bike gets its fuel from the pump... so any gravity source prior to the filter would work. MotionPro makes an actual hanging fuel jug for carbed & FI'd bikes with graduated marks.

[JezZedexE1]

The whole premise of using the tank is utter amateur anyways.

That's me, an amateur. That is why I asked the questions. Page 2-8 of the manual.

[Streetfighterkz]

Sorry if I confused anyone. I was at the office and not thinking clearly. Just goes to show you shouldn’t text and work at the same time.

Later, Doug

[JezZedexE1]

Not a problem.

Starting again, all I need to do is plug the return and have a container hanging above the bike. The fact the return is capped will make no difference to the set-up & running of the bike!

Thanks.

[Charlie @ Evergreen]

Correct me if I am wrong but if you block off the return line from the FPR that goes to the tank your fuel pressure is gonna skyrocket up into the 60s. My valve on tank was stuck closed at one point years ago and that was the result.

[84zx750e1]

Correct me if I am wrong but if you block off the return line from the FPR that goes to the tank your fuel pressure is gonna skyrocket up into the 60s. My valve on tank was stuck closed at one point years ago and that was the result.

Charlie you are correct if returned blocked it will flood with fuel.

[Betterthanfabio]

I was working on mine and put a bung in the return line for some reason I can't remember. Forgot and turned on the kill switch. Fuel gauge reads to 100lb went past that.

[JezZedexE1]

So blocking it off is not a good idea then?

Joking aside, I have done most of what I wanted to do. Small hanging fuel tank with a return valve just to one side at about the same height of where it would be using stock tank fitted. It does run better now, but I still have to do the final adjustments to get the sweet spot I have heard about. I have a suspicion the return valve was a bit sticky/jammed, causing the trouble with starting.

[JezZedexE1]

Went for a ride and all seems good. Only thing is the rev's are a bit slow to drop. Time to pull the return valve apart and give it a clean or swap it over for another one to see if there is any change.

[Kawadoodle]

I pulled mine apart, it was seized up due to corrosion and the o ring had deteriorated. Cleaned everything up and fitted a new oring of similar size. Result, worked perfectly.

[JezZedexE1]

I have a new o-ring which fits but it may not be the correct size. The one I put in has an I/D of 4.4mm and a 2mm c/s. O/D 8.4mm

I think 4mm might be a better fit/size. As a matter of interest, what material is recommended/preferred? NBR Nitrile, Viton,etc. ??

[Kawadoodle]

For long term compatibility then choose viton. The NBR nitrile ages quicker, I believe, if there's ethanol in the fuel.