Fuel assembly

530 Views 18 Replies 2 Participants Last post by rvf16g, 24 d ago

Cak2024

Discussion Starter · 28 d ago

New to the forum and rc51 lyfe. My question is, what is the function of this my finger is pointing to. ?. Recently bought 2000 rc that been sitting 8 years and while replacing pump filter I noticed it disconnected. New assembly otw but I'm curious. Thx in advance

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rvf16g

· #2 · 28 d ago (Edited)

Fuel reserve indicator, thermistor, when the fuel tank thermistor warms in the absence of fuel to cool it off its resistance decreases and the fuel light comes on. You then have 5lt of fuel left out of 18lt

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Cak2024

Discussion Starter · #3 · 27 d ago

Ty so much for quick response. My other question would be will still work properly even tho that connection isn't being completed. Or would it not have a open circuit and render assembly useless. Sorry not a mechanic by any means but want to try my hand in learning as much as possible... thx again in advance.. new assembly should be here in week though.

rvf16g

· #4 · 27 d ago

Cak2024 said:
Ty so much for quick response. My other question would be will still work properly even tho that connection isn't being completed. Or would it not have a open circuit and render assembly useless. Sorry not a mechanic by any means but want to try my hand in learning as much as possible... thx again in advance.. new assembly should be here in week though.

You're welcome.
Yes, it will work fine, non essential to running engine, you just miss the indication of low fuel.

Cak2024

Discussion Starter · #5 · 27 d ago

I really appreciate the feedback so fast. Guess I'll have a new spare assembly. I'm definitely going to try this one this afternoon. Ty ty

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Cak2024

Discussion Starter · #6 · 27 d ago

Got it running thx again

rvf16g

· #7 · 27 d ago (Edited)

2

Cak2024 said:
Got it running thx again

You're welcome.

In case you want to repair the electrical connection of the reserve sensor you will have to grind/drill the green insulator (brown in your case because of fuel varnish/residue), uncover the link/pin and solder a wire from the sensor to that link. You can reinsulate using JB Weld WaterWeld which is fuel proof. The color of the wire on the outside of the assy is actually brown/black but the angle of the photo is misleading.

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Keep in mind that your assy has non OEM parts, fuel pump, hose clamps and possibly hoses. If fuel pump is Quantum or of similar quality you're good. I would be concerned about the hoses, they have to be SAE30R10 (J30R10) type, submercible to fuel otherwise they will deteriorate.

Regarding fuel varnish/brown residue you can use carb cleaner to wipe it out by hand and fuel additive in the tank to clean the whole system with running engine. I would also be concerned about the injectors' state after so many years of the machine sitting, if you experience unstable reving of the engine.

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Cak2024

Discussion Starter · #8 · 26 d ago

Ty, i def want to do fuel system clean out. It didn't want to run by itself for about first 3 min. But then started idling fine. First breather in 8 years you are Def correct, I've still got a couple other steps. Changed oil yesterday, prob coolant and clutch bleed tonight... ty again for the advice, hopefully I'll be able to return the knowledge one day soon.

Cak2024

Discussion Starter · #9 · 26 d ago

Guess my only question would be, is there any main components of the thermistor, that would need to be intact, just to rewire. Cause mine looked raggedy. The connection had broke from directly from the thermistor, i resoldered but then had broke from housing itself as I was trying to load assembly back into rank.
And unfortunately I couldn't find just a thermistor to ordered which lead me to first seek what the part actually was cause I couldn't find it..thx in advance

rvf16g

· #10 · 26 d ago (Edited)

Unfortunately i never found the specifications of the SC45/RC51 thermistor but can be done experimentaly. We could check the resistance/impedance with the sensor submerged into fuel in a bottle and next with the sensor in open air, dry. For this we need ofcourse a working sensor. I have seen reports for other motorcycle models of <wet resistance> = 10 x <dry resistance>. Keep in mind that the negative is the body/bracket of the sensor.

Make sure you flush the cooling system with appropriate chemical like Prestone prior to changing coolant.

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Cak2024

Discussion Starter · #11 · 26 d ago

I appreciate that, I'll Def use the Preston. And as soon as I find suitable replacement for thermistor I'll have to check back on testing and I'm really basic to mechanics, but want to try my hand with bikes not so much on cars lol...

rvf16g

· #12 · 26 d ago (Edited)

Seems it is a bit more complicated than i thought. The thermistor is supplied a 12V voltage from the battery via unknown resistance (maybe the dashboard fuel sensor light?) and it heats up.

If your sensor was connected, you could probably turn <key on>,press <run on>, even run engine (apparently some circuits supply power to the thermistor only when running?), wait for a few minutes for the thermistor to heat up, then immediately press <run off>, remove key, disconnect fuel pump connector and measure the resistance between the brown/black and the green wires on the fuel tank wiring side. Doing this with low and high fuel level you could find the resistance range of the thermistor but keep in mind that it changes slightly as air/fuel in the tank change temperature.

By the way it is called NTC (Negative Temperature Coefficient), the greater the temperature the lesser the resistance (Negative).

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Cak2024

Discussion Starter · #13 · 26 d ago

Probably need lil more training before I'm comfortable tackling that aspect. Lol. But update bike is running I had to bleed clutch it wasn't engaging at all. But now it's engaging but it's a tough lever pull.. and at warm up Temps hard to get into 1st from neutral at stop lights had to turn off to click in first. Any thoughts sorry to bug you, u teas possibly air still in clutch..

rvf16g

· #14 · 26 d ago

The SC45/RC51 does not have the smoothest clutch/gearbox by default, and this, below working temperatures, gets worse but there are modifications.
If you push forward with your feet the bike a bit at stop lights does it engage 1st gear?
What engine oil did you use? Is it 10W40?
Did you change the clutch fluid (DOT 4.0/5.1) or just bled the circuit? You need new fluid after so many years of inactivity.
There is a possibility that you have clutch master/secondary cylinder spring and/or clutch drum springs worn. Some clutch discs can get stuck together and not disengage when clutch lever is pulled.
Typically such a motorcycle needs master and secondary cylinder rebuild kit and new clutch discs and springs.
Read this Difficulty getting into 1st gear.

Cak2024

Discussion Starter · #15 · 25 d ago

Ty I'm Def going to look into it dome more this afternoon... ima try the rocking it also. I did use 10w40 and dot 4. I noticed on that thread link a remarkable about being layer down, and unfortunately this bike was, and on left side dragging foot shifter. It does seem to shift smooth just having the neutral to 1st issues but Def going to bleed all old fluid again. Try to flush it thru. I really appreciate all of the insight and advice.

Cak2024

Discussion Starter · #16 · 25 d ago

Drove today and yes the bike does ho into 1st if u walk it forward a bit, ty for tip. Clutch us still stiff as I didn't get a chance to bleed it this afternoon, and friction or catch zone on clutch is bout very end of my lever release is thus typical of 51s...?... ty in advance for feedback..

rvf16g

· #17 · 25 d ago (Edited)

Cak2024 said:
Drove today and yes the bike does ho into 1st if u walk it forward a bit, ty for tip. Clutch us still stiff as I didn't get a chance to bleed it this afternoon, and friction or catch zone on clutch is bout very end of my lever release is thus typical of 51s...?... ty in advance for feedback..

Do you mean little travel (short pull distance) of lever to disengage (friction zone) or vice versa?
Do you feel friction while pulling the clutch lever or is it smooth?

Cak2024

Discussion Starter · #18 · 24 d ago

Very short pull to engage half inch maybe and it's smooth just a tough pull. But Firtnetly i dont have to squeeze it to handle vars cause it engages so early lol.

rvf16g

· #19 · 24 d ago

Since it disengages with short travel it can't be air in fluid, you would have longer travel.
If you have no friction and leaks it can't be master/slave cylinders/seals too. Are the master/slave housings/cylinders OEM? Maybe someone changed analogy for shorter pull.
Possibly your clutch drum springs are worn/hard or previous owner has installed harder ones.
Regarding 1st gear maybe from the fall or abuse of previous owner there is internal damage but I would eliminate everything else prior to spending time and money on the gear shifting mechanism, axle, star, drum, forks, gear dogs.

In any case i would personally overhaul the drum plates/discs and springs, replacing them with OEM new ones. I would also, just in case, replace at least the slave seal.

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