TPS Adjustment: Was 840 - Now 590 Can't get to 500 - No Way!

[Tempest]

Following on from my (beginners!) Carb take apart (which has gone well so far, thought of course no idea till it's back on the bike!)

I was told about setting the TPS to 500.

I did a search on these forums, and elsewhere and indeed, this 500 number seems to be the agreed value, some saying some even come out the factory nearer 900! (I don't understand how that can be right, but anyway...............)

So, I checked mine (never touched it before) and it gave a reading of 840 (don't recall the bike having any issues in the past, but anyway, following forums advice I luckily has the right, security star keys and to cut a long story short, I was only able to get down to just over 600

Puzzled.... I looked at how it worked and connected, and saw the only way it could be any lower was if the throttle stop screw was unscrewed a bit (never touched that ever either!)

I see adjusting this screw moves the closed position of the butterfly's.

So, as I say, I unscewed the throttle stop, which allowed the butterflies to close fractionally more than they were before, till I got to the point where, the edges of the butterflies were then physically the STOP and not the stop screw (can't go any further) so I turned the stop screw back just a fraction, to take any pressure off the butterflies, so it's just barely touching the stop screw.....

After I did this, and with the TPS body swung as far as it will go, the lowest I can get is a reading of 590.

To get to 500, I'd need almost 1mm more travel.

Now, I am in engineering, and I COULD modify the two screws (grind the threaded shank of the screw down, where it passes thru the TPS body) and probably just about get to 500.

What are your thoughts?

Firstly, as the bike (I thought) was ok, and this was at 840, and now at 590, do you reckon this 500 would be right for "ME" ?

Secondly.... this throttle stop screw, as I said, now it's stopping exactly at the point where the butterflies are phsically pretty much touching the bore of the carb.... Is that right, or does there need to be a slight gap for the bike to idle ok?

Advice would be welcome... Thanks

[8541Hawk]

First the "fix" is to slightly bend the tab that drives the TPS so you can get to the 500 ohm reading.

The reason that they come from the factory with different (and usually high readings) is that they are set from the factory for best emissions not best performance.

As for where the butterflies are set, well you won't really know what is right until you get the bike running.
Yes there is a small gap but no "set" place to adjust them.

This is also why it takes a few times to actually get the TPS to the reading you want.

Adjust the TPS and the idle changes.
Adjust the idle speed and now the TPS reading has changed.

So you can either set it "close enough" and be done with it or spend some time and get it dead on, it is up to you.

[popkat]

you have to adjust the Tickover back up to get it to idle, you want 12-1300 rpm. Don't worry much about the TPS position I'd be surprised if you notice any difference anyway, bring Idle back up and set it the 600 or so you got and leave it at that.

[Tempest]

Thanks to you both.

Ok, well, as I said, I've probably lowered the tickover speed down too low at the moment, to get my 590 result.

I've done a bit of calculation/measurement, and if I grind the screws down on dia. where the screw passes thru the TPS unit, leaving full thread on the end, then I can probably get 1mm more travel, and I need just over 0.5mm to get to 500 NOW.

So, spinning the thread off the bolts in that area, 1mm a side (that will be the thread depth plus a bit) I think I can go under 500 now, but by the time I screw the throttle stop back up, I'm probably going to be pretty much there.

As I said, the bike ran ok in the past (well I thought so) and it must of been at this 800+ value.
500 seems a GIANT change, but hey.... If forums say 500, then 500 (or as near I can get) it shall be

I have jets cleaned (ultrasonic tank) and I manually cleaned the two needles, spotless, floats cleaned and the float shut off valves, that's all back together with the float bowls back on, and done up super tight again with a nice screwdriver.

Other than fiddling with the TPS I'm pretty much at the "now how the hell does this go back on stage !"

Going to get a gallon of Shell's Best for the restart (when I get to that point)

Also, before I do that, I need to fix the very slight drip I seemed to just started to get from the fuel tap area.
It was not there before I awoke the bike from it's far too long sleep. But I noticed a smell of petrol and damp on that flappy black plastic bit that kinda wraps around the fuel tap.

Need to take the tap off / investigate that (And advice re that aspect, before I do something I should not, would be much appreciated)
I also thought, ok, I'll change the fuel filter also (may of got some gunk in the tank that caused some of this carb blocking) but then it struck me.. The fuel pipes come out of the tank direct to the carb.... So no fuel filter????

Appreciate advice re the fuel tap area I need to address... Thanks

[Wicky]

Fuel filter is internal to the tank - http://www.bike-parts-honda.com/pieces- ... STORM.html

Try fitting a new rubber vacuum diaphram in the fuel tap to stem the drippy leak.

[Tempest]

Fuel filter is internal to the tank - http://www.bike-parts-honda.com/pieces- ... STORM.html

Try fitting a new rubber vacuum diaphram in the fuel tap to stem the drippy leak.

Almost looks like 2 vertical filters in that exploded view!

I just need to take something apart 1st I guess, to "get in there" and see what conditions are like. anything split or perished.

There was no leaks ever, till just now, when I tried to restart bike, and one carb float was stuck, so wondering if this caused anything pipe/pressure/fuel wise to cause this to happen?

But either way, I want to get at that / those filters so I can thoughrally clean the tank out with fresh fuel and remove any crud on the filters, as there is bound to be.
Likewise, I don't want any crud getting straight into my lovely cleaned carbs !!!!

[RickTheHuman]

Like Popkat said, all you have to do is bend the lower metal tab down to create a larger gap that the TPS fits into.
Remove TPS to access and bend it very gently with pliers. You will easily get 500 ohms this way. Much easier than machining bolts.

[Tempest]

Like Popkat said, all you have to do is bend the lower metal tab down to create a larger gap that the TPS fits into.
Remove TPS to access and bend it very gently with pliers. You will easily get 500 ohms this way. Much easier than machining bolts.

Thanks.

Well, it's too late now
And at work tomorrow.

On the grinder I use, honestly grinding the bolt threads away to high accuracy will be a doddle on what I use at work

but will also look at the bending option tomorrow evening also.....

As I say, fuel tap/filter is the next on the list before I can go much further, and reconnect things

[8541Hawk]

Like Popkat said, all you have to do is bend the lower metal tab down to create a larger gap that the TPS fits into.
Remove TPS to access and bend it very gently with pliers. You will easily get 500 ohms this way. Much easier than machining bolts.

Hey I guess I have a new name now.......

[RickTheHuman]

Like Popkat said, all you have to do is bend the lower metal tab down to create a larger gap that the TPS fits into.
Remove TPS to access and bend it very gently with pliers. You will easily get 500 ohms this way. Much easier than machining bolts.

Hey I guess I have a new name now.......

Apologies 8541Hawk.... woops

[8541Hawk]

Like Popkat said, all you have to do is bend the lower metal tab down to create a larger gap that the TPS fits into.
Remove TPS to access and bend it very gently with pliers. You will easily get 500 ohms this way. Much easier than machining bolts.

Hey I guess I have a new name now.......

Apologies 8541Hawk.... woops

No worries...... I thought it was pretty funny and was just giving you a hard time.....

[8541Hawk]

Though I do agree with Popkat that this isn't really a big deal.

As long as you are kind of close you should be just fine.

It does smooth things out when you pull it down from the 800-900 ohm range ,they seem to run at, but needing to be dead on isn't worth the effort IMHO.

[popkat]

If you can get the fuel filter out without damaging it then you can clean it and put it back in, check the O ring is in good condition though, fuel filters aren't cheap for these..
You can strip and clean the petrol tap, they can get stuck and a bit mucky with old fuel inside, just make note of how it goes back together, it's worth doing before buying new parts.

[Tempest]

Thanks again for the info.

Ok, well, taken on board the fresh comments about reaching the 500 value. when I searched these forums (after 1st finding out about this thing) people were saying how accurate trying to get it, 501, 502 etc etc, so from that it sounded like it was deemed important. Glad to hear now it's no so critical as those posts made out.

Secondly, yes, would be nice to give fuel filters etc a nice clean in an ultrasonic bath.

My only uncertainty so far is that, from memory, the tank has the central fuel tap? Then at least 2 more tubes to the right and left of that one.
And without looking can't recall how they all attach. I guess I have to take all these tubes off the tank to get to everything?

Actually.............

After reading some posts here about filter tearing, and expensive to replace..............

Perhaps rather then disturb these, it would be simply more sensible, once the tank is off to just wash the tank out, slosh it around, again and again with clean/fresh fuel, to wash anything out the tank, and check fuel runs clean, than disturbing things and do more harm that good... What do you think?

I to need to address the central tap though, as I said I had a tiny tiny leakage (drip hanging there kinda leak) before I started this..... But removing the central tap/part isn't as bad is it?

Not my bike, but pretty sure it's just like this:



I had a tiny tiny drip just hanging there from that low point on the tap.

So, do I need to remove this tap from the tank, or just take it apart where is it?

Thanks

[popkat]

You've already got the pipes off as you've removed the tank and carbs. Remove the tap take it apart and clean it out, pop it in the ultrasonic bath once the diaphragm is removed. The fuel filter sits inside the tank where the tap goes, you'll see it when the tap comes off. once you've got the tap back together put a small pipe on the small hole at the rear and suck/blow, you'll hear and feel it work the diaphragm, you'll know it's ok then. Once back on the tank and with some fuel in it there should be no leak, turn the tap to on position there should still be no leak.