TPS

520pilot · Mar 21, 2013

Guys,
Some feed back if you can assist...not for me but another Berg Brother on an 06 Fe 450.....he's a bit of a mad scientist for sure but has an issue that points to carb...just wondered, has anyone had a TPS fail or disconected it on a 450....if so could you share what the bike did when this was done / suffering this affliction

Appreciate your input

Cheers

Chas · Mar 21, 2013

On my KTM's, which should be similar to the Bergs in this regard, I cannot discern much if any difference when the TPS is connected or disconnected. The main function of the TPS is to add ignition advance under part throttle conditions acting much like the vacuum advance in cars a few years back.

Idle · Mar 21, 2013

Mine hasn't been plugged in in over a year. On a 550 and 650. I was warned that fuel economy would suffer, but it doesn't affect it enough to matter. The main thing is it makes it smoooth. It also doesen't overrev when it breaks traction. It just revs a little, then hooks up and goes.

It goes back to the stock default ignition map/curve. A rpm based advance.

With it connected, it seemed like any moderate wheelspin at all and it would just run away and make you close the throttle.

It lessens the hit, but I could barely tell a difference when I first disconnected it.

If might be more noticeable on a 450 if you really analyzed it.

You can rule out the TPS being maladjusted if you unhook it and there's no change in it's running.

Lots of folks leave them unplugged. What they do is advance the timing way too much in certain conditions. No load high rpm and closed or partially open throttle.

Think coasting down a long hill,,, popping and backfiring because the ignition is so far advanced, it's sparking way too early. It's just too much needless violence happening in the CC, just going down a wee hill..

520pilot · Mar 22, 2013

Ok guys...appreciate your input my mate's 450 has suffered a few afflictions and after checking / replacing stator and finding a valve spring that needed to be replaced he still finds the following (for his 06 fe 450)

Now starts perfectly
runs well from teh bottom rev range up
but suggests that it still feels flat once it gets to operating temp.
set valve clearance

He's replaced needle and main jet
gone back to standard on all jetting

But still finds the same, says when he changed carbs from another 450 it seemed to run perfectly even at high engine temp....so it points to carb....this test is being done again in careful check conditions to make certain it's correct and results are qualified

Hence I wondered just how much the potential of faulty / badly set TPS might come into play....doesn't sound like it's a real possibility though after reading your posts. He's no fool, being part of a Nitro funny car drag team, so he knows engines inside out....he is a bit nuts and for sure is retentive, but seems to think it's still lacking in power and flat in mid to higher rev range

I told him to buy a 550, makes the front of your pants stick out and stretches your arms, but it may not be the best case answer (although my 550 is superb)

He's been over the carb to the best of his ability yet can find nothing that seems out of place, so, from the Berg community any ideas...we can strike from the list

Valve adjustment
compression
bad fuel
stator
needle and jets
and I think TPS point is clearly not the answer

Ideas....?

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