CentralCoaster

Since when does a carb'd bike need a throttle position sensor?

I loosened the brackets on the carbs to help remove them to do the valve cover gasket. When I put em back together, apparently the throttle sensor spring and plastic piece fell part way out and got smashed in there.

The plastic pin broke off inside the sensor, so now the sensor doesn't turn.

Can I still ride it tomorrow without this piece? What does the TPS do? Looks like $100 for a new one.

CentralCoaster

Ok, so it controls ignition timing. So I'm guessing I'm gonna get no extra spark advance at higher rpms and the bike won't make much power. Should I even bother putting the bike back together for the ride tomorrow or just wait till the new one arrives? Is it good enough for an easy ride?

We've got a ride out to Vegas planned for Thanksgiving too. Dammit.

VTRsurfer

With retarded timing (no spark advance at higher RPMs) you will run hot. Of course with the torque our bikes make it would probably still be rideable, but I don't think I'd risk it.

VTRsurfer

Try going "around the block", not too far from home, and watch the temp gauge. But I don't think a destination ride would be a good idea until the new TPS arrives. If you don't twist it too much, it would probably be okay for a short one. Just keep the RPMs down. Nice riding weather this weekend.

CentralCoaster

I found one guy on a CBR forum who said he didn't notice a difference, and this other guy says the same here:

https://www.superhawkforum.com/forum...&highlight=tps

I managed to get it superglued back together, and it works on the bench at least. I'll install it and set it to 500 ohm at idle and take it for a spin tonight to see what happens.

FWIW, it appears to be nearly the same part as used on many Honda cars of the same timeframe. These have the connector at a different angle and it looks like they'd be a tight fit on the Hawk, but I found a post from someone that said they've used em. The car units are available on ebay for $30, or you can go to a junkyard. Honda does not sell them seperately from the throttlebody (and they're attached with those stupid secure screws.)

Local dealers want $110 for the bike TPS and may not be able to get it until next Friday. Ron Ayers wants $80 and takes a week to ship even overnight stuff, two weeks otherwise.

inderocker

I've ridden with it unplugged and haven't noticed any difference.

killer5280

That has happened to me, too. Forgot to plug it back in and didn't notice much, if any, difference.

CentralCoaster

So the glue didn't hold up, I left the part off. Bike ran a little louder than normal, but felt fine.

Without the sensor am I getting more advance, or less advance with throttle? And is either case going to burn holes in the piston or something on a vegas trip in cold weather? I'm trying to decide whether to buy one local and get it before the trip or order online and save $40. I'll keep a close eye on the temp this week.

Fuel mileage was unchanged.

VTRsurfer

If the TPS controls spark advance, you will get less spark advance with it disabled. EXCESSIVE spark advance will cause detonation, which could eventually blow holes in pistons. I've seen it. I have 2 pistons in my classroom that look like someone smashed a hole in them with a hammer, both caused by detonation.

So with LESS advance, holes in pistons are not in your future.

CentralCoaster

That was my first thought, but another guy was telling me the sensor would actually retard timing more under heavy throttle to prevent detonation. This makes sense to me, assuming that timing is advanced by something else.

On my carb'd truck timing advances at idle (high manifold vac) and at higher rpms (centrifugal weights), but backs off under heavy throttle (due to low manifold vacuum). Not a big deal for now, as this trip to vegas is going to be like something out of easyrider.

CentralCoaster

From FSM:

"The ignition control module (ICM) varies ignition timing according to the engine speed. The engine coolant temperature (ECT) and throttle sensor signal the ICM to compensate the ignition timing according to the coolant temperature and throttle opening."

"Throttle sensor... inspection

Disconnect the throttle sensor connector. Start the engine. Connect the throttle sensor connector when the engine speed is 3500 rpm or above. The engine speed should increase."



Ok, you got me, sounds like it does advance the timing, because that usually increases engine speed.

Hawkrider

I have an extra TPS I'll sell you for $50. PM me if interested. I'll test it on the bench before I send it.

CentralCoaster

Definitely interested, assuming it's not the car unit. Where did it come from?

BTW, do you know if these are M5 screws holding it on?


PM me with where to send the money.

Hawkrider

No, it's not the car TPS. I bought an old set of carbs a while back and the TPS was still on them.

Dunno about the screws. I will slot the stock shear bolts with a Dremel and send them along though. They are removed/installed with a flat head screwdriver.

PM sent.

CentralCoaster

Thanks man, but don't bother with the screws, I already slotted mine.

Luckily I was able to remove them using minivise grips on the top one and a hammer and punch on the lower one. So I didn't have to pull the carbs off.

Hawkrider

Ah, too late. It's already boxed up! PM sent on shipping info. Thanks for the purchase!

Gregw

Is there a restocking fee for returned screws?

Hawkrider

Yes, and it's really high...thus you're screwed. (Sorry, couldn't resist...)

CentralCoaster

Har. Har.