Okay, I see the TCI... whats this beside it?

[Chaharly]

Hey guys, got the bike pulled down pretty far so I'd like to pull the plugs at the TCI and give em a good look over and a cleaning. Underneath I can see the TCI and the two plugs that go to it, but whats this thing beside it? I'd like to pull the plug on that too and clean it. Just curious

 

 

It looks like it might be the MAP sensor?

[snyper316]

Hey guys, got the bike pulled down pretty far so I'd like to pull the plugs at the TCI and give em a good look over and a cleaning. Underneath I can see the TCI and the two plugs that go to it, but whats this thing beside it? I'd like to pull the plug on that too and clean it. Just curious

 

https://www.venturerider.org/forum/attachment.php?attachmentid=115677

 

It looks like it might be the MAP sensor?

Yes it's a vacuum sensor for tellimg the TCI WHAT your carbs are doing.

 

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[cowpuc]

My guess is it's the vacuum operated spark advance Cha. Another guess would be that if you followed the vacuum line you see coming out of it it would lead to the number 2 jug (left side front cylinder, left side when sitting on the bike = same side as the shifter is on. On the 83's that line is not plugged into the nipple on the intake where you hook the sync gauges to but, I believe on all following 1st Gens (I know the 84's are like this cause my 1st first gen was an 84 and it was) had that line hooked directly onto the intake nipple in place of the rubber plug like the other 3 jugs are.

Simply put, vacuum on that line is what advances/retards the ignition timing..

Thats my guess buddy!! Now hang out for a spell and see what the gurus say..

[bongobobny]

Yup, that puppy is your "Boost sensor" which gives the TCI the proper information for spark advance when accelerating. It is a VERY important part! With neither vacuum or pressure, it should be putting out 2.5 volts, and with vacuum, the voltage changes one way and with pressure, it changes the other way. I forgot which way is which but it's range os zero to 5 volts...

[Chaharly]

Thanks guys! While I'm this far into the bike i aim to check third voltage while not running. The manual shows taking it out and jumpering it with a battery and testing the voltage out of the signal wire. According to my manual it should read 2 volts.

 

I should be able to test it by slipping a pin through the plug on the sensor wire and be able to test it right on the bike right?

[cowpuc]

Thanks guys! While I'm this far into the bike i aim to check third voltage while not running. The manual shows taking it out and jumpering it with a battery and testing the voltage out of the signal wire. According to my manual it should read 2 volts.

 

I should be able to test it by slipping a pin through the plug on the sensor wire and be able to test it right on the bike right?

 

Seems viable Cha but still wonder of unplugging it (cant never go wrong going by the book) and cleaning the terminals real well and checking the lead for 12vdc and then jumpering like the book says would be the better option if you can get at it. Clean those terminals on the TCI real well too..

[Chaharly]

Seems viable Cha but still wonder of unplugging it (cant never go wrong going by the book) and cleaning the terminals real well and checking the lead for 12vdc and then jumpering like the book says would be the better option if you can get at it. Clean those terminals on the TCI real well too..

 

 

Gotcha! Think I'll take some brake cleaner and take the airbox off. So i can get to everything a little easier

[luvmy40]

The easiest way to check the boost sensor is to disconnect the vac line from the carb or manifold and hook it to a mighty vac style vacuum pump. With the engine warm, at idle, no enrichment, pull a slight vacuum. if the idle changes, the sensor is working.

[videoarizona]

The easiest way to check the boost sensor is to disconnect the vac line from the carb or manifold and hook it to a mighty vac style vacuum pump. With the engine warm, at idle, no enrichment, pull a slight vacuum. if the idle changes, the sensor is working.

 

What a simple but great idea!

Geesh, thanks for that!

[luvmy40]

Just be careful to not pull too much vacuum. You could damage the diaphragm.

[cowpuc]

The easiest way to check the boost sensor is to disconnect the vac line from the carb or manifold and hook it to a mighty vac style vacuum pump. With the engine warm, at idle, no enrichment, pull a slight vacuum. if the idle changes, the sensor is working.

 

GREAT IDEA 40 :clap2:... Wonder if doing it with a syringe to pull the vacuum if you could test the viability/integrity of the vacuum line system in the process,, DEFINITELY got the old beaner thinking here @luvmy40 = YOU DA MAN!!

Thanks!

[luvmy40]

You could probably pull enough of a vacuum with your mouth if that's all you have to work with.

[Chaharly]

@luvmy40 that is great advice, but I've got the battery and everything out at the moment. Cleaning stuff up and wiring up the new fuse box. I couldn't get it off because the screws were froze on but managed to with a friend test the sensor on the bike and everything checked out there. The TCI spades definitely looked dry, but not corroded. Ill pick up a file and clean it out and spray a little lithium in the plugs before putting it all back together.

[Venturous Randy]

This would be a really good time to take the TCI off and move it to the top of the air box. You will not have to lengthen any wires as you can move the wiring harness around the side of the airbox and have enough room to plug it up. The hardest part is getting the screws on the TCI to break loose as they have been in a pretty bad environment for a long time. It also may help to cut one of the TCI mounting bosses off so you can mount the TCI a little closer to the battery to give a little more room for the cover.

Given that there seems to be a bit of voltage loss by the time the current gets to the TCI, I mounted a small relay next to the TCI with fused power coming from the battery and the power that was to go to the TCI was used to power the relay. There is probably only about 9 or 10 volts that goes to the TCI after everything goes thru ignition and safety switches and the CMU.

Randy

[Chaharly]

This would be a really good time to take the TCI off and move it to the top of the air box. You will not have to lengthen any wires as you can move the wiring harness around the side of the airbox and have enough room to plug it up. The hardest part is getting the screws on the TCI to break loose as they have been in a pretty bad environment for a long time. It also may help to cut one of the TCI mounting bosses off so you can mount the TCI a little closer to the battery to give a little more room for the cover.

Given that there seems to be a bit of voltage loss by the time the current gets to the TCI, I mounted a small relay next to the TCI with fused power coming from the battery and the power that was to go to the TCI was used to power the relay. There is probably only about 9 or 10 volts that goes to the TCI after everything goes thru ignition and safety switches and the CMU.

Randy

 

I'm surprised they put all that extra wiring in there for the TCI anyways. No wonder there's a huge draw, but it must be designed to work on the lower voltage? Can I ask what you mean bu TCI Mounting boss?

[Venturous Randy]

I'm surprised they put all that extra wiring in there for the TCI anyways. No wonder there's a huge draw, but it must be designed to work on the lower voltage? Can I ask what you mean bu TCI Mounting boss?

 

The two tabs that stick out the sides of the TCI with the holes that are used to mount the TCI.

I found that with the TCI laying on the airbox with the connector pointing to the left, that by cutting off the mounting boss that is closest to the battery and sliding it back more against the battery will give it a bit more room for the cover.

You would want to mount it with the connector pointing to the left because that is the side the wiring harness will need to be pulled up through.

Randy