Hunt for a Boost Sensor

[MasterGuns]

I have been trying for some time to figure out why my 86 VR doesnt get the mileage some on here claim. Mine, ever since installing the 89 motor (and even with the original 86 motor) struggles to get just slightly over 30 mpg. In addition, the bike has always seemed not to have the umph at higher rpms. My old 88 ran like a scalded dog all the way up to redline. And I have done about all one can do, carbs, sync, plugs, wires, caps, compression is great, valves are right on, no vacuum leaks etc. Well, after reading another thread earlier this week about boost sensors, today I pulled the b/s vacuum line from the manifold, applied vacuum with a mity vac and it would hold nada, nil, ziltch. I had no choice but to pull the necessary stuff to completely remove the rubber vacuum line to check it out and it is just fine; no cracks, plastic connector or balancer, whatever that little gray plastic piece is called is just fine as well. Applied vacuum to just the hose and it holds vacuum just fine. I then pulled the b/s and tried applying vacuum direct to the sensor and you can suck air through it like a straw. That is the culprit in my mileage issue and can't help but call it the culprit in the lack of high end performance.

 

So, does anyone have a good one they are willing to part with? If so, please let me know and I will gladly pay your price. There are several on fleabay but no way of knowing they are any better than the one I just removed.

 

Hope this works.

 

Thanks so much

 

Herb

[dingy]

I have been trying for some time to figure out why my 86 VR doesnt get the mileage some on here claim. Mine, ever since installing the 89 motor (and even with the original 86 motor) struggles to get just slightly over 30 mpg. In addition, the bike has always seemed not to have the umph at higher rpms. My old 88 ran like a scalded dog all the way up to redline. And I have done about all one can do, carbs, sync, plugs, wires, caps, compression is great, valves are right on, no vacuum leaks etc. Well, after reading another thread earlier this week about boost sensors, today I pulled the b/s vacuum line from the manifold, applied vacuum with a mity vac and it would hold nada, nil, ziltch. I had no choice but to pull the necessary stuff to completely remove the rubber vacuum line to check it out and it is just fine; no cracks, plastic connector or balancer, whatever that little gray plastic piece is called is just fine as well. Applied vacuum to just the hose and it holds vacuum just fine. I then pulled the b/s and tried applying vacuum direct to the sensor and you can suck air through it like a straw. That is the culprit in my mileage issue and can't help but call it the culprit in the lack of high end performance.

 

So, does anyone have a good one they are willing to part with? If so, please let me know and I will gladly pay your price. There are several on fleabay but no way of knowing they are any better than the one I just removed.

 

Hope this works.

 

Thanks so much

 

Herb

 

 

Send me a PM, I have a good one I will part with.

 

Don't use it any more.

 

Gary

[Grisolm1]

Got one here you can have. Not 100% sure of condition bought as part of an 89 that was wrecked so should be ok. Pm me if you need.

[bongobobny]

Guess you're all set! Yes I have a spare too...

[dingy]

Gunney,

 

Sending you two of them, one of an 83 and one from an 88.

 

I tried bench checking the 83, but I didn't get reading I expected. Didn't try to check the 88 so as to not mess it up.

 

Should be there by Tuesday.

 

Tracking # 9101785091401089768147

 

Gary

[Guest Swifty]

I have been trying for some time to figure out why my 86 VR doesnt get the mileage some on here claim. Mine, ever since installing the 89 motor (and even with the original 86 motor) struggles to get just slightly over 30 mpg. In addition, the bike has always seemed not to have the umph at higher rpms. My old 88 ran like a scalded dog all the way up to redline. And I have done about all one can do, carbs, sync, plugs, wires, caps, compression is great, valves are right on, no vacuum leaks etc. Well, after reading another thread earlier this week about boost sensors, today I pulled the b/s vacuum line from the manifold, applied vacuum with a mity vac and it would hold nada, nil, ziltch. I had no choice but to pull the necessary stuff to completely remove the rubber vacuum line to check it out and it is just fine; no cracks, plastic connector or balancer, whatever that little gray plastic piece is called is just fine as well. Applied vacuum to just the hose and it holds vacuum just fine. I then pulled the b/s and tried applying vacuum direct to the sensor and you can suck air through it like a straw. That is the culprit in my mileage issue and can't help but call it the culprit in the lack of high end performance.

 

So, does anyone have a good one they are willing to part with? If so, please let me know and I will gladly pay your price. There are several on fleabay but no way of knowing they are any better than the one I just removed.

 

Hope this works.

 

Thanks so much

 

Herb

OMG, your problem is exactly what I'm getting after doing exactly what you did (except I put in an '87 motor). Please, please tell me if another sensor solves your problem; I'll be looking for that sensor too!

Hey DANO, hey MUFFIN...whaddya think about this post?

[MasterGuns]

Thanks Gary. You know, I've read lots of posts about relocating the TCI to the top of the air box. Thought this would be as good a time as any to do so. I a thread or two was from those that had room on top the air box for both the TCI and the boost sensor. Well, simply put; "there is no way both these will fit on top of this air box". I've tried every which way possible. TCI is no problem space wise. But add the b/s onto the top of the airbox and I about cooked my brain tryin to figure that out. Even looked as some pics but no way on this one. Why? Who knows. But I finally did find an alternate home for the b/s and that is on the left side behind the airbox and just left of the top of the rubber thingy that catches spilled gas when filling up. Seems to fit there just perfect. I wonder if anyone else ever located the b/s there. I don't see why it would matter. Any comments would be appreciated. I know, pics are worth a thousand words. Also, I noticed that some mounted the TCI on top of the airbox with the two air holes up (up side down from the original mounting) and some mounting it with the air holes down. Does it matter? Does anyone think water could enter those two holes while on top of the airbox? Just curious. Perhaps I should remove the other ear and turn it over with the air holes down.

 

Anyway, can't wait for an operational b/s cause I don't think this one has been working since I bought this thing.

 

See ya and you didn't say anything about my $ offer.

 

Herb

[Grisolm1]

Swifty - If it turns out you need a sensor its yours. Just pm me. Can't see where position of the sensor would matter as long as hoses and wires are going to/from same place as original. It "might" make a difference in orientation I.e. not sideways or upside down but 95% I think this won't matter either. Easy enough to check on the bench if orientation does matter. Pull a vacuum, do electrical measure and then rotate the unit to see if reading changes. My bet is it won't.

[bongobobny]

Yah! Bench testring involves hooking up 12 volts to the sensor then using a voltmeter you should see around 2 volts at the output. Use a vacuum pump, or suck on a clean hose then blow in it, and the voltage should be greater with vacuum and less with positive pressure. I had one bad one that read around 8 volts constant...

[reelay]

my bike does not have a consistent idle high then low like 880 then high like 2400 after hitting the throttle all the cables are fine idle stop working good , if i disconect the boost sensor it idles back to 1200 hundred every time i hit the throttle. when i test the sensor it does not hold vacuum . electrically it read 2.57 volts and goes down with vacuum and up with pressure. what do you all think. thanks lee

[frankd]

Herb,

 

After you get a module that will hold a vaccum, you can tell if it's working by----

 

With the vacuum line disconnect (plug the carb port), have somebody run the motor at 3,000 RPM.

 

Use your vacuum pump and draw a vaccum on the sensor----if it works, the RPM will jump up.

 

Now that mine's working (I had the original vacuum leak), my bike sounds way different running through the gears at light throttle and also cruising at a steady speed. My gas mileage hasn't jumped way up though. I think it had been running about 38MPG or so, and to Maintenance day and back I had a couple of tanks about 42MPG, one @38 (headwind) and one @ 40MPG. That's probably an increase of 2-3 MPG, but I haven't had a run that's been easy on the petrol though. On the way to MD and back home, most of the time we were hauling the freight.

 

Frank D.

[frankd]

Lee Ray,

 

In order for the bike to return to a proper idle, you can't have any vaccum leaks, and the carbs have got to be synchronized (AKA 'synced'). Check the carb. boots and make sure that both sides of all 4 are tight, and not leaking. You can spray some WD-40 on the boots to check for leaks. If it's leaking, the idle will change when it draws in the WD-40.

 

BTW, the idle on these bikes is supposed to be set @ 1000 RPM.

 

Frank D.

[reelay]

i already checked for vacuum leaks, checked all 4 diphrams,and synced the carbs. mainly i was wondering if the boost sensor is suppose to hold vacuum mine is like sucking on a small straw.bike runs pretty good with vacuum hose unhooked from sensor no popping just revs up a little slow. with sensor hooked up it revs up faster but takes alot longer to come back to idle. thanks for any info. Lee

[Squeeze]

... but takes alot longer to come back to idle. thanks for any info. Lee

 

That's definetely a Sign of a lean Condition or a Vacuum Leak. If you checked everything for Leaks, it's a lean Condition in the Idle or above Idle Circuits withing the Carbs.

[Squidley]

It seems I am on the list now too, I pulled the '86 I just bought down to the frame and pulled the TCI for relocation on the airbox and decided to pull the boost sensor also. Well it doesn't hold a vacuum and has a hole in the case. If anyone has another boost sensor I'd love to chat with you...

[saddlebum]

Excuse my ignorance but is it a boost sensor or vacum sensor. I have only ever seen boost sensor's on turbo charged engines. Not being a smart a## just looking to be educated.

[dingy]

It is actually apressure sensor in that it varies the output voltage dependant on the difference between normal air pressure and what the intake manifold/carb venturi pressure is, which is lower than normal, so it would be refered to as a vacuum.

 

 

I think parts fiche calls it a boost sensor and it may even be molded into sensor housing.

 

Gary

[Squidley]

I think parts fiche calls it a boost sensor and it may even be molded into sensor housing.

 

It's on the cover of the one I pulled off, says boost sensor on it...

[Naked Rider]

http://www.venturerider.org/forum/showthread.php?threadid=60709

[Grisolm1]

It seems I am on the list now too, I pulled the '86 I just bought down to the frame and pulled the TCI for relocation on the airbox and decided to pull the boost sensor also. Well it doesn't hold a vacuum and has a hole in the case. If anyone has another boost sensor I'd love to chat with you...

 

Sorry, just promised mine to Swifty.

[reelay]

i just bought one off of ebay (10.00) not a bad price if it works its off a 1200 and i have an 88 1300 but yamaha shows it as the same part number,we will see thanks for the info ,Lee

[reelay]

got the boost sensor today that i bought off ebay, it holds vacuum , but i read a post on here that said voltage should increase with vacuum , mine decreases the chart in the book is kinda confusing but i think decrease might be correct. what do you guys think. Lee