Boost sensor vacuum restrictor

[Neil86]

Sooty on all 4? Watch the "choke" plungers on each carb as the lever is rotated.....all moving out and back in?

[Squeeze]

Sooty on all 4? Watch the "choke" plungers on each carb as the lever is rotated.....all moving out and back in?

 

I second this Thought.

[Condor]

IIRC, those Hoses have different inner Diameter, the short one has around 4.5mm, the longer one is very tiny, 2.5 maybe. I don't know a Reason for the Arrow on that Thing.

 

I think the only reason for the direction arrows are to install the restrictor closer to the manifold. The Carb Tune instructions state the same thing. Maybe it keeps the hose from colapsing do to heavy pulses??? I've never seen the vacuum taken off the manifold other than #2. The '83's pull pre-butterfly vacuum and I don't think there's a difference in the boost sensor, but there is in the TCI and how it responds to the signal.

[Gearhead]

Couple comments on the float level measurement. One, I do it with the engine idling. Shouldn't really make a difference, but try it. Two, did you burp the tubes? Air bubbles in the tubes will make it read, let's see, high (which isn't your problem, but check it out). Open the drain screw a turn or so, lower the gage down so the fuel almost runs out the top, then lift it up as high as it will go. Do this a couple times to get the air bubbles out.

 

Jeremy

[Guest daveor]

No idea if it would make a diff or not, but when you did a carb sync. did you do it at an idle like the book says or at approx 3000 rpms? Make sense to do it at 3000, how often do you care if they are synced at the stop sign? I had a Yamaha tech tell me the 3000 rpm sync was the way to do it at a Venture Rally where they did a safety and emissions check. DAve

[mbrood]

With a clear line on the drain tube and held up against the carb (with the drain screw opened)... shouldn't the level be .63" below centerline of the diaphragm for the 86-93 and .55" below for the 83-85?

[Oldgold]

Lots of good suggestions, the sooty plugs certainly point towards too much fuel or too little air, if the choke fuel enrichners aren't the culprit take a look at the condition of the main diaphragm needles and seats, I'm assuming the new bike never gave you good mileage, previous owner may have modified main jets, needles, springs, since you were getting better mileage at lower speeds you would have been running on the pilot fuel circuit, once you get up around 3,000 rpm the diaphragms are starting to lift the main needles and that really lets the fuel in.

[Gearhead]

With a clear line on the drain tube and held up against the carb (with the drain screw opened)... shouldn't the level be .63" below centerline of the diaphragm for the 86-93 and .55" below for the 83-85?

 

Yes, I just double-checked for the 87 and you are right. Re-check your fuel levels with the method I outlined (burping the lines).

 

Jeremy

[CrazyHorse]

You can lower the needles easily on that bike the needles have I think 5 positions if you lower them you might get better mileage.

[CptKirk]

Had to go back to work so haven't had a minute to work on the bike BUT I do sincerely appreciate the brainstorming you guys have put into someone else's issue. Not a common thing these days.

 

This is a great forum and a great group of people. I'll be back at the problem in a few days after I get away from the salt mines.The concepts put forward are well thought out and speak well of each of you.

 

So thanks for the assistance. I'll take a work through each one until I find the source of the problem as the bike is fun to ride and has every option available. It is cleaned to the frame and hasn't looked as good since it was bought new. There are some pics of the toy run in an album in my profile.

 

Once again THANKS for your help.

[CptKirk]

Had a couple hours to burn before night shift so checked the carb levels again with the engine running.

I burped the lines to ensure no air. Repeated several times. Pictures attached show the way I did it and the results with the motor running at idle.

Absolutely no air in the lines during the test.

Any thoughts on the result? The level is lower than the carb slide center line by a little over .5"

Edited September 29, 2008 by CptKirk

[CptKirk]

You can lower the needles easily on that bike the needles have I think 5 positions if you lower them you might get better mileage.

 

Are you talking bout the slide needles or? Great idea but how to go about It?

 

I checked the "choke rods" there is slack in the cable when choke is full off and they all bottom out and move smoothly through choke lever ranges. So that's not the issue but nice to know.

 

I removed the vac sensor and replaced it with another one I had from an 87 as well.. The previous had a voltage test of 3.08 volts using the procedure in the manual. The one that is in now has 3.19 volts. They both show a voltage drop when vac applied to the line and a volt increase when pressure applied. Both held steady voltage when vac held. Engine RPM changed when vac line removed from nipple on both.

 

Restrictor as back in line. No time to test ride the bike but will head out on the highway if the weather is decent tomorrow evening.

Edited September 29, 2008 by CptKirk

[CptKirk]

No idea if it would make a diff or not, but when you did a carb sync. did you do it at an idle like the book says or at approx 3000 rpms? Make sense to do it at 3000, how often do you care if they are synced at the stop sign? I had a Yamaha tech tell me the 3000 rpm sync was the way to do it at a Venture Rally where they did a safety and emissions check. DAve

 

Great idea and did exactly that tks for the concept as it's a good one.

[CrazyHorse]

Are you talking bout the slide needles or? Great idea but how to go about It?

 

 

Take out the diaphrams and unscrew the the needle cover and pull out the needle see what setting the washer is at and see if you can put it to the next setting that would put more of the needle into the carb and try it out. Then check a plug to see if it s to lean. I tried this from 5bikes and it worked real well for my set up. No gaurantee it will work for you. Its easy to change back and forth. I went from about 33 mpg at 4000 rpm 70 mph to about 42 mpg. The 1990 I have the needles dont have different settings but 83-85 do. I had to use washers and remove the old plastic spacer. I have a set of 84 carbs and I noticed the needle is much more tapered then the 90 so it would dump fuel in more so at higher rpms I wonder if your needles have been raised in the past lowering them might help. You can just take off the side panels and unscrew the lower fairing top to get to the diaphrams

Edited September 29, 2008 by CrazyHorse

[CptKirk]

I'm reading that the vac sensor should put out 2.0 volt. I have three of them. One is an 83 other two are 87.

 

None of them give the reference voltage of 2.0 volts.

 

I am using storage pack 12 volt source.

Is the igniton voltage different?

 

I really don't want to take things apart again. I didn't think to check before I put the cowls back on.

It seems unbelievable that all three sensors from different bikes won't give the 2.0 volt reference while bench testing.

 

Sunny 29C here today still good riding weather. There is no global warming?

[mbrood]

Kirk,

 

The fuel level looks "about right"... the book calls for the spec I posted.

down from centerline... .63" for the 86-93 and .55" for the 83-85

 

What IS the sensor putting out with the engine off but the ignition key on?

 

Mine puts out a bit "more" voltage than "spec."...

[CptKirk]

Kirk,

 

The fuel level looks "about right"... the book calls for the spec I posted.

down from centerline... .63" for the 86-93 and .55" for the 83-85

 

What IS the sensor putting out with the engine off but the ignition key on?

 

Mine puts out a bit "more" voltage than "spec."...

 

No idea as I've been using the manual bench test with a 12 volt DC supply.

The manual doesn't show a test procedure for an in frame test, at least not the one I have.

 

No doubt inserting a probe would give me that but it's back in the bike and a royal pain to get at. No Manual tests shown for ignition Voltage that doesn't demand 12V min constant. So..............

 

Switched voltage could well be the best test but why no test in the manual? the manual is actually not the best I've ever seen you ever find that. Makes me feel like a high functioning moron wrote it. No credits in the title as to the author other than YAMAHA. Good bike poor manual.

 

. The ign/charge is 14.2 volts running on a new batt.

 

The 87 sensors came of of running bikes from Pinwall Cycles,the newest one is in the bike now. Petty much working on the balance of probability that I have at least two good ones out of three.

 

Not including a non functional (no hold vac) 87 version and the 83 version that takes it's vac cue above the throttle plates so it has to have a different low/midrange curve making it a spare for my 83 (Puts out3.09 on DC unswitched source)

 

Funnily,the messed up 87 version stills puts out 3.19 volts but no vac voltage output curve in bench test just flat line on pressure or vac 3.19 V constant output so it's fubar.

Edited September 30, 2008 by CptKirk

[CptKirk]

Went for a ride to a place called Fauqier BC Today, mountains and winding road. It's the other side of the summit of the Monashee mountains.

 

Speeds variable fom 45 mph to 90 mph used cruise for about 40 percent of the ride.

 

Changes since I last rode it, restrictor is in the line with the newest vac sensor I had in hand and a resynch at 3000 rpm.

 

After doing the math from metric to US measure I got 37.98 Miles per US gallon.

 

I will have a look at the plugs in a bit and have a go at lowering the slide needles to see if an improvement can be gained. The new sensor is a help and puts out 3.19 V using the manual bench test procedure. The resynch couldn't have hurt either.

 

Posted some pics just in case you might find them interesting. If you're out in BC Canada the ride to Fauqier is a nice day with some great food and a couple free ferry rides along the way. Just watch out for deer and cattle.

Edited October 2, 2008 by CptKirk

[Gearhead]

I went from about 33 mpg at 4000 rpm 70 mph to about 42 mpg. The 1990 I have the needles dont have different settings but 83-85 do. I had to use washers and remove the old plastic spacer.

 

Jimbob, how much did you lower those needles? I'm fixin' to do the same on my 87, as soon as I get some spare time (without something else in my life breaking - grrrrrrrr) to get her back on the road.

 

Kirk, your 38 mpg is right in line with what most get, including me. Some get more, some less, but most are right in that range.

 

Try this for your vacuum advance: remove the vac line from the carb, plug the carb so no leak, set the engine idle to 2000 rpm or so. Apply vacuum to the line. A MityVac is ideal, but I think mouth suction is sufficient. Does the engine change speed?

 

Your fuel levels look about right. I like to get a little more precise. I make a sharpie mark right in the middle of each slide cover for reference. Then I make two marks on my measurement tube, one .63 lower than the other. I line the upper mark to the center of the cover, then read the fuel level as even with, above or below the lower mark which is the target.

 

Jeremy

[CrazyHorse]

Jimbob, how much did you lower those needles? I'm fixin' to do the same on my 87, as soon as I get some spare time (without something else in my life breaking - grrrrrrrr) to get her back on the road.

 

Kirk, your 38 mpg is right in line with what most get, including me. Some get more, some less, but most are right in that range.

Jeremy

 

 

I'm going to have to take one out and measure it. My micrometer battery died and cant measure. 5bikes is the one who told me about this. My carbs are modified I used the original 1983 pilot jet 42.5 instead of my 37.5's and I used the 180 air jets instead of the 170 of the 1990. Bike seems to idle better and no popping. Seems to have a snappier throttle but my mileage when I cruise at 70-75mph at 4000-4250 rpms (My indicated speed is 80-85 speedo is off.) was 33-34 mpg. Not good enough for me. 5Bikes lowered his needles and improved his mileage. I used 2 small brass washers in place of the plastic spacer on the bottom of the c-clip and 2 above the 2 above help hold the needle in place if you dont use these the needle moves around to much. The 1983-85 carb needles have I think 5 adjustment levels our 1986-93 do not have any adjustment they are also much more tapered then ours they dump in alot more fuel at higher rpms good for speed not for mileage. Now I can cruise at 70-75 mph (GPS speed) at 4000-4250 rpm and get 40-42 mpg. Power still seems pretty good. Might be slightly lean. I dont know if you giving you a measurement will equate since my carbs are different then stock but I'll get a measurement for you anyway.

[CptKirk]

Looks like all my problems with mileage were the vac sensor. Mileage seems right according to the wisdom here. Would have been nice to polish it up a bit with the needles but that's life. Certainly appreciate the help from all of you. Bike is put way for now as it's just plain getting cold up here.

I replaced fork seals this year but they were an ebay item and they still weep oil. So that will be next seasons first issue. I did the job very carefully but no real joy will go over it in another post.

Tks large for the assist on this thread.