replace all Yamaha carbs Chapter 2

[99yam40]

Re: replace all Yamaha carbs Chapter 2

I would think that should be a good manual if it is the Yamaha one.
I would not think that the thickness of the gasket would be that much of a difference in the setting, but I could be wrong.

You may be able to borrow tools at your auto parts store with a deposit, does not hurt to call and find out.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Me and a buddy went to the lake today and ran WOT while spraying fuel into each of the 3 carbs, 6 throats. We had the spray bottle set on stream and was able to target accurately each carb throat trying to find problem with a specific cyl.
Ran the test 3 times and never heard the engine speed change or any change in the tach. Either we did something wrong, which I can't imagine what or the guys at the shop who wanted to put on 3 carbs lied. They said it ran 5800 RPM while spraying fuel.

Anyway I have the parts to build the DVA and a spark tester and vacuum gauges are on the way.
I will now focus on the electric side and post updates.
My manal says to set the spark tester gap on 9mm . Do you agree?
What am I looking for? Just that the spark can cross the gap?

I am curious , is there anyway we could have done anything wrong on the fuel test?
Really want to eliminate that circuit and move on to something else.

 

[boobie]

Re: replace all Yamaha carbs Chapter 2

Somethings wrong here. When ever you spray fuel into a carb at wot somethings got to change. Either it boggs down or picks up and goes like hell.

 

[99yam40]

Re: replace all Yamaha carbs Chapter 2

does not sound right to me either, should have seen some change. As too much fuel hit the different cylinders that were running normal or enough to fire hit the ones running lean if they are running lean.
As I said before plugs are cheap and that helped last time, but checking voltage inputs and out puts to see if they are in spec will tell you something

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Was I correct trying to direct fuel into one cyl at a time or should I have tried for multiple throats ?

My manual says use plug BR7HS-10 (engine P150TLRX)

Do you agree ?

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

br7hs-10 is correct.
if you suspect an issue with cyl 2 or 5 carefully test the crank position sensor voltage output and carefully test the cdi ign coil primary outputs with a DVA meter or compare all six CDI outputs with a multimeter set on the AC scale. the DVA readings would be the best.
yes 9mm is about right for the spark test gap.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

going to dig into the manual some more and learn about each sensor.

Am I correct that the only way to measure some of the voltages is by piercing the wire insulation?

 

[99yam40]

Re: replace all Yamaha carbs Chapter 2

back probing the wire at the connectors is better than poking holes in the insulation if you do not have the test harnesses needed.Here is a post that talks about it some.http://forums.iboats.com/showthread.php?t=446598

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

the manual isnt gonna TEACH you jack.
you either have an understanding of basic electronics or your still simply gonna be lost, like 90% of trained techs are simply stupid. they passed a one time open book test, maybe.
luckily your, and mine, tax dollars coughed up something just over 350K to train me.

your engine electronics is basically stone age.
still whoops techs for some reason.
you were going to blindly spring for 1400 dollars worth of carbs, yet you balk at spending less than 600 on test equipment.
dunno.
actually I do know, same as why most shops DO NOT have the correct diagnostic equipment.
the techs and the owners simply DO NOT know how to use it.
most figgure if the big hammer and cresnent wrench dont fix it, replace something.
trust me, its all to common and with the economy upside down the increase in mobile techs simply magnifys it.

 

[jeffersondodson561]

Re: replace all Yamaha carbs Chapter 2

DO NOT use the champion plugs, use the correct NGK ones.
the float is set with the gasket installed, find another book.
the vacum/pressure guage and some T fittings should be less than 20 dollars.
its not a high tech tool.

That's the beauty of Yamahas, their is a sticker with the correct plug in the cowl. You should use this plug unless a service bulletin says otherwise.

 

[jeffersondodson561]

Re: replace all Yamaha carbs Chapter 2

Me and a buddy went to the lake today and ran WOT while spraying fuel into each of the 3 carbs, 6 throats. We had the spray bottle set on stream and was able to target accurately each carb throat trying to find problem with a specific cyl.
Ran the test 3 times and never heard the engine speed change or any change in the tach. Either we did something wrong, which I can't imagine what or the guys at the shop who wanted to put on 3 carbs lied. They said it ran 5800 RPM while spraying fuel.

Anyway I have the parts to build the DVA and a spark tester and vacuum gauges are on the way.
I will now focus on the electric side and post updates.
My manal says to set the spark tester gap on 9mm . Do you agree?
What am I looking for? Just that the spark can cross the gap?

I am curious , is there anyway we could have done anything wrong on the fuel test?
Really want to eliminate that circuit and move on to something else.

The best way I have found to diagose a carb problem is to run it at idle or off idle. All fuel flow goes though the main jet. At wide open throttle the fuel mixture is going through the main jet up the immulsion tube and into the combustion chamber. If you test it at idle or off idle the fuel has to go through the main jet, up the idle circuit, though the bypass circuit and into the combustion chamber. Much easier to diagnose rpm changes.

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

jeff jeff jeff
quit again.
actually on this 150 carb even the pilot fuel jet is involved at WOT.
however its not your issue.

other than that, jeffs got it.

its also why that carb has no air to fuel mixture screw.

wanna debate it anyone?

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

Rodbolt,

I think I have bought all the test equip. you suggested except the test wheel, which I am trying to do at the lake when time allows.
Granted I don't have it all in hand yet, waiting on the mail.
Don't think I am totally incompetent , just have zero experience with any 2 cycle engines. My last one ran 14 years before I sold it with near nothing for problems.
Have managed to keep all my junk and farm equip. running for years.
I will admit I ask a lot of questions due to a strong desire to learn.
Did finish top of my class 2 years in auto tech, but the technoloy I learned on is old, that was in the late 70's. Just stating that to set some background for basic knowledge.
I am cetainly not a know it all, just a guy trying to do it myself because the options for good tech help locally is darn near zero.

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

not saying your incompetent at all.
but I think your chasing ghosts due to frustration.
its time to restart with the basics.
that engines ign system uses 2 pulser coils to control spark timing on 4 cylinders, cylinders
2 and 5 are controled by the ECU based on signals from the crank position sensor.
other than that there isnt much difference in operation between that v6 and your weed eater.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

not saying your incompetent at all.
but I think your chasing ghosts due to frustration.
its time to restart with the basics.
that engines ign system uses 2 pulser coils to control spark timing on 4 cylinders, cylinders
2 and 5 are controled by the ECU based on signals from the crank position sensor.
other than that there isnt much difference in operation between that v6 and your weed eater.

Well said , I agee 100%
Just thinking this morning I am going in circles. I am going to get all my equipment and run all the test wires and go to the lake (40 miles) and run all the electric test.
May be awhile before I post. Hope you guys will check back in.

Tell me if I basically have this right : Pulser coils and crank pos. sensor
output low volts to CDI based on flywheel postion.
CDI uses this data to output to primary of ign coils at the correct time.
Basically how it works ?

Out of curiosity I did look up cost for the YB1626 test wheel. I can't find a source anywhere.
Would like to know were you buy one, JUST in case .

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

last one I bought was close to 300 dollars.
some years back at a suzuki school in atlanta the instructor gave us a tech bulliten published by mercury about how to cut down and modify aluminium props for various mercury engines to use as a test wheel.
but the YB1626 is only avalible new from a dealer.
you may see one on ebay.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

several on ebay but part number don't match

please go back to me last post, I added question about basic ign circuit
confirm or correct my thinking

 

[rodbolt]

Re: replace all Yamaha carbs Chapter 2

the position of the pulser coils tell the CDI when to fire the capacitors in the CDI assy.
the crank position sensor synthesizes the spark for cyls 2 and 5.it gives the CDI information about where and how fast the flywheel is turning.
lose a pulser and you not only lose one or both the cylinders it controls but the ECU will go into bypass mode and you will lose 2 and 5.
lose the CPS signal and you lose 2 and 5.

 

[colayn]

Re: replace all Yamaha carbs Chapter 2

I have all the wiring run. Used 20 ga wire from a CNC control from my old job
Hope that is OK, I think you said very low amps

1 wire to engine block grd
6 wires, one each to CDI output
2 wires to crank pos. sensor
4 wires to pulser coils

Couple questions so I don't "assume"
1- are all voltage DC ?
2- Do I only need the DVA for the CDI outputs ?
3- crank pos sensor, do I check volts across each lead, or each lead to grd?
4- pulser coils, check across each paired lead, or each lead to grd ?

Will check timing at idle and WOT while at the lake as well

 

[99yam40]

Re: replace all Yamaha carbs Chapter 2

Some of the voltages will be over 100v coming out of the CDI and some going in also, is the wiring insulation rated for that high?
You sure do not want to have the higher voltage jump into some of the low voltage sensors through the insulation if it is all in a cable or bundle.

Have you found the steps in the manual and the voltage specs you are looking for on the different parts.

As I said before I would run the cranking test and 1500RPM test there in the drive way to make sure they read properly and are in spec before running 40 miles to the lake

How about charge coils are you going to test them also?
You have low speed and high speed charge coils according to the specs posted by Don in post #14 and it also says which lead to put on which wire too for the no load, loaded, and 1500 tests.
Your manual should also give this info