Fuel levels 5mm below bowl seam? Fluffy below 3000...

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thekelzer
Posts: 77
Joined: Sat Oct 12, 2013 12:49 am

Fuel levels 5mm below bowl seam? Fluffy below 3000...

#1 Post by thekelzer » Thu Sep 22, 2016 11:55 pm

Any correlation ?

Bike seems fluffy on the lean side when just cracking the throttle or trying to leave a light. Pulls clean above 3k to past redline. Spark plugs look wet-ish after normal riding....let's not say wet, so much as coal like.

Ivan's needles (can't remember which needle)on 3rd position...180 main. Stock pilot...(I think).
Tommy Crawford chambers. K&N on elephant ears....
Carbs sync 'd today too....they were pretty much bang on.

I appreciate the help.
KK

Blobber
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Location: Lancashire, England

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#2 Post by Blobber » Fri Sep 23, 2016 6:48 am

Hi KK,
I have Ivans needles (the ones for use with a standard engine) set at one notch higher (weaker). I have set the needles weaker due to the fact I cannot get hold of any N-8 14 hole needle jets. I'm using the Keyster replacement ones which are the richer O-8 14 hole. Any way bike runs really nice particularly when under load but stumbles a bit when under low load small throttle openings and lowish revs, say when cruising in traffic.

I have been playing around with the small air jets in the carb bellmouth.

These are easy to access and it is similar (although not the same) to alterering the pilot jet but a much easier task.

My bike was a bit rich particularly low down and I've cured the issue with upping the air jet from #1.1 to #1.3. Made a massive difference in how clean and crisp the engine runs. Also tried #1.4 and was too weak bogging down at low revs when trying to pull away.

Your float should be set to give fuel level of 3.5mm below bowl seam.

Incidently although my bike was running rich the plugs never looked too black. They were a little on the dark side but better than looking pale and weak mixture. Now with the pilots changed the plugs are perfect brown
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

thekelzer
Posts: 77
Joined: Sat Oct 12, 2013 12:49 am

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#3 Post by thekelzer » Fri Sep 23, 2016 11:00 pm

Thank you for the help Blobber.....ill look into the air jets, might be just the ticket.

Can you leave a stop light below 3000 rpm? I cannot.

KK

Blobber
Posts: 186
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Location: Lancashire, England

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#4 Post by Blobber » Sat Sep 24, 2016 5:55 am

my bikes is like riding a 4 stroke at low to mid revs plenty torque will pull away on tickover/1500 revs easy.
Sounds like yours is running weak on the pilot circuit and then rich on the needle. Could be low fuel level causing the low throttle problems and then you have raised the needle to compensate.
I'm no expert I've spent years playing around with jets and needles to see what the effects are.
If it were me I'd get the fuel level right first check the pilot jets and pilot air jets are standard and try the bike.

If the pilot circuit is still weak (needs loads of revs to pull away) then it may be that the pilot jets needs to be increased a size due to engine mods etc. You can then fine tune them by changing the pilot air jets which is an easy task.

My bike has never been so extreme like it wont pull away at low revs so most of my tuning has been quite subtle. Yours sound like there is something very wrong and it may just be the fuel level.

The worst condidtion I had was putting in #1.4 pilot air jets and it felt weak and needed revs to get it going. As you open the throttle you could feel the engine struggling to pick up. This I guess is how yours feels?
good luck
Bikes:
RZV500R FZR1000 forks wheels JL pipes
RD350LC N2

2002tiil
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Location: Veendam, the Netherlands

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#5 Post by 2002tiil » Sat Sep 24, 2016 12:07 pm

Is 5 mm below bowl not too low?

thekelzer
Posts: 77
Joined: Sat Oct 12, 2013 12:49 am

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#6 Post by thekelzer » Sat Sep 24, 2016 6:06 pm

That is the question then 2002Tii....

So, according to the factory manual the float height should be 21mm +- 1mm....which equates to (again quoting the factory manual)... a Fuel Level of 1.5mm +- 1mm.

I was told by several folks who may or may not know WTH they are talking about.... that the float height should be 24mm.....which equates to a fuel level of 4.5mm +- 1mm....meaning I'm in the ball park.

So that's the struggle.

Any guidance is always appreciated.

Aloha,
Kelly

p.s. Yes Blobber...that is precisely how it feels....lean until 3000. (Starts and idles fine hot or cold (cold using the choke))

silverstrom
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Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#7 Post by silverstrom » Sat Sep 24, 2016 11:02 pm

The float height is 24 mm. It's wrong in the manual. Yamaha issued a revision. For the best results check the level with a clear hose attached to the bowl drain. If your float level is too low it will typically only cause problems at high RPM when the bowl can't supply the amount of fuel the engine needs.

thekelzer
Posts: 77
Joined: Sat Oct 12, 2013 12:49 am

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#8 Post by thekelzer » Sun Sep 25, 2016 12:56 am

Rips past redline ..... Fuel qty isn't a problem.

I appreciate the reply 'strom!

Ok, well, I'll fiddle with it.

What's interesting, is the P/O installed a 44t rear sprocket, maybe indicating he was having the low end response issue as well.

I'm looking for complete chain and sprocket kits is std ratio now....

Aloha,
Kelly

silverstrom
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Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#9 Post by silverstrom » Sun Sep 25, 2016 4:23 am

thekelzer wrote:
What's interesting, is the P/O installed a 44t rear sprocket, maybe indicating he was having the low end response issue as well.
Not necessarily. I have a 45 on mine.

2002tiil
Posts: 140
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Location: Veendam, the Netherlands

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#10 Post by 2002tiil » Sun Sep 25, 2016 1:43 pm

Correct me then:

21 mm float hight is incorrect. okay:

It must be 24 mm, but:

1 mm below bowl measured with fluid.

or

4 mm below bowl measured withe fluid.

Just to be 100 % sure.. and i have terrible bad sight :smt045 :smt045 :smt045 :smt045 :smt045 :smt045 :smt045

The bike should run to measure this (says the RD bible): Are the figure really different with or without running the engine?
When it;s not running, i set the fuel cock on pri. and measure or should it just be on on??

2002tiil
Posts: 140
Joined: Mon Jun 01, 2015 5:49 pm
Location: Veendam, the Netherlands

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#11 Post by 2002tiil » Thu Sep 29, 2016 3:23 pm

I presume that upper question is stupid or toooo hard to answer :smt005

Why the question? I see 1 mm under bowl, machine not running.
Measured the floats. tried it anyway, but due poor sight i can't read the micro meter...

So, it must be okay then.

thekelzer
Posts: 77
Joined: Sat Oct 12, 2013 12:49 am

Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#12 Post by thekelzer » Fri Sep 30, 2016 3:17 pm

Too hard for ME to answer..... I'm lost too ! ha haha !!

rd84
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Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#13 Post by rd84 » Sat Oct 01, 2016 8:09 am

I tried my bike with engine running and also tried with the fuel tap set to prime - the result was the same - so I don't know why the manual says the engine should be running. I set the float height to 24mm as per the instructions in the manual and its not given any problems. Set this way the fuel level showed about 1mm below the carb bowl joint - I just used the carb overflow lines held upright as my gauge - however I drained the line first - then held up the overflow line as near the carb bowl as I could get it then turned the tap to prime - and waited awhile until the carb bowl was full - keep flicking the line to get any bubbles out to give the best possible fuel level reading. - The engine runs fine and feels sharp and responsive at all throttle settings.

Cheers
Paul

2002tiil
Posts: 140
Joined: Mon Jun 01, 2015 5:49 pm
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Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#14 Post by 2002tiil » Sat Oct 01, 2016 10:51 am

Paul, much apriciated!

BurntCastor
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Re: Fuel levels 5mm below bowl seam? Fluffy below 3000...

#15 Post by BurntCastor » Sun Oct 16, 2016 1:00 am

I had sluggish bottom eme Changed air jet to .7 - helped a lot. Then did a 520 chain coversion and the drive sprocket was one tooth larger than stock. Used stock tooth ratio when I did comversion and that really made it crisp down low.
Bike has JM chambers, pods on ears. Mostly stock.

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