Exhaust Question
Mike Beaty
plug is toast.
I have two questions:
1. Can a leak in the exhaust pipe cause plug fouling?
2. Can a dirty pipe cause plug fouling?
I have a small crack in my FMF 2-stroke pipe located right before the
"fatty" part, right by a welded on bracket. I'm hoping that this is a
contributing factor to my plug fouling saga.
Thanks for the help.
sturd
> I've got my bike down to not foul during a ride, but after it sits, the
> plug is toast.
Small chance of this but happened to me recently so:
You may have a crank seal leak. As the bike cools a little,
the clutch side seal will suck in some crank oil. Does it smoke
more than normal under load (going up a big hill)? Does it
spew anything out of the tranny vent?
Go fast. Take chances.
Mike S.
Mike Beaty
amount of tranny oil came out as I put in.
Is the seal you are talking about #37 in the following picture?
http://images.powersportsnetwork.com/fiche/images/Yamaha/1991/Motorcycles/441_cylinderhead.gif
I have also leaned out the jetting & repacked the silencer. I'm
running Yamalube 2r at 32:1.
Could improper timing cause plug fouling?
-Mike
Chris Buckley
> I think I've eliminated a crankseal leak. After a few rides, the same
> amount of tranny oil came out as I put in.
>
> Is the seal you are talking about #37 in the following picture?
> http://images.powersportsnetwork.com/fiche/images/Yamaha/1991/Motorcycles/441_cylinderhead.gif
>
> I have also leaned out the jetting & repacked the silencer. I'm
> running Yamalube 2r at 32:1.
>
What kind of riding do you do and how about your skill level??
sturd
> Is the seal you are talking about #37 in the following picture?
> http://images.powersportsnetwork.com/fiche/images/Yamaha/1991/Motorcycles/441_cylinderhead.gif
>
No. The seal I'm talking about is on the crankshaft, between the
bottom
end and the clutch cavity.
Mike Beaty
girl on an XR50. I've only been riding a bike for a couple/few months.
I'm doing mostly woods riding.
There are some areas where I open it up all the way. During some of my
jetting runs I was in an open field, 2nd gear and opened it up to full
throttle. I jetted it as lean as I can and the plug still fouls.
Chris Buckley
42-48:1 for slowish trail/woods type riding.
Wudsracer
wrote:
Mr. Beaty,
Look at part #17 on this photo:
http://parts.yamaha-motor.com/partimage.gifx?d=88990,2,0
right side crank seal.
You can get very accurate parts diagrams here:
http://www.yamaha-motor.com/sport/parts/home.aspx
It's the factory Yamaha web site. You can open windows in a new frame
or window, and/or save them as a jpg file for further use.
Jim
DirtCrashr
>My skill level is definitely low. I'd compare myself to a 12 year old
>girl on an XR50. I've only been riding a bike for a couple/few months.
> I'm doing mostly woods riding.
>
>There are some areas where I open it up all the way. During some of my
>jetting runs I was in an open field, 2nd gear and opened it up to full
>throttle. I jetted it as lean as I can and the plug still fouls.
IMO you should jet for third-gear plonking around, 2nd opened up a bit
just enough to get you into 3rd. But 2nd can be a rocket and get out
of your hands.
I start in 2nd and up shift to a safe gear where I won't come onto the
pipe and wheelie uncontrollably...
MX Tuner
>My skill level is definitely low. I'd compare myself to a 12 year old
>girl on an XR50. I've only been riding a bike for a couple/few months.
> I'm doing mostly woods riding.
>
>There are some areas where I open it up all the way. During some of my
>jetting runs I was in an open field, 2nd gear and opened it up to full
>throttle. I jetted it as lean as I can and the plug still fouls.
"Which" jet did you change?
Why can't you go leaner?
MX Tuner
'03 Honda CRF480R
'06 Suzuki Hayabusa 1300
'06 Nissan Titan LE
Mike Baxter
>My skill level is definitely low. I'd compare myself to a 12 year old
>girl on an XR50. I've only been riding a bike for a couple/few months.
> I'm doing mostly woods riding.
>
>There are some areas where I open it up all the way. During some of my
>jetting runs I was in an open field, 2nd gear and opened it up to full
>throttle. I jetted it as lean as I can and the plug still fouls.
>
Please answer the following questions:
What elevation are you riding your bike?
What size pilot jet are you using? (don't just answer "stock")
What size main jet are you using?
What needle are you using?
What position is the needle clip in?
How much oil is running out the rear of your silencer?
Mike Baxter
Mike Baxter
He's not running too much oil. 32:1 is just fine with a properly
jetted bike.
Mike Baxter
CrashTestDummy
<m*g*b*06...@comcast.net> wrote:
>Please answer the following questions:
>
>What elevation are you riding your bike?
Normal elevation, about four foot off the ground.
>What size pilot jet are you using? (don't just answer "stock")
Stock.
>What size main jet are you using?
Stock.
>What needle are you using?
Whatever my [heroin] dealer has in stock.
>What position is the needle clip in?
When I'm inhaling?
>How much oil is running out the rear of your silencer?
Oil?
CrashTestDummy - '85 RM-250
f.j.bradf...@verizon.net
Mike Beaty
and I dropped it to 35. I'm sure they sell smaller pilot jets, but I
wasn't sure if I should go leaner than what is specified for OEM.
Mike Beaty
What size pilot jet are you using? (don't just answer "stock")
35 (45 = stock)
What size main jet are you using?
350 (330 = stock)
What needle are you using?
stock
What position is the needle clip in?
1st clip position.
How much oil is running out the rear of your silencer?
Enough to drip all over the swing arm, rear tire and rear brake after a
half day of riding. A couple times when I have dropped the bike on the
right side (crashed as I often do), I leave a puddle of spoodge on the
ground.
-Mike
Mike Baxter
I forgot your bike is older and uses the Mikuni carb. I would go back
to the stock jetting. My friend had a 1992 YZ250 that ran great with
stock jetting at a few hundred feet ASL. What you probably have is a
worn out needle seat or the leaking crank seal as other have
suggested. The vibration from the bike causes the needle to vibrate
and the needle wears the seat. I had a bad crank seal on a 1991 CR250
that caused me to oil foul plugs, but the bike ran good. It would
only load up after long slow sections, but would clean out quickly or
foul the plug.
I would replace the needle and seat. You can order the part you need
here: http://www.carbparts.com/mikuni/vm20_44_parts_list.htm
If part # 34 doesn't fix the problem, then try the crank seals.
Mike Baxter
Mike Beaty
in the parts list. I see a valve seat, but I'm not sure if this is the
same thing:
http://www.carbparts.com/mikuni/mikuni_tmx_tms_series_carburetor_part.htm
Mike Baxter
Carburetor Parts Warehouse
4207 Ridge Rd.
Cleveland, Ohio 44144
(216) 635-1099
carb...@hotmail.com
They should be able to help you.
Mike Baxter