WR400 jetting reccomendations wanted
Eric Hedin
is opened quickly. The plug is sooty but has a white on the ground
electrode and has fouled a few times (it also fouled before I installed the
muffler). Other modifications include removing the air cleaner restrictor
and changing the cam timing to yz specs.
The stock jetting is as follows:
45 pilot
OBDXM needle with clip in 4th position
168 main
I figured that since the plug had white on it, the main jet is lean, so I
changed to a 172. Because of the sootiness and fouling I figured that the
midrange is rich, so I raised the clip position on the needle. I have a 48
pilot on order which I hope alleviates the bog. Am I on the right track? Any
suggestions would be greatly appreciated.
Thanks!
-Eric
wr250
mboyer
specs, 48 pilot, 172 main, no change to the needle, changed cam timing and
had a power core IV, it ran quite well with this setup [sea level to ~1000ft
or so]
**** Posted from RemarQ - http://www.remarq.com - Discussions Start Here (tm) ****
Michael L. McKinley
playing with the carb and just generally getting a feel for my new
bike. Well for some reason I decided to blip the gas real fast just
so I could enjoy that great sound. Guess what, the damn thing died.
So I'm thinking to myself it must be a fluke so I do it again, same
result. Ok now I've got a problem with my carb even though it runs
great when I'm riding it. Must be something I did while playing around
right. Well after screwing around with it for a few hours I call
my buddy with the same bike. He goes out and checks his, sure as
shit it does the same thing. My point is that you may have a real
bog. But if you are cracking it open real fast and it bogs, well it
might have been there all along and you just didn't notice it until
you started blipping it from an idle.
Good luck
Mike
99 YZ400
Eric Hedin wrote:
>
> I put a fmf megamax muffler on my wr and now I have a bog when the throttle
> is opened quickly. The plug is sooty but has a white on the ground
SNIPAGE
Drehwurm
wrote:
>muffler). Other modifications include removing the air cleaner restrictor
>and changing the cam timing to yz specs.
Have you removed the anti-poping-device from the carb? This influences
the pilot circuit quite a bit!
>OBDXM needle with clip in 4th position
This should be OBDTM - I don't know if a OBDXM exists but it would be
way off.
>I figured that since the plug had white on it, the main jet is lean, so I
>changed to a 172. Because of the sootiness and fouling I figured that the
>midrange is rich, so I raised the clip position on the needle. I have a 48
>pilot on order which I hope alleviates the bog. Am I on the right track? Any
I don't recommend raising the clip - go for the (very lean) OBDVR
needle from the YZ or even better an OBDVP needle in 3rd position
which is a very good compromise.While I'm running an 48 pilot for cold
weather, it won't cure the bog. Try the following things:
1) set your fuel screw to 2 1/8 turns out
2) check if the acc. pump works correctly - VERY IMPORTANT! Open the
throttle all the way and look at the actuating arm of the pump (right
side of the carb). It should follow the opening of the throttle almost
imediately (!!!) and go to its end point without hesitation. With the
throttle all the way open, push with a screw driver on top of the
actuator arm to check if it really goes down all the way.
If the pump doesn't work correctly, you will experience a low end bog
like you describe. Drop me a note if you find a problem with the pump
and I can give you some good advice from my own experience.
Michael
************************
* mpe...@ibm.net
*
* 98 Yamaha WR400
************************
Rowdy
<snip throttle blip makes 4s engine die>
If you do a REALLY quick throttle blip, like rolling it open between
both your hands as quick as you can, every engine without CV carb will
die. All Dell Orto KTMs, my WR and Drehwurm's WR400-WB-E series.
Reason:
- the stock KTM Dell Orto's nowadays don't feature a pumper carb
- even the pumper carbs can't squirt in enough fuel
when the slide is ripped open
- 4 stroke guys like to set their bikes to idle at low rpms
When i did set the idle real low on my late KLX650R, even she,
featuring a truly fine CV carb, would die when blipping the throttle.
Background:
Actually those pumper carbs are a poor man's fuel injection system
without the proper metering of a computer controlled system. They
*should* measure - throttle-opening-speed and rpms dependant - the
correct amount of additional fuel into the lean charge. No chance
without electronics. (hail to cannonwhale for introducing EFI into off
road bikes, that move was over due!)
I came from CV carburated bikes (XT600/TT600 twin carb, KLX650R CVK-40
Keihin), did a test ride on the KTM620 of my buddy, ripped the
throttle open in low rpms, made the bike bog(?)/hesitate and
immediately regarded it as inferior design since then.
You can imagine my facial expression, when both me and that buddy of
mine, managed to make my new WR400F bog by a rather harmless sequence
of throttle moves. It happened BY CHANCE when going round the block, i
almost fell to the inside of a turn!
Solution:
- set the idle to higher rpms (helps a lot, works instantly)
- go richer on the pumper (anyone done that??)
(you can't go richer with any other circuit, as this would mess up
the
jetting when riding with constant throttle position (e.g. no pumper
action))
- forget about blipping the throttle real hard, doesn't happen in real
world,
e.g. has to be considered a cockpit error, as the WR - even with YZ
timing -
hasn't got much power down *very* low anyhow.
- She's a screamer, act accordingly!
I learned to adjust to using a different rpm-range within a year.
Now i simply don't get caught *accidentally* using that super low
end
of the powerband, hence no bogging troubles any more.
YMMV
Rowdy
WRZ400F '92
yz40...@my-dejanews.com
keep the back fires out of your air filter. Have you seen what a backfire can
do to the foam filter? It will put an end to a days ride in a hurry. The only
thing you can do for jetting is play with it and keep an eye on the plug and
how it runs. Don't forget about the fuel screw on bottom of the carb. It has
alot to do with low end carberation of the bike .<3713...@news1.us.ibm.net>,
"Eric Hedin" <ehe...@ibm.net> wrote:
> I put a fmf megamax muffler on my wr and now I have a bog when the throttle
> is opened quickly. The plug is sooty but has a white on the ground
> and changing the cam timing to yz specs.
>
> 45 pilot
>
> I figured that since the plug had white on it, the main jet is lean, so I
> changed to a 172. Because of the sootiness and fouling I figured that the
> midrange is rich, so I raised the clip position on the needle. I have a 48
> pilot on order which I hope alleviates the bog. Am I on the right track? Any
> Thanks!
>
> -Eric
>
>
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