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94 KDX Boggs When I Snap Throttle???
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Posted by: Colorado KDX---------------------
I just bought a 94 KDX. I'm trying to work out,why it boggs when I
snap the throttle off idle. If I roll it on slow it revs great, but
doesn't have the power to get the front wheel up and over things.
The bike has a stock pipe with 45 pilot jet and 140 main didn't check the clip #. The plug has a nice tan burn. Thanks, Al
Posted by: Fred T---------------------
that pilot seems OK, but the main seems small to me, but I'm not familiar with 94 model carbs. Bogs are an indication of being lean. You may need to turn your air screw IN 1/8 to 1/4 turn and try that. I'd suggest a plug chop at WFO to make sure your main is big enough and be sure to use fresh gas. Crappy gas will maike them run....well...crappy.
Posted by: Colorado KDX---------------------
What is a plug chop? I Ran it wide open then cut the throttle. For the plug burn. I forgot to tell you that I am at 5800 Ft Elevation. The air screw was
set at 3/4 of a turn out. I went too 1/2 out seems to run a little better -not sure?? Is this to far in? Do you think clip postion could be a factor??
Posted by: DANIEL JOSEPH---------------------
If you twist the throttle hard and the bike bogs try turning the air scew in some, if that doesn't do it your pilot may be lean.
Posted by: David Trustrum---------------------
Or blocked, or if you’re real lucky the slide has a groove worn in it that is causing a leak. If this is the case you will need to replace it (don’t expect to find a good condition 2nd hand one they all do it & sit down for the price)
If you are talking just off closed throttle bog, Keep turning the screw in, & if it gets better but not enough go the next size up. Do check for airleaks in the manifold/airbox, filter first though.
Needle position is worth a play too, raising it a click. Do one thing at a time & remember throttle position -not revs determines which jet to adjust.
Posted by: Jim Crenca---------------------
My 94 (that came with a FMF pipe) & nearly stock jetting that bogged too. I think needle type & clip position will make the biggest difference as well as airscrew (main jet does sound way too lean). IMO, plug color is only accurate after a 3rd or 4th gear WOT plug chop. I think the R&B carb thread in archives has some needle recomendations for stock carbs as well as modified.
Posted by: Colorado KDX---------------------
Thanks for you help guys. Changed the pilot to 48 and moved the clip
down from 4 to 3. Air screw out 1 turn . The bike has a lot better responds
Still thinking about playing with my main jet.(richer)How will I know when it is
to rich?
Posted by: BRush---------------------
Check the main jetting by doing a plug chop. This link should get you started:
http://justkdx.dirtrider.net/carbtuning.html
Posted by: acutemp---------------------
Colorado KDX,
In your original post you list your main as a 140. If this is right I would put in larger main and see how it runs. It sounds like you have a lean main and rich pilot combo. I would think that a 42 pilot 150 main would be much closer to what you need. Even at your elevation a 140 main is way to lean IMO.--Dan
Posted by: Colorado KDX---------------------
Knowing that the guy before me ran the bike this lean shoud I
expect engine damage? Would a compression check tell if things are
wrong. He told me that it had 130 psi cold compression! Seems a little
low, but I figure that was because it was cold . I remember a post saying it should be about 160 psi warm? I didn't run the engine
at full throttle very much this weekend so I hope I didn't do any more
damage. Thanks for you help, Colorado KDX
Posted by: David Trustrum---------------------
If it didn’t seize up it is probably fine. Truth be known it would probably be time to pull the top end & clean the powervalves. You can treat it to some new rings while you are there as they are pretty cheap. Use the [search] key above & look up ‘powervalves’ They should be stripped & cleaned every so often to avoid damage.
Posted by: Colorado KDX---------------------
Looking at the bike log it says he replaced piston and rings about
1500 miles ago. So I would assume it might be do? Also
it said he used a wiseco piston, so will I need to use wiseco ring?
Also I have never torn into a 2 stroke with a power valve. Is
it hard to do? My only top-end job was on a KTM 550. And
for some reason KTM didn't feel it needed a power valve.(And I
know why-my broke rear fender) Thanks, Colorado KDX
Posted by: David Trustrum---------------------
Use the [search] key above & look up ‘powervalves’
Posted by: Colorado KDX---------------------
Sorry man! I'm a little slow on this machine! The search at the top
just shows me old posts. Is that what you are talking about?
Posted by: David Trustrum---------------------
Yeah, in there should be enough info on how to do it & clean them. It is easy once you make the logic jump & see how it all works.
There should be heaps of info in old threads to arm you to jump in one rainy afternoon. (& look on the justkdx website).
Posted by: Colorado KDX---------------------
One thing I can't figure out is, if my bike was jetted so lean with a 140
main then why does it still drool from the silencer to pipe
connection? I run 40/1 mix Honda hp premix- is this the problem?
Posted by: David Trustrum---------------------
No. Remember that your jetting can be lean on one jet & rich on the others.
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