power loss at full throtte?

[cooldude3552000]

i, I have a 92 Yamaha wr200(2stroke) and I have had this problem since the day i got it.

When I am running full throttle(dirt or pavement) in 6th gear(flat out as fast as it will go), it will pull strong and fast around 3/4 throttle but if I twist the throttle all the way it looses power. It won't speed up and slows down a little(sounds sorta like its running out of gas), if I let off to around 3/4 throttle then it runs strong again.

Also if I am just cruising around slow in a lower gear like 3rd or 4th and twist the throttle all the way it won't speed up, it might speed up like 1 mph but thats it. If I twist it just to like 3/4 throttle then it will speed up very fast until I let of on the throttle.

I know the bike has not been rebuilt in at least 2 years (I have owned it a year and the guy I bought it from had it a year and never did it). I am planning on doing it this week.

Anyone have this problem? How do I fix it or is it normal?

Thanks!

 

[kxguy967]

the main jet is what controls WOT. id go one size smaller and see if that helps.

 

[cooldude3552000]

sorry but what do you mean by "go one size smaller" do you mean lean it out 1 turn? Sorry but I am still learnig when it comes to dirt bike engines

 

[FruDaddy]

I would try to richen it a size or two first. But to be sure, find (and read) Spanky's jetting guide, and do a series of throttle chop tests to make sure. You can begin searching for the jetting guide at the top of this page.

 

[skipn8r]

By what you've described ("sounds sorta like its running out of gas"), I'd say it sounds like you're lean at WOT and need a larger main jet.

 

[2-strokes-4-life]

with the main jet one size smaller would mean the next smallest jet.take off the float bowl and the main jet should be the jet in the middle with like a little plastic plate over top of it.take it out and it will have a number stamped onto it.increasing the number gives you a bigger or richer main whereas a lower number will give you a leaner main.from what you are describing it does sound like you may want to install a larger main.remember to always change jets one size at a time then do a plug chop test to see how its running.

 

[NO HAND]

From experience, when you get a very noticeable lean bog like you describe, you are at least 2 jet sizes from where you want to be. I'd go richer on the main and avoid riding in the lean spot until you correct the jetting.

 

[ellandoh]

definitely, richen the main jet 1 or 2 sizes. and if youre going to do a plug chop test i suggest you search for threads on the subject by rich rohrich , his outline on the method is the ONLY right way to do it, contrary to popular belief
the main jet is a brass 6mm nut in the center of your float bowl. take it out and goto nearest dealer and tell parts guy you want 1 and 2 sizes larger/richer. they should be approximately $6 a piece

be sure to let us know how you like your new WOT :nod:

 

[dune-addiction]

If you're that far off on the main jet, just do a plug test to determine if you're lean or rich. You will definately have to adjust more than one size either way.

 

[ellandoh]

sputtering, blowing smoke, spooge, fouling plugs, wet plugs are symptoms of being rich ...................maybe he left that out i dont know, my cousins ride was bogging lean WOT and 1 size cured it completely

 

[i_955]

If you raise the main jet by 1 or 2, you might have to raise the clip on the needle one clip (leaning 1/3 - 3/4 throttle). That will help ballance out the change.

 

[ellandoh]

If you raise the main jet by 1 or 2, you might have to raise the clip on the needle one clip (leaning 1/3 - 3/4 throttle). That will help ballance out the change.

possible , but if he is new to jetting he should do one change at a time and get back to us :nod: start with the main only

 

[nephron]

Cooldude, have you done routine maintenance on the bike? I can only wonder, you getting the air or idle screw mixed up with the main and all... ;) ie, have you cleaned the filter? Looked at the plug? A BADLY plugged up air filter will create a rich condition at WOT. Also, you need to tell us if the bike 'four-strokes' (rich) or lean bogs (waaaaahhhhh) at WOT. We can't help unless you tell us this stuff. And just think if you could fix it without having to take that whole carb thingy off! :yikes: :yikes: :yikes:

 

[cooldude3552000]

I clean the air filter all the time. I replaced the spark plug a while ago and it did nothing. There is no goop or oil coming out of the pipe, but it does smoke alot but I turned what the manual calls a "pilot screw" a little bit to the right to make it leaner and now it barely smokes at all(performance is the same).

Can someone post a picture of the this "jet" that I need to replace so I know what to take out.

I'm not really sure how to describe the sound, but no matter what gear I'm in, if I turn the throttle all the way it doesn't speed up(if I'm in 6th gear it slows down a little). It stops screaming like a 2 stroke and gets quieter(it doesn't have high pitched scream of a 2 stroke but doesn't have the "low pitched tractor like four stroke sound").

Someone on another site said I should check my reeds, they said they had a similar problem and new reeds fixed it.

Someone on another site said I should check my reeds, they said they had a similar problem and new reeds fixed it.

 

[ellandoh]

my post on the 1st page describes it. you say you have the manual see if theres a pic in there??
if not i believe it will be the only gold colored 6mm nut in the center of the float bowl chamber.
if theres room on your bike to just loosen the carb boots and turn the carb so you can get to the bottom. take out the large drain bolt and look straight in the hole, you will see the nut im talking about. use a 6mm socket on a screw driver type 1/4" drive to get it out . ten minutes and youre done :cool:
im not guaranteeing its a 6 mm nut it could also be a flatblade screwdriver but regardless it is the one accessible from the drain hole

 

[cooldude3552000]

I finally got a chance to go to the dealer. I got the next 2 sizes up, I also had them order a top end gasket set so I can rebuild. I also ordered Boyesen power reeds(15 bucks on e bay new in package) and a Wiseco top end rebuild kit (80 bucks on e bay). The guy at the dealer said that the new jets should fix my problem and between that, the new reeds and a rebuild my problem should definitely go away(this guy actually seemed to know what he was talking about.) I also ordered a new uni air filter (stock one was worn out) supposedly UNI filters are slightly better than stock so hopefully with all of this my bike will run much better and a little faster.

 

[cooldude3552000]

I have.

I am going to try the new jets tomorrow and see how it runs.

 

[CspineRider]

You dont have to take the float bowl off to change the main jet. just loosen both clamps on the carb and twist the carb to where you can get to the bottom of the float bowl, you will see a nut, probably 17mm-19mm in size. Make sure you turn off your gas at the petcock and undo the nut and some gas will poor out. Get a 6mm socket and unscrew the brass main jet. Replace the main jet but being careful not to over tighten as brass tends to strip easier. Replace the nut on the float bowl, twist the carb back into place, tighten your clamps, turn your fuel on, raise the choke and fire her up.

 

[FruDaddy]

The Woyeson reeds are a great addition, but you may have to go even richer because of them. Get the bike jetted and runing right before installing it. That way, if you need support once the reeds are in, you can reference the original jetting specs when you ask for help.

 

[cooldude3552000]

when you say I will need to go richer with the new reeds, do you mean just turn the mixture screwn richer or do you mean get an even bigger main jet? i will deffinetly get it running right before installing the reeds.

 

[Chokey]

The Woyeson reeds are a great addition, but you may have to go even richer because of them. .

In my experience, the Two-Stage Power Reeds make the jetting very rich, especially the pilot circuit. You'll most likely have to go much leaner on the pilot, and somewhat leaner on the main jet.

 

[FruDaddy]

I had to go richer the last time I installed the reeds. I haven't put them in a full size bike, only minis. But it does affect the entire range. Start with the idle circuit and work you way up

 

[cooldude3552000]

thanks, I just finished installing the jet(1 size up). The bike ran better than it ever has. It has a much better sound too. Unflortunetly, the bike still has the problem with full throttle(alittle better but its still a problem). I am going to wait until I get all the parts to rebuild and the new reeds. Then I will instal the next size jet. Hopefully then it will run great.