YZ125 Jetting

[whyzee]

YZ133 Jetting

members,
While I’m waiting for my cylinder to get back from Eric, I decided to service my carb.
Eric is doing the AMA over-bore and ‘Mo-Better Everywhere’ porting job. I have heard that the bike will run richer with the over-bore.
While cleaning and inspecting the carb, I noticed the jetting is not what I was told… ’360 main w/ clip in center’, actually the main is a 330 and the needle was clipped on top. Stock is 350 w/ clip in center. The current setting seems it was too lean for my stock cylinder, maybe not?, the plug was never white, usually dark tan to black, depending on the day.
The weather here in NC is usually humid and ride temperatures are between 60 and 90F., the elevations where I ride are 500’ ASL max.
With the modifications, is there someone who can give some good jetting specs? I don’t want to run this thing too lean when I get it back and screw up a new Wiseco and my cylinder.

Here is everything I can think of that might help:

Stock exhaust.
Mikuni TMX36SS with:
330 main jet.
S-9 main nozzle.
6BEG9-69 needle; clipped @ top.
55 pilot jet.
5.0 throttle valve.

Maxima Super M. @ 32:1
Sunoco BLUE 112.25 octane leaded cut with 93 octane leaded pump fuel, cut 50/50.
NGK BR8EG.
Boyesen pro series carbon fiber reeds.

Also, the throttle stop screw set on mine was rusted, so I got a new one, (#14 in the below HTML), my manual shows NO setting for this, anyone???

http://216.37.204.202/Yamaha_OEM/YamahaDB.asp?Type=13&A=110&B=30

Is anyone with the 133 set up running an FMF fatty, and how do you like it, did you notice a difference?

I have heard the CR guys talking about shortening their stock silencers 50 mm., any YZ’ers that have tried this, results?

Last, The pilot jet is very course on its exterior, unlike the smooth main jet surface, is this normal?

In advance thanks for any help and any advice.
Dave
:confused:

 

[NO HAND]

First of all, congratulation for the 133 kit. This is so awesome. I rode a 00KX133 and was so amazed that I sent my cylinder for the same treatment. I doubt that your engine will run richer with porting and overbore. I am quite sure that it is going to be too lean, and you will need to richen the jetting. My stock jetting was 360 main, needle in 3rd clip and low speed 50. The main was fine but the low speed was too rich. I went for a 35 low speed and it was perfect(stock porting). With Eric's mid-top porting (not 133 yet), I had to bump to a 380 main, needle 2nd clip and low speed the same(35). Now that I have the 133 kit ported for mid-top, I will probably have to rejet. I have yet to assemble the bike.

My guess for your bike is that if you start with a 370 main, needle on 3rd clip and 60 low speed, and go down gradually, there will be no risk of running too lean. The fact that you went for more everywhere means that you might need to richen all across the board, not only the main as in a mid-top porting. While you wait for your cylinder, I would go at the dealer and find all the main jets from 330 to 400. Get some low speed jets too; ie 40 to 65. Find an aftermarket company that sells the jets. Not OEM because it's a big rip off. The idle screw that you ordered will need to be adjusted once you have finalized your jetting. Then you can turn clock wise to increase idle speed and vice verca. Don't bother shortening the silencer. The cr guys have to do all kinds of mods just to catch up on the yz. This is something that the cr needs. You should repack it though. This does make a difference. Use insulation glass wool. The pilot jet may have some corrosion, you may try co clean it but be careful not to scratch or change the diameter of the inner hole, this is what counts. I would call Eric for the baseline Jetting because I see that your stock jetting is quite different than mine. Though I can help you out to jet the bike once it is up and running.

 

[whyzee]

133 jetting

Thanks No Hand,
Are you sure regarding needing to richen the main? Talking to Eric yesterday, I could have sworn he said the main would need to be leaned out and the pilot richened because of the bore. Maybe I just heard him wrong. Now I’m really #^%* confused. Silencer is spotless, every darn hole reamed & cleaned, & re-packed, yea, I think I’ll leave the silencer length alone, I thought it might give it a better hit.

Anyone use this place:
http://www.carbparts.com/

Thanks,
Dave

 

[NO HAND]

I was trying to figure out what you would need as far as jetting by comparing with what I had to do on my bike after the mid-top porting (not 133). Eric Wil have a much better idea than me for a starting point. I haven't had the chance to run my 133 yet. The thing that does make a difference in jetting though is the type of porting. You asked for more better everywhere. This is why I was figuring that you will need to richen slightly everywhere too. On my bike I had the porting for overrev only. That explains why I had to increase the main and reduce the low speed jet. If you are sure that Eric told you to lean the main, that's the way to go. If not, you may be better playing it safe by trying richer at first and see what it does. Or even better, call Eric again. I'm sure he'll be happy to help. It is a very busy time for him now because of the 2002 that everyone wants to have done before the season starts. It's easier to give him a call than wait for an answer here.

 

[whyzee]

Eric's response is to leave it stock and follow "The Ride and Feel Method", non-committal, and that’s ok. He WONT give baseline settings, period.:(

 

[Pit_Monkey]

he says that in his book that its impossible to give baseline settings but i think that if you call your local dealership or even rpms then you should be able to get some good feedback.

 

[whyzee]

call your local dealership or even rpms

RPM in Covina, CA?

If you are talking about a different RPM, let me know so I can pull this link, but if this is who you were refering to, you might want to read this:

http://xdb.server101.com/forums/showthread.php?threadid=646

I'm just hoping to hear from someone who has had a 133 or 144 job done, and discuss what direction they truly went in regards to: Pilot, Main & Clip position.
Dave:think

 

[Pit_Monkey]

well thats good to know about something like that!! needless to say they will never get my buisness!! the reason why i said them was because i have one of their catalogs and in it they say that after you get work done for them they call you and give you some base line jetting info. i dont know how useful that info would be as i agree with eric on this issue that jetting is all indevidual and base line settings are virtually no help but i figured id let you know that they have base line info if ya need it.

btw i had the 144 kit done by eric with the mo better porting done and head mods for regular gas and when i asked about jetting info i was told to use the trial and error method because you can never tell what jetting will work for one specific bike in one spot at one time, because of all the variables.

 

[dell30rb1]

Hey! i have no ansewer to your questiuon, but I live in raleigh too! You are the only one on the forum besides me to live in raleigh. Where do you live? I live off of 5 points-near glenwood ave.

 

[whyzee]

Dell'
I know of at least 6 of us on the forum who live in Raleigh

Pitt,
I totally understand where Eric is coming from. How do you like the new motor?

No Hand,
Thanks again for your help

Dave

 

[Pit_Monkey]

i love it, however i ride the hard and i wish that i got the mis to top porting done instead of the more better every where. if i get another cylinder ported that is what ill get done.