I was thinking about machining a "hybrid" needle at work on the lathe. I have plenty of time, and I need to learn the machine (lathe that is) anyways. I have been having trouble with plugs fouling. Now granted.. I have come a long way mainly because of what I've read in here over the last two years. I've went from fouling about two an hour to two a day. Still learning. Compression is good, seals are replaced, float height's set, and all of that good stuff. I am fouling while averaging 1/2-full throttle. I took all of the measurements on my current needle to get a feel of it. It looks like it has 5mm of adjustment...(each groove being 1mm). I know a needle is only about 30.00, but I am basically just playing, and trying to learn. I know the taper rate. I wonder if I could make a needle and at the top attache a small collar with an even smaller set screw. And with this.... maybe get 10mm of adjustment....does it need to be a softer metal so that the seat does not wear? Or a harder metal so that the seat wears to it?
Needle?
- Thread starter colbyc28
- Start date
I'm not against anybody playing or experimenting. However, I don't think you understand fully how the needle works. There is a certain amount of travel. When you twist the throttle, there is only so much movement. certainly this is more than 5mm. but for the progressive transfer to happen, everything must take place in a small area.
Once again, feel free to try. I would just believe instead your current tune is not right. If you are fouling at 1/2-full throttle, then it's your main jet that should be the culprit.
Is your bike new, or new to you? Is the carb stock? Is the bike stock? Is your ignition in good shape? are you sure?
There are a few really good discussions on reading plugs properly. It won't take more then a few mintues of good hard riding to be able to read a plug. Make a jet change, or plug heat range change, test again, repeat.. You could have your bike good enough to have a plug last longer then a day.
Once again, feel free to try. I would just believe instead your current tune is not right. If you are fouling at 1/2-full throttle, then it's your main jet that should be the culprit.
Is your bike new, or new to you? Is the carb stock? Is the bike stock? Is your ignition in good shape? are you sure?
There are a few really good discussions on reading plugs properly. It won't take more then a few mintues of good hard riding to be able to read a plug. Make a jet change, or plug heat range change, test again, repeat.. You could have your bike good enough to have a plug last longer then a day.
- Thread starter
- #3
Dew....thank you for the input. That is what I am looking for...opinions from you guys. The bike is not new... an 89 YZ 250. I have been through the whole thing, except the packing in the silencer. I understand that the movement of the needle exceeds 5mm's. But the starting point is adjustable....(the notches). Why do they sell optional needles? I would think the length would be the only difference....but then again, I could be wrong. I am by no means arguing your post..just trying to get a better feel for the situation. I am on the "leanest" main they offer. I am on the second from "leanest" pilot. My plug reads rich...(black and wet).
colbyc28 said:
This should prove enlightening :
http://justkdx.dirtrider.net/jetneedles.html
http://www.factorypro.com/tech/needle_jet_wear.html
If I had an 87 250, and it was still rich after leaning the circuits like you claim, 1st, a leak down test, and 2nd, if the previous owner has removed material from the cylinder. And definitely get on that packing, it makes a big difference! For some reasons the engine is getting a mix that is either too much, or not mixed with air properly. No one has been drilling their own jets have they?
- Thread starter
- #7
Forks, they cylinder was sent off and re-sleeved last year. New rings and piston at the beginning of this year. The jets have not been drilled...they too were bought new at the beginning of this year. I will get on the packing as you suggest. Thanks.
87, should have been replated. There are a lot of bad things can happen, when they have to match exact stock port dimensions.
81 most all mx bikes were plated and water cooled. The manual knows all?
Pete Payne
MX-Tech Suspension Agent
- Nov 3, 2000
- 933
- 38
Nicasil and plating of the cylinders goes way back past 93 even in production cylinders .
Kawasaki used chrome plating of some sort back in like 81 or 83.
The Honda CR125 was nicasil . I had one of them .
Kawasaki used chrome plating of some sort back in like 81 or 83.
The Honda CR125 was nicasil . I had one of them .
Wasn't the 78 Honda chrome bore on the 125 and 250. I had Kustom Kraft pushing liners in them. I thought Kawasaki was first.
2strokerfun
Member
- May 19, 2006
- 1,500
- 1
I liked the link on needle and needle jet wear. I fought my jetting for a year and a half and finally decided the needle and jet were just too worn out to jet effectively. Replaced and ran like brand new. And I think I paid $8 for my last needle from Sudco.
Pete Payne
MX-Tech Suspension Agent
- Nov 3, 2000
- 933
- 38
whenfoxforks-ruled ,
Yeah I kinda think Kawasaki might have been the first to offer it on a production bike .
Pete
Yeah I kinda think Kawasaki might have been the first to offer it on a production bike .
Pete
The Yamaha TD1B 250cc production road racers had chrome plated bores as early as 1965. A couple of years before that they had some weird hard anodizing directly directly on the aluminum in the bore, but it wasn't very reliable.
