Posted September 05, 2001 - 06:27 AM
Taffy, we did get sidetracked by the main jet/main air jet discussions. I remember your first few attempts were very favorable without the APJ. I'm still interested in hearing what you find out as variations are tried. I still have a book of notes on my jetting tests.
Posted September 05, 2001 - 12:59 PM
Posted September 05, 2001 - 01:54 PM
i revisited that 'patrick burns' write up on keihin tuning. he's added quite a bit more to his article.
i note that he agrees with you (or you read it!) that a SMALLER PAJ makes the low speed mixture richer. MMMMMM!
sounds like he knows his stuff. he puts a great deal of importance by the straight diameter of the needle. he ignores the fact that the taper point moves with the narrowing or broadening of the needle.
rich rohrich in another article agrees that there should be no plug colour and that the reading is at the bottom. at last someone can hear me. i stopped visiting the YZ side if for nothing else but this argument.
one of these days i'm going to practice and will blag a 37mm wr250 carb as well. i've tried to borrow one on the wr/yz250 site but there aren't too many east anglian owners of said model to choose from. no matter i will get my man.
Posted September 06, 2001 - 09:45 PM
Have you put a 48 pilot in yet?
This absolutely sounds like a lean condition that I had early on with my 2000.
When the idle races, try opening the choke, does this drop the idle?. If so you have a lean condition.
Posted September 06, 2001 - 11:24 AM
Posted September 06, 2001 - 01:24 PM
I remember when I bought my bike. The 42 pilot was sooooo lean, that the bike would not idle properly. I kept on messing around with the idle to get it right. I figured that maybe the butterfly valve in the carb bore was broken or didn't seat properly. It was very frustrating.
I brought it back to the dealer and they cranked the screw way out to like 3-4 turns and wha-la, the bike mysteriously idled again. Your symtoms sound very similar.
Posted September 06, 2001 - 03:48 PM
Posted September 07, 2001 - 09:12 PM
The idea of using the choke on any kind of permanent basis was not the essense of what I was trying to communicate.
The concept of maybe only using a small amount of choke or only pulling in out and then pushing it back in, so that you could see that the idle would drop back down to normal instead of racing was more the point. I was only suggesting it as a way of very temporarily enrichening the circuit to verify a lean condition.
Yes a 45 pilot with 3 turns should atleast not be way too lean. So maybe check and make sure that the throttle linkage seats positively against the idle set screw. Who knows maybe there is something wrong with the cables that is keeping it from returning all the way.
Posted September 07, 2001 - 01:33 PM
Posted September 09, 2001 - 08:23 AM
EFP on clip 5 (EKP equivelant being clip 7)
PS 1 1/2 turns out
dropped the needle to clip 4 (EKP = clip 6)
improvement with the bike no longer misfiring on 1/4 throttle but bad higher. some surging at an even 1/2 throttle. bike riding at tickover idle still snaps and pops the wheel, great for dead start wheelies which are no problem.
dropped needle to clip 3 (EKP = clip 5)
ran a lot better with only the midrange misfiring. no surging. not as good at snap wheelies.
swopped to the EKP needle on clip 4 (EFP =clip 2) so i've gone down one clip position if i were to have stuck to the EFP. ok!
bike ran as sweet as a nut everywhere, but snap wheelies are dead.
adjusted the PS up and down 1/4 turn and fluffy either way so went back to 1 1/2 turns.
tried EKP on clip 3 (down one).
felt just as strong and seamless power everywhere. snap wheelies?-where's my hour glass gone!
you were right about the needle clip setting, so thanks and well done.
everything is a big improvement except the snap from dead which has completely gone. sure, after 2 yards it flies but you have to wait.
there was also a feeling on the last two runs of the engine revs having to build before it would spin. it seemed to be crisp enough but i may do a little tinkering with a 48 PJ just to be sure.
if we take it that EKP/clip 3 = EMP clip 4. what is your experience with _ _ M and also _ _ N off a closed throttle. i know i have a DXM in the box, but i can't remember 13 months ago-too many beers!
remember i used to think that too much of the "straight" part was blocking the ET? i still think so. my answer was to have a wider needle with a higher taper in a drilled out ET? you said i only need a thinner needle (even though the start of the taper drops down the needle).
i would now like to try an EMM or EMN. i want to get that snap back.
your thoughts mon ami?
Posted September 09, 2001 - 02:19 PM
Posted September 09, 2001 - 09:26 PM
Well done also, good of you to share all this.
The EMN had more testing than the EMM. Mainly because I didn't have the EMM until later. I prefer the EMN more than EMP also, but then ride near sea level and about 50F(cool) mostly. The EMP recommendation is aimed at the general population and warmer/higher climates with consideration to the success on the forum with DVP before. (Not likely to foul a plug.)
The EMN is close to EMP but rolls on smoother and will not hesitate as easily. This makes clip positions 4 or 5 both work great (EKP#3/4) and more flexibility on pilot screw settings, less sensitive. It might be pushing luck with clip #5 and a full APJ stroke though. With EMN#5 in slow/wet riding conditions I would use caution with the pilot screw (make it lean) to avoid fouling. Similar to your run 2, EKP#5. Reducing the pump was a different situation though. This became a favorite (EMN#5) with less than 50% pump flow.
EMM didn't get the full checkout. It is highlighted as an excellent setting with 1.0mm pump stroke. (EMM#5, Test run #28!! ) EMM#6 was slightly too rich at 1/4 throttle. Then we went off searching the main air jet issues and development stopped.
EML#4 was only run early on with full APJ. It was a 2-stroke MX type feeling. It was running too rich at the crack of the throttle, even on a slow roll-on. It also sputtered on the road in a very narrow range near 1/8 throttle. This wasn't much of a surprise as a 2.705mm diameter is common for a CR500 2-stroke. Jetting rich on a track is one thing, but sometimes I'm 50 miles from my truck off-road and can't afford to be fouling plugs.
Given the pile of testing, EMM#5(EKM#4) is close to the richest needle setting possible with no APJ that I can see for a reliable set-up (not to foul plugs). This would allow a minimal pump stroke with careful tuning of the pilot and screw. This is where I would look to pick up the development searching for the last thread in regards to minimum APJ. Maybe FHM/N#4-5 also.
Hope the discussion and insight is helpful to you and others.
[This message has been edited by James Dean (edited September 10, 2001).]
Posted September 09, 2001 - 11:26 PM
seems you gave up on that EMM needle too soon, considering that that EML was obviously well juiced up.
interesting how i had my EKP on clip 3 which will equate to an EMM on the middle clip when i get it.
yet again it looks like i'm leaner in the UK (how many times have i said it?)
i would have thought anyone here (especially with an '01 WR or '00/'01 YZ) could experiment with that lack of snap by lifting or dropping the needle. when the needle is rich (high) the bike over the first two metres/yards is awesome.
if you remember i did my initial test based on the observation that i had to open the throttle grip 3mm before anything happened. WE'RE BACK THERE AGAIN!
if i could buy a fatter needle straight that started it's taper 3/4mm higher, to go with an emulsion tube(ET) to suit i would get it today.
anyway i think i'll scratch the EMN and go straight for the EMM.
Posted September 10, 2001 - 06:42 AM
Your test run three is a good reference, EKP#4 was "sweet as a nut everywhere". Add the little richness from the EMM and this will fill in the exact first 3mm of throttle you are looking for.
Posted September 15, 2001 - 07:18 AM
i was on
EKP clip 3
std euro silencer with PB header
so tried the EMM on clip 4 so the only difference is the straight bit.
above 1/8 throttle the same. but at tickover as you open the throttle nothing and then the revs rise gently but not in tune with your hand!
PS down to 1 then .5 turns and it improves response.
swop 45 to 42 PJ and PS back to 1.5 turns
bike is better still. no hint of leanness or hot running
idle screw turned in to 1 then .5 again. again each improves low end response.
PAJ SCREW down to 100. PS back to 1.5.
bike is better still!
i am going to work toward 40PJ and even the 75 PAJ.the needle may even come down one more clip as well but we'll have to see.
the richness at tickover has allowed me to turn the pilot system right down. i can't tell wether that slow build up of revs from a closed throttle is from being too rich with the _ _ M or the fact that the taper starts way too low (lean). i of course put my money on the low taper.
another experiment will be to see if by lifting the needle about 3 clips the snap wheelies come back.
let you know.
Posted September 15, 2001 - 09:42 PM
You say stock Euro silencer, are you referring to the big stainless sealed type? I have one too, If that is the type you have, are you pretty happy with it? I really like how quiet it is.
I'm wondering if all my rough running problems might get better if I go back to it.
Posted September 15, 2001 - 02:32 PM
the euro silencer is the same as the canadians,aussies, etc get. we all get it except the usa. no screws on the end no vortip or whatever.
it's square ended and not particularly pretty.
i love it because it is so quiet. nobody does a pipe that quiet bar the manufacturer. crertainly mine isn't stainless nor is any other i've seen.
i'll have a think on your rough running, see if i can think of anything.
Posted September 15, 2001 - 11:10 PM
Posted September 16, 2001 - 08:22 PM
What diameter will you drill the 2mm step to? If more than 2.95mm, the result may be nothing more than equal to changing the clip position richer.