RMX Mid-range Hesitation

[Uncle Alpo]

Hmm http://www.dirtbikeworld.net/forum/showthread.php?p=957508&posted=1#post957508

From the looks of those pictures the older dual, two-piece valves are a better design. I've run the snot out of my original '89 valves with no problems at all. The plating is a little worn here and there (primarily because I'm sometimes lazy about cleaning them), but they work great.

[dirtynidge]

Hesitation has now moved to 1/4-1/2 throttle, quite annoying on technical stuff. On fire trail where I can keep motor singing it absolutely flies on topend but woes down low.

I pulled plug out after ride and it is a caramel colour so has been a lean bog low down. I'll raise needle back to 2nd clip for ride on tues and look at changing it when I do topend in the next couple of weeks.

What needle should I look at next?? Im thinking CEK or DEK in 2nd clip to keep it a bit richer 1/8-1/2 but still keep the topend similar to what it is now (with 1469H in 1st). Any thoughts??

JD's spreadsheet has changed my life!!!!!

[hallsy]

Are you thinking CEK-3 and DEK-2? I like to experiment with what I have, maybe save some $ in the process, or not:bonk:.

A couple ideas...

DEK-2 = R1469H-1.5, ever hear of a 1/2 clip shim? A small washer that goes under the needle clip to raise it a bit. It can't be any larger than the O.D. of the E-clip and @ .40-.45mm thick. That could be tuff to find, yet the washer on the PJ's airscrew might be close and could be filed down if needed...

How about the 1471N, got a use for it? With a drill and a small file could you turn it into a 1469N? Not exactly CEK-3 but 1469N-5 with a 172 main, looks to be in the ball park. Neither are a permanent solution but they may help you to further define which direction you want to go.

[Uncle Alpo]

You can get stainless shims at Radio Shack, Fastenal, etc. They're called electrical washers and a pack is ~$2. The ones I have are .53mm thick.

[dirtynidge]

Now your talking my language, tinkering on the cheap!!!

I am pulling out the needle files, micrometer and chordless drill as we speak.

I have a big bolts box in the back of my work van and would bet there is an M4 washer in there waiting to be modified to a 1/2 clip spacer.

Thanks guys, will let you know how it goes

[dirtynidge]

Due to slightly over enthusiastic polishing with wet & dry paper the 1471N has ended up slightly closer to 1468 than 1469. Hard to tell for sure as I left my micrometer at work and only have verniers.

I kinda like the look of 1468N in 5, look a very linear power delivery, hope it isnt too rich 1/8-1/4 throttle. Will give it a try in clip 4 too, that looks a good middle ground between the clips 1 and 2 with 1469H.

[hallsy]

I did get some washers once from the local hardware store. What I noticed with them was even though they are small they varied in thickness. I used one in the Mikuni but haven't tried shimming a Keihin. If you look in your slide you'll see the recess that the E clip fits in, this allows the needle to float around. That float may help reduce wear on the needle/needle jet and or help prevent the slide from sticking. FWIW when I made my shim I tried for 1/2 clip thickness but made sure to maintain just a wee bit of play in the needle. In any case I'd only use these for experimenting.

[dirtynidge]

My improvised R1469N (prob closer to R1468) felt rich and blubbery down low, but great on top.

I have just filed up a .45mm clip spacer so I can give the 1469H a go in clip 1.5, replicating DEK in clip 2. Will try it asap.

I have to get this jetting good, I borrowed a mates 05 WR250F on the weekend and my ability instantly doubled! I hate to admit I loved it!! He is selling it cheap as too, the maintenance just scares me, oh and I love my RMX.