Just Fixed One And Then What Happens.....

[clav3]

Yea, try a 36 or 38 pilot, put the needle back in the 3'rd groove and ride it!

I will restate my opinion, the Kiehins can be a better mixer and higher performer, yet a pain in the butt that most do not want or need!

Thought it might be something like that.

I'm no expert like some and I've only owned two Sherco 290s. Both pinged there heads off in the low mids using the standard D36 needle on the third groove.

Funny how the Gassers dont do this.

I originally bought the keihin for more power but found I can run the bike either smoother or harder than a dellorto,with no mid pinging, cleaner top end, no horrible popping on rev down. Sounds like a few good reasons to give one a go and there's alot of very good riders on the planet that would agree. But like I said before, I'm no expert.

I'm still not convinced that my problem is the carb, but, keeping an open mind.

[copemech]

So Clav, I am still a bit unsure about how it is with the dellorto back on, as in the first post you seemed to state that it ran well, yet in the second you referred to the pinging.

All I can tell you is I never fixed mine(dellorto) by messing with the needle.

I think fuel has a lot to do, yet not all.

I had to up the pilot to what I had previously considered unrealistic(example, 33 to 38) to get it in range with smoother and better power and little to no pinging. I think there is a logical theory behind all this, but it seems some even varies with the carb itself.

You can run the main down to 112-115 range if you want it to clean out and rev clean to the moon.

Try it!

Edited May 5, 2009 by copemech

[neo]

Yea, try a 36 or 38 pilot, put the needle back in the 3'rd groove and ride it!

Yes I remember doing this some time back. But it still ran lean for me and I wasn't keen on the power delivery either.

I know where your coming from Clav .....I just wish I could put my finger on something definite with this issue.

I was just re-reading your first post below.....your issue is so close to my own it's not funny ....but I'm struggling to think what this proves....I wonder if Sherco did anything on their new bikes when they went over to the the PWK?

Best of balance.

Neo

Edited May 11, 2009 by Neo

[clav3]

So Clav, I am still a bit unsure about how it is with the dellorto back on, as in the first post you seemed to state that it ran well, yet in the second you referred to the pinging.

Yesterday I put the Dellorto back on to rule out an air leak or piston problem. 33 pilot 3 3/4 turns out and standard needle on bottom clip. The standard config when the bike was new was too lean and had engine ping in the mids.

This was the first post!

Both pinged there heads off in the low mids using the standard D36 needle on the third groove.

This was the second!

It ran well in the first post because, as I stated, the needle clip was down on the bottom position.

I've spent hours with my first 290 and some with the second on pilots and different fuel types, even racing fuel. This was with the Dellorto. The only thing that helped was when I ran a richer needle setting and softened the timing slightly.

I think softening the timing is why you have had success in getting your bike to run well, yet in one of your other posts you did say the midrange ping was still unaddressed by the factory.

I,m not changing my timing! I have two timing maps and with the dell it pings in the mids. With the Keihin it dosen't.

You wouldn't believe my dissapointment when I rode my new 08 first time out of the crate and heard that horrible engine knock.

All the hours spent trying to get rid of it on my 2000 came rushing back to haunt me.

I've spent way way too much time dicking around with the Dellorto carb and had much more success with the Kiehin.

And yes I have tried a 35 and 38 and even higher pilot on the 2000 with Dellorto. Just made the bottom end rich and poppy and still pinged in the mids.

And yes I have tried a 115 main in the Dellorto on my 08 and have not once been able to clean it out. I know I could just keep going leaner on the main until it dose but......... I have a Kiehin and until two weeks ago, was over the moon with its performance.

Neo my bike arrived in September 07 and I nearly ride as much as you, so it has a few hours on it already. When I did the engine teardown about six months ago to fix a twisted crank, new rings were installed and the piston was just within tolerence so I kept it.

The problem may be piston wear, I dont know.

I've ordered a new float bowl gasket, top gasket and needle valve for the Kiehin and should arrive Wednesday.

Fingers Crossed.

Has anyone ever notice the Kiehin idling slightly rich when bike tipped foward and slightly lean when tipped back?

Edited May 5, 2009 by clav3

[copemech]

Mine always gave me a rich mix downhill, would occasionally die out if I did not crack the throttle to keep it cleaned out. Always had to shut off the petcock if parked downhill or it would flood.

Not unlike Neo, one might be surprised what one may find in these things upon careful inspection. Moisture, venting(tank and carb) and inline filters are all important and often overlooked.

Lets not overlook PROPER and thorough cleaning practices where there are particuler problems, such as removing jets and screws, passing things through them and all the little orfaces, as well as using compressed air to blow thing out!

Trust me, I have done plenty of quickie cleans with a bit of carby spray, but sometimes it just does not do the job. It is just a blow and go!

Tip of the day, occasional floaty idles (lean condition) and loss of power are usually moisture induced.

So Clav, how did you twist a crank?

Only one I have ever seen sounded just like piston slap, but it was not!

Edited May 6, 2009 by copemech

[neo]

I will add that I don't believe a PWK can be completely cleaned out unless you remove those two tamper proof screws.

I was shocked at how many holes and pin-holes where under there. I reckon even water could stay trapped in that area.

Best of balance.

Neo

[clav3]

So Clav, how did you twist a crank?

Only one I have ever seen sounded just like piston slap, but it was not

Yea thats the sound.

I held it wide open for no more than realisically three to four seconds to clean it out and it cleaned out like never before.

Then I gave it a little blip and rattle rattle. Thats the risk you take.

Ryan Young said "Pat Smage did it to his crank in 08. Ray Peters to his crank in 2000. You can weld the pin to keep from happening, but it is very rare! 2 times out of over 1000 bikes imported, well now three with yours".

I put a brand new Kiehin on today.

The bike runs ok but still not right. All the settings are still way richer than two weeks ago. (42 1 1/4 turns out to 45 1/4 turn out. Seems like it needs a 48 but I haven't got one. Also needle needs to be richer. I was able to run 42 5/8 turns out with jjh needle in middle. Although Ifound this setting weak in the mid, the idle was still quite rich......This setting is now impossible.)

I feel I've had to richen the Dellorto settings slightly. ( with the needle all the way up it used to run 33 pilot at 2 1/2 turns out and now 33 pilot at 3 3/4 turns out.) I must add It seems to run very smooth with the Dellorto.

Maybe the Kiehin fluctuates more with slight engine changes or wear?

It's comming down to piston wear or a seal...... I THINK?

[copemech]

Well Clav, that pretty much sums up my experience with crank issues as well.

Trying to rationalize all this , yes there is a possibility that seals could be leaking a bit, yet due to the sensitive nature of the Kiehin, I am wondering if weak reeds could not be a problem as well.

This theory of worn pistons and such just does not seem to hold well with me, as the carb only meters what goes through it. Volumetric efficiency would not normally come into play, as in the case that the 125's can use the same basic setup as the larger bikes.

With my timing set back a bit, the Boyesen reeds installed, I found mine would rev incredible heights even with the Dellorto. I had to go down to a 110 main to totally clear easily! Long story made short, this is an unusable rpm range that could cause major damage! And thusly, the 115 was reinstalled as a rev limiter. Leonelli claims the limit at 13,000 i belive, done that, no need!

Maybe I am off base, maybe not. Jon Stoodly has a lot of experience in this area, maybe he will chime in here with some thoughts.

[clav3]

Carby perfectly clean, neadle and seat looks brand new, checked engine and manifold for air leaks, installed a new pilot jet and reeds, cleaned tank, fuel tap, air filter, breather hoses, tryed different fuel, made sure tank was venting.

From page 2.

The reeds were the first things replaced. Standard reeds.

[jse]

Well Clav, that pretty much sums up my experience with crank issues as well.

Trying to rationalize all this , yes there is a possibility that seals could be leaking a bit, yet due to the sensitive nature of the Kiehin, I am wondering if weak reeds could not be a problem as well.

This theory of worn pistons and such just does not seem to hold well with me, as the carb only meters what goes through it. Volumetric efficiency would not normally come into play, as in the case that the 125's can use the same basic setup as the larger bikes.

With my timing set back a bit, the Boyesen reeds installed, I found mine would rev incredible heights even with the Dellorto. I had to go down to a 110 main to totally clear easily! Long story made short, this is an unusable rpm range that could cause major damage! And thusly, the 115 was reinstalled as a rev limiter. Leonelli claims the limit at 13,000 i belive, done that, no need!

Maybe I am off base, maybe not. Jon Stoodly has a lot of experience in this area, maybe he will chime in here with some thoughts.

Interesting thread! A conundrum wrapped in an enigma you might say, and it took a while to follow through to the end......

I think the presenting issue was: "The air mixture is continually varying too rich, too lean, too rich, too lean, too rich, too lean!!!!...but is getting leaner and leaner and the airmix screw (on the PWK28mm) is hitting the stop now", I may ask, what exactly are all the observable/felt symptoms/under what conditions, that lead to the diagnosis? That might be a good place to restart.

I think Stork mentioned the 215 PSI cranking pressure as being a little too high and a decoke might be needed (probably in the headpipe also), and I tend to agree that should be looked at. Although unusual in this age of full-synthetic premix oils, the buildup of carbon in the combustion chamber can cause various problems, such as elevated octane requirement. Compression cranking pressure (not totally related to compression "ratio", which is a mechanical measurement, and in racing two-strokes is usually measured as the ratio of the cylinder volume from the closing of the exhaust port by the piston, to the volume of the combustion chamber at TDC-this is referred to as "corrected compression ratio") that is too high can cause sometimes unsurmountable problems with carburation.

Jon

[kramit]

Try adding an extra base gsk just for kicks....worth a try.

[neo]

I dechoked the exhaust header pipe and box today...great fun!!...even with all the smoke

The header pipe was only about 5% blocked but the main box did look a bit gluey and clogged.

I'll do the compression test again when I get it all back together but I all I did last time was keep kicking the bike over till the compression gauge wouldn't go any higher (about 5 or 6 kicks)...not sure if this is the right or wrong way but that's what I did.

Also, with the "wandering mixture" thing...what about Cope's previous theory of leaking mains bearing seals??...seems like a good possibility to me.

Best of balance.

Neo

[jse]

I dechoked the exhaust header pipe and box today...great fun!!...even with all the smoke

The header pipe was only about 5% blocked but the main box did look a bit gluey and clogged.

I'll do the compression test again when I get it all back together but I all I did last time was keep kicking the bike over till the compression gauge wouldn't go any higher (about 5 or 6 kicks)...not sure if this is the right or wrong way but that's what I did.

Also, with the "wandering mixture" thing...what about Cope's previous theory of leaking mains bearing seals??...seems like a good possibility to me.

Best of balance.

Neo

Neo,

What brand/type of premix oil is used?

Make sure the throttle is wide open, the plug is properly grounded away from the plug hole and rapid, strong kicks for accuracy, usually 5 or 6 is enough.

Yea, the "wandering mixture" is the weird thing about the problem. It's kinda like an infrequent misfire, they're the ones that will drive a mechanic nuts, as it's hard to pinpoint the related possibilities at the time the symptoms occur. Once you're established the symptoms, you look for patterns and relationships to follow the path to the cause. Most bike problems have a consistancy of effect-occurance, like leaking main seals, or manifold leaks, or chipped gears etc. so it's pretty easy to track, but something that reverses, like rich to lean mixture, exhibits opposite effects and sometimes one has to look for causes "outside the box".

Jon

[neo]

Thanks Jon,

I've been using Castrol TT Fully Synthetic for about a year now. And when I took our 125 engine apart recently it was almost a clean as whistle...so I'm quite confident it's good stuff

Best of balance.

Neo

[stork955]

Gday Neo, in cases like this I think it's really important to diagnose carefully and logically, looking at one area at a time. This is how many of the bikes I work on come to me - it takes a couple of hours to fix the "fixes" to get to the root issue... Like Jon said, what are the exact conditions you notice that lead to the fluctuating mixture issue? eg - hard starting, cutting out occasionally when idling or at very small throttle openings, misfiring at high load and rpm etc. The best way to diagnose mixture issues is to look at the plug as it is the window into the engine, there are many good plug reading charts on the net that you can download to use as a comparison for yours. Sometimes with 2-strokes its hard to determine if a lean or rich mixture is the problem -sometimes they can give a similar symptom. I also reckon it is best to start with good solid basics, like clean carb and filter set to "factory" specs, clean pipe (which you have now done - that makes a huge difference in itself to general performance) and good general engine condition which you also have by the sounds of things. Stick with it!

Cheers,

Stork