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Buell Forum » Knowledge Vault (tech, parts, apparel, & accessories topics) » Troubleshooting (Poor Starting/Running/Handling/Ride Issues) » Archive through May 25, 2007 » Soft spot at 1/4 throttle « Previous Next »

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Gunslinger
Posted on Monday, April 30, 2007 - 07:04 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The M2 seems to be running a lot better right now. I still have a bit of a soft spot at about 1/4 throttle or just above. It seems like a lean spot. A local Harley mechanic suggested putting a shim (washer) under the head of the needle. Most needles have a circlip to allow a bit of adjustment, just not the stock Keihn.

Any thoughts?
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Sparky
Posted on Monday, April 30, 2007 - 11:32 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Glad you got it sorted out.

If you don't want to go with a Yost (or similar) adjustable needle, shimming is a good thing.

I kept increasing the numbers of washers on my mostly stock 98 S3 to get rid of a roll-on ping problem and mid-range flat spot. I wound up with an 0.080" thick stack of washers that cured the pinging and immensely improved the throttle response. Didn't seem to hurt mileage any and didn't cost anything either! : )
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Gunslinger
Posted on Monday, April 30, 2007 - 11:43 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thanks Sparky. The guy at the Harley dealer said to move in small increments. sounds like good advice.

My understanding is that on a CV carb the slide does not start to move until about 1/4 throttle. That corresponds with where I am having the trouble.

What do you think of the suggestion of (on a clear stretch of road), getting up to cruising speed, then opening the enricher partially? It makes sense. If I am lean at that throttle setting it should smooth out.

If I went with a yost, what needle would I want? I am not sure what my stock needle is. That should be stamped on it, right?
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Sparky
Posted on Monday, April 30, 2007 - 03:38 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

You're welcome.

Re The guy at the Harley dealer said to move in small increments:
I would start with 0.020" washers and add more if a trial indicates it's still lacking.

Re opening the enricher partially at cruise:
Maybe that would work as a test but not as a solution. I think the enrichener is mostly effective at idle and may not overlap the 1/4 throttle range. Also its operation is progressive, so, guessing here, a little enrichener might work as would a half-way setting but full-on might flood it.

Re Yost setup:
I think their kit comes with 2 needles, one for mileage and one for performance. Each needle has 5 or 6 slots. You start with a default setting and experiment to find the best position.

Re stock needle:
Mine was marked NOKK and it was different than what was in my 96 S1 which I replaced with a Yost. I may be wrong, but it shouldn't matter too much what your needle is as long as it responds to raising with washers for the 1/4 range and doesn't go rich at the upper RPM range.
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Djkaplan
Posted on Tuesday, May 01, 2007 - 02:24 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Does it happen with slow throttle movement, or quick movement, or both? If the accelerator pump isn't working right, it'll cause a bog or flat spot when the throttle is rolled on.

What are your baseline specs now? I did 2 3/4 turns on the idle air screw with .041" shim stack on my stock needle (2000 M2) and a 45 pilot (slow) jet. The bike runs great with just a "Keihin cough" now and then.
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Gunslinger
Posted on Wednesday, May 02, 2007 - 01:05 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

A little background here. I just got the cam position sensor replaced and that took care of the misfire. It had been worked on by a local, non-afiliated mechanic who thought the misfire was due to it being too rich and fouling the plugs (even though they looked fine) and had leaned out the idle mixture as far as it would go without stalling. When I got it back with the new cam position sensor it was idling rough, and running too fast with the enricher out. I gave it 1/6 of a turn out (it was right at one turn) and the idle settled down. It still had a soft spot at about 1/4 throttle. I asked about shimming the needle (Thanks for the info Sparky and DJ) and was going to get something to use for shims, when I got the idea of marking 1/4 throttle with tape so I could tell exactly where I was when riding. I was getting some surging when crusing at 75 mph, but looking at the tape marks, I was well short of 1/4 throttle. That said, and someone correct me if I am wrong, the needle was not yet into play. I took the idle out another 1/6 turn. Perfect. It is running like a new bike now. I am still only about 1 1/2 turns out on the idle. Just for future reference, I was told that anything more than 3 turns it is time to go to a larger pilot jet. I have a 45 in there right now. What is the next size up?

(Message edited by gunslinger on May 02, 2007)
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Gunslinger
Posted on Thursday, May 03, 2007 - 01:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Well, I noticed a drip on the bottom of the carb. What I have heard referred to as a Class II leak. Turns out the diaphram in the accelerator pump was in the process of disintegrating. Swapped it out, but have not had a chance to road-test it.
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