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General Category >> Rubber Side Down! >> Idle adjust versus jet needle washer
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Message started by Daemon on 09/16/04 at 22:25:21

Title: Idle adjust versus jet needle washer
Post by Daemon on 09/16/04 at 22:25:21

I've seen lots of partial information on the net about getting rid of backfires by removing the white spacer (or putting in a smaller washer) on the jet needle in the diaphram assembly. I've also read some articles that suggest a full 3 turn ratio on the idle adjust screw eliminates backfires as well. Has anyone tried that in this forum? Its been suggested also that if you intend to re-jet at 155 or higher (for those at 125 & 145's) that if you removed the white spacer you actually degrade your overall performance. On the Heise forums I read that someone had changed their exhaust to a supertrap (diagonal slash pattern type), left their spacer on the jet needle, never re-jetted and had significant hp increase tested with dyno AND eliminated the backfires. I was curious if their idle adjust had been altered as well. I've been planning on putting a thinner spacer in my 02 but will probably play with the idle adjust for a couple of days first unless someone with the voice of experience will give me some suggestions?

Title: Re: Idle adjust versus jet needle washer
Post by gitarzan on 09/17/04 at 15:52:09

This week I rejetted to 157.5 (They were out of 155 jets.)

I was going to replace the white washer with a thinner one, but buggered up a screw and decided to leave it alone for now.

I don't really know how many turns my idle screw is at. I just turned until the max RPMs were achieved and left it there.

My opinion of the results: I think it lost a little at the bottom end, but not much. It seems to have a little less pull and is more likely to lug at low RPM, but really not that much worse. It seems, however, to rev faster and has a little more snort in the mid ranges. When I rev, it seems to get into the redline areas faster and has better response while moving, at the expense of the chugging dept. It also seems to be a speck smoother, but maybe that's my imagination.

I did also add a swig of Sea Foam to the gas tank. You can get it at Advance Auto Parts as well as NAPA.

Whatever, It was nice to get the bike back up and running after a few days downtime.

Title: Re: Idle adjust versus jet needle washer
Post by Greg_650 on 09/18/04 at 03:45:46

I missed out on a bunch of posts lately because of Ivan. Anyone interested in that can visit this page.

http://www.digimaging.net/images/267_IvanAsheville03web.jpg

As for your 157.5 main jet....Do you seem to have a "flat spot" in your throttle response when accelerating through mid-range?

Title: Re: Idle adjust versus jet needle washer
Post by klx650sm2002 on 09/18/04 at 04:59:32

Your main air jet is 0.024" if You went to a 0.022 or 0.020 You could come down a main jet size, keep the top end and restore the midrange.

Clive W :D

Title: Re: Idle adjust versus jet needle washer
Post by klx650sm2002 on 09/18/04 at 05:18:54

Then again perhaps You shouldn't, That is what you would do on a flat slide and probably doesn't apply.

Clive W :D

Title: Re: Idle adjust versus jet needle washer
Post by gitarzan on 09/18/04 at 07:15:22

Greg_650 wrote:

As for your 157.5 main jet....Do you seem to have a "flat spot" in your throttle response when accelerating through mid-range?

Well, it seemed to run "looser". Kind of like the engine was on a muscle relaxer. It revved easier and didn't seem to have the tightness it had before. It kind of reminded just a little of my old beloved 2 stroke where high revs were the name of the game.

Before it seemed almost muscle bound. It had a lot of tug at low RPM but higher revs felt like it was pushing the limits. Now it seems like momentum wants it to keep revving, rather than fighting it.

That was just a short trip around the hood. It rained yesterday and right now the taillight seems to have croaked. I'll have some more in depth opinion later.

BTW it still backfires like a donkey in a beanfield.

Title: Re: Idle adjust versus jet needle washer
Post by Greg_650 on 09/19/04 at 03:03:57

gitarzan wrote:

BTW it still backfires like a donkey in a beanfield.

Pardon my memory, but old timers disease won't let me remember all of your bike setup.

I got the stock spacer part...What exhaust?

I'd try to eliminate the Sea Foam from "the mix" until done tinkering with jets. After all, a "swig" of the stuff isn't a precision unit of measure ::)

Do you see any black smoke when you rev the engine while it's sitting still?