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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> What's the worst jetting you've ever seen? /cgi-bin/YaBB.pl?num=1433641289 Message started by koehlerrk on 06/06/15 at 18:41:29 |
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Title: What's the worst jetting you've ever seen? Post by koehlerrk on 06/06/15 at 18:41:29 Question folks... what's the worst carb jetting setup you've ever seen on one of our bikes? Asking because I just spent the last 90 minutes pulling my carb off, re-jetting it, and putting it back together. First off, bike is nearly stock, has a 6" uni-pod filter, Dyna muffler, and a Raptor petcock. Been running it for the last two weeks and it's okay, bu it seems to lean out above 3800 rpm or so. Figured she's running too much air now, and needed a rejet. Thought I had a stock carb, still had the brass plug in place when I started. A half turn out screw adjustment helped the backfire, but she still didn't run like she should. First mistake, assuming no one had fugged with this carb. Opened it up and saw the main jet had obviously been wrenched on. Pulled it, it was a #150... no big deal. Pulled the pilot jet... WTH? A 35? Am I reading this right? Went and got my big magnifying glass.... yup, still a 35 jet. turned the idle screw in and it had been out almost 4.5 turns. But, the worst is yet to come. I pull the top off the carb, and pull the needle. No white spacer. In it's place there's a piece of black rubber hose that's about 5/32" long. No wonder she's leaning out! Put everything back together with Lancer's jet kit, used the reference here for the K&N filter and HD muffler combo... settled on a 52.5 pilot, 152.5 main, two washers on the needle, and 2.5 turns on the screw. Comparing the holes in the pilot jets, yeah, that 35 is only 2/3 the size of the 52.5... dang that thing is tiny! Put her all back together and fired her up. She runs better, sounds better, can't wait to see how she drives now. My guess is a whole lot smoother. So... what's the worst carb setup you've ever seen? |
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Title: Re: What's the worst jetting you've ever seen? Post by Serowbot on 06/06/15 at 18:50:50 Yer' pilot is taking the cake on that question... Maybe he was tryin' for a Mpg record... :-/... ...or maybe he was trying to correct for a bad petcock with jetting... :-/... Best luck ;)... |
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Title: Re: What's the worst jetting you've ever seen? Post by Dave on 06/06/15 at 18:55:05 The idle fuel mixture screw should not be adjusted by turning it to 2.5 turns......it should be adjusted by running the engine and adjusting the screw until the engine runs the smoothest. You can start at 2.5 turns - but then you need to adjust it. Turn the engine idle speed down a little bit less than 1,000 rpm, then turn the screw in and out until you find the smoothest idle. If you have to turn the screw out more than 2.5 turns the pilot jet is too small. If you have to turn the screw in more than 1 turn from seated...the pilot jet is too big. The ideal setting is 1.5 turns......there is no reason to turn the screw out more than 3 turns the adjusting screw no longer has any effect....as the tapered needle on the screw is no longer restricting the flow through the seat. https://www.youtube.com/watch?v=zm5mB3R8Ucw Once you have the idle mixture screw set properly you can then turn the idle speed back up. You don't want the idle speed up high when you adjust the screw - as the slide and needle jet may be flowing fuel and will make adjustment of the idle fuel mix impossible. |
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Title: Re: What's the worst jetting you've ever seen? Post by justin_o_guy2 on 06/06/15 at 19:03:37 Dave? If you have to turn the screw in more than 1 turn from seated...the pilot jet is too big. I'm confused. |
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Title: Re: What's the worst jetting you've ever seen? Post by Serowbot on 06/06/15 at 19:09:36 Yup,.. dat's right... Less than 1 turn open,.. you are pretty much shutting off the idle mix to make up for too much pilot jet... ...or you may have a sticky throttle butterfly that won't close all the way down... |
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Title: Re: What's the worst jetting you've ever seen? Post by koehlerrk on 06/06/15 at 19:10:37 Dave, yes, the 2.5 turns was just the note on the chart... it's a starting point, nothing more. I'm planning on firing it up tomorrow morning, warming her up and adjusting the screw to the correct idle point per those instructions. After that, going riding for a bit to see how she's working. Biggest change is that she's a whole lot quieter already... will keep you all posted on my progress. Rick |
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Title: Re: What's the worst jetting you've ever seen? Post by justin_o_guy2 on 06/06/15 at 19:18:36 And there I was, confused, trying to understand how to turn a screw In from seated. |
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Title: Re: What's the worst jetting you've ever seen? Post by Dave on 06/07/15 at 04:44:50 37282E2934330232023A28246F5D0 wrote:
I might have worded that poorly. I meant to say that if the ideal mixture occurs with the screw turned out at anything less than a full turn....the pilot jet is too big. Mikuni recommends using a pilot jet that results in the mixture screw being out close to 1.5 turns. I believe for our low performance engine you can live with anything between 1-2.5 turns....anything beyond that you should try a different pilot jet. |
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Title: Re: What's the worst jetting you've ever seen? Post by koehlerrk on 06/07/15 at 05:38:44 Well, just got back from a half-hour test ride... man what a difference! She winds up a whole lot higher than before, just pulls and pulls and pulls... had her up to 75 in third gear, uphill to boot! She runs, oh my goodness does she run! Power comes on steady, just a nice smooth push right up to the top of the rev range. But... Down low is still an issue. Too rich. She bogs and stumbles off the line, get her moving and all becomes well. Still doing that even with the screw turned in to 3/4 of a turn. Going to let her cool off and I'll swap out that 52.5 pilot for the 50. That one issue aside, she runs like a whole 'nother machine now! Thank you all for the help. |
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Title: Re: What's the worst jetting you've ever seen? Post by justin_o_guy2 on 06/07/15 at 19:33:47 112A2730212D36302B232E31420 wrote:
I might have worded that poorly. I meant to say that if the ideal mixture occurs with the screw turned out at anything less than a full turn....the pilot jet is too big. Mikuni recommends using a pilot jet that results in the mixture screw being out close to 1.5 turns. I believe for our low performance engine you can live with anything between 1-2.5 turns....anything beyond that you should try a different pilot jet. [/quote] Now I get it.. I wonder if anyone will notice that I notice things. |
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Title: Re: What's the worst jetting you've ever seen? Post by koehlerrk on 06/08/15 at 02:58:55 Justin, saw it, but my brain corrected it on the fly... yeah, it's kinda hard to "screw in" a screw that's been seated. Swapped out the pilot jet last night, put the #50 in. Idle seems to be better, will know more when I ride her to work this morning. Let it idle last night to warm up, adjusted the screw, she seemed real happy at 1-1/4 turns. Again, time will tell. |
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Title: Re: What's the worst jetting you've ever seen? Post by justin_o_guy2 on 06/08/15 at 07:42:04 OH, FWIW, that is certainly the worst case of Look what i found in my carb I'm aware of,. Wow, rubber tubing, fine tuning goin on there. |
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