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Idle drop tuning

Old 09-16-2011, 08:35 AM
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Idle drop tuning

Did a ride the other day..... Started out at pretty much sea level and ended up on a nice twisty that took me to a lake around 5500ft. While heading up I noticed the bike was running pretty smooth...
Looks like im running a little on the rich side. The manual states in the idle drop procedure to hook up an aftermarket tach. Just wondering where people are splicing in to get the signal?
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Old 09-16-2011, 09:10 AM
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If it runs better at high altitude and not as well at sea level than you are lean, not rich. (less air at altitude, so the mixture gets enriched by that)
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Old 09-16-2011, 09:10 AM
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I use a Mk 1 ear....... in other words I listen for the RPM drop.
It just the way I have always done it.....
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Old 09-16-2011, 12:26 PM
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A inductive tachometer works fine. Just wrap the tach wire around the spark plug wire. This works great for idle drop.
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Old 02-06-2012, 09:49 AM
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Thats a good idea. Never would have thought of that.
Im going to dive back into the hawk and see if I can get it to run better, not that its running bad right now but I want to see if there is room for improvement. Plus its bugging me that I dont know this carb that well.

I have to say that I have alot of respect for the people here that have spent numerous times pulling there carbs off to tune and figure out how to get the SH to run at its best. The sharing of their knowledge has helped me out a ton. I dont think I can remove these carbs as many times as they have. There is just so much stuff to remove that there is no quick way about it.

Ive been reading old posts about tuning and jetting and I guess Im having a hard time trying to grasp how to feel or know when your running lean vs rich on each circuit without a dyno. I guess I need to experiment. Time consuming....

Right now I am running 48 pilots, 175 front/ 180 rear mains. Stock needles shimmed .040, 2 1/2 turns out on the mixture screws. Like I said before, when i hit higher altitudes the bike seem to run better. I think I was up at close to 6k alt. vs 600ft where I live. Also my tailpipes are sooty too. The last time I pulled the new plugs, they didnt look rich. It actually looked on the lean side with some white deposits on it. Im going to pull the plugs today and check again since its been a couple thousand miles now.
I tend to run my bike around 3k to 7k range. The bike starts instantly with a pull of the choke. After a minute no choke. Idles fine. Pulls ok throughout range with maybe a little dragging at top end....like close to redline area.
Lately sometimes if I am in town stop and go alot, the SH will die on me at a light. Lastly, I have yet to do a power wheelie. I feel like I am getting on the throttle hard too. I only mention this cause maybe I need to do a compression test. My gearing is +1 on the rear sprocket, and I would think as compared to others here that it should be pulling the wheel off. All it does is feel lighter when i am going thru the gears. Maybe its just my inexperience too.

Last edited by jeephawk; 02-06-2012 at 10:26 AM.
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Old 02-06-2012, 12:02 PM
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My first question would be about the main jet sizes and why the change from 175\178 to 175\180 ?

Also did you shim both needle .040" equally? Also did you add .040" to the washer that was already in place or is that the total shim stack size?

With that info I can tell you what I would do for a base line.
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Old 02-06-2012, 01:03 PM
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Previous owner had installed 50 pilots with 195 mains and installed a bunch of washers on the stock needles. Something like 4f and 5rear or 3f and4 rears.
No tps and pair blocked but no flipped over. And some emission lines werent capped some were. Fixed all that and set tps to 500.
I searched locally and all I could find was a 175 front and a 180 rear mains so I went with that. Also installed 48 pilots.
As far as the washers go I went with your instructions and ran 2 washers front and 3 rear. 2 1/2 on mixtures. Ill try to take some pics of the plugs when I get them here soon.
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Old 02-07-2012, 12:37 PM
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here is a pic of the front plug. Surprised my camera picked up the detail on it.
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Old 02-07-2012, 12:42 PM
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nuther. Plugs have about 6k on them.
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Old 02-07-2012, 02:35 PM
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In my opinion that plug looks way rich, did you do a clean plug chop? If that plug came out of a 2 stroke I'd say fine at least you're not going to seize but too rich for a modern 4 stroke. Again IMHO.
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Old 02-07-2012, 05:26 PM
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Did you plug one of the slide holes on the front carb? If not, you should try it as in stock form the front cyl goes rich in the mids making it hard to read the plug.

What I would do, is first do the front slide mod,if you haven't, and then take one shim off the rear needle, The larger jet should actually with a 178 for things to be right and then your shim stacks would be right but until then the rear is going to run a bit rich so no need to open the slide early.
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Old 02-07-2012, 07:22 PM
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Yeah I plugged the slide hole. Basically I followed your setup with exception to the 178 jet cause all I could find locally was a 180. Ill order a 178 and go from there. Ill get some new plugs while I am at it so I can get a good reading.
Im thinking maybe turn my mixture screws in a half turn and see how it runs?

Its running pretty good right now. It starts easily. Warms up quickly. Idles fine, and pulls the same all the way up.

I had the chance to ride another vtr and it ran a little stronger. It felt like his had a better top end maybe. Mine was smoother but his had more pep to it, if that makes any sense. He didnt know what was done to his bike other than full Jardine kit.
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Old 02-12-2012, 06:17 PM
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well I took the carbs off and cleaned them up. Double checked all is clean and went ahead and turned the mixture screws in a 1/2 turn. Runs better as far as power goes but it pops on decel alot now.
Still waiting on the 178 jet for the rear.
I ran about 30 miles and Ill check the plugs tomorrow.
I really need a good tool to get at the mixture screws. I dont know how anyone can adjust these on the bike.
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Old 02-12-2012, 06:29 PM
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Slot them and get a motion pro carb tool
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Old 02-12-2012, 07:18 PM
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IMO, if that plug was removed after a track day I'd say the mains were a bit too large. But it sounds to me like the bike is mainly street. That said, most of your riding is done with the carbs running on the needle, not the main (unless you're psychotic ). My "professional" opinion on this one is that you should lower your needles a notch, clean the plugs, and check again after a good ride.
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Old 02-13-2012, 03:55 PM
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Update.... So I bought a Motion Pro mixture tool and did some tweaking. Decel pop has been reduced after I synched the carbs. Did a seat in pants dyno and its running pretty good.
Engine sounds differnent at idle though. Not sure what thats about. Has a throatier sound to it.
Still waiting for the 178 jet to come in. Ill ride till it comes in with some new plugs in it and see how its burning.

Last edited by jeephawk; 02-15-2012 at 09:25 AM.
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