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View Full Version : 1992 vlx tuning help!



Harley94
05-18-2016, 3:39 PM
Building this vlx, I CANNOT get any power out of over 50% throttle and very poor throttle response.If I let it run very slowly up I can get to maybe 60% but no more. Running straight pipes, no air box. I've had the carbs apart 4 times. New needle and seats, seat crush gaskets, rejetted to 120 mains and 42 pilots from factory 115 and 40, all emissions equipment deleted, all ports plugged except bowl and slide vents. Almost no improvement with rejet. Carbs have been completely disassembled and ran through ultrasonic cleaner. Any ideas what to try? I'm losing my mind

LeDom
05-18-2016, 4:18 PM
Sounds like lean, do you have any bigger main jet? Maybe a 130 or 132.5 will do
Go on a ride and while at WOT, turn the bike off and check the plugs, if they are gray or while then you're too lean

Westboundbiker
05-18-2016, 5:42 PM
Some useful charts on throttle position vs working carb part:
http://www.caferacer.net/forum/attachments/technical/8769d1408111516-cb500-four-4-1-exhaust-dilema-jet-chart.jpg
http://kawtriple.com/mraxl/carb/jettingeffects.jpg
http://www.jackbhart.com/firefly/bing2.jpg
http://www.gadgetjq.com/keihin_tuningparts.jpg

Biskyxj
05-18-2016, 7:32 PM
I went from an air box to just a pod filter. And made my own baffles that have some healthy flow.

Stock jetting was a 45 pilot and 135 main.

I am running a 52 pilot and 150 main now.

My bike was a California model so it was exceptionally lean from the factory. I never realized how lean until all the changing of my jets.

I know may mot be a whole lot of help but just some food for thought. Get yourself a large range of jets and keep tuning until you get where you want it.

Harley94
05-18-2016, 8:59 PM
I also have a California model. I'll try going up some more. I have a set of 150s and a set of 48s on hand I could try, other than that I'd have to go buy a set to go up. Thoughts? Thinking I might throw these in and if it's too rich at least I'll have a ballpark idea. Right now at WOT the bike barely even stays running

Biskyxj
05-18-2016, 9:16 PM
Yeah let me know what happens. And put some kind of baffle or a lollipop in those pipes man. Need a little something in there to break up that resonating wave coming out the back.

Harley94
05-18-2016, 9:20 PM
Those charts were awesome westbound. Also I tried to get a baffle in the pipes, I couldn't get anything rigged that wouldn't blow apart. Any ideas? The only thing that stayed close was a tightly rolled ball of foil that filled about 65% of the pipe, held in with a sheet metal screw from the bottom

Biskyxj
05-18-2016, 9:52 PM
I will take one of my baffles out this week and take a pic. But basically its one of these http://www.jpcycles.com/product/4410020?utm_source=none&utm_term=%5B74947137970%3Aproduct_type_l1%3D%3Dveh icles%2520%26%2520parts%26%2520product_type_l2%3D% 3Dland%2520vehicles%26%2520product_type_l3%3D%3Dmo t&cid=Google+SEARCH+NON-BRAND+PLA+-+Shopping+Campaign&adpos=1o1&creative=42040109650&device=m&matchtype=&network=g&gclid=CjwKEAjwpfC5BRCT1sKW2qzwqE0SJABkKFKRXcydVVaw Am-cnyOvR_KZlkGSRKKnlzzCjS4-9N58RhoCWq7w_wcB

Jasonisdico
05-18-2016, 11:59 PM
Make a lollipop. Basically weld a washer that has the same OD as your pipe's ID to a bolt. Drill a hole toward the end of your pipe and slide the lollipop in and through. Bolt it down with a nut. Start with it blocking almost he whole pipe for maximum back pressure and work towards less till you get s healthy compromise.


Also, I think one vent is supposed to be left open on your carb? Although I may be wrong(might just be on my intruders). You could also try spraying starting fluid around your intake and vents while the bike is running. Careful not to spray your pod filter. In change in RPM while spraying means you have a leak somewhere.

Harley94
05-19-2016, 1:22 AM
Cool, I'll try the lollipop tomorrow. Right now I have no pod filters, just open carbs and true straight pipes. I said fuck it and threw the 150 mains in with 42 pilots. Also about .5mm of shim on each needle. I'm sure it'll be rich but at least I'll have a ball park idea of where I need to be. Also the proper ports are open(slide and float vents), and no vacuum leaks

Biskyxj
05-19-2016, 8:47 PM
So whats the status?

CreeperJake
05-20-2016, 11:01 AM
Are you sure your carbs are synced up?

Harley94
05-22-2016, 2:44 PM
I got it running more or less good. 42 pilot, 150 main. Still no air box or lollipop, it's got a little hiccup on the off idle hit. I richened up the mixture screw, added about .5mm of shim on the needles, I'm gonna go up to 44 pilots later today and I think that should take care of it

Biskyxj
05-22-2016, 3:00 PM
Is it a CV carb or slide carb

Harley94
05-28-2016, 10:25 AM
It's a cv carb. I went to 45 pilots, got on it to test ride it, and it's having an issue with intermittent spark loss on both cylinders now. Shut off on me a few times on the last ride, now I can't keep it running long enough to get down my street. Kickstand and neutral switch are removed and grounded. Figure it has to be the cdi or the ignition is grounding out somewhere. Any ideas how to test either?

Biskyxj
05-28-2016, 9:49 PM
First suggestion is get a service manual. Test the coils. The primary and seconday side have a specific ohm reading they should fall into.

Theres my shot in the dark. And double check for bad connections on your aafety switch eliminations.

Harley94
05-29-2016, 5:28 PM
I'd be skeptical of the coils since both cylinders die at the same time and intermittently. My feeling would be that is has to be something controlling the spark. Also from my understanding the pickup coil for each cylinder operates independently of the other. I checked all my grounds of safety switches, all seem good. Also the neutral light always stays lit, so if the bike believes it's in neutral it shouldn't kill itself even if the kickstand switch loses ground. Battery is new and charged, so I figure it's gotta be the firebox or the ignition is grounding out