Toybreaker

2nd the 27.5 pilot, buy 270-330 mains and do a bunch of plug chops to determine best jetting. I ran 280 mains, 27.5 pilots and the needle 2 grooves from the top (toomey needle) in the winter at Glamis, Every bike is different and unless you plug chop it or use a chassis dyno with a sniffer in both pipes you will be guessing.

Cold seize is when the piston and or rings have too much friction with the cylinder wall and have an intimate dance with one another..... scoring. Happens when the engine is cold, and usually happens with someone running cheap premix at 50:1..... too many rabbits in the hat to go into what premix is good at what mix ratio.... Run quality oil at appropriate mix ratio and let the engine warm up before beating on it.

warmer air means thinner air. if anything it would need a leaner pilot. Pilot jet is off idle, your idle issue is not jets. Pull the carbs and clean them, Take em all the way apart and clean every orifice, then blow them all out with compressed air. Clean all the jets while you have them out (torch tip cleaners are my go to, cheap at any welding supply store.)

I started porting banshee cylinders by copying a set of my friends. Took measurements from the top and bottom of the cylinder and mapped it all out. Then after I did that set actually read up on it and learned what I was actually doing.... port timing, not increasing volume. Made my own degree wheel at work with a rotary engraver and .090” thick plastic, and did my next set with the degree wheel. That set was better than the first, Sent from my iPad using Tapatalk

https://www.ottofrei.com/Foredom-A-69224-Right-Angle-Attachment-Use-with-Foredom-Angle-Grinder-H.30-Foredom-Handpiece I have an actual Foredom made 90* attachment, Like i said I have had mine for over 25 years, and they were given to me by an old timer that retired..... His kids could give two shits about machining tools....

i use a foredom, had it for 25 years so my part numbers won't help you.... and a mix of burrs, cartridge rolls and extensions to make them reach where I need em to. I port cylinder heads as well... Its cathartic until all the aluminum and fine cast iron starts to make me itchy....

you do any wet riding without an airbox you are going to suck up water, and if it runs after that It will run like hammered dogshit. Keep the lid get the filtered pop in "holes", go with the aluminum cone filter adaptor for the stock airbox.

What Ginger said.....

You're a LEO, work the angle "its good training to get the crew knowledge on how to do it poperly" plus you get to ride you Shee on the clock.

FMF's are good for the woods, decent power low to mid. SLP's are better. There is a thread in the board somewhere that does a dyno test of almost ALL the pipes people talk about on here.

1968 A5 still in the browning box, Local gunsmith/Dealer valued it at $1400 will edit post with all info and pictures. Gun is an 8 on the 10 scale. I have 3 shotguns and I only need 2..... (Wife and I shoot trap) Looking for complete stock engine, or Crank/cylinders/pistons ready to go. (stock cylinders 65 or under bore,)

Those are cool....

Ok, Which Keihin carbs? What jets are currently in those carbs? What other mods (bolt on stuff, pipes, cool head, etc) are done?

If you aren't too worried, move the clip to the last spot closest to the needle point. Otherwise take em off and drop a size on the main, and take the next size down from that just in case.

Last name? I am in Maine, Know a few people around here who ride banshee's.... Fucked up here though, anything but factory exhaust gets you a ticket.

30 pilot, 320 main to start, put the clip on the needle closest to the tip. should be super rich with that, Buy 27.5 pilot, 270-340 mains, and a toomey needle (or equivalent) Oh and 2 or 3 set of bowl gaskets and the allen cap screw bowl fastener sets (you will thank me later) Oh and buy 20-30 plugs so you can do plug chops after every tuning change to verify where it is at. My 98 had a dune port with 21cc domed cool head, vf2 reeds, fmf pipes, dyna ignition, stock timing and stock tors deleted carbs. In glamis it liked 27.5 pilots and 280 mains. Wifes 96 is stock port, cool head with 21 cc domes, boysen reeds, toomey piped, stock carbs and likes 27.5 pilot and 270 mains.... I spent so much money on plugs I would have though I had stock in NGK... each bike is different.

Nothing wrong with the J-arms. Fix what needs fixing on your bike. The swing arm is steel so it can be repaired (welded. Just make sure whoever welds it knows what the fuck they are doing.... If they do not drill both ends of the crack before they weld, hit them with a BFH in the nuts.) or you can replace it with a round house swinger... lots of options. And stock suspension banshees SUCK in the dunes. at the least go with +2+1 arms and dual rate shocks up front and get you rear shock reworked for your weight and going over the whoops. Night and day difference.

https://www.vitosperformance.com/product/vitos-head-stud-kit-yamaha-banshee-cylinder-10-lon-pdhsk?gfid=p785-c1348 yes same design for domes.... GOOGLE is your FRIEND!

What he said.... to optimize it read the jetting sticky. and prepare to do a BUNCH of testing and plug chops. 27.5 pilots and 300 main to start. needle clip in the middle.

Or see if there is a thread repair kit for that size. Doing a thread repair is easy if you have access to a drill press with a decent vise. (even the harbor freight benchtop model works for this...

Depends on end use. Stock head? Stock Carbs? Lots of info left out here..... Play port? Full drag port? Go with a site sponsor, Be TOTALLY HONEST with what you want. If you aren't sure don't start yet! If all you do is fuck around, a play port would be best. Need a cool head and possibly a little larger than stock set of carbs.

True, but since the tank is over the carbs, gravity will do a fine job keeping them fed.

With CPI's Bigger carbs would help. 36-40mm Now is the season to look at Sled parts....sled carbs are cheap. I was tempted to buy a set of 40mm PWK's? for $100 just to flip them... you leaving in first or second gear?

you going out there to have fun or be competitive? Competitive, $3500 is not going to cut it. Keep your eyes open for a non-running or basket case bike. Use the engine as the base for your build, I'd go with the Driveline 421 assassin or 392 assassin builds, 19cc domes ported by driveline for your specs, CPI or Shearer pipes, 35-38mm carbs, Dual pingle for the tank Straight cut higher (Top speed) ratio gears for the primary drive, billet water pump impeller, Bearing modded shift drum, shift star, clutch torrington bearing, ceramic clutch ball and barnett steel with R1 fibres. If you assemble it yourself it should be close to $3500, depending on how much the cases and trans cost you. Keep a watch on the FB marketplace and craigslist too.... sometimes you can get lucky.

Do a leak down test. There are more than a couple how to's to build your own on here. Honestly throwing parts at it doesn't do anything except drain your wallet. Keep It Simple Stupid Pick 1 thing, work through that 1 thing. document changes and results. Not fixed? Move on to another thing. Start with the leakdown, that will tell you the health of the rings and reeds, as well as tell you if you have any air leaks.... Air leaks will kill the bike quicker than shit. Second go with fuel delivery. Did you COMPLETELY disassemble the carbs, Tank/Dip/ultrasonic clean, rinse with brake cleaner then blow out EVERY orifice with compressed air? Put the Slides in correctly on the correct side carb? Fuel is good.... then move on to the stator, Again many DIY hold your hand tutorials on how to / what to check. Ohm checks, air gap, where the best place for ground is etc. Stator checks out, ok Check the coil. Ohms, grounds, Wires, boots.... Next would be a short in the harness or one of the switches.... Have fun trouble shooting if this is the issue. Remember when you change more than 1 thing at a time you can't point your finger at a single change and know what you fixed.