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Some fmf pipes like fatties take a bigger pilot like a 30 or 32.5. your describing in some ways a pilot jet problem the problem you describe sounds carb related . If you have access to or can borrow a cdi try changing that what’s the deal on the engine? Is it ported, what size domes are in the bike? leak down test for sure, go to Home Depot or buy one from STB. This needs to be done. is your cross over tube attached well to your carbs? is there light showing at the reed pedals?

Buy JL Engineering stator or have him convert your stock stator to DC. His set up is slick your carbs are to big and use pwk’s your suspension is a good choice why would you want to build a stocker 4 mil with your pistons at that bore? That’s just dumb. You’d be way ahead doing a 392. pro mods are great. i would never do a lockup unless I needed it. you would be way ahead buying built banshee. You’d pay half price compared to building one. Even shipping across country would be feasible. going with a 421 is going to be hard on gas, you would be better off building a smaller motor if you want to ride 8-10 hours

Buy JL Engineering stator or have home concert your stock stator to DC. His set up is slick your carbs are to big and use pwk’s your suspension is a good choice why would you want to build a stocker 4 mil with your pistons at that bore? That’s just dumb. You’d be way ahead doing a 392. pro mods are great. i would never do a lockup unless I needed it you would be way ahead buying built banshee. You’d pay half price compared to building one. Even shipping across country would be feasible.

Defined talk to driveline, actually I would send in the engine. There are tons of stuff in your bottom end that should be looked at. HD clutch and pancake bearing is a must. send it in for the work. Your going to fly!

And yes factory ports. No porting done to those cylinders

Boyesen ports (boost ports) is drilling an additional hole next to each side of the intake. Disregard what I said earlier, it’s mostly for drag racing and squeezing out extra horse power. You don’t need them for what your doing. those are stock reeds. Get yourself a set of vf4 reeds for the most performance. The guys at driveline will set you up

I’m sure Bill had said on here he was seeing big results with the Boyenssen ports added. Sent from my iPhone using Tapatalk

That will be a sleeper

I think FAST is carrying fox floats right now for a good price. theyre great shocks! im curious if you are going to go with a high port cylinder or low port. The low port will be a good all around. ask Lane about boost ports. I know they’ve been experimenting and seeing great results with increased hp

Did you hear back from any shops?

A 392 is a 68mm bore on a stock crank a 421 is a 68mm bore on a 4 mil (stroker) crank a stroker crank on stock cylinders are called 4 mil stroker (or stocker) and the cc will change on the bore the 392 and 421 are most commonly made by CP Industries (cubs and servals) and by Driveline (assassins). They are nicasil coated

It’s a pipe made by SLP. You can check my graph in the dyno section.

Here’s a couple of set ups. Some with your pipes. It will give you a rough idea of what to expect. 1500-2 should for sure get you there. As you can see a stock stroke stock cylinder can really rip when ported. the stock stroke driveline set up with t5s is 67hp without porting on the low port cylinder. moots of options. Talk to a builder

1500-2 theres a member here (Builder) where owns west coast atv parts. You may get this set up used for a lot cheaper. He has quality stuff. if I had 1500-2 I would weld stock crank, have the cylinders ported and spend the rest on +2+1 a arms and fox floats. You’ll be fast and stable

And an impeller upgrade.

I’ve been down that road..... send in the engine for the work to a sponsor. Port cylinders, case port the cases to match cylinders, cool head with cut domes for the stroker crank. internally, you’ll need a heavy duty clutch. It’s best to put on a billet clutch basket like a mattoon or chariot....but not entirely necessary. You won’t need a lockout. have the roller detent mod and shift star mod completed which aids in shifting. If you have some extra money a pro mod transmission (you can read up on this) is worth the extra. new seals and of course the 4 mil crank. Most people use HotRods cranks, they’re good. you can keep the stock carbs BUT if you see a set of Keihin PWK 28s that would be my choice. I ran 72hp on stock carbs with no problem. you can keep you T5s but if you want huge bottom end and tq buy SLP, if you want a good all around pipe I like Pro Circuit, if you want top end drag style get some Shearers or CPI. if you can’t wait there’s a brand new 421 driveline set up in the for sale section.

Send a PM to BansheeHP on here. He is a sponsor (Driveline) best bang for the buck, 4 mil stock cylinder. They haul ass. HJR, FAST, and Driveline all have been quick on responses and service.

Try swapping out the cdi new reeds may require more jetting

If your on a budget go to your local machine shop. Fee hundred will just be bore and pistons. You’ll need head work and gaskets. save

Did you lose a ring and that’s what caused the damage? The pics of your pistons suck. you have lots of bores left. Great time to add some serious power

That’s a pretty standard choice. Make sure you measure your squish with a piece of solder. YouTube SouthTexasBanshee and he will show you how to measure it.

Sky’s the limit. How much do you want to spend?

I think your mains too big. Buy a 142 and report back

Good luck and have fun. Tons of options on these engines

https://en.m.wikipedia.org/wiki/Squish_(piston_engine) Hers the thing, your going to need to tear it down if you want to make it run real good. Adding compression won’t amount to much. Options for big power increase in order of expense: port your stock cylinders, new bore and pistons 55+ hp driveline 392cc stop end with stealth head 65+ hp ( dyno of this with t5 in the sponsor section of you dig) 4 mil stock cylinder stroker set up. 70+hp