Okay so I'll pick up a hone after work today and I'm ordering a 81mm. I can't seem to get the pictures to load up but heading your advice. It doesn't seem to bad. The guy that originally built this thing before the people I got it from that burnt it up, supposedly was still trying to tune this thing in. It's got an aftermarket pipe and a egt gauge so I'm guessing he was still figuring it out before he died so fingers crossed when I do the leak down test, it's all good there and it was because these of roaders I got it from ran to lean of fuel or didn't pick up where he left off on getting everything dialed in. I think it's only been ridden by them for 15 min the last 15 years lol. So I'll order up the piston today and grab a hone and nicely touch it up. The pictures aren't wanting to load up for some reason at work here but I have them. I'll get them up as soon as possible

I'd pull the top end off to check the condition before ordering a hone or piston, you may find it needs to be bored.

Yeah I second this.
Not sure what the score is because no pictures but he'll have to tear this Engine apart anyways to clean out all the blown piston aluminum which will be all over the bottom end.
He still has to inspect the big end rod bearing and crank bearings as well.
CO

From what I am gleaning from the info provided, it's a fuel issue.
Might be a bad pump, corroeded pick up tubes in the tank, jetting way off or poo fuel.
CO

If you do end up buyin a hone. Do not buy a ball home. They bounce around when going over the ports. You want a flat stone hone.

Take your time do not get in a hurry.

Do you do a leak down test? Fuel pump flow test?

I didn't get to do any leak down cause it was already disassembled, that's what I'm thinking as well CO. The cylinder didn't look that bad as I was telling CO on another thread, I can't catch my nail on it or anything. I'm guessing it was never fully times and when these folks got it from him they just ran it like it was good to go and bam. I am finally able to load up the pictures now that I'm home.

I'm not liking all that rust at the very top inside that cylinder.
Looks like the piston was at TDC (Top Dead Center) and it had a coolant leak into the cylinder.
It sat there and rusted up for a few years.
A pic of the bottom end and piston would be good as well.

Week need more Pilot guys to chime in here.
CO

So when I picked it up the had the head already off so it's been sitting a car port for a couple years and just the moisture in the air at top dead center left some surface rust but when I was messing it, it wasn't too bad it seemed like.

Below are some pdf's that are not related to the current problem you got but are none the less important for future reference.
CO

You can get a free pdf Pilot manual here: https://drive.google.com/file/d/0B851Fd ... kU1QQ/view
CO

EDIT: Serial numbers:
FL400R A (89) FL MODELS, JPN, VIN# JH3TE160-KK000044 TO JH3TE160-KK004102
FL400R A (90) FL MODELS, JPN, VIN# JH3TE160-LK100001
no ending vin for 1990 fl400s
CO

Sweet! I appreciate it. We were lucky to have a service manual with the first one we got now to have a parts finder is even better to cross reference and all that. Was planning on messing with the pilot some more tonight but I tried to replace u joints really wish on my Dodge and they are the plastic sealed in type instead of clip and I ended up with the wrong u joints so that's gotta wait till tomorrow, went to the store to grab some stuff for dinner too the good ole cj and rear caliper froze up on me. What a night lol.

The plastic seal type are factory. They do it to save money.
They're replaced with a clip type ----- No ??
You remove them with a torch. Cut out cross head, heat up cap with torch, push out cap with clamp or hammer and punch. CAUTION molten liquid plastic will squirt out of the fill hole. That will hurt so find fill hole and stay clear. Wear safety glasses.

Your life seems like mine lately.
Gota dig up a water line at mom's place tomorrow. Fun fun fun.
CO

Anyone have a parts list for the leak down test? Like what they used and what not to specifically work for the pilot

the Pilot it's self looks pretty clean.
if I were you I would price out what all it is going to take to repair the Engine then look around to see if you can scrounge up enough Rotax conversion stuff, but that's just me

I have a 670 and can tell you it turns that puppy into a big dog, then do a long travel kit and now it's a full blown werewolf

I was looking at the rotax build on one that I almost bought back in April. It needed a bunch of stuff the whole pilot was in boxes and he wanted 3500 for it all and wouldn't budge. The only thing with the rotax I was noticing back then was that farr off-road kinda stopped doing his thing on making the pieces you need custom built. That and the long travel I haven't seen around anymore either. I wish Honda would start building these again. They would make a killing. 2wd buggy would sell in today's market so easily.

Farr is out of the game as well as ATV Motorsports in Phoenix. ATV motorsports (formerly atv racing) made the majority of all the LT setups around. Neil doesn’t do the 500 conversions anymore either. He still sells some parts on his website but call first to see if he actually has it. I picked up a CR500 conversion Engine and was able to source a pipe through him. Chris at CW racing does 500 cylinders for the pilot so I sent it all off to him to have gone through.I will have a ATV motorsports 500 cylinder and piston, rings possibly for sale. Don’t hold your breath on a power bloc clutch though, they have been on order forever.
Bob

More detailed pictures of the piston/rings ?

Remove the head nuts hopefully they come right off, you will notice the tops of the head studs are rounded, hold the cylinder in one hand and hit the top each stud dead straight and centre of the stud what your trying to do is shock the threads so the studs can be removed, get two nuts that will thread on to the studs (they are metric) lock them together as a lock nut you should be able to unscrew the studs and remove from the cylinder.

Plenty of Pilot Engine CSI's on this site you can browse start here viewforum.php?f=25

Is there a reason to take the head studs out? I'm new to two strokes so bare with me, I appreciate your guys help lol. I can grab some pictures. I haven't taken the piston off yet.. Barely had any time to play with it this weekend. I should have a 81 piston here this week. I figured I would still just hone it to clean it up really easy. And go from there.

So here is the pictures of the old piston. I have the new piston as of today so I'm about ready to hone and start the fix. Any input

What does the cylinder look like? Assuming it will/would clean up with a hone I would of measured the cylinder then just in case the New piston may be out of spec. Also be sure to check that ring gap. I doubt all that piston went out the exhaust. Wouldn’t hurt to flush/rinse tear apart that trans. If it craps a bearing it will get real expensive then. It’s sucks to spend money but do it once even if it costs $$$.

You have to do more than just hone the cylinder.
That Engine has to be split because all that piston poo is in the bottom end and in the bearings.
Hole in piston --- poo fuel and it detonated.
CO

Okay so if I split the case am I worried about anything falling apart? Lol. What is to be expected when splitting it?

I have never taken a FL400 Engine apart. I own 3 FL350's.
We need the Pilot guys to chime in here or you can spend a lot of time using the search box and looking up rebuilds.
It should be basic just like the FL350 Engine with a few differences.
Yes things will fall apart because that is the plan LOL.
Seriously, it should be quite basic. Take your time.
CO

Edit: One comment I would like to make is that make sure you put the right length bolt in the right hole. On the FL350 cases some of the bolts are very close in length but if you put it in the wrong hole it will be a few threads to short and therefore not have enough thread engagement. Then when you torque it up you strip the 2 or 3 threads that it was holding onto. Not sure if the Pilot is the same.
CO

I guess if you are a gambling man like me, you can put some diesel fuel in the bottom end and slosh it around and dump. Repeat. Then blow out with air. I have done this on my brothers Engine a couple of times back in the day when we were blowing them up daily (Not lying). It's your machine and your dollar --- you make the call.
CO

2 stroke engines are simple if you have the proper tools, difficult to find the flywheel puller, also be very careful separating the case half's if you decide to do it, don't stick a screww driver between to pry them apart, the case half's are a metal to metal seal and if they are damages it will cause a leak.
listen to CO when it comes to melting pistons he has a lot of experience :) there are several factors that could be causing that, detonation, too lean, this could be jetting or could be an air leak, high compression, bad gas.
show a picture of the cylinder head, may be able to tell if it has been cut causing high compression, better gas will help, run at least the best pump gas you can get and if you think mixing more oil will be better, that is not always the case, more oil means less fuel = leaner AF mix.
bottom end IMO needs to come apart, it has probably not been rebuilt in 30 years, new bearings and seals should be done and think about having the crank rebuilt with a new rod or at least new bearings will be a good idea also, like mentioned there is now bits of aluminum from the piston in the bottom end, bearings do not like that stuff.
maybe contact CW and see what they charge to go through it for you.

Regarding the Rotax kit, without having Farr doing it any longer does make it more of a challenge besides the Engine mount there is a modifies head pipe and chamber and you need the electric starter setup with the pull start removed.

Tools required to split case:
Head stud removal socket (or two nuts)
Flywheel puller
Case splitter
Crank puller (install)

I would bet it has a milled head since I see washer's