Yes that's it.Pilot has aftermarket large gas tank that takes up the space where stock airbox went.Is the seal that Important? Airbox is mostly to keep filter out of the rain or splashing from puddles

That's a good point & I agree. I overthought it with the pre-filter setup.

And I should clarify on MY pilot that's what airbox is for,that's probably not true in every application.When I got Pilot it was just running uni-filter straight off the carb,I wanted more protection than that

Decided to do pre-filter on side,I won’t be using one in pic,have new one ordered.I Put pipe on,that was the last thing to do before firing her up.I checked compression before first start,about 180.
Started her up and went thru a couple heat cycles,that’s it for today

Well I've about completed the break in process but I'm worried.Took it to atv park Sunday,did one 5 minute ride,let it cool off,then 10 minute ride than cool off,than 15 minute ride.When Pilot is is sitting still and I give it some high revs Engine sounds great,but when I was driving it and got down on it it didnt sound right,don't know if it was piston slap,rings out of groove,or my paranoia It also wasn't running that great,but I'm sure that's a carb problem.Running this chinese keihin pwk 38 air stryker knockoff,it had 170 main jet in it{same as my other carb that was in it before} but I went up to 175 for break in.Going to go down a jet size to 172 for next ride.Was hoping to go Sunday to a friends deer lease that has some long straightaways where I could do some plug chops but it doesnt look like weather is going to cooperate.I'm off tomorrow,I'll change the jetting and I need to check compression again.
Plug looked a little rich but better than being too lean

Well Want to friends deer lease and the rain head messed it up worse than we thought.Tried to do some plug chops but don’t know if the straightaway I had was long enough to do a proper Job and it probably didn’t matter in the end anyway.
Started out with a 170 main jet, did a plug chop,and went down to 168 and did another plug chop.Pilot is not really bogging But it doesn’t have the power it should and it is missing at full throttle.
After 2nd plug chop I want to check the choke to make sure it was operating correctly and the whole Choke assembly pulled out of the carb when I went to pull it up.(Remember this is not the carb that I was running before but Keihin Chinese knock off.)so I screwed that back into the car. Was messing around with it some more and checked the air mixture screw and it was screwed all the way in,So I do not know how that would have affected the plug chops?
So it’s still not running worth a crap, see no difference in those two jets, so I start messing with the air mixture and that doesn’t seem to make any difference either.
So then I go down to a 160 Main jet and that just makes it run worse So I don’t even bother doing a plug chop.
It was time to go,So when I had 170 jet in it would it have made a difference if choke assembly was screwed all the way in And air mixture screw wasn’t screwed all the way in I don’t know.
I am still being very paranoid about the way the Engine sounds.
It sounds fine when I am in neutral and a rev it up When driving it and giving it for throttle it doesn’t sound right, but what I’m hearing just could be because it’s not running right and it’s missing?
Checked compression and it’s great(186)so if something wasn’t right with Engine I would think it would show up in the compression reading Which if anything has went up since initial testing after rebuild.
I am going to ditch this carb and try another chinese knockoff(PWK 40) I bought and try it,if it’s still running like crap then I will go back to original carb

I can’t remember if it made this loud knocking before,if that’s coming from the Engine or that’s the clutch and I’m just paranoid.

Those aren't plug chops ---- you have to cut them.
You are looking for a smoke ring at the bottom of the porcelain.
I believe you want a 1mm smoke ring. PM adnoh or use the search box.
Those plugs look lean to me.
CO

Yeah I knew they need cut open but I figured it would be a waste of a good plug since I don't know how the test was affected by the choke not screwed in and air screw not adjusted properly so why bother,especially if I'm going to try another carb.Not going to bother adnoh,if he saw the other post and chimed in he would do the same here if he wanted to.
Thanks for responding though,beginning to wonder if I was being blackballed since no ones responded to my post in this thread for a while

Yeah the site is almost ded.
The few that are left are not posting much anymore and are probably just trolling (looking but not signing in).
I love this site and it's the homepage on my computer.
I try to comment on almost everything to keep the site alive and I am sure most are sick of my comments but that's why I do what I do here.
It's unfortunate but all things grow old and die eventually.
CO

Is plug pic shown on the screen the actual color, sometimes the flash or fstop on camera will make the plug look lighter in color that the actual color. The color here to me looks lean.
I found I get a good reading of what the airfuel is doing by running at least 30 seconds wide open.
Can you go back to your original leaking carb to get a (somewhat) baseline for comparison...

30 seconds?!! I was lucky if I was able to get 10 seconds from start to stop.
I am going to try this other chinese carb first,if it runs like shit with it also I will try to see if I can still use original carb if it’s still useable

I see a few things to comment on. Please don't run untill I do. I see no dark color on threads. You need two to three. May not have enough run time on it. What really peaked my interest is the one of tip side view. This has to do with timing which is fixed. So octane level has an effect here.
Measure that length from end to where the color changes.
You may be bumping the Rev limiter is why it's four stroking. Got tach. Don't go leaner untill your sure your not. Also thread on stator causing not to rev out. If reved out before doubt it's damaged. Don't cook of the top end

what gas are you using? I'm like CO and strongly advise the use of a high octane fuel, AV gas is your cheap race gas, you may not get as much power as a true race gas but you will reduce the chances of cooking the top end.
also, you can get a bore scope camera from Amazon or Ebay for less than $30, stick it down a plug hole so you can get an idea of what the piston is looking like without pulling it apart.

I am using AV gas
Bore scope is good ideal

Please don’t quite posting! Even simple stuff like your pictures of the gun racks you made etc....I think that is all cool!

Even at times if you or someone else doesn’t know the exact answer to a question etc....at least give your best opinion. Some times things like that will help the next guy out to look at things from a different perspective.

And back to the gun rack thing....that is cool also. Sharing things like these will keep the forum alive.

Later, SB4x4

OK not to get off topic too much but I have a question and a comment.

I don’t know enough about two strokes but from my days of building race car engines etc...I’ll say from the pictures the plug looks like the Engine is running lean.

That being said....does anyone know what the advertised compression ratio is suppose to be on the FL400R Engine?

Is it 10:1, 11:1 etc...

I’m trying to get a understanding on gas limitations on a stock machine/Engine would be?

My Pilot is totally stock and from what I know the Engine has never been apart. I’ve been running premium pump gas (93 Octane) and running the oil at a 32:1 mix. The machine has been running great with no issues. In fact during the week of the 4th of July riding the trails we put around 100-120 miles on all the wheelers and the Pilot ran great.

I understand about doing head work/piston work/exhaust and porting work etc.. and changes will have an effect on what you can run for gas etc...but I need some where to start. Being as my machine is a 1990 I do plan on pulling the Engine this winter and have it gone thru but would like to have more of a understanding of them.

Thanks!

Advertised compression ratio was 6.2 to 1 in the manual.

As for the fuel thing (oh god am I gona do this again LOL) I only run AV fuel because it solved Engine explosions for me. I blew 9 pistons in a row before I figured these FL350's out. At least twice it never made it 100 yds before it blew up (NO LIE).
The FL350 and the FL400 are two completely different animals. It may not seem like it but they are.
There are members here who have blown engines on the FL400 and when they switched to AV fuel all premature Engine deaths ceased. Engines must be in fine tune condition to run as advertised. These things are 34 yrs old now and I bet very few are in fine tune condition. That leaves the door wide open for the grim reaper.
CO

I did read your post and seen your pic’s of the burnt hole in the pistons! Yikes!

Avgas I could get from the airport I would assume....that being said I have access to plenty of race gas. I go past two gas stations on the way home and you can buy it at the pump.

One station has 100 octane unleaded fuel and another station has 110 octane leaded fuel. I run the 110 Octane in my ‘68 Firebird 400. It currently has a rebuilt 455 with 12:1 compression. Makes right around 550hp.

I’ll say my Pilot is in good tune. When I got it I took it to my motosports shop (Mikes Motosports) and had them go thru it and check everything. They also work on the kids Banshee. So as I get more info and understanding of these machines I’ll rely on my mechanic. He hasn’t let me down on all of our other atv’s we have on they’re work/service.

Any thoughts on running the 100 octane unleaded fuel or the 110 octane leaded? I’ll say I’ll stay away from the leaded fuel as the Pilots where built and run on unleaded gasoline from the get go.

SB4x4

Thought of this and again I’m not trying to hijack the thread....

Picked up a Speedchasers Cool Head. By changing the head and nothing else any concerns/thoughts on rejetting etc...?

Installed chinese keihin pwk40 last night,test run on street in front of house this morning.Put 170 main jet to start.Definitely running better than the other carb,not missing on top end speed like it was but didnt have the low end power I remember,maybe jetting will change that? BUT,it's still making that weird frickin noise when I give it full throttle that it never made before,I don't know what the hell it is and it's driving me crazy!! Like I keep saying,it doesnt make it when I rev it sitting still,only when driving it.I would stick a camera BACK THERE AND and record it but I don't think it would translate,I think you have to be sitting in drivers seat to hear it.
Does anyone agree or disagree with the statement that if the noise was coming from the Engine{like piston slap or ring out of groove}that the compression would be going down? Or if it was Engine it should make that noise when Im sitting still and revving it high?
thanks
Forgot to add,done for today,just wanted to see how carb change affected it before driving 2 hrs somewhere to test it.Seems like it was running good enough to do some plug chops,but wont be able to go somewhere and do those for 2 or 3 weeks

It's almost impossible for us to help on this issue unless we can hear it.
I bet money that it is probably your belt slipping on the clutch because it is worn out.
This would sound like a chirping or even a bad rattle (like it did on my machine).
Measure your belt width.
This would also fall in line or look like a jetting issue because of no top end.
How badly are your shivs worn ??
That's all I can think of right now unless I hear it.
CO

Thanks for commenting. I don’t believe it is a belt issue because it was not making this noise before rebuild, It would be weird for it to immediately start Happening now, but I do have a different belt that I can put on it just to see if it changes anything.
I DO have top end,It was lacking the power at bottom end.
I do not know what the “shivs” are you’re talking about?
Thanks

I know those comet 102 C clutches Can make interesting noises, did you do any work on the clutch, I know you were asking about lubrication.

Yes I have remembered to lubricate clutch with some comet clutch lube,Could be the clutch noise but it really bothers me since it never did it before. My instinct is telling me that it’s coming from the Engine but I just don’t know what it is