89mm is a cr500

How come a pilot cylinder cant be bored to 89? I cant see why it couldnt but then again I know very little about 2 stroke engines. Can one be re sleeved to that size? Just askin

the 400 cylinder is shorter so a plate will need to be used and the liner used is also super thin to fit. the transfers are super narrow as well after its modified.

So does that mean it could work with a base plate? even if it is thin?

yes it has been done many times over the years

For use with the CR500 pistons in the 400 cylinder they install a bigger special sleeve you can buy from LA sleeve, I have one of these cylinders in my shop.
http://www.pilotodyssey.com/500cc.htm

FL670 had a Pilot with one of these conversions.
http://www.pilotodyssey.com/PO/viewtopic.php?t=1145
http://www.pilotodyssey.com/PO/viewtopic.php?t=1144

so la sleeve can install that into the pilot cylinder? If so why are people getting the studs and case modafied? Seams the sleve would be much simpler gor a 500 conversion. Am I missing something?

Port layout is different on the CR500 cylinders they are using when they do the case modifications.

Let me tell you something about that CR500 mod over the years I have rode with 4 different Pilots that had the ATV Racing CR500 mod and drag raced them all and during the whole drag race was right along side them every step of the way, we raced on hard pack and soft sand even up tall sand hills same results, two of these conversions were also running race gas had the high compression.

A full mod 400 will run with the CR500 mods why bother, heck I was having traction problems with my Pilot not really sure how I could hook up any more power, when I swapped to my 440 sled Engine that's why I detuned it by going to a 2 into 2 pipe and with just a single 38mm carb rather than twin AAEN modified pipes and 44mm twin carbs.

Why are you considering a bigger bore than the 400, whats your goal?

EDIT (added more)
If I was going to go to a CR500 cylinder it would be one of Calvin Pollets 500 cylinders you can get it up to 583cc

http://www.cpindinc.com/pub/view_product/63?lm=5&name=3101-9779-144

If you go with the CR500 you will need the pipe too the 400 pipe is different I would get the pipe specs from Calvin and have one of your local pipe builders build you a pipe to his specs, my first choice would be Bills pipes they seem to have high quality products.

No clue how good that CR500 pipe is from ATV Racing could be a copy of the stock pipe for all I know, if you get the pipe specs from Calvin you could reverse engineer the ATVR pipe (measure it) see how well it matched the CPI design.

CPI was suppose to make a adapter to bolt right on the Pilot bottom end dunno if it ever happen see this post.
http://www.pilotodyssey.com/PO/viewtopic.php?f=1&t=8999&start=0

Curiosity mostly, I am a gear head threw and threw, people have been spending a fortune on the 500 mod and it seemed so much simpler to bore to the 500. 100 cc displacement more is a decent increase. has to do something Layin in bed sicker than ever just askin is all. If I was going to increase power I would put a 583 or 670 in it, looks much cheaper to do than mod a whole Engine for a modest gain. How is the power of your 440 compaired to the 400 pilot?

Yes with your fab skills I strongly suggest you do the Engine swap with the 583 you more than double the HP and can maintain the reliability of the the all stock Engine those 583's are about as reliable as you can get.

The 440 Engine I used was rated at 85-92 HP depending on the year and the model sled they put the Engine in, that was with the factory twin pipes and the factory dual 38mm carbs, I detuned mine by using a factory 2 into 2 pipe and a single 38mm carb I would say its a honest 70 hp, I am clutched at 7600 RPM at the moment, I was running my Pilot Engine at 7800-8000 depending on my mood and where/who I was riding with

When we ride for the most part we all ride in a group so power is not really a problem, if I was to go racing I would take it up a notch, go with the twin pipes, change the disc valve timing, raise the compression and take the RPM's to at least 9000 RPM's where the Pilot engines cant go well for long anyways....