This is the 1991 carb info ..

 

Thanks for that screen shot, now it makes sense. Above the numbers is "VE" so I would have to assume it is a "VE90C" 32mm, the factory carb for this bike. It does seem hard to believe that it still has the factory carb if the displacement has been increased that much. Do you know what carb came on a 400 or 450 of the same year? I imagine it would have been bigger than a 32mm, right?

 

<div class="FTQUOTE"><begin quote>No I mean the cylinder drops down into the crankcases approx. 1 1/2" .. </end quote></div>


My bad... sorry.
It seems we are both trying to help though... and thats the main thing, as you seem pretty darn sharp.

 

I have posted a few pics on my page, not sure how much help they will be. You can't really make out the numbers stamped on the cylinder, the 421 is stamped and cm3 is raised like it was cast in it. Is that how they normally do it from the factory?

 

I can see the numbers, but I cant really see anything that looks abnormal about it.
Maybe they have had it resleeved... not sure...

 

If the cylinder had been resleeved, would the individual doing the machine work somehow remove the original numbers and just restamp the updated engine size? If that were the case, I would think I would be able to find some evidence that the factory numbers had been ground off. If it is indeed a 421 than i would probably want to up the carb size right, maybe ~40mm? I also wonder what the cam specs are in this thing if it has even been changed, the carb obviously hasn't. Anyone have a recomendation for a cam suited for trail riding and a little mud digging, I certainly won't be racing it. Thanks again for everyones help, this forum seems to be a life saver for me and a lot of other people out there.

 

There are so many if's and maybe's on this subject, the only true way to know is pop the head off and have a look first hand. Anything other then that would only be speculation. You certainly wouldnt want to buy a larger carb and a larger cam without knowing what your dealing with first.
Its only about an hour job to R&R the head. Get yourself a new head gasket and remove the head, measure the cylinder, then you will know all the answers to your questions.

 

This is a TRX300 cyl. it has 281cm stamped into it ..

 

The winding down sound you hear is probably the one way clutch. It is no longer " ONE WAY " anymore. To confirm this your kick starter should not work and it should "freewheel" as you go down a hill, as if you had it in nuetral. Even thoug you are actually IN GEAR. If you are freewheeling you can kinda blip the thumb throttle while you are going downhill and it will catch and slow down for a few seconds before it speeds back up. The one way clutch can be costly if buying it new. I bought my replacement off of ebay.