87 250X cam and piston upgrade.

[VT250X]

I am planning to upgrade my stock 250X engine with a piston and cam. Thanks to WIlkin250r and the others that have posted very important info in the following link.

http://www.exriders.com/vbb/showthread.php?s=&threadid=162307&perpage=15&highlight=250x&pagenumber=1

I also found this website and it was very helpful. However there were several holes which were filled by the link above.

http://www.off-road.com/atv/xupgrade/

I also have the Clymer manual, but there is some techincal stuff that isn't in there. I was planning on using the WebCam 55-581 and the standard bore Wiseco 12.1 piston.

Here are some of the questions I have. If you don't understand what I am asking, please let me know. I will try to re-phrase them.

* Where should I get the feeler gauges? If Sears had a set would they be OK or should I go to NAPA or someplace like AutoZone or Advance Auto Parts? Are any brands better than any others?

* The Cometic top end gasket kit C7143 shows it's made for a 75mm bore where as the Wiseco catalog shows the bore as 74mm with a stroke of 57.3mm for the 250X. Is the 1mm difference between them really a big deal?

* If I am replacing the cam AND piston should I get the complete gasket kit or would the top end include what I need?

* Cometic does not list the thickness of the gaskets themselves. They do say they can make custom thickness on some of there gaskets. After I determine the "squish" of my deck height should I get custom gaskets to reduce it to the proper "squish" ? I plan on using the solder method described by Wilkin250r.

* I know that some of you use a high temp sealer instead of a base gasket. (Honda HT or similar). Have you still had good luck or should use that instead of a gasket if I need to shave off the approx. .020? If not Cometic then what other brands of gaskets should I look into?

* I am planning on using the standard Wiseco Piston 4440M07400 and they say it has a compression ratio of 12.1. Would I need to run race gas?

* WebCams also says I need to rejet and have an after market exhaust (obviously) but they also mention needing a new valve spring kit. Are thier's any better than anyones else's or do I really need to worry about new springs at all?

It's taken me over an hour to write this post. If I am leaving anything out please let me know and thanks a ton for the input and help.

LM

[bwamos]

Originally posted by VT250X
* Where should I get the feeler gauges? If Sears had a set would they be OK or should I go to NAPA or someplace like AutoZone or Advance Auto Parts? Are any brands better than any others?
The Craftsman feelers will be fine.


* The Cometic top end gasket kit C7143 shows it's made for a 75mm bore where as the Wiseco catalog shows the bore as 74mm with a stroke of 57.3mm for the 250X. Is the 1mm difference between them really a big deal?

Not really sure on this one, but I'd think it would be fine. Your piston doesn't move up that far.


* If I am replacing the cam AND piston should I get the complete gasket kit or would the top end include what I need?

You'll just need the gasket below the piston and the one between the piston and head. The head cover uses liquid gasket.


* Cometic does not list the thickness of the gaskets themselves. They do say they can make custom thickness on some of there gaskets. After I determine the "squish" of my deck height should I get custom gaskets to reduce it to the proper "squish" ? I plan on using the solder method described by Wilkin250r.

I'm of no help here. Sorry.


* I know that some of you use a high temp sealer instead of a base gasket. (Honda HT or similar). Have you still had good luck or should use that instead of a gasket if I need to shave off the approx. .020? If not Cometic then what other brands of gaskets should I look into?

Am I wrong.. or isn't the thick base and head gaskes a 400ex issue vs. the xr400? I don't beleive it's a 300ex thing.


* I am planning on using the standard Wiseco Piston 4440M07400 and they say it has a compression ratio of 12.1. Would I need to run race gas?

On air cooled, anyhting above 11:1 will require race gas or at least a 50/50 mix, because the engine runs hotter and thus more prone to pre-detonation. Do NOT use octane booster.


* WebCams also says I need to rejet and have an after market exhaust (obviously) but they also mention needing a new valve spring kit. Are thier's any better than anyones else's or do I really need to worry about new springs at all?

300ex/250x's have really weak valve springs and your valves will float/bounce with an agressive cam. I got my HD ones from Sparks. They are cheap.

You'll need hard faced rockers for your webcam. With the age of your 250x you'd have to replace the rocker arms anyway with any new cam.

As a note.. I beleive in the Clymers and Honda manuals.. it says to use 17 ft-lbs on the head cover bolts. The small 8mm head ones. It should be 7 ft-lbs. 17 ft-lbs will twist them right in half. I figured that one out the hard way.. lol.

I also got heavier clutch springs on my 330.. but you may not need them on yours. If you notice your clutch slipping after rebuilt.. you'll want to replace.

[VT250X]

Thanks for the info bwamos.

As far as the thick base being a 400EX issue only I have no idea. I assumed the principle applied to all the motors so I figured I would ask to be sure. There's a lot of variables mixing stock and aftermarket stuff.

As far as your concerned since it is air cooled and would have a compression ratio of 12.1 then I would at least have to run 50/50 race gas and NO OCTANE BOOSTER. I guess I will have to wait and see. Since I don't ride a whole lot it would probably be better to run race gas just to be safe. My buddy races and that's what he uses so it's readily available.

I will check out the Sparks springs you mentioned as well as hard faced rockers. I kind of figured I might need new ones, but I was unsure. Do you have any reccomendations on the rockers? I will wait to see how the clutch is before I spend the money. It's pretty strong now, but you never know.

So can anyone else confirm the thick base gasket as being a 400EX issue only?

Thanks again bwamos for your input.

LM

[bwamos]

I'd jsut go with 11:1 comp piston. You can run premium pump with out any issues. And it's a very nice setup. I have no problems running with your average 400ex (pipe/filter/cam). Of course any more motor work and they still smoke me.. but that's to be expected.. lol.

You're not reall gonna see much difference between an 11:1 and a 12:1. You'll only see lie 1-2 hp difference tops between the two. No reason to spend the extra cash on the race fuel not to mention the inconvienience of storing it etc..