Okay, I've thought about going with a 416, higher compression piston, cam, mild porting, and FCR carb. What kind of gain do you think I would get with a stock bore, higher compression piston (10.8:1 or 11:1), and XR400 or GT Thunder cam? Please help. Thanks.

 

Over winter I did the 10.5 piston (stock bore),head porting,and GT Thunder cam.I havent had too much chance to run it I still have some jetting to do,but it felt plenty strong. I'm happy so far.

 

What are you wanting to do with the quad? If you are planning to MX it, what type of track is it? [traditional MX or supercross/stadium]

 

I ran against 2 heavly modified [RED]440's[/RED] this weekend on a M/X track. (Both had about [GREEN]$3500[/GREEN] stuck in their motors.) The track is clearly a [BLUE]Banshee[/BLUE] track. (Having lots of wide open straights.) I must say that my stock motor ran as well, if not better than the 440's. I came from last place, and wound up in second. I fought with the first place rider until the end. He beat me by only a tire. I believe that I will be leaving my motor stock for awhile. I am planing on changing my pipe to the CURTIS X-6 though. This would be the reason why:

http://albums.photopoint.com/j/View?...721&p=47235195

Not sure why, or how this happened!!

 

Higher compression negates the loss of low end by a wild cam, to a point...

I have a friend that went the route of the GT Thunder cam and is very happy with it - I haven't gotten to ride it yet to compare to my identically prepared bike with the XR cam. My guess is it will pull thru the mid and top much better.

I use the XR mainly for fuel economy for 2hr+ long races on the stock tank. It produces enough low end that I don't have to scream the engine to make power. With my setup I have more power and get better fuel economy than stock bikes. If it weren't for fuel economy for long race fears, I'd be running the GT-T cam in an instant.

With the combo you mention, expect fairly significant gains throughout the powerband.

 

Well, there are two local track in particular that I am talking about. One is a wide-open, 1.1 mile, traditional MX track. The other is a little bit tighter. It's called an SX track, but it's outdoors, and more like an MX if anything.

ANYWAY, I talked to my local motor builder, and told him I didn't want to go too radical starting off. I may change things later. He suggested a stock bore 10:1 piston, and an all-around cam. I also had him check on a 3-angle valve job. Do these 3-angle valve jobs help out? Is it worth doing? Also, will I be pleased with these mods? I would like about the same kind of power delivery as what I have now, but just on a higher level. What do you guys think? Thanks a lot.

 

Can anyone help?

 

I used to have a 10:5:1 piston stock bore, web cam and no porting. I like this set-up a lot I lost no bottom end and gained power everywhere.

If you don't want to lose bottom end get the 10:5:1 piston
GT Thunder cam
FCR Carb

You will now most likely if you want all the power you can get, you need a high flow header pipe.

With those mods you will not be disapointed at all. Now I ride in the dunes only, so I changed my set up.

 

LDJ,

Which Web Cam did you have with your setup you described? Was it the track cam, or all-around cam? Did you put in aftermarket springs, rockers, etc.? If you didn't, did anything get worn, or beat up? Thanks.

 

I have the 450/451 grind, which is the step below the race cam. I don't have to use springs, but I would recommend rockers. My cam has held up well no problems, but web cam recommends hardfaced rockers. I took a look at mine a while back and it is slowly starting wear, but there are about 50 hours on the cam at least. I still feel the same power increase. I talked to webcam and they will hardface my rockers for $250 and will fix my my cam for free. Pam at web cam said that my cam should look the way I described it to her, she said it is not worn out.