Ok, looks like I'm not the only Viper owner looking for more juice.
I went with the Hetrick Racing power up kit 'C'.
It came with a Koso pipe, not the Hetrick made pipe. I'm not sure why. From what I can gather on the phone, it fits a little better on the E-ton and they have a hard time keeping enough stock of their own pipe. But the Koso is nice, chrome, and revs nice and sounds good.
The pipe goes in fairly easy. I removed the oil injection tank. I capped the inlet to the injection pump, but did not remove the pump unit itself. I left the feed hose from the pump to the carb, but I put a plug in the line so no air could be sucked in throught the oil injection hese. I would have capped them, but due to time constraints I could not get small vacuum caps. The only tricky part is the battery. It needs to move. I got creative for a temporary fix, but you will need to make a small metal pan to hold the battery and weld it in place to really do it right. I am going to. I just will not give up that electric start!!!
I also did all the clutch springs, drilled out the throws on the clutch shoes, and put in the weight set. I run a uni filter and outer wear. It ran the same with 120 and 125 main jets. I think I will switch back to the 125 just to be on the safe side. I can not see any difference.

But know this-
I am disappointed. It sounds great, it has more power, it has more top speed. But it still can not spin up a set of sand gecko paddles. I wanted to try out a much lighter set of skat-trak gliders a frien had, but the wheels would not fit the Viper (he has trx90's). The gliders are lighter, shorter, and wider!!! Looks like they should work better. The power is still not where I need it. The 7 yr old and the 11 year old both want/need more. And the stock trx90 hondas will out dune my piped Viper all day long. I think it is because the Honda has a shiftable 4 speed trns.

I think I may try the big bore kit with the 20mm carb on the other one. But I will leave the pipe and trans stock. But that's likely 6 months away. If anyone else has feed back, I want to hear it!!!!! I am on a quest. I'm tired of digging my kids out of the sand every 2 minutes when we go on a ride!

 

There are still bolt-ons you can add to boost low-end power. 20-24mm carb, high compression head, reeds. Don't have paddles yet but I've no doubt it would spin the hell out of them with my 55lb daughter on it. Course I have that "Hetrick" style pipe, 20mm carb and high compression head and it'll spin the tires pretty good with my 190lb butt on it. Not to mention haul me up some pretty decent dunes. Wondering if lighter rollers or stiffer springs would help you? You have a lag on take off or anything?

I mounted my battery over the left rear wheel with 2 "L" brackets, a back brace and plastic ties (about $5). It's held good and really doesn't look that bad. It's also easier access for charging, which is nice if it sits up. And I replaced it with a better battery because size wasn't as much of a factor. Starts easier with more cranking power.

 

Talking with Jon at Miniatvs.com I was going to get a pipe from him for racing MX. He said I would gain mid and alot of high end but my low end would suffer. Told him that wouldn't work for me, he suggested I stay with stock exhaust unless I do the head, cylinder, and piston mods he offers. Price seemed very reasonable so all my stuff is on the way to him including our complete clutch. He does some machining to them also. I marked out a random distance on our dirt road and timed my little one to get an average. Will compare these #'s to the modified when all is together and see if any real difference. We need low to mid performance as we have alot of corners and deep sand in them with short straights comparitivly to other tracks.

As far as the trx 90 out performing yours maybe it is due to the tork a 4-stroke produces on the low end? I have a '87 trx 125 my kids learned on and it has unbelievable power low end but wont go very fast. 2-stroke or 4-stroke, I fought this except we wanted to race, so 2-stroke it is. Would have been a 4-stroke other wise.

 

Not true. It's not like having a clutch. You set the tranny to rev higher out of the hole with that pipe through springs and rollers. It hits and hits hard at any speed with the correct clutching. Same as Hetrick's. And Jon knows that.

 

I'm sure Jon knows what he is talking about. May be my misunderstanding or ability to cummunicate what he said. I agree with what you say also about correct clutching. That's why my clutch is going in also. The engine work that he will be doing is to get even more out of it. I would think kinda like putting headers on a car. You get results, but it is just a start of what really needs to (or could) be done.

 

Yes, but the average Joe can add pipes, reeds, heads, clutch kits and carbs whereas tearing into an engine is more complex and expensive.

Be sure to tell Jon to go easy on the compression. Having a faster mini isn't worth compromising reliability.

 

Well, I'm thinking of maybe taking .040 off the head to bump the compression. I need whatever I can get out of this thing. My boys both weigh in at about 80 pounds. The quad does better with knobbies in the sand though.
And I have the lighter (4.5) rollers, the yellow torsion spring, the red clutch springs, and the drilled out clutch throws in there already.
It just bogs down in the powder. Sand kills it.

 

do you think it was a waste of time and money or worth it? I know you were expecting more but what's the bottom line for you?

 

Go lighter on the rollers, Don't waste the money on the motor. I would say to get a bigger carb if you are going to do anything more besides the cvt. The cvt is where your problem is.

 

I agree with Tommy about the cvt and the carb having a bigger impact than the head (although I think it would help). If you do go with a higher compression, don't forget to bump your octane!