Which Reed Valve System Offers Highest Performance

Question:

Hey guys, I love your site and mag. I always try to look at your articles on here every couple of days and try to get a magazine every month to keep updated with what’s going on in the biz (most accurate info in the biz today)! I’d go for a subscription but school keeps me pinching pennies but anywho I have a couple of questions for you guys.

I wanted to know which reed valve system would be the best one in regards of overall performance increase: The Boyesen reed valve system or the V Force 3 reed valve system. What advantage does one have over the other?

Also, I was wondering what the advantages were to gutting an airbox and if there are any dissadvantages to doing this.

Oh and one more thing, when school is finished I plan on buying a well used (8600 miles) 1999 RMK 700 (and a subscription from your mag I might add) with new rings, pistons, seals, bearings, and lots of other new parts replaced in 2005, from a friend and was wondering which not so expensive mods would give me some well needed HP (I think its rated hp for that year was something like 115).

It has some clutch work and gearing work to give it more down low snap as well as Carbon Tech reed petals and a boost bottle, and a custom made can too (actually sounds mean). Please give me some input.

From one of your favourite fans,

Chad

Reply:

Thanks for your question(s)!

First, the reed valve replacement issue. Both systems you speak of are good performance improvers and the difference between them – if there is in fact any – would be unquantifiable for even a hard core tuner – unless you used a dyno.

These reed valve systems increase the motor’s ability to “scavenge” – or pump air. That’s the deal in a 2 stroke – move more air, mix fuel in with the air and you make more HP.

This requires more than just reeds to take it to its upper most level and will be the answer to what you could do to the used RMK 700 you are looking at.

If you run big reed cages you are allowing the motor to take in more air. Next step, processing the air internally requires porting. Hog out the transfers, raise and open up the exhaust port. Finally, get rid of the air – install a honking big set of tuned (twin pipes).

This will net you a motor which, in my humble opinion, will drive you nuts. It will be pipey, lose torque (bottom end) and will scream like a wild banshee with a shift RPM increase of more than 1000 revs. How’s that sound?

Personally, I wouldn’t do this to an enemies sled. Install the reeds. They’ll improve low end response. Maybe a fatty single pipe that enhances torque and do the proper jetting to make it work and live. Do stuff that’ll make usable power – not peak power. Tighten up the squish with a shaved stock or aftermarket head.

Or, better yet – here’s a suggestion. Take the extra cha-ching you would spend on copious speed equipment and buy a newer, bigger displacement sled in better condition, with less miles.

At the end of the day, that 700 will only make so much usable HP. Sure, you can twang the thing until it screeches RPM but you’ll end up with a clutching and jetting sensitive annoyance that you’ll hate.

Good luck!

Motorhead Mark

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