Well as many of you heard my intake valve got bent do to a broken valve spring.[img]i/expressions/face-icon-small-disgusted.gif[/img] The valve didn't only get bent it snapped off at the retainer! Now here is the reason I am going with a Rev Limiter!!!!! When you flash your engine or otherwise rev it up with out a load or Miss a shift and over rev, you reduce the integrity of the Springs. Well that spring had just said I had enough of you missing shifts and revving me up so take that SUCKA!!!![img]i/expressions/face-icon-small-mad.gif[/img][img]i/expressions/face-icon-small-shocked.gif[/img] So word to the wise I guess, get a rev limiter!!!!! It is going to cost me almost $500.00 bucks to get this stupid thing fixed and mine was only a minor valve problem! Buy the way if any of you guy's would like to try your hand at a 720 I have an extra cylinder I would like to get rid of. It is set up and all ready to go. You just need the new Cometic Gasket and away you go!

 

i over-rev'd, broke a valve, and it cost me a lot more than $500 when everything was fixed. i now have a rev limiter.

 

I agree. What cdi are you going with?

What do you want to have the limiter set at?

Also, did you lose your shim when the valve broke?

 

It's the whole shim under bucket set-up thing, wrong spring to begin with.....listen to Gary, he really does know his stuff!

 

punisher, pm me wit a $ for that cylinder, i may be interested, also would i be able to use a stock head wit it?

 

Im a born again rev limiter person too. As far as shim under bucket; that does not prevent the piston from smashing into a floated valve and bending them, it simply keeps the shims where they belong when the piston hits the valves. The shims are retained in the bucket instead of being flipped out of their buckets and bouncing around the cams.

 

well after running with mario and tony i'm a firm believer in the 720, i had some mechanical problems to start but they were from a oil reduction valve being in the engine, kind of one of those after market things that can get you, after getting that taken care of and a new tvi race head, my 720 is great. it was slower than azsands 760, as you would expect, i lost to jeffs 830 as you would expect put after that it was a good chance for a win. i would say kmduners stage three was a great runner, and with a smaller rider was right there with me, but i think they would be about the same money wise, so i would lean again to the 720, plus he had dual carbs and everyone said there a must for the big bores. as far as reving the rotax i'm sure there bullet proff at 7800 rpm, but i know that yellow 680 of garys has had the revs put to it hard and that thing still runs, very good. at what rpm do the valves float with the race springs? if those duals can't take 2000 more than stock i wonder why run them because i've heard for a fact they rob power? just a question i have been wondering since someone told me there running stock springs was that you azsand? mrs sandmans dad put dual springs in his c-5 vet and lost 20 horse but based on a 500hp engine that would mean you lose like one in a ds. well won't be changing the rev box but then again i may be on here later saying i wish i had.

 

hey DS650BAJAX, why didnt you come out to DS days at sand mtn this last weekend. We were all there. If you would have lined up to race i am sure you would have missed a shift. I missed a couple, one of them my revs went sky high, over 9000 i am guessing. Everything still seems ok though. I guess if i break mine, i can get a big bore [img]i/expressions/face-icon-small-wink.gif[/img] [img]i/expressions/face-icon-small-cool.gif[/img]

 

Hillbilly what are you talking about?[img]i/expressions/face-icon-small-confused.gif[/img]

 

I have the shim under conversion and dual rates from web, I like to rev and my motor likes it too, but like Mark said the shim under only comes into play after you bring a spring or cram a valve.
I plan on nos this winter, and I'll dam sure be sporting a rev limiter before the bottle goes live.

with a stock motor the hp drops off just after 6K on the tach, never saw much use for a rev beyond 8K, but I've yet to see a dyno chart of a motor setup like mine to know where the numbers fall. I'll be going on a dyno soon to find out, and prolly get the vortex programmable cdi later on this winter (if i go thru with the n2o plan).