Fmf Power Valve Cyl. Vs. Drag Ported 420 Cyl

[axle]

Hello. I need some help making a desicion and would greatly appreciate any help you all would offer. first off a friend of mine has a set of FMF power valve cylinders that he has not been able to get running right and I jokingly made the comment today that I would trade him my top end for his top end and he said o.k. seriosly I also just bought a set of cyl. off ebay with the intention of sending them off for a 420 kit and drag porting. my question is should I trade him and go that way or just continue with the ported 420 kit. which way would be the best as far as power wise providing I could get the FMFs running the way they should.

 

And My second question:

This Last weekend I went to the texas sand drags but before I went I changed the domes in my cool head to a 16cc and ran race fuel. I got four test and tune runs in on friday night and on every pass it banged out on the top end of every gear saturday morning I rejetted the carbs and made my first time trial run and it ran even worse so I went back to the pits and went the other direction with the jets to see what would happen. still banging out, them I changed the Plugs still banging out. then I closed the gap to on the plugs to .018 and it quit banging out and seemed to run alright but did not seem to have the power that it usually does.

 

If I were to get an after market ignition to get a hotter spark. and open my plug gap back up do you all think this would cure the problem or do think maybe the race fuel is the problem. I ran the fuel straight( didn't mix with Super Unleaded) With H1R @40:1

 

again any help would be appreciated.

[00BANSHEE]

On the cylinders.... The FMF powervalved cylinders are actually the 400cc T-Rex setup. If he will trade you, I would jump all over that. Then send them to K&T Performance and have them port them and set them up for you.

[MULLET~BOY]

lucky basterd thats all i can say

[raxen]

Go for it.

[axle]

thanks for the input. I guess I'll trade him and see if i can make them run. But I talked to racers edge today and they said I would have to change the power valves after every 20 hrs. of use. I've also heard that you really dont get that much more power than stock cylinders unless you are running a stroker crank.

 

Thanks Again

[MULLET~BOY]

i think if you drop them on you your looking at mid 60's if you get like a full drag you could get like 80 hp out of em if you have some extra cash drop a 4mm stroker in it and get a full dragg that thing would rip

[00BANSHEE]

thanks for the input. I guess I'll trade him and see if i can make them run. But I talked to racers edge today and they said I would have to change the power valves after every 20 hrs. of use. I've also heard that you really dont get that much more power than stock cylinders unless you are running a stroker crank.

 

Thanks Again

Hey axle, your right in the fact that as far as peak HP goes you can probably get as much from your stock cylinders, but the low end you will retain with the powervalves is well worth it if you are going to use the bike for more than just drag racing.

 

What happens to the powervalves that makes them need replaced after 20 hours? I have never heard that before.

[axle]

The Guy Didn't really say. I just asked him how long they should last and he said they should be replaced every twenty hrs. sounds like BS to me, but hey he sales them so who am I to argue right.

[MULLET~BOY]

sounds like bs to me about having to replace them evry 20 hours

[axle]

I allready have a 4mm Stroker crank that I tried In my last set of cylinders but It was recommended by my porter to go back to the stock crank and it would run better.

 

(It ripped on the top end but on the bottom end it ran like crap.) Port timing Issue I guess.

 

So what do you all think about the FMF cylinders w/ drag porting, The 4MM stroker crank and getting rid of my T5's and getting some CPI in frames.

 

Also I have 34MM PJ's do you think these would be good enough or should I look for some different carbs also.

 

I dont Mean to ask so many Questions But I'm Tired of spending My money in Places that turn out not to help.

[Josh A.]

If your going to drag iwouldnt even run the powervalves

[axle]

How would you go about removing them?

[raxen]

Why would you remove the powervavles to drag? It seems like all the drag shees that I see spend all of this extra cash to get a T-Rex kit, Cheetah kit, etc. because the power valves provides more power throughout the band. You need to measure the disance from the top of the cylinder down to the port to determine if you can even use a 4mm stroke in it. These monoblocks are stroke specific. As far as removing the powervalves, how long was it ran before you? I've got a set of older powervalved cylinders from an older bike and have been running them hard way past 20 hours with no problem. The CPI in-frames are an excellent choice for this setup.

[00BANSHEE]

How would you go about removing them?

Don't remove them. If this is something you end up passing on let us know the guy's name and number. I already have people in line waiting to make this swap.

[Meat_Head]

You do not need to change the powervalves after 20 hours of use thats bullcrap.