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Discussion Starter · #1 ·
Does anyone out there know of anyone that is running a 13.1 JE piston with the HRC Kit? Would like to know how this combo works or if it is worth doing?
 

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I am sure it would be hard on the bottom end, make a lot of heat, require race fuel. I would not do this on a recreational bike. Also the HRC cam is designed for stock compression. 13:1 could use a more agressive cam to help bleed cylinder pressure.
 

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I have the JE 13.8:1 w/ an HRC cam. No problems with it what so ever.
 

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Discussion Starter · #4 ·
What gearing are you running with that set up and are you pleased with the way your bike performs? I have the same set up as you except for I run the 13.1 Piston with a 13 frt and 36 rear and it just doesn't seem like it performs the way it should any suggestions? I am also running the sparks pipe, and filter with no air box lid and a 190 main jet with Sunoco 110 race fuel. Please help me get this straightened out you guys seem to know your stuff. Thanks alot!
 

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Originally posted by desert_450r@Aug 10 2004, 01:00 AM
Black450R,

Can you explain what you mean by this? --- Maybe the Mai Tais are clouding me noodle right now :wacko: :wacko:

QUOTE
13:1 could use a more agressive cam to help bleed cylinder pressure.
[/b][/quote]
The more compression you have the more lobe seperation you can run without losing to much bottom end torque. The lower compression means smaller cam to run correctly. A Sparks hot cam would be a lot more suited for a 13.1 piston than the HRC. Both will run fine but the Sparks will take more advantage of the extra compression.
 

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Discussion Starter · #6 ·
Hey Black 450r not sure what you mean I called Sparks racing and asked them if I needed to change the cam in my bike and they told me no. The person I talked to today said that changing to a FCR carb would make a noticable difference in the performance more than changing to an aggresive cam. Not sure what to do?
 

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Discussion Starter · #7 ·
I think I created some confusion here. I have a sparks pipe, sparks air filter, no air box lid, 190 main jet, HRC cam, 13.1 pistion, and the head has been ported. To me the bike doesn't perform the way it should. I thought that by adding the piston I would get back the bottom end I lost with the HRC cam and still have top end, but the bike seems worse all the way around. I am running a 13f and 36 rear. You are very knowledgable and would appreciate any suggestions on what else to do to get this bike to run better.
 

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Originally posted by 04450r@Aug 11 2004, 10:17 AM
I think I created some confusion here.  I have a sparks pipe, sparks air filter, no air box lid, 190 main jet, HRC cam, 13.1 pistion, and the head has been ported.  To me the bike doesn't perform the way it should.  I thought that by adding the piston I would get back the bottom end I lost with the HRC cam and still have top end, but the bike seems worse all the way around.  I am running a 13f and 36 rear.  Thanks
I have almost the same set up as you, except I have the 13.8:1 JE. I gained a lot of bottom end and didn't lose any top end. I have a 182 main, 14/39 gearing, and 113 octane VP Late Model +. Awesome increases all around. What race gas are you using? Depending on your elevation, you may be too rich.
 

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Discussion Starter · #9 ·
I am running 110 Sunnoco race fuel, at sea level. Does your fan come on alot? Mine comes on alot, it doesn't stay on it just runs for a while. The inside of my pipe is solid white I figured that I was too lean. Are you using the stock carb?
 

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Discussion Starter · #10 ·
29FTEX, what set up are you running? Does the 14f 39r seem to be a good all around gear for you? Is there a big difference between the 13.8 and 13.1 pistons? These are probably stupid questions to you but just curious

Thanks.
 

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Originally posted by 04450r@Aug 11 2004, 04:36 PM
29FTEX, what set up are you running?  Does the 14f 39r seem to be a good all around gear for you?  Is there a big difference between the 13.8 and 13.1 pistons?  These are probably stupid questions to you but just curious

Thanks.
I had the 13/38 w/ just the HRC kit. Now, w/ the 13.8:1 I went to the 14/39 because it added so much on the bottom that I could go back to the stock front tooth. I guess it all depends on the terrain you ride in as to what works best for you. When we go to Little Sahara, OK in October, I'm going to try the 13/38 again because of the drag of the sand.
I have Elkas all the way around, and the rear link and shock really helped on the hole shots, besides lowering the quad ~ 2".
As far a a difference in the 13:1 and 13.8:1, I have no idea how much it actually does add. For me, the change was night and day. Compression= HP. I'm leaning toward going with the 500cc FST big bore. It's fast now, but I want more.
 

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Your jetting is off man, you need to get it squared away before you tear up your engine. If you are running an oxygenated fuel you will need to bump your main jet up about 3 sizes to accomendate for the extra oxygen. I would imagine that the octane of the fuel has something to do with the jetting too. I know if you are running alchol you need to run a much bigger jet for it to run the way it should.

I haven't really run high octain fuels in any of my quads so I don't know about the jetting, but I've run oxygenated fuels and alchol before so that's why I offered up some info on that. Hope it helps.
 

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Discussion Starter · #13 ·
Thanks for all the info it has been very helpful I ran the bike yesterday and had a mechanic look at the plug and he says that the motor is too rich, so we changed the jet to a 175 then ran the it some more and the plug looked much better. I feel that I am heading the right direction now. I have also added a set of Holeshot HD's all the way around (stock size) these tires may be bogging the bike down also. Once again thanks for the info. I have been away from quads for about five years I've been running a dirt track race car and things are much different the car I was racing ran on alchol.
 

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Originally posted by Black450R@Aug 9 2004, 09:17 PM
I am sure it would be hard on the bottom end, make a lot of heat, require race fuel.  I would not do this on a recreational bike.  Also the HRC cam is designed for stock compression.  13:1 could use a more agressive cam to help bleed cylinder pressure.
[snapback]14146[/snapback]​
i was doing a piston search and found this............is it me or does this not sound right..........actually most of this thread sounds WRONG
 
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