HRC Power Up Kit or Thumper Racing 680 KIt???

4 replies to this topic
  • TommieZZ

Posted January 01, 2008 - 08:54 AM


I want a reliable supermoto XR650R. Right now I have the Edelbrock carb
& the Pro Circuit compete exhaust on it. My question: Would the Honda HRC kit be the way to go or the Thumper Racing 680 kit? Thanks

  • BWB63

Posted January 01, 2008 - 05:00 PM


I would go with a 102.4mm Nikasil bored and stage two cam for the money. HRC has a very good piston but, the major $$$$ you pay just for the kit is out ragous. You can get a HRC cam chain, Stainless Steel valves, stage two cam, Lukes racing Nikasil overbore with wiesco piston, gasket set, and still have money left over compared to the HRC kit. I would at least get a Falcon rod, I like the Corrillo rod myself because it is rebiuldable.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • hondacrf150f1

Posted January 01, 2008 - 06:20 PM


I was looking at the HRC kit on XR's only and they didnt say much about it, i mean what makes it $1G? You can get a high comp piston for $250, is the other 750 really in just the cam?

  • Maroast

Posted January 01, 2008 - 09:36 PM


You can get a HRC cam chain, Stainless Steel valves, stage two cam, Lukes racing Nikasil overbore with wiesco piston, gasket set, and still have money left over compared to the HRC kit.

That is awesome!!! With that weisco piston can you still run pump gas? Or does the added displacement and high comp piston make pump gas completely out of the question? By this time next year (or hopefully sooner :banghead: ) I plan on doing this.....but i want to turn this piggy into a 680 street tard... and only want to run 93 octane.

So, is 93 octane in a 680 with an 11:1 piston & stage II cam out of the question?

Thanks! :busted:

  • BWB63

Posted January 01, 2008 - 11:25 PM


On 91 octane I get pinging but, most of that is due to the sharp edge left on the piston for the machining that was done for the 3mm oversized intake valves. If done right and say 1mm oversized intake valves and the relief cuts were smoothed there shouldn't be any ping with 93. You do not have to go 11:1 they make a 10:1 or 10.25:1 weisco piston. Well the oversized intake made the low end a little softer and a lot more power mid to top rpm. This is a good thing when the engine is putting out this much power!!!! I have way to much power down low with 14/48 gearing to be used and with 15/47 the bike feels just about stock at the bottom rpm's. 14/48 and the bike will pull the front end up at 55mph like a stock bike does in second. It will come up fast enough to flip the bike, with no clutch. With 14/47 the bike pulls third up just like a stock bike but, you are doing 60+ and with any pump, clutch or reason it will come up in forth and walk the bike right up in fifth over a rise at 90mph. I don't run straight pump fuel so this is a mixture. From 44rwhp to 58rwhp is a huge difference in how the bike responds. Mike Powell's bike is Nikasil and I think has stock valves. It is very abrupt and David Gray said, it was almost impossible in the rocks when racing the Baja 1000. With this I would say that moving more of the power into the upper rpm's with the biggest exhaust and bigger intake valves that I have makes the bike a little more controlable and you have the power to lift the front through the bigger whoops at higher speeds. Porting the head has been to much in every case so far....except motard so, I think for dirt stay with stock porting.

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.