Higher comp. and cam?

10 replies to this topic
  • Frank ZX

Posted August 22, 2007 - 05:21 PM


I'm thinking of installing a hi compression piston and hi po cam.Any susgestions,and how much power can I gain?I want to go as cheap as possible.Thanks in advance!

  • Maroast

Posted August 22, 2007 - 07:34 PM


bike? :excuseme:

  • Denn10

Posted August 22, 2007 - 07:56 PM


he has a L frank do a search theres a few from the last month or so and one in the last week prolly. everything ive read about em people say they love it!!

  • martinfan30

Posted August 22, 2007 - 08:39 PM


i'd like to do this too. ive seen some posts where guys have gotten(as they stated) mid to hi 40's HP with cam, piston, exhaust and intake mods. like too see a dyno of it. when i get around to doing it i will visit the local dyno bike shop and post.

  • Frank ZX

Posted August 22, 2007 - 10:17 PM


Thanks Denn10.I forget,it's a XR650L.I was thinking about a JE stock bore piston,the cam is where I'm not sure what brand to go with.If and when I get this done,I'll get it dynoed.

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  • crmc33

Posted August 23, 2007 - 03:09 AM


A dyno print of my L engine with 102.4mm wiseco piston, hotcam stg 1, Mikuni VM40 roundslide carb and mild head porting and standard ignition is shown on www.motopike.com under the 'motorcycle development - Honda Supermono' section.
Its typical of the type of gains you would get with a few perfomance parts. I guess a std 650L would be making about 10HP less at peak torque.
Anymore gains than this cost a bit more time and money ;o)

Hope that helps.

PS. The latest hotcam stg 1 cam now comes with its own sprocket carrier ready fitted. (the early version used the original cam's sprocket carrier) Its a great cam for the money IMHO.

  • MartinDKtm

Posted August 23, 2007 - 03:32 AM


On the description it said a mikuni hsr48. Do you run the round slide 40 or the hsr? If its the round slide how is the throttle response with it? Does it lag a little cause theres no accelerator pump and no delay in the opening like a cv carb does.

  • crmc33

Posted August 23, 2007 - 06:49 AM



I have used both VM40 (Ive bored it to 42.5 to match the intake) and a HSR48.
I used the VM40 with the standard NX650 central intake and the HSR48 with a long custom made intake. Throttle response is great with either. I removed the pumper off the HSR as it didnt need it.

I have gone back to the VM carb temporarily as the long intake was too restrictive and I think the engine likes as shorter intake as possible.

The biggest problem with the VM carbs is vacuum pressure, making the throttle action quite heavy, especially when combined with a short action throttle tube.

My aim now is to test the VM and HSR back to back using short intake rubbers. My dyno man reckons the HSR48 is just too large but Im not convinced. It carburated fine with the HSR48 but I had a spearate problem with the cyl head sub rockers rubbing on the valve retainers. I think Ive got to the limit of exhaust valve height!

The rubbing of the sub rockers was just keeping the valves open a little. Fortunately it blew the base gasket before damaging the valves.
Just fitted a new base and head gasket. Used Yamaha bond (three bond) on the base gasket as insurance this time. Also ground the sub rocker arms so they are thinner btwn the tips and their pivots.
Also gonna run the engine total loss ignition. The removal of the flywheel will give it more lively acceleration. (saves 5Kg off crank + starter gear which has already been removed). Im aiming for a reliable 60HP. I might get there one day!

  • crmc33

Posted August 23, 2007 - 06:52 AM


Forgot to mention that the dyno curve shows the power before the VM40 carb was bored to 42.5mm - i.e. its in its standard 40mm ID form

  • Frank ZX

Posted August 23, 2007 - 02:01 PM


CRMC33,that is a awesome bike!Keep us posted on your hunt for 60hp.

  • crmc33

Posted August 23, 2007 - 02:14 PM


I will keep you posted. Lots on the go at the moment with revised intakes and ignition ideas.

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