January 30, 2014 at 12:07 pm #20674
Can I get some opinions on the choices of reeds that are available for my stock 2001 CR250 sprint shifter kart?
1)honda stock reeds
2)boyesen superstock fibre reeds
3)boyesen superstock carbon reeds
4)boyesen proseries reeds
keep in mind this is for a fun-not race application with max rpms not exceeding 9,500
as per Viper racing helpful instructions
February 10, 2014 at 12:34 pm #21553
I just put together a 2003 CR250 sprint kart. I left the power valves operational. Stock it was a disapointment more than a 125 but not much more. I swapped the stock Mikuni carb for a PWK air striker and swapped the OEM reed for a Boysen RAD. That woke it up a lot.
So what would be the next logical step to wake it up some more.
February 10, 2014 at 3:56 pm #21564
thanks for the reply Brian,I chose not to go the RAD valve route,(for now)as I think it will be more than enough HP stock for me to handle I can always change it later.I left in the powervalves as well.Sorry to hear that your not happy with how the project turned out compared to a 125.From my notes on older posts I believe the next step would be replacing the stock Honda ignition module with a Viper racing one.
February 10, 2014 at 4:27 pm #21569
The early 1986/1987 reed block with the nylon stuffer is probably the best until you get upward of 10,500rpm. The stock Honda reed petals are fine, but this one is fitted with 2-stage Boyesens. Just cut of your inlet rubber level if it has protrusions and shape the stuffer and rubber to blend in nicely. Loads on Ebay
The what’s next question is always difficult. Depends on your intended use and where you want to end up.
Pipe, Ignition, Porting and head
February 11, 2014 at 5:02 am #21653
I’m not finding anything for upgraded ignition for a 2003 seems like the 2001 is readily available but not the 03.
Nigel it definetly had more power than a 125. The problem was that there was no top end. If you look at the power curve for an 03 it hits around 46 HP @ 8000 RPM after that it really falls off. I never messed with the OEM Mikuni carb so maybe it could have been dialed in and made better but the Air Striker was much better even before it was jetted. I ended up with a 180 main 55 pilot clip in mid position. Between that and the rad valve it really woke up the top end. Now it’s considerably faster than a 125 but not as fast as the CRF450.
February 11, 2014 at 6:27 pm #21808
Thanks Chris I’ll give that a try
February 12, 2014 at 7:29 am #21885
that horsepower and rpm seems low.The charts that I have seen on the forum for a mildly tuned 2001 CR250 are 55HP at 9500 and the curve up to that point is quite linear? And with a new box you get another 5hp and another 500 rpm with the same engine.
How does the kart compare to your CRF250 kart?
February 12, 2014 at 8:04 am #21888
It has more than the the CRF 250 That’s about the same as a stock honda (kart kit). I don’t know if the HP is acurate I’m going by what’s on the net.
February 12, 2014 at 9:06 am #21891
If you have the time,and feel like going through the old forum archive,you will find a few dyno curves posted by Ian at Viper,I remember there was one of his race engines and it was 62 hp,32ft/pounds torque,but I dont recall the max rpm.There just happened to be a curve of an almost stock 2001 cr250 posted which was perfect for me.
February 12, 2014 at 4:35 pm #21903
If the bone stock 03 bike engine is 45HP Which seems to be what the bike guys are saying That’s with the OEM Honda pipe. I got my pipe from Mike at Shark Shifter (Knowledgeable helpful guy). Lets assume the kart pipe has no effect on HP. I ran the kart all stock before doing any mods and I don’t have any way of knowing for sure but I think the carb and RAD valve probably added a good 5HP the difference was dramatic. If that’s true then it’s putting out around 50 HP.
I should probably think about getting rid of the power valves and going with Ian’s ignition system.
February 13, 2014 at 4:04 am #21934
Ian I don’t think I need the power valve and I don’t have TPS. Do you have an opinion on power out put with the mods I did (RAD valve + PWK Carb) along with your ignition system? Do you know what the HP is on the stock engine?
I sent you a PM for price and avaiability of your ignition system.
February 16, 2014 at 1:04 pm #22102
I would think you should have 50 Hp at present if your not exceeding 9,500. (You can see above that we have 56Hp at 9,500rpm).
The limiting factors will be compression ratio (too high?), ignition (Too much advance above 9,750 rpm) and pipe (depending on the rpm range and exhaust duration that it’s designed for)
I do have your mail. I should get to it tomorrow . . . . . Bloody hectic!!
Apologies to the people who are waiting for product, exhausts, heads, ignitions, etc. I expect to be fully caught up by the end of next week and thank you for your patience. This time of the year is always madness.
The new engine has taken over my life for the last 6 months, . . . . but we are getting there.
February 11, 2014 at 5:54 pm #21807
Let Ian update you, but I remember him talking about the after market ignitions didn’t work well, I believe it was because the stator assemble had a wacky voltage…. Then they bolted on the earlier stator assembly, but the timing had to be offset because the stator plate was timed differently on the two motors. Then I believe he was swapping the guts from one and putting on the case reed stator plate, so the timing was all good. At some point he was using some sort of regulator/filter to tame the stator voltage, I’m not sure if that’s what he ended up with or not.
Bottom line, nobody makes a direct fit after market CDI box for the case reed, at least nothing that works…
BTW Ignition timing is probably why your hitting a wall.. Try retarding the ignition as far as it will go, and see if the top end improves…
February 12, 2014 at 3:28 am #21838
February 12, 2014 at 5:19 pm #21908
On our race motors, we use the ’01 Honda Generator with Viper HPI box. This is a great race system, but generally speaking, it won’t operate powervalve, powerjet or work with TPS.
I think we are there now with a system that runs from the ’05-’07 generator. We are testing this year on our own karts. This comes in 2 versions. The first is as above, the second can run with powervalve, powerjet and TPS.
Here’s a dyno run of one of our CR250’s. It has over-rev to 11,500, but this run is only to 10,900:
You can zoom in by holding down the Ctrl key and tapping the + key
Ctrl and 0 (zero) to go back to normal
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