Project CRG HPV-4 Go Kart

Project CRG Go Kart: From Basket Case to Bitchin
By Mike Kojima

Lately the MotoIQ staff has been Karting a lot to get our speed fix for few bucks.  Running MotoIQ is an expensive endeavor and we have had to mostly give up racing cars for now to keep MotoIQ growing and strong. Looking for cheap used Kart parts on Craigslist one day, we happened upon an ad for what seemed like a lost cause.

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 Project CRG HPV-4 Go Kart
We thought that the kart was pretty rough and in poor condition but noticed that the engine looked pretty new.  Turning the crank by hand showed it to have good compression.  Basically we first bought the kart thinking it could be a source of spare parts for Christa's race program but now its just too nice.  It is way too big for Christa to drive though!

There was an early 2000’s vintage CRG Heron kart for sale for the very tempting price of $300, super cheap for such a machine.  The ad stated that it didn’t run but for $300, the picture looked like it was complete, straight and equipped with an IAME HPV engine of some sort and a Mychron III electronic dash.  Well we figured, it was worth a look since Italian CRG karts have an excellent reputation, the kart was new enough so its technology would not be too out of date and the parts on the kart were worth way more than $300. Used HPV engines usually go for around $1000 if they are in decent shape for instance.  Worst case we could use the engine as a spare for Christa.

 Project CRG HPV-4 Go Kart
The main reason why we bought the Kart was for its Parilla IAME HPV-4 engine (no it does not stand for Human Papillomavirus Vaccine ).  The engine looked to be in pretty good shape compared to the rest of the Kart.  An HPV engine usually goes for around $1800-2000 dollars new and around $1000 used.  The differences between the HPV-4 engine and the HPV-1 used in Christa's kart is a pipe tuned for more top end power and a larger WB3A Walbro carb.  The HPV-1 puts out around 8 hp and the HPV-4 puts out around 18 hp in stock form.

Checking the Kart out we found it to be very weathered but in OK shape, the frame was straight, by spinning the crank by hand, the engine had decent compression, but the brakes didn’t work.  The engine was an HPV-4, the most powerful variant of the venerable piston port two stroke IAME Parilla HPV engine range that pumps out 18-20 hp at around 16,000 rpm. The HPV race classes use a spec clutch and a spec pipe which we like because clutch and pipe tuning in other classes like the Yamaha KT100 classes are a major hassle and expense. The cool thing is the engine looked to be in good shape; it looked newer than the rest of the kart. The frame looked like it had been repainted in some parts with house paint. The steering wheel was oxidizing apart as was the old plastic bodywork, every part on the kart was rusted, especially the axle and fasteners but everything was there.  If anything we could use the kart for spare parts.

 Project CRG HPV-4 Go Kart
The other reason we bought the Kart was this Mychron electronic dash which was worth about the price of the Kart!

The owner told us he had bought the kart used a few years ago from a racer and had wanted to use it but could not figure out how to start it and had lost interest in it.  He pushed it out into the patio/back yard to rot and wanted to get rid of it as it was taking up too much room around his house.

 Project CRG HPV-4 Go Kart
The Walbro WB3A carburetor is a diaphragm pumper type that uses crankcase pressure pulses to pump the fuel.  It was hopelessly gummed up with old fuel and oil residue.  This was the reason why the engine would not run for the previous owner.  A good cleaning and an $18 rebuild kit make the engine a strong runner.  We added a foam filter from Empire Karts inside the airbox.

 Project CRG HPV-4 Go Kart

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Der Bruce
Der Brucelink
Wednesday, January 05, 2011 6:25 AM
What a deal! I'd say I need to be on Craigslist more, but that would only lead to more trouble than I've already gotten myself into!
Mike, I've been wondering and looking. Is there really a class that suits the 76" 200lb variety of racer who wants to be competitive? Or am I relegated to honing skills with autocross prior to getting to NASA or RLTA type of racing? A personal goal for me!
Mike Kojima
Mike Kojimalink
Wednesday, January 05, 2011 6:39 AM
I think your height won't be much of a problem, weight either because the minimum weight is something like 340 lbs (I am not 100% sure but something like this) You just won't have to ballast much or at all.

The pedals have a lot of adjustment and so does the seat mounting. They make pedal etender platforms if your legs are really long.

I think real karts are much faster and more fun than K1 and the indoor places. Once you have your kart, its much cheaper as well. I totaly rebuilt this kart over a weekend so they are pretty simple.
Wednesday, January 05, 2011 6:45 AM
That's awesome! I was thinking of doing it as well, but my size really puts me at a disadvantage (75.5" and over 250lbs) ha ha. There are a lot of Kart venues around where I live as well.
Markus Frank
Markus Franklink
Wednesday, January 05, 2011 8:26 AM
Nice article Mike!
Makes me wanna rebuild my oldschool air-cooled kart as well.
Wednesday, January 05, 2011 9:36 AM
Nice job with the resurrection! If I manage to make it down to Southern California I definitely want to go Karting with you guys.
Der Bruce
Der Brucelink
Wednesday, January 05, 2011 10:24 AM
Thanks Mike, I appreciate the feedback!

Now I just need to find a steal on a kart, there doesn't seem to be too many deals in the Pac. North every time I look. BTW, you're so right on how affordable parts and rebuild kits can be for these.
Wednesday, January 05, 2011 1:31 PM
The black oxide metric bolts are usually 12.9 grade. Are the stainless steel bolts from BB a replacement strong enough for this application? Are they even close in strength to a 8.8 grade metric bolt?
Mike Kojima
Mike Kojimalink
Wednesday, January 05, 2011 3:07 PM
Worst case its slightly less than 8.8 which is plenty good enough. I don't know the alloy though. We kept the stock bolts for king pin and steering linkage.
Thursday, January 06, 2011 3:45 AM
Most "commonly available" stainless steel alloys are exceptionally weak compared to tempered carbon steels used in bolts. Take 304 for instance, it has a yield strength of 250-300 MPa (~35-45 ksi). I imagine most of the socket cap bolts on the cart were 180 ksi UTS, and probably over 1000 MPa YS. There are very strong stainless steel bolts as well like the NAS630x series, which uses the nonmagnetic A289 Superalloy and has a 160 ksi UTS IIRC.

Typically non-certified stainless steel bolts are weaker in yield than 7075-T6 aluminum bolts, so I'd be VERY wary of running them for anything but a cosmetic/non-structural application. Anything below about 250 deg F on a vehicle and not stressed greatly and I'm inclined to go with aluminum bolts if I want something moderately fancy since they're lighter, don't have corrosion issues when anodized, and at least the material has a known YS.
Mike Kojima
Mike Kojimalink
Thursday, January 06, 2011 7:02 AM
I think the alloy is 316 so we are looking at over 500 MPa, the threads are rolled and the head is forged and a rolled undercut. Looks like a good bolt.

Its why I didn't use these bolts for steering and the motor mounts. I use stainless bolts a lot for karts and race cars for non critical areas. I think a corroded fastener is a lot weaker and race cars and karts always have dissimilar metal corrosion problems.
Rudy Pantaleon
Rudy Pantaleonlink
Thursday, July 07, 2011 2:51 PM
thanks for a great article, it inspired me to do the same with a 2002 CRG kart i found also on craigslist, i will be buying it this weekend, and im aking a loist of the things il'll need to do. i have a question, how did you modify the nerf bars to fit the new style bodywork?
Mike Kojima
Mike Kojimalink
Thursday, July 07, 2011 4:22 PM
We used the new style nerf bars. Our chassis could use both new style and old style.
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