CR 125 Build Help

Charles Frerking · Joined: 15 Aug 2012 Posts: 21

Ok, so I detonated the top end of the Vortex that came in the kart when I bought it. If I could say anything about the motor, I'd say it got me absolutely HOOKED on 125 shifters.

I picked up a 1994 CR 125 motor awhile back, in case this happened. My plan is to do a top and bottom end rebuild on the motor, and give it a good once-over. Other than the obvious like engine mount and exhaust, what are the absolute MUST haves to make this motor work in my kart?

I'm thinkin kart specific items like kick start block off, CDI box, etc.

Any help would be awesome! Trying to keep this thing on a budget!

Jim McMahon · Posted: Tue Feb 26, 2013 8:02 am Post subject:

You could rebuild the Vortex.....Often you can clean the nikasil with muratic acid, slap a piston in, check for air leaks, jet the thing up and go.

Failing that, what do you intend running with the CR? I noticed in your FS ad that you mentioned Stock Moto and if thats the case, this 94 aint gonna do it. Its not "Stock Moto" legal. However if the '94 is just for fun/practice or a track that doesnt care too much it'll be OK. Can you post pics of what you have? If the motor came off a bike you might consider a pumparound carb, there's some debate about that however.
_________________
CES Grattan pre-entry is open. TaG, Shifter, KPV, KT100, Animal\LO206, enduro or superkart.
Click Here to enter Grattan online

Charles Frerking · Joined: 15 Aug 2012 Posts: 21

Jim McMahon · Posted: Tue Feb 26, 2013 8:44 am Post subject:

Michael Taksa · Posted: Tue Feb 26, 2013 8:57 am Post subject:

What Jim said, plus fuel pump, or two, if you get pump around they will come with the carb, and a "pulse fitting" for the pump, be carefull on the mount, chances are you have a 32 mm frame, but the spacing is different between CRG, GP, PTK and Birel, Tony, Top, etc, 90 mm as opposed to 92 mm between the two right side frame rails

Charles Frerking · Joined: 15 Aug 2012 Posts: 21

Michael Taksa · Posted: Tue Feb 26, 2013 10:12 am Post subject:

To get motor from bike running:
install pulse fitting
get a filter or airbox for carb
get a carb
get exhaust pipe and silencer (need to mount these somehow, higly recommend the oringed exhaust header that mount to cylinder insted of stock one, and highly recommend "Hegar" exhaust and silenced mounts)
plumb fuel system wtih return line (need pumps and fuel line for this)
mount the motor, (need motor mount, I think MBA is 32-92)
This should get you going. Nice to have, but not necessary:
Remove and plug the power valves
Remove and plag kick start gears
May want to eventually remove kick start boss and go with straight reed cage as opposed to stock angeled one.
Eventually Mod the cylinder, lower head and get programmable ignition, but this is way down the list.

Charles Frerking · Joined: 15 Aug 2012 Posts: 21

Ace Rossi · Posted: Tue Feb 26, 2013 10:39 am Post subject:

Get with Jason at Swedetech for any or ALL your Honda stuff! If your gonna want less problems out if the box, look at a GFS... Smile

Vernon Head · Posted: Tue Feb 26, 2013 10:44 am Post subject:

Everybody uses the RLV R4 pipe, which comes with a mount.
You need a silencer that accepts the 1" OD of the pipe and a mount for it
Get the O-ringed exhaust header as already stated
Get the appropriate motor mount
Pick up a Keihin PWM or PWK 38mm carb, and pump-around fuel pump system (or GFS if money is not a problem)
You need some way to mount the fuel pump, the coil, and the ignition box. Lots of shops sell the mounts, or you can just bolt them to the back of the seat.
Get lots of 1/4" fuel line
You'll need a front gear that goes on the engine (typical sprint size: 15 or 16)
You'll need an axle gear (24, 25, 26 are good) and a 428 chain
Remove the power valve assembly and get the O-ringed plugs (they need to be blended) from a kart shop
Use 98 octane race gas or higher, 4-6 ounces of oil per gallon (synthetic or castor)
Get some CarbonTech medium reeds
Leave the cylinder, piston and head stock

joseph hollinger · Posted: Tue Feb 26, 2013 11:05 am Post subject:

www.metal-matrix.com/s
_________________
A lie gets halfway around the world before the truth has a chance to get its pants on. -- Winston Churchill.

Jim McMahon · Posted: Tue Feb 26, 2013 11:24 am Post subject:

Could you get the VHSH30 from your Vortex to go onto the CR? I think the boot on the CR might be bigger though. That's what I'd be doing! It's a great carb for a shifter, would require a little to get your jetting figured out but after that you'd be fine.
Yes the pumparound setup came about because of fuel metering issues under cornering. The pumparound removes the floats completely and maintains fuel level by way of flow and return lines on the carb, as well as dual fuel pumps.
another setup utilized is the square mikuni fuel pump with a built in bypass.
_________________
CES Grattan pre-entry is open. TaG, Shifter, KPV, KT100, Animal\LO206, enduro or superkart.
Click Here to enter Grattan online

Tyson Henry · Posted: Tue Feb 26, 2013 12:39 pm Post subject:

Also a standard PWK or PWM with a smaller valve inlet seat and needle. Works great also.

Charles Frerking · Joined: 15 Aug 2012 Posts: 21

this is all really helpful information, keep it coming. I feel more confident about doing this myself rather than purchasing a pre-prepped motor - I can handle all of these things.

Todd Kageals · Joined: 15 Jun 2012 Posts: 271

If you are just out for fun, you can keep the carb that came with the '94. My kart ran just as well with that setup as it did with the pump around. I was not racing it though. I just got finished rebuilding two motors for stock Honda. I had lots of questions like you. The guys here were great and provided lots of help. Feel free to ask any questions you have. For your purposes, forget the power valves if they are operational. No need to spend money on the plugs and you won't notice the .1 sec you lost! Pipe, silencer, radiator, mounts for all the above, water hose or kit, fuel pump and a T....should get you going for not too much money. Also, save money by running a CR125 radiator. I could not get temps up above 125 with that radiator even when on track.....but again.....I was just having fun, not racing at that time. Good luck.