Planet Minis

sdg920 · 07-23-2008, 03:35 PM

I have an 04 SDG and want to bump the horsepower! Does anyone know the best big bore kits for these 3 valve heads?

SHADE · 07-23-2008, 03:43 PM

Sell the the motor, and get a yx or a gpx worked.

Kurlon · 07-23-2008, 03:44 PM

Your cylinder can be safely bored to 54mm, possibly further but I don't have any confirmation of that. You'll need to get a short rod/6v piston and cut your own valve reliefs in it. Crower G2 grind cams have been confirmed to work in the 3v head.

Upgrade the exhaust, the stock pipe has a goobery weld at the motor end that chokes it down, and isn't mandrel bent, both of which are robbing you of HP. TBolt has access to X2 pipes for a reasonable cost that are slightly larger, with much better welds and bends, but look similar so you can maintain the 'sleeper' look of a 'stock' bike. : ) (Or you can go CHP Ultima, works well on those motors.)

sdg920 · 07-23-2008, 11:01 PM

who do you suggest for the piston and how to put the valve reliefs in the top of it? that seems like alot of work....any other tips

Kurlon · 07-24-2008, 06:35 AM

I like Dr ATV for oddball build parts, and you could use a dremel to grind out valve reliefs, or find a machine shop to fly cut some for you.

sdg920 · 07-24-2008, 10:00 PM

Im new to this whole thing so bear with me...should i just buy a dratv 54mm bore cylinder? and would i have to buy a bigger crank? any advice will be greatly appreciated...

Kurlon · 07-25-2008, 06:42 AM

The SDG 3v 107 motor has it's own unique stud spacing, so a Dr ATV cylinder won't slip on. Which is really too bad as the stock cylinder weighs a ton. You should be able to find a motorcycle or machine shop in the area that can bore your cylinder out for you. Get your piston FIRST so they have something to bore it to.

If Mark at AHP Minis has any left, there are stock bore high compression pistons that will just drop in. He modified a batch of his high comp pistons with the correct valve reliefs for the 3v head, and they worked really well. I think he's sold out of them though, check with him to make sure.

You won't need to change your crank, so no worries there. If you want to do some work on the bottom end, you can get a lightened oil sling for a GPX 125 and install that, along with a lightened flywheel. It'll help make the motor spin up a little quicker. Call up SDG USA and order a 'shift fix kit' while you're at it, just as a precaution.

sdg920 · 07-25-2008, 11:59 PM

I believe you just gave me the best info i have gotten since i've had this bike...ive been doing nothing but asking ?? to some of the local, more exp. riders, but you just nailed it on the head. Ive been riding in the Midwest Pit Bike series and feel its time to go faster, maybe ride 12" class!

Kurlon · 07-26-2008, 06:40 AM

See if you can find a shop that specializes in tuning inline four road race bikes, specifically porting. (They know how to port a multi-valve intake, slightly different rules from a normal 2v head.) Give them the head and see what they can do with it. You should be able to unlock some ponies there as well.

sdg920 · 07-26-2008, 10:05 AM

I know just the guy for the job! thanks alot man

Kurlon · 07-26-2008, 11:30 AM

Sweet, keep me in the loop, I wanna know how it comes out.

07-23-2008, 03:35 PM	#1 (permalink)
sdg920 PM Newbie Join Date: Jun 2008 Posts: 10	Sdg??? I have an 04 SDG and want to bump the horsepower! Does anyone know the best big bore kits for these 3 valve heads?

07-23-2008, 03:43 PM	#2 (permalink)
SHADE The Hammer Join Date: Jan 2005 Location: So*Cal Posts: 5,137 Awards Showcase Total Awards: 1	Re: Sdg??? Sell the the motor, and get a yx or a gpx worked.

07-23-2008, 03:44 PM	#3 (permalink)
Kurlon Baron Von BanHammer Join Date: Feb 2005 Location: Windham, ME Posts: 7,857	Re: Sdg??? Your cylinder can be safely bored to 54mm, possibly further but I don't have any confirmation of that. You'll need to get a short rod/6v piston and cut your own valve reliefs in it. Crower G2 grind cams have been confirmed to work in the 3v head. Upgrade the exhaust, the stock pipe has a goobery weld at the motor end that chokes it down, and isn't mandrel bent, both of which are robbing you of HP. TBolt has access to X2 pipes for a reasonable cost that are slightly larger, with much better welds and bends, but look similar so you can maintain the 'sleeper' look of a 'stock' bike. : ) (Or you can go CHP Ultima, works well on those motors.) __________________ http://www.x386.net/TTR 2004 ST3 - 'Duckie'?!?! 2005 CRF70RR - MiniGP Weapon 2005 CRF70 - Dirt Donk 2008 Pitster Pro X4 Motard 1991 GS500E - LRRS/CCS #771

07-23-2008, 11:01 PM	#4 (permalink)
sdg920 PM Newbie Join Date: Jun 2008 Posts: 10	Re: Sdg??? who do you suggest for the piston and how to put the valve reliefs in the top of it? that seems like alot of work....any other tips

07-24-2008, 06:35 AM	#5 (permalink)
Kurlon Baron Von BanHammer Join Date: Feb 2005 Location: Windham, ME Posts: 7,857	Re: Sdg??? I like Dr ATV for oddball build parts, and you could use a dremel to grind out valve reliefs, or find a machine shop to fly cut some for you. __________________ http://www.x386.net/TTR 2004 ST3 - 'Duckie'?!?! 2005 CRF70RR - MiniGP Weapon 2005 CRF70 - Dirt Donk 2008 Pitster Pro X4 Motard 1991 GS500E - LRRS/CCS #771

07-24-2008, 10:00 PM	#6 (permalink)
sdg920 PM Newbie Join Date: Jun 2008 Posts: 10	Re: Sdg??? Im new to this whole thing so bear with me...should i just buy a dratv 54mm bore cylinder? and would i have to buy a bigger crank? any advice will be greatly appreciated...

07-25-2008, 06:42 AM	#7 (permalink)
Kurlon Baron Von BanHammer Join Date: Feb 2005 Location: Windham, ME Posts: 7,857	Re: Sdg??? The SDG 3v 107 motor has it's own unique stud spacing, so a Dr ATV cylinder won't slip on. Which is really too bad as the stock cylinder weighs a ton. You should be able to find a motorcycle or machine shop in the area that can bore your cylinder out for you. Get your piston FIRST so they have something to bore it to. If Mark at AHP Minis has any left, there are stock bore high compression pistons that will just drop in. He modified a batch of his high comp pistons with the correct valve reliefs for the 3v head, and they worked really well. I think he's sold out of them though, check with him to make sure. You won't need to change your crank, so no worries there. If you want to do some work on the bottom end, you can get a lightened oil sling for a GPX 125 and install that, along with a lightened flywheel. It'll help make the motor spin up a little quicker. Call up SDG USA and order a 'shift fix kit' while you're at it, just as a precaution. __________________ http://www.x386.net/TTR 2004 ST3 - 'Duckie'?!?! 2005 CRF70RR - MiniGP Weapon 2005 CRF70 - Dirt Donk 2008 Pitster Pro X4 Motard 1991 GS500E - LRRS/CCS #771

07-25-2008, 11:59 PM	#8 (permalink)
sdg920 PM Newbie Join Date: Jun 2008 Posts: 10	Re: Sdg??? I believe you just gave me the best info i have gotten since i've had this bike...ive been doing nothing but asking ?? to some of the local, more exp. riders, but you just nailed it on the head. Ive been riding in the Midwest Pit Bike series and feel its time to go faster, maybe ride 12" class!

07-26-2008, 06:40 AM	#9 (permalink)
Kurlon Baron Von BanHammer Join Date: Feb 2005 Location: Windham, ME Posts: 7,857	Re: Sdg??? See if you can find a shop that specializes in tuning inline four road race bikes, specifically porting. (They know how to port a multi-valve intake, slightly different rules from a normal 2v head.) Give them the head and see what they can do with it. You should be able to unlock some ponies there as well. __________________ http://www.x386.net/TTR 2004 ST3 - 'Duckie'?!?! 2005 CRF70RR - MiniGP Weapon 2005 CRF70 - Dirt Donk 2008 Pitster Pro X4 Motard 1991 GS500E - LRRS/CCS #771

07-26-2008, 10:05 AM	#10 (permalink)
sdg920 PM Newbie Join Date: Jun 2008 Posts: 10	Re: Sdg??? I know just the guy for the job! thanks alot man

07-26-2008, 11:30 AM	#11 (permalink)
Kurlon Baron Von BanHammer Join Date: Feb 2005 Location: Windham, ME Posts: 7,857	Re: Sdg??? Sweet, keep me in the loop, I wanna know how it comes out. __________________ http://www.x386.net/TTR 2004 ST3 - 'Duckie'?!?! 2005 CRF70RR - MiniGP Weapon 2005 CRF70 - Dirt Donk 2008 Pitster Pro X4 Motard 1991 GS500E - LRRS/CCS #771

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