Lets talk ktm 300 xc

[relentless rider]

Ya the 300xc has the linkage its the only thing I dislike , but it has more gound clearance than the none link bikes , just have to have a little trials riding background and press the front tire on the big stuff and pop it over instead of slide n the skid plate .

 

[mtn-doo]

most modern EFI has temp and baro corrections KTM doesnt do much of anything, but the jap bikes all do they just arent very accurate below 32F

The Husky, Berg and a couple others I have fiddled with have Baro comp or "smart system", like our auto's. Very nice. However, all of the MX450's, "race bikes", I have worked with have what is referred to as a "simple system". Inlet temp sensor only, corrections based on inlet temps, no density altitude corrections. Not bashing the MFG's though. No OEM would use a complex "smart system" for a moto bike. Makes sense why they don't. Race teams, pro team tuners, etc. will all make fuel maps for "that race day" anyway. No serious race team would rely on an "auto" system for their race bike. That is why Athena "Get" and all of the others provide fuel programmers for the professional Race Teams. They are not Baro-compensating systems. The enduro and street bikes would benefit and enjoy a smart system. There are several in those applications. More practical for an OEM to apply it there.

The new KTM450XCW,

KTM 450 XC-W ,
System; EFI / EMS

Quote, "The engine management system from keihin with electronic fuel injection and 42 mm (1.65 in) throttle body ensures spontaneous, powerful responsiveness and handling, along with maximum performance. Automatic temperature and altitude compensation are state of the art."

wow, pretty impressive....

 

[relentless rider]

There is a 2 stroke efi 500 on you tube .yz/cr500 fi is the key words to find it...but from the sounds of it the smart carb is the best

 

[summitboy]

Once u try a Smarty you will forget EFI LOL unless you want a little hairdryer !! They run very well. Ill have casts coming for my 200 and 300 !

 

[relentless rider]

What would stop a guy from turboing a 250/ 300/500 carb bike? Pressurize the flot bowl with a boost signal from the charge tube, have a small oil box with a pump ,

 

[summitboy]

Millar has a customer who has a turbo hill climber. Its pretty neat. I'd like to see some video LOL

 

[mtn-doo]

Once u try a Smarty you will forget EFI LOL unless you want a little hairdryer !! They run very well. Ill have casts coming for my 200 and 300 !

Very true. The technology is just hitting the market. The Smart carb is way beyond a simple EFI system. There is no comparison. 8/10% more power, near total atimoziation, altitude and temp compensating, 30% better fuel economy... Going with a current "simple EFI" system is practically going backwards. The simple EFI systems are like an old school carb, but worse,... they have no jetting options! That is why there is so much buzz about programmers. They need to have a way to electrically "re-jet" the simple EFI units. Expensive and a hassle. In some ways, worse than a carb. A properly jetted carb out-ran ALL of our EFI bikes. Just for thought...

 

[J&L Snowhawk]

Snowhawk

Can we get a rack set of these for a 800ho rotax. I might stick w a doo in hawk if possible

 

[mtn-doo]

Can we get a rack set of these for a 800ho rotax. I might stick w a doo in hawk if possible

Yes, they have some rack set's out there. Timing doubles with cables is a pain. Corey discussed rack sets and I believe they are now or will soon be available.
Give them a call.

 

[M5-]

Hopefully APT will have a 4 stroke carb soon. My KTM 450 is getting the single sump conversion and a punch out to 517. Its a different animal than the 570 Berg or the KTM 530/525/ which are strokers. 90% of the power increase from the big bore comes in below 1/2 throttle so I'll be able to pull the EXC gears a lot longer without revving the pi$$ out of my bike on a pull. That said it'll still wind out like the 450 because of the 450 stroke.

If I had an auto compensating carb for it I can't see needing a FI bike anytime soon. If this pans out like I hope the bike may not get any wheels put back on it, I just need to iron out the fueling, then I can go shopping for a 250 or 300, LOL.

As for the turbo carb bike it'd actually be pretty simple, no worse than a sled and I've done a bunch of those.


M5

 

[backcountryislife]

As an owner of an older 300, I'm giving serious consideration to putting a 380 top end on mine & using it for SB... I can't see anything that makes it ideal for SB hurting me in the mountains on rock.

55ish HP without much work, seems like that would do just fine.

I've ridden plenty of 4 strokes... no thanks. I won't buy one for a SB just to leave it sitting in the summer, I just hate how they feel. I also wouldn't ride a turbo yammie either though...

 

[byeatts]

As an owner of an older 300, I'm giving serious consideration to putting a 380 top end on mine & using it for SB... I can't see anything that makes it ideal for SB hurting me in the mountains on rock.

55ish HP without much work, seems like that would do just fine.

I've ridden plenty of 4 strokes... no thanks. I won't buy one for a SB just to leave it sitting in the summer, I just hate how they feel. I also wouldn't ride a turbo yammie either though...

Yep me too. been waiting for an EFI KTM 300

 

[backcountryislife]

Yep me too. been waiting for an EFI KTM 300

I ride the same elevation spread every day at lunch that I do on the weekends on my sleds...

I'm ok with carbs & simple tuning, but I wouldn't complain about EFI either I suppose, I just don't want to deal with a controller on my bike.

 

[Burn Down]

I ride the same elevation spread every day at lunch that I do on the weekends on my sleds...

I'm ok with carbs & simple tuning, but I wouldn't complain about EFI either I suppose, I just don't want to deal with a controller on my bike.

I think the smart carb might just be the ticket. I listened to the KX500 that mtn-doo built and it sounded amazing no stumbling or anything, just nice and crisp... The other 500's and smaller carb bikes stumbled or didn't run all that clean.

A 380 ktm would be a good one. I think I might start building a 500AF bike next summer. Might just ditch the sleds altogether.

 

[summitboy]

Careful with the 380's. I know APT has had issues gettin the regular 380s tuned. Might be worth a call to APT to find out.

 

[CATSLEDMAN1]

2 strokes and dun

got my new 136 snobike build bout done, off to powder coating now and some assembly required before 1st ride.

thanks for the encouraging 250 2 stroke comments and pm's. Still like some feed back on YZ 250 main jet........185 ready now.

Got two yz250 engines on my bench down to last nut this afternoon, one new crank and works, one just needs crank bearing, both sat for 4 or 5 years and condensation not kind to bearings with chitty oil, both came apart drier than dry on the inside...........way not good, but so far with parts, less than 700 in both when fresh.

can't say my 2 stroke bikes have suffered much when you ride from 4000-8000, especially with the newer flat slide Mik's &. Khieins seems the flatter the slide the less altitude affects them. When I get the 250 snow worthy, I'll dig in my junk box and try one of the early smart carbs, got a 36 lectron and a 38 metatron snow carb. Maybe plug a vent and make it smart. When I put the early smart carb on my 1982 ski doo racer it was quite a step up from the old round slide mikuni. Killer then was lack of needles available.

I'd buy lunch or beer or both if someone would stop by the shop with their smart carb, like to see what they changed this go round.

 

[mtn-doo]

got my new 136 snobike build bout done, off to powder coating now and some assembly required before 1st ride.

thanks for the encouraging 250 2 stroke comments and pm's. Still like some feed back on YZ 250 main jet........185 ready now.

Got two yz250 engines on my bench down to last nut this afternoon, one new crank and works, one just needs crank bearing, both sat for 4 or 5 years and condensation not kind to bearings with chitty oil, both came apart drier than dry on the inside...........way not good, but so far with parts, less than 700 in both when fresh.

can't say my 2 stroke bikes have suffered much when you ride from 4000-8000, especially with the newer flat slide Mik's &. Khieins seems the flatter the slide the less altitude affects them. When I get the 250 snow worthy, I'll dig in my junk box and try one of the early smart carbs, got a 36 lectron and a 38 metatron snow carb. Maybe plug a vent and make it smart. When I put the early smart carb on my 1982 ski doo racer it was quite a step up from the old round slide mikuni. Killer then was lack of needles available.

I'd buy lunch or beer or both if someone would stop by the shop with their smart carb, like to see what they changed this go round.

Lunch and Beer? How far away are you? Ha.. Wow, 20 years is a long time ago. Those principals began the basis of this technology. That technology has been so developed. Amazing where it is today. Would love to give you a tech tour, but I would suggest calling and visiting with Corey or go on line to powerapt.com and see what has become of that technology. Corey would love to hear some old lectron stories. He would love a visit from a guy like you. Give him a call. I'm in Kalispell. Would be glad to show you a smart carb. If you want to chat, give me a call. There is too much info to get in a quick reply. Randy 406-249-1132

 

[ktmrider714a]

I have a 11' 300xc That was a lot of fun on my Mountain horse short track last year. The bikes power is perfect for the Offroad/desert racing And it is in stock form except for the FMF silencer. My question is what add ons could I do to give it more power in the snow Yet not sacrifice it's ridability and Offroad performance in the dirt? In the snow I could always have more power I started mixing my gas a little bit richer On the snow bike because I was worried I was pushing it too hard. Any power adder suggestions?

 

[mtn-doo]

I have a 11' 300xc That was a lot of fun on my Mountain horse short track last year. The bikes power is perfect for the Offroad/desert racing And it is in stock form except for the FMF silencer. My question is what add ons could I do to give it more power in the snow Yet not sacrifice it's ridability and Offroad performance in the dirt? In the snow I could always have more power I started mixing my gas a little bit richer On the snow bike because I was worried I was pushing it too hard. Any power adder suggestions?

I just received a new 13, 300XC from a friend and customer for a build project as you are describing. He has given permission to make the project "public" as a thread for everyone to enjoy and maybe encourage others who have 250's, or 300's, 380's etc. I will start it soon.

As for power, I would recommend a fairly simple recipe.
- SX 180psi head, Slavens Racing
- mild porting, opens up and cleans ports. Strong bottom end and pulls hard all the way to the top.
- A DEP or PC pipe. More hp gains in the mid range and less fade on top.
- Red Exhaust Spring
- 250 SX CDI Box, more timing advance in the low and mid, builds power very quickly and is agressive, then a lot of over-rev on top.
- Make sure you have more than enough AIR. Any labor for air at all will greatly hurt your performance.
- 38MM Smart Carb. The APT carb nearly totally atomizes fuel. Even greater atomization than EFI . That equals more fuel surface area which gives a near total burn. Bigger "bang", more energy, better temps. That results in significant HP gains. Dyno test's on 4 stroke and 2-stroke engines resulted in an 8 - 10 % gain in HP across the board. On a 50HP bike, that is 4 to 5 HP. That is huge.

With this combo, you can accomplish a minimum of 5HP easily. That gets you pretty close to 450F numbers. Mid 50's. Don't be afraid to let her sing. The 2-stroke is designed to run WOT under a load for days. You are not even revving as high as a 450F. Your 250/300 stabilizes about 8 to 8.5K It sounds higher but is not. Your 4 stroke race motors are around 10K and rotating a cam and cycling valves at that RPM. Your 2 stroke isn't revving as high and no valve train involved. Let her rip!

 

[ktmrider714a]

Thanks for all the info mtn-doo, looks like I need to get busy just a question, what ratio do you premix your gas?