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TPI FUEL INJECTION: WILL IT REVIVE TWO-STROKES?


MXEditor

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Photo: KTM 300 EXC TPI - Six Days ISDE Edition 

Two-strokes are still a hot button when it comes to talking about dirt bikes these days. The old "two-stroke vs. four-stroke" debate has been beat to death and many of us are sick of it, but it rages on regardless. 

OK!! So four-strokes won, the Japanese factories, AMA and EPA got what they wanted and it's over...two-strokes, once the powerhouses of motocross, have now been relegated to the shed, gone out of fashion and not used by any top racing team in MX or SX. 

But the two-stroke is still gasping for air thanks to KTM and maybe even Honda... who officially stated they'd converted to a four-stroke company years ago, so that's a surprise! 

Why is it still here?  

Because it's awesome that's why...two-stroke engines pack more horsepower per pound than four-stroke engines, and even if that statistic was equal, the number of complicated, fragile and expensive parts in a modern four-stroke will always cost more to replace. 

Granted the replacement interval for four-stroke motorcycle engines has gotten longer and longer but you'll always have the complication and expense factors to think about...and that's good for the manufacturers...a nice balance between reliability and the need to replace worn parts makes for a good bottom line, but that's another discussion. Obviously less moving parts and making more HP/lb are excellent attributes that appeal to motorcyclists and maybe not so much to the manufacturers at large. 

Three years ago, I wrote an article that talked about advances in two-stroke technologies and the possibility that these technologies (EFI, DFI, TPI) could help the two-stroke gain more market share. One of the conclusions was that EFI using DFI was too expensive, bulky and heavy to be a reality on off-road motorcycles and that has turned out to be the case when looking at how the technology is presenting itself in production form. 

KTM have been the leaders in two-stroke motorcycle engine design and accompanying technologies so it was only natural that KTM would be the first major motorcycle manufacturer to provide a viable cleaner-burning technology to the two-stroke arena. The first bikes to display this technology are the KTM 250 EXC TPI and the KTM 300 EXC TPI. Honda also has filed a similar patent but has not put any examples into production and looking at the patent drawings, it appears to be an industrial design featuring a pushrod, not suited for high-performance applications.  

What does this advancement mean, and is this the saving grace technology that two-stroke fans have been waiting for? 

No. But OK, it's a great advancement in terms of the accomplishment - but how does it impact the market as a whole? It's great if you ride enduro bikes in the EU...but will TPI bring two-strokes back to off-road bikes?  

Maybe, but motocross only bikes won't be included. Why not?  

Because the Japanese factories have a lot of time and effort invested in four-stroke technology and it's not going away. They influenced the sanctioning bodies and promoters to implement unfair displacement rules that favor four-strokes. 

So why did KTM do it? 

Because a lot of folks ride two-stroke enduro bikes and KTM sells a lot of them both in Europe and here in the USA! Although KTM doesn't make two-stroke streetbikes per se, they do have two-stroke enduros with plates and lights and these enduro models are homologated for use on EU public roads, which means they have to adhere to tough new Euro4 emissions limits, as well as be prepared for the upcoming Euro5 restrictions. 

I've spent a lot of time in the EU and small bikes matter...in fact small motorcycles are the norm not the exception. You see lots of small two-stroke bikes and scooters...but the EU impose restrictions on emissions so these bikes need to have some kind of emissions/clean air technology if they are to survive and prosper.  

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Photo: New for 2018 KTM TPI Unit

KTM has come to the conclusion that Transfer Port Injection (TPI) is the EFI delivery system that has won the war against its Direct Fuel Injection (DFI) rival which was the technology explored earlier by KTM. Why? 

DFI seemed good and had been proven on the street in a few smaller two-stroke applications and a bunch of four-strokes but when all the support hardware and electronics were installed on an off-road machine, things didn't play as well. Weight, expense and complexity all played into KTM abandoning the DFI technology. But they didn't stop looking for a cleaner burning two-stroke solution. TPI wins that war until something better comes along. 

TPI wins for now because of its unique new design which according to KTM features "two lateral domes, holding the fuel injectors supplying fuel into the rear transfer ports. Thus the loss of unburnt fuel is reduced for less emissions, a more efficient combustion and reduced fuel consumption. A little tube in the back of the cylinder is connected with an intake pressure sensor, which supplies pressure data to the control unit."  

KTM continued: "The TPI engine is fitted with a newly developed throttle body made by Dell`Orto. It features a diameter of 39mm. The airflow is regulated by a butterfly connected with a twin-cable throttle cam, which is operated by a new handlebar throttle assembly.  A throttle position sensor provides airflow data to the control unit, while a bypass screw allows the regulation of the idle speed. The cold start device also opens a bypass supplying more air. Via an oil intake tube oil supplied from the oil pump is mixed with the incoming air to lubricate crankshaft bearings and cylinder/piston etc." 

Another great advantage is no more pre-mixing the fuel with oil, there is now an oil tank and metering system controlled by the ECU and this allows a very precise, variable and minimal mixture of oil to be burnt resulting in lower emissions.  

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Photo: KTM 2-Stroke TPI Engine for 2018

Smaller niche companies that make two-stroke off-road machines in the same niche could be expected to follow this trend, possibly by licensing the technology from KTM or creating their own variants. This could include brands like Sherco, Ossa, Beta, TM, Gas Gas and the KTM-owned Husqvarna brand. 

So more cool bikes in Europe but what does it mean for riders in the USA? 

It could mean a little or a lot. Could this mean that KTM will be able to certify two-strokes with an emissions label indicating for "on-highway use"? This would be the hurdle to cross...once they've passed emission in places like Californis, the whole pie is up for grabs – here is what the California regulation says now: 

"Off-highway motorcycles must have an emission label affixed to the vehicle indicating certification by the manufacturer for on-highway use when converting to on-highway or dual registration. Registration guidelines for off-highway motorcycles converting to on-highway or dual registration require verification of the emission label." 

For KTM two-stroke riders, this technology would make sense to scale to the whole two-stroke lineup from EXC to SX. Imagine a version of the 250 EXC with lights that's legal for the streets here...and you ride it to work like the ultimate hooligan, or just be able to get a street plate to ride to your favorite riding destination. 

In conclusion, most people thought two-stroke was dead but maybe, just maybe, technology like TPI will make it feasable for KTM to expand their offerings using this technology. The first step it seems would be the ability to pass emissions both in the EU and USA, then maybe apply it to US market machines.  

If that happens we'll be first in line to try them. 

__________________________

ThumperTalk wants Your Comments On This Article:

Is this a stopgap or a technological step forward?

Would you ride a two-stroke street bike?

Aren't those Six Day graphics awesome?

Tell us what you think below!!

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I just sold my 250 XC to buy a Husky 350.  I originally planned to buy the 350 FS, because it's got a plate, allowing me to ride dual sports, and to tie trail systems together in So Cal.  I rode the FS & was disappointed by the power.  It just felt sluggish to me.  I thought about buying the 450FS to get some of the power back, but I wanted a smaller, lighter power plant.  So, I opted out of the FS & bought the 350 FX, because the motor is just so much better when emissions aren't taken into account.  And it's even dual mapped for real punch if I want it.  That said, if anyone produces a 2 stroke (with all it's benefits) with a plate, and it can get out of its own way, I'll buy it in a heartbeat.  I just love the power curve, the light weight, and the easy & cheap maintainability of a 2 stroke motor.

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Lol, a heavier, more complex motor... And obviously coming at more cost too... Sounds like a very 4t'ish problem... 

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Back in the eighties when Orbital was playing around with the high pressure injection two stroke I had hopes that the world would get to experience efficient and powerful two stroke power in both two and four wheels.  However, this technology was bought by general motors and was apparently shelved.  The transfer port injection seems ideal for motorcycles, since space and weight is at a premium.. no super high pressure pump needed!  I would love to see this technology revive the smell of racing castor.. but with the investment in four stroke technology that has been laid out by the manufacturers, will they be willing to invest in TPI?  Obviously KTM is.. but will the others?  That remains to be seen.. Money is a big issue for the Japanese right now...   

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But the two-stroke is still gasping for air thanks to KTM and maybe even Honda...

What does Honda have up its sleeve? Don't tease me!!!  Spill it!  

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KTM customers buy ktm's largely because they change every year and these days marketing is everything.  TPI is a big change and it will move units.

The other oem's met the new regs without a complicated FI system, so obviously they didnt NEED to do it, but the customers had been screaming to get some fancy tech on 2 strokes for years.

It does seem to be a significant net gain in complexity for a barely discernible gain in efficiency/rideability. If there are teething issues, it could play really well into the hands of Beta and Gas Gas.

One thing i've never understood over the years however is this 'fragility' concept on the 4 stroke.  I found on the two stroke i was way more likely to damage a pipe, drown the engine, nip a ring on a port/lean seize etc.  The valve trains are pretty rudimentary and reliable on the 4T enduro's (not revved like an mx bike).

Bikes havent really advanced in the last 10 years IMO.  The last real frontier for improvement is in suspension tech IMO.  Engines, weights, ergo's etc are all about as optimised as they can practically get.

 

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"The cold start device also opens a bypass supplying more air."  ??? Don't we need more fuel to start a cold engine  ?

Or is this for hot starts after a stall ???

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2-strokes dead?  What planet are you from?

Sure....4's have taken over the MX/SX world, but that is not a level playing field. If it was, I bet the results would be different.

Looking at offroad riding, extreme enduro, endurocross, etc. the 2-smokes rule. They are lighter, more nimble and as noted, put out more power for an equivalent displacement.
 

Personally, I see more and more of my offroad riding friends ditching their 4-strokes and becoming smokers.

Dead? Hardly....

 

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Will it revive the two stroke fever? No. Glaringly no. Because we all know that 2 strokes can not compete with the 4 stroke equivalent under AMA rules. So the YZ250 makes 45 hp. Great. When it's competition off the show room floor is cracking out 53 to 60hp with better tracking suspension and power delivery due to years of testing and design, it's a moot point. Add in the expense of the efi system and it could actually kill the two stroke all together.

The economy is what will revive two stroke. When people are looking to join a sport on a budget they are going to look for fun cheap entry level machines. 10k for a bike plus the parts and upkeep shy people away. Where as 6k for a 125 or 7k for a 250 with minimal parts cost and knowledge to due the required maintenance, it's a win. As the economy improves more people will buy entry level machines, which is why Yamaha and KTM are still offering mx versions. Off road is a whole different story.

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15 hours ago, trailrydr9 said:

But the two-stroke is still gasping for air thanks to KTM and maybe even Honda...

What does Honda have up its sleeve? Don't tease me!!!  Spill it!  

Honda has nothing up it's sleeve, there will be no new two stroke motorcycle coming from Honda ~ PERIOD.  Honda declared that it was a 4 stroke company years ago ~ make that DECADES ago.  Even in the hay day of 500cc two stroke GP's Honda tried racing a 4 stroke and got their rear handed to them (Google Honda NR500).  Nope, Honda will never build a new two stroke motorcycle ever again unless their mandated to do so.

 

16 hours ago, Monk said:

Lol, a heavier, more complex motor... And obviously coming at more cost too... Sounds like a very 4t'ish problem... 

Heavier by "about" 5 pounds, but no more complex because the basic 2 stroke design didn't change.  Nothing firm on the cost but even if it's the same as a 4t it'll still be lighter and easier to work on than any 4t.  FI is a good thing and KTM will sell out, plan on seeing more and more of these as riders learn of the advantages of FI, just like the 4t guys did. 

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2 stroke will go on in any case , people love it expecially for enduro , 300s 2 strokes are the kings of extreme enduro , just see Jarvis , Walker , Gomez , Roman , Young , Bolt ... do I have to go on ?

There is nothing like a high torque 50-55 hp 300 2 strokes , pure power .

I think EFI is the future for a 500s 2 strokes come back in MotoGP

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Two strokes today are cross country/enduro race bikes but not suitable for MX/SX.  I currently have a 2011 250xcw which is a great bike.  I live in the central sierra mountains near Yosemite NP.  The forest district closest to me (MiWok district in Stanislaus NF) requires a Californication Green sticker to ride in the summer months.  So my smoker ends up in storage.  Many riders in CA avoid non emission compliant (red sticker) bikes for this reason.  

The articles here talks about making the TPI bike into a plated street legal dual sport.  That is a pretty big step.  I hope KTM just gets the bike certified to meet CA off road emissions so I can get a green sticker on it.  If the bike can meet Euro 4 street requirements I'd hope it can meet CA off road requirements.  Not sure how much this costs to do the certification but it will be a game changer here in the Republic of CA.

I am saving up now to buy a TPI smoker but also sitting on the fence to see how this unfolds.  The big wants compared to my 2011 are the counter balancer, better mileage, no premix, and updated suspension.  I suspect it will be 2019 before I am really in the market.  

Edited by ktm_fastguy
typo

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3 hours ago, andrzej said:

2-strokes dead?  What planet are you from?

Sure....4's have taken over the MX/SX world, but that is not a level playing field. If it was, I bet the results would be different.

Looking at offroad riding, extreme enduro, endurocross, etc. the 2-smokes rule. They are lighter, more nimble and as noted, put out more power for an equivalent displacement.
 

Personally, I see more and more of my offroad riding friends ditching their 4-strokes and becoming smokers.

Dead? Hardly....

 

Agreed 100%. 2t are alive and well because they're good at what they do and are simple and reliable machines, perfect for the woods! I'd rather have a 4t on the MX track but a 2t anywhere else. 

Edit: btw I had no issues registering my 2 stroke Beta 300rr  for street use in SC.

Edited by jacob429
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If I was an enduro or hair rider I wouldn't think twice, the 2 rules. However I ride MX and the rules here are unfair to say the least. I want to shed the weight and the complexity of my 4, BUT cannot even begin to compete with motors with twice the displacement. 

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One of my concerns is that the Kahleephoneeahh Apparatchik Accolytes (the KAA?) would simply move the bar higher were KTM/others to come out with 2T meeting California license plate emissions requirements.

Otherwise, I'd welcome pretty much any technology that gets me a plated, lightweight, tractable, reliable, easy-maintenance, "affordable", relatively powerful, off-roadable bike with easy parts-availability and an assured range of about 100 miles per tankful or battery charge (and reasonably-quick re-charge time if applicable).  What currently hits closest to these marks for me is my California-plated, suspension-modified, instrumented 03 CRF230F Honda.

Edited by BSAVictor

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21 minutes ago, BSAVictor said:

One of my concerns is that the Kahleephoneeahh Apparatchik Accolytes (the KAA?) would simply move the bar higher were KTM/others to come out with 2T meeting California license plate emissions requirements.

Otherwise, I'd welcome pretty much any technology that gets me a plated, lightweight, tractable, reliable, easy-maintenance, "affordable", relatively powerful, off-roadable bike with easy parts-availability and an assured range of about 100 miles per tankful or battery charge (and reasonably-quick re-charge time if applicable).  What currently hits closest to these marks for me is my California-plated, suspension-modified, instrumented 03 CRF230F Honda.

I think the Beta 250 or 300rr 2 strokes meet all these marks and pretty sure they're green sticker.. What can I say I'm a Beta guy now. 

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Not going to revive 2 strokes, just going to keep them as an option. Also going to add price increases and that will keep the so called revival in check as more and more are buying used due to the crazy expense of buying new... this is just extinction slowing down a bit... (dirt bikes in general). This is a remote saving grace that is far more plausible in the big picture than over priced e-bikes. 

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Having only recently(this May) joined the 21st century with a 450X, the thrill of my 2 stroke is still fresh. Yes the 450 is amazing and has a plate, a kickstand, and headlight. Exactly what I was wanting. It's predecessor, a highly modified '97 CR500, does not give up anything in the performance dept. Yep the 450 has better suspension- so they say, I find it is a push with the 500 due to its pork. Power delivery smoother? nope I dciked with the 450, it is violent and hard on the rear tire. Which one would I rather do a top end on? Hmm both my wallet and shop time prefer the 500. The 500 is quicker and faster, it is fun on the trails(which is all I ride now). Give me an injected one with a start button and a plate, and I am ALL in!!!

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43 minutes ago, jacob429 said:

I think the Beta 250 or 300rr 2 strokes meet all these marks and pretty sure they're green sticker.. What can I say I'm a Beta guy now. 

Yeah I'm all for growing new competition for "the big player companies"; that pushes big guys to keep improving so as to keep their customers, which in turn keeps doors open for customers to keep winning in satisfaction--whether by way of older big guy producers or newer growing producers. 

I shoulda made it clearer that I want a California license-plated bike.  Also, I'd like to see more bricks-and-mortar Beta shops, and more Beta owners before I would take the plunge.  I'm no longer any sort of "early" adopter. (I do admit to occasional bouts of "early synthesizing", tho.)  I guess so much stuff is online-ordering---with relatively quick delivery---that the bricks/mortar issue is less of a problem!

P.S.  Also wrongly omitted my requirement for e-start on an internal-combustion-motored bike!

Edited by BSAVictor

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19 hours ago, Terracer said:

Back in the eighties when Orbital was playing around with the high pressure injection two stroke I had hopes that the world would get to experience efficient and powerful two stroke power in both two and four wheels.  However, this technology was bought by general motors and was apparently shelved.  The transfer port injection seems ideal for motorcycles, since space and weight is at a premium.. no super high pressure pump needed!  I would love to see this technology revive the smell of racing castor.. but with the investment in four stroke technology that has been laid out by the manufacturers, will they be willing to invest in TPI?  Obviously KTM is.. but will the others?  That remains to be seen.. Money is a big issue for the Japanese right now...   

I thought I read Honda had purchased Orbital  Engine or the technology around the Orbital design.  This was way back in the 90s I think.

I see more and more 2 strokes at the Enduros and Rougher Dual Sport rides I attend.

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1 hour ago, BSAVictor said:

Yeah I'm all for growing new competition for "the big player companies"; that pushes big guys to keep improving so as to keep their customers, which in turn keeps doors open for customers to keep winning in satisfaction--whether by way of older big guy producers or newer growing producers. 

I shoulda made it clearer that I want a California license-plated bike.  Also, I'd like to see more bricks-and-mortar Beta shops, and more Beta owners before I would take the plunge.  I'm no longer any sort of "early" adopter. (I do admit to occasional bouts of "early synthesizing", tho.)  I guess so much stuff is online-ordering---with relatively quick delivery---that the bricks/mortar issue is less of a problem!

P.S.  Also wrongly omitted my requirement for e-start on an internal-combustion-motored bike!

Not sure what your plating requirements are there. Had no issues getting my Beta 300rr plated in SC. I get your point about shops, I'd have to go over 3 hours to the nearest Beta dealer. Normally I do just about every bit of service myself so that makes things easier. 

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Reviving 2 strokes??? To me these bikes are just what are being sold to us. It's either buy it or not. Is that reviving 2 strokes?

As far as 2 strokes and mx? It's politics. It's companies protecting their investments in 4 strokes that screw up 2 strokes. USA doesn't have pros racing 2 strokes.. well yea if it's a 250 racing against a 450. That's all about companies. It's not about what dirt bike riders want..Meanwhile the price of riding goes up and up.  Just look at the Canadian MX races. They allowed 2 stroke 250's to race with 4 stroke 250's.. That was the first year.. then there was grumbling because the 2 strokes were smoking the 4 strokes so they changed the rules that the 2 stroke 250's had to be stock the next year to be able to race the 4 strokes.. I guess that's a level playing field now? At least 2 stroke 250's are on the line with 4 stroke 250's in the pros.  I like a carbed 2 stroke.. maybe a smart carbed 2 stroke?. ..And I'd still love a big bore 2 stroke to come back.. maybe not a 500 but a nice 350 or 400 cc . He since we are here and now where there's fuel injected 2 strokes.. ..Manufacturers can do almost anything they want. Dirt bike riders are like piggies and we just get what they give us to buy.. and what do we do? We just buy.... I'm keeping my carbed bikes though.. and I'm going to keep riding them and watch what happens with the new bikes.  I just watched this the other day.

 

 

 

Edited by hawaiidirtrider
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I like all tech that go's into these bikes, I sometime wonder if, why bike company's arn't working on turbo diesel FI engines? yes in a bike! I know it sounds strange but if the big co-makers really put some R & D in to the TDI it could do very well? check this out http://newatlas.com/go/4272/

http://www.dieselmotorcycles.com/technology.html

The torque, the fuel range, compact engines, turbo FI or supercharged, reliability? Yamaha has been manufacturing small diesel engines for years...

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2 strokes are not dead in my world. In fact, they are very much alive. New tech is great, and if the west coast nazi state can approve it for dual purpose it will be great for all the coolaiders. I would love to see this tech explode in all makes.

Side note: Not all states are nuts like the west coast nutters, you can put a plate on any bike you like in some states, and many do. There are even loop holes in the comi state of CA. You see all sorts of bikes that shouldn't be plated, and yet, they are illegally. 

If the west coast sets the pace for plated bikes, we are in for a rude awakening. 

 

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From 2020 EFI would be the future for 2 stroke , now manufacturers can do some tricks to pass emissions tests , but with EURO 5 and 6 that won't be enough , even the ktm solution for tpi it's not enough as only the direct injection can pass ( if you see some TPI unboxings , you can see that it still comes with closed exhaust , so they had not solved completely the problem ) .

Beta , Sherco and Tm are ready with EFI , lets see how it goes .

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      Was riding my 450, testing out a new speedometer, shifted into 2nd, moved a couple feet and heard a loud crack noise from engine area. Will not turn over, sounds like its jammed or seized from moving. My guess is tat the timing chain just exploded and fouled everything up. Haven't found time to open it up. Thought I'd go to forums to get some opinions on what to look at first. As far as back round info: Engine was opened up to replace some gaskets. replaced my valves and adjusted rockers to .05mm. Timing chain taken apart a couple times. Shifts through gears fine even though it doesn't run. I am not very fond of ktms or dirt bikes in general but fairly mechanically inclined. I don't know what to do so here I am on the forums. Any help or advice is much appreciated. Thank you.
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