2t jetting question

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giantjoe
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2t jetting question

Post by giantjoe »

So I was at a dealership investigating whether my next bike will be a 2t or 4t and the dealer said something that really scared me. A 2t requires rejetting every 10 degrees!? Is there any merit to this statement?

If I get a new bike, it will either be a light 2t, or a fuel injected 4t, I'm trying to discern if the maintenance required for each would offset the negatives of the other.

According to rumor:
2t + lightweight, easy to work on, less $ for rebuild, more power
2t - stalls easier, peaky power, mix gas, rejet often, new top end yearly.

4t with EFI + never rejet, can tractor well, smooth power delivery, easy fueling
4t with EFI - heavy, computer failures possible, expensive new top end every couple years, bike itself is expensive

Discuss
Last edited by giantjoe on Sun Mar 27, 2011 3:25 pm, edited 1 time in total.
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Bruce
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Re: 2t jetting question

Post by Bruce »

What is a carb??? lol With the EFI, I need to start my bike every time I want to ride it!
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Re: 2t jetting question

Post by steve-o »

giantjoe wrote:So I was at a dealership investigating whether my next bike will be a 2t or 4t and the dealer said something that really scared me. A 2t requires rejetting every 10 degrees!? Is there any merit to this statement? NO

2t - rejet often, new top end yearly. NO

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Re: 2t jetting question

Post by Dobi »

Perhaps you were at the wrong dealership. I get 2 seasons out of a top end easily, and jetting is set once and left (unless you go to sea level). I have ridden here, Moab, Kookanusa, Kelowna, and Cornergrass and never bothered to re-jet.

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Re: 2t jetting question

Post by Dakota_c69 »

My first off-road dirt bike was a 250EXC 2T, actually my first dirt bike. I bought it because KTM was the only company producing off-road 2T bikes. At the time, I picked two stroke for all the reasons you listed in your 'Pros' list. From your cons list, the only one of them that was an issue with me was the peaky power. I never had to rejet, I rebuilt once in 2, almost 3 years and it wasn't in terrible need of it, and that rebuild was Cheap, even though it was done by a mechanic. My problem with the power was I was bad at riding it "on the pipe" (lack of experience). Don't get me wrong, I really had a lot of fun on that bike, but I always found myself trying to find a way to get into the power band less frantically. I lowered the gearing and played with the power-valve, etc. That bike could lug really good for a 2T. The key to that statement is the "for a 2T" part. One other con I found about the 2T that I didn't like was that is wasn't stable. The front end deflected and in the higher speed stuff, it didn't feel planted. Of course, I didn't know any of this until I rode a WR450. I couldn't believe the difference that stability made to my confidence level.

In the end my 2 Stroke was stolen and I have been away from dirt biking for 5 years or so. Last year I got a chance to ride a 450XCW, and it convinced me I needed a new dirt bike. This time I went with the four stroke (Husaberg FE570). I am now a beginner alllll over again. I had the bike out in the Irricana gravel pit and got to try it out a little. The slick conditions and my lack of skills made me take it slow, but after a few minutes, I was comfortable enough to try some of the smaller hills. Riding a 570 now (wanted a 450, but this deal came along) and it has HUGE power and that made the hills FLAT. After a couple of quick zips up those little hills, I tried some experimenting with some of the issues I had when I rode my 2T. When riding the 2T, I always struggled with the sudden hill. What I mean by that is, you come around a corner in 2nd gear loping along and there sits a hill climb. Now you're s'posed to clutch it onto 'the pipe' and tear to the top....Me, not so good at that. So with my new (to me) 570 I approached some of those hills in second gear just barely moving and tried making the climb. Well, with that four stroke there is NO Pipe. It is all pipe, there is always torque....and I liked it alot. This may all be a different story in real single-track conditions, but I like my chances.

The other side of this coin is I worried about all the Cons in your 4 Stroke list too. Reliability wise, the thing I am considering was my bike used to be a member of the Corner Grass Racing Team (Thanks Lee) and the bike survived that environment for 40+ hours with no issues and runs flawlessly today. Articles like this helped as well:

http://husaberg.org/forum/viewtopic.php?f=5&t=14210

I am ABSOLUTELY sure it's life will be much easier with me, so if CGRT didn't break it, I can't imagine I will. I, however, am not looking forward to the rebuild $$$. As far as initial pricing being high, I have seen some REALLY good pricing on the 2010 Bergs!!!

Sorry for the long post...
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Re: 2t jetting question

Post by Dobi »

Glen, we can do the top end on that Husaberg for not much more $ than a 2 stroke and in not that much more time. You just have to supply the Big Macs.

I re-did the piston and rings on my last 4 stroke (450SXF) at 105hrs and the scuff had barely started to wear on the piston and the valves had yet to move from new.

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Re: 2t jetting question

Post by giantjoe »

The biggest problem I'm facing is that the DR-Z is bulletproof. Maintenance is low, I can just ride the thing and it works. But with that rock solid reliability comes weight. A lot of weight. I haven't ridden a 2t in 20 years and it was a CR80, that bike felt like it was binary. Either dog slow, or like a bullet out of a gun.

I have so much confusion, I need to ride a 2t a few times to see if the weight savings is really that worth it. The wife suggested I should buy a $2000 smoker to find out if I like them.
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Re: 2t jetting question

Post by steve-o »

modern day big bore 2t's are alot more different than the 1990 cr80 you last rode.

lower maintenance than your drz guaranteed.

$2000 might buy you a 1992 cr 80, so not a good resemblance of what you might get with a a real investment.

I don't do this often, BUT, if you want you can try mine. It has a tall seat and is sprung roughly for your weight. Limited time offer :D

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Re: 2t jetting question

Post by giantjoe »

Very generous, thanks. See you at the guided rides maybe?
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Re: 2t jetting question

Post by Dakota_c69 »

Well, I have managed to drop the Berg twice so far while manuevering i the snow. I had no problems picking it up. I can't imagine you will either... When the Berg is in motion, it is s'posed the bike feels like a 2 stroke according to all the reviews! This is due to the 70 degree engine.

As for maintenance... Change the oil and filters and this should go just fine!

I am positive it will feel lighter than your DRZ. And you can give mine a try if you like.

Dobi, That means another 60+ hours before the next rebuild... No Big macs till then? You gonna be hungry...
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Re: 2t jetting question

Post by absurveyor »

Joe you are trying to apply a science to personal opinion. Having ridden 4t for two years and now being a "2t guy" I too am like you, I want to set it and forget it. I will give you some of my limited observations:
Both bikes take setup time. 4t carb and 2t carb. Both bikes equal. EFI changes things, but wait you can use a programmer now to make it run better, more time and potential problems. Ask anyone with an efi sled or atv what you do when the engine light comes on.
Suspension setup needed for both bikes.
Maintenance
4t oil changes and 2 t transmission oil changes. Both bikes equal.
Both bike need air filter maintenance.
Tire wear the same (unless you loan Dobi your bike then replace after use!)
Valves vs topend? I checked my 4t valves regularily and everything was ok, and Scott showed how easy shimming is. 2t topends seem to vary but 2 years looks about right, maybe more because you ride smooth. So lets simplify and call this a wash for durability and cost.

So you are now left with the basic question. which is more fun to ride? Borrow someones 2t for a whole day. it took me about 3 days to learn how to ride the 2t before I figured it out. In an hour a 4t guy will not be able to appreciate the benefits of a 2t. after 4 hours you won't go back, and your back will thank you.

From experience, never buy something cheap just to try it out It costs more in the long run and it is usually no comparison to a 4 or 5 k good used bike. If you don''t like the 5 k bike it is easier to sell than the 2 k beater bike. Lots of offer to try bikes, that is the way to go.
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giantjoe
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Re: 2t jetting question

Post by giantjoe »

Thanks everyone for your input. Here's my plan...

Ride my bike for the year, try to get on as many 2t as possible. At the end of the year sell my bike and have some cash in hand for a good deal on either a brand new 2010 model, or someone's year old bike they're trying to dump.

Please lend me all your bikes fellas. I need to know what's up.
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Re: 2t jetting question

Post by dirtyboy »

absurveyor wrote:Valves vs topend? I checked my 4t valves regularily and everything was ok, and Scott showed how easy shimming is. 2t topends seem to vary but 2 years looks about right, maybe more because you ride smooth. So lets simplify and call this a wash for durability and cost.
absurveyor had some excellent points. But if you have to rebuild a 4T the cost is substantially more than a 2T. Just drop your 4T in a creek and see the repair bill compares to the 2T.

To simplify both engines have; crank, piston/rings, but only the 4T has camshaft and valves. For durability and cost I don't think that there is much to argue about. The 4T has more parts to break/wear and replace and more things to adjust. The 4T benefits come from the different power/torque curve compared to the 2T.

Also in my experience the 4T is harder to jet correctly (like when you replace the silencer and try to make it quieter) and needs jetting changes for temp/altitude more than the 2T does. A 2T can be a little boggy or down on power but there is nothing more annoying than a 4T (jetted incorrectly) continually flaming out every time you try to loft the front wheel.
Dirt Rider Magazine 2011 KTM 250XC Bike Review wrote:Why can't the four-strokes dethrone this do-everything smoker? Why don't they try?!
Dirt Rider Magazine 2011 Yamaha YZ250 Bike Review wrote:When ridden in the meat of the power, this bike is very fast! This is often a dying art that you don't see from many kids these days that never got the chance to ride 125 and 250 two-strokes. I believe that riding these premix burning machines makes you a better rider and helps you with line selection compared to its four-stroke brothers.
Also, team GG gave me grief last time I commented so I figured I should include their brand as well to keep..........well you know what I mean. :lol:
Dirt Rider Magazine 2011 GasGas XC 250 Race Test wrote:Given the nasty conditions of the race I would not have chosen to race a four-stroke over the XC 250.
Having said all this, I've ridden a 2T for the last 6 years (and 4T for prior 5 years) and am starting to think about 4T bikes again. :D

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Re: 2t jetting question

Post by giantjoe »

Oh thanks Dave. :crazy: What a help you are...
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Re: 2t jetting question

Post by Brass »

As with so many things in life, this really is a personal choice based on your preference. Yes you can adapt yourself to ride a bike but at some point you'll end up saying that you like one more than the other.

Try as many as you get your hands on. You'll see that each is set up differently. You'll find that the same year, make and model bike belonging to two different people will behave differently. In the case of the KTM 2t, you'll want to ask what power valve spring is installed. They are very tunable for power delivery.

Jetting makes a huge difference to any bike. If they are on the lean side power will be crisp, jetted rich (of "fat" if you're a car guy) they will be sluggish and slower to build power. Again, each bike owner will have a different set up.

Talk to Mediumdee, he couldn't get off my 200 fast enough, too much power for him :smirk: Actually, my setup was on the abrupt side at the time and he had trouble keeping the front tire down. A few small (free) changes to the jetting and power valve and it's a completely different bike to ride now.
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