School me on 2 Strokes

Now, I've done a few track days and 2 stroke machines fascinate me.
However, I've never gotten a chance to talk to anyway about them. I've
read a little bit about them, but it seems like anytime the words "2 stroke" are
mentioned, rebuild seams to follow. Rebuid = $ and I get nervous. For
something like a 2000 TZ125 or Aprilia 250, how long does an engine last?
What kind of rebuild schedule would you get from track days or racing. Are
these things just huge money pits?

 

I am running a TZ250 two stroke as a track day bike. I am learning how to work on them this season more than I am riding mine for sure. Despite this, I am still enjoying the bike for its potential. I am getting closer to being able to keep it in running condition and what its likes and dislikes are.
Finiky beasts to say the least and they are also more costly in maintenance than a standard 600cc track bike. One thing to keep in mind, when a 2 stroke is running correctly ,its an experience that is definitely hard to duplicate on any other kind of bike. I would expect that this sentiment would be echoed by some of the other more experienced 2 stroke riders here. They are light like no other bike in its class and boast an impressive power to weight ratio. If ridden well, a 250 will give most 600cc riders a tough time on the track depending upon the layout and the company you keep.
You can expect to do the top end after every 4-5 track days, which consists of new pistons, rings, piston wrist pins, bearings and head gaskets. You can also expect to need cylinders stripped and replated as well, this is when the 4 piston sizes (Yamaha) available cannot give you the tolerances you require to give good compression.
Lower ends costs more, requiring the rebuild ($500) or replacement ($1000)of the crank shaft connecting rods, seals/bearings. Most times this coinsides with doing the top end over. Guys will tell you to rebuild the lower end from anywhere from 1200-1500 miles. You will have to get familiar with your bike to see what it will tolerate and keep a journal of the maintanance and take measurements of the free play on the connecting rods when building top ends. Running them for too many miles will more than likely end up in fewer rebuilds onthe crank and more money in the long run. I expect a good crank to last one track day season.
There are not too many special tools required, just patience and good mechanical common sense.
From what the fellas have told me when I was shopping for a 2 stroke last fall, parts for TZ's and Honda RS bikes are more readily available than for Aprilia RS250's. Also the performance difference between the TZ/Hondas is a good deal apart from what the Aprilia can put out. The TZ/RS bikes are true factory race bikes, the Aprilias were a blend of factory race/consumer friendly bike meant to try to develop a 2 stroke race class in the US and elsewhere.
A good choice may be to look into owning a TZ125 instead for your first 2 stroke in order to cut some of your operating costs by approximately half.
2 strokes are definitely a labor of love. You have to like them or at least be willing to give them a chance. They are simply an ingenious design and the mechanics of the bike are not too difficult. You just have to be someone who takes maintenance seriously and you will have to like tinkering with them. You have to like to play with rebuilds, carb settings, mixing of fuel and hunting on ebay and these kinds of message boards to get some less expensive spare parts together for yourself. All other comsumption parts can be had from RSCYCLES.com or Accu-Products.com. You can even head into your local Yamaha or Honda dealer and give them the part numbers of what you need and special order them. Most everything for Yamaha TZ's and Honda RS's is still being made by their respective factories which is huge.
Ken

 

They're so not hard to keep running or running well. Replace the piston and ring every 300 miles. On a TZ125 that'll cost you about $70 total and take about 15 minutes. The money you save on tires alone will more than pay for the maintanance versus a 600 and a) they're competative right out of the box. No need for aftermarket pipe, shock, bodywork, clip ons, brakes, chain, etc etc etc. That right there is worth several grand. And b) you can race the same bike for many many years and still be competative. No need to buy the newest bike every other year and c) If kept in good shape your GP bike will be worth as much as you paid for it for a long time. Need any more advice go to the usgpru website.

 

GP Bikes

I didn't really get mentioned so I'll chime in.

Most 2 strokes (except the Aprilia 250 cup) are world level, Grand Prix race machines built by the factory with one purpose. Therefore there is no comparison to a street based machine like the common 600cc track bike. The Honda RS250 & Yamaha TZ250 machines are some of the fastest bikes around most tracks and will teach you more about racing in 1 season than 2 or 3 on a 600 bike. If you want a street/track bike buy a 600, if you want a real race bike buy a two stroke. If you want to save $$$ while racing, buy a 125 instead of a 250.

I used to not like Ducati machines as they seem to have all sorts of issues comparied to every UJM (universal Japanese machine). After race a 2 stroke, I've realized that Ducatis are race bikes and must be maintained as such. The bikes come from a different design philosophy and are therefore pure bread race machines.

Another thing no one mentioned about 2 strokes; you can't buy speed. It has to be learned. With a few minor exceptions, you need to learn how to tune your bike and then ride it to 99% of it's capabilities before you go spending money on stuff you don't really need.

The Honda RS125 is the most popular 2T followed by;
TZ250
RS250
TZ125

Yamaha's may have cheaper parts but when you break something at a race and it's a Honda part you need, someone will have what you need.

Keep reading and you may just fall in love with a 2 stroke sooner than you think.

 

Is there a difference in terms of performance between the RS and TZ?

 

rs125 vs. tz125
- more go-fast parts for the rs125 (but they do cost $$)
- tz125 takes a bit more tuning skill to get the most out of it (stock vs. stock)
- tz125 is more roomy
- tz125 handles better (from what I've heard/read since I haven't ridden a tz125 or rs125 to their limits)
- tz125 top ends are currently 1/2 the price of the rs125
- dry clutch on the tz125 is a bonus in my mind; less clutch drag and easier to change
- more parts availability as was said for rs125 parts in the paddock if you don't have what you need

usgpru.net and tz250racing.com for more info

 

There is always the Aprilia 125 which by the way thanks to Honda is cheaper to do a top end!!!

 

Riding GP bikes produces a medical condition to the facial muscles that someone termed "permagrin".

 

Rider skill taken out of the equation (i.e., I'm sloooow), will a 125 GP bike be at all usable for track days? Will race it eventually, but will spend the first few times riding whatever 2 smoke I get at trackdays.

 

125GP track days

Yes, a 125GP bike will be perfect for track days. You'll get all sorts of 4T guys pissed off when you pass them on the outside of almost every turn. It's great fun to say the least. When I started track days on mine, I got all sorts of great comments;

"Damn weedwacker guy"
"I'll get you on the straights"
"How did you get that thing in your truck" (I don't have a ramp as I just pick up the bike and put it in)
"That bike is a lot faster than it looks"
Etc.

Like I said, you just may fall in love with a 2T before you know it. One of the main advantages is that they come 100% race ready. When I was looking into racing I had two options;
Option #2 - Buy a salvage title SV650 for approx. $1000, spend an additional $500 on body work, $150 faring stay, $300 rearsets, $150 chain & sprockets, $400-750 exhaust. I already had a penske shock and CBR F3 forks for the SV but the cost of "race preping" an SV was way more than...
Option #2 - Buy a 100% race ready 125GP for $3500-$6000

You have to realize that a "prepped" SV650 is not competative in most race clubs until you spend another $1000-$5000 on motor work, Mag wheels, weight loss etc.
So I sold all my SV650 parts and bought a real race bike.

I will have to admit however that if you're new to track riding and or racing, I would recommend buying a 4T for simplicity. At the average race/track day, you'll see 2T guys constantly working on their machines and "playing" with everything to get it just right. You'll see the 4T guys sitting around and smoking while they wait for their next session. It's a matter of preference really but for learning to ride fast on a race track, all the "maintainence & tuning" a 2T is a hassle and distraction when you should really be consentrating on riding & working out your limitations. Once you put in 10-15 track days on an "easy" bike like an SV650 then I'd say go buy a real race bike and learn to race. If you've raced before, all this is a mute point.

My 0.02

 

+1. I'm a 2-stroke guy and I bought a 636 for trackdays. It drove me nuts to have diesels parked in every turn. I rarely found someone that looked stable enough to pass on the outside. I guess it depends on the org.

 

Thanks for the info. I've done a fair amount of trackdays (8 this year, plus 2 days at STAR school, about 10 or so last year) and can appreciate the "sit in the chair and bench race between sessions" ease of 4 stroke bikes.

Last year, I used my SV650 as a track/street bike, and picked up an '01 GSXR 600 over the winter as a dedicated track bike. Having lots of fun with it, but I find myself casting envious glances at the guys in the pits with the 2 strokes...

Got a line on a TZ125 that needs only a few minor bits to get track-ready, so I might jump on it...

 

I don't know about Hondas, but the 99 and older TZ are inexpensive to maintain. The 00 and up are twice the amount of money. You can go to any Yamaha dealer and order parts.

When you crash a 2stroke, usually you move the handle bars back in place dust it off and go on. If you do break something it is usually minor. When you crash a 4 stroke it cost money and no one at the track usually has what you need to fix it.

And how many 4stroke guys can put all the stuff (bike,stand,fuel,etc.) into a four door car and go to the track?

 

If you're not already convinced to go get a 125 then you never will be, however, I need to address this myth about the constant tinkering on 2Ts. Yes, I said myth. Someone once said that we work on our bikes because we can not because we need to. If you maintain it and don't do anything stupid you can sit in a chair and not even look at the thing all day. Chances are you'll be bored and start messing with this or that. Big difference is that if something does break at the track with a 125 you can fix it, most times on a "street" bike your day is done. For further proof and shear ironic comedy check out the discussion on the usgpru site abou the future of 2T and you'll see much hand wringing by GP guys about the possibility of having to work on 4Ts in the future. I'll let you on on a secret; they're both easy if you have a clue, but a real GP bike can't be matched for pure racing enjoyment. Now go get one and make it a Yamaha so you don't end up supporting the evil red empire.

 

To be honest, I agree with all of the posts following mine, my situation is getting a used bike set up properly that has had some SO SO mechanical care prior to my ownership.
Getting a used bike of any brand is always a crap shoot. Knowing the care of the machine before you buy it isn't always a luxury we are afforded. I bought a beautiful bike from out of town, but some of the things were not up to par mechanically.
As already suggested, there are lots of knowledgeable fellas here more than willing to help with advice and mechanical know how. TZ250racing.com has been a valuable resource for me. The folks both here and there have answered all of my newbie 2 smoke questions without fail. More have taken my franctic phone calls to help diagnose my problems with plenty of accuracy. The fellas here and on TZ250racing.com have been terrific.
Once I get all of that sorted, which will be soon, I will be confident that my 250 will be more than reliable.
Go for it and have fun.
Ken

 

I'm not sure why you would say that about the newer ones. Can you give an example?

 

So say you have a guy coming from a bunch of track days on a Ninja 650/SV
who wants a TZ. What would you recommend? TZ125 or 250? Any specific
years or things to really look out for?

 

Hi Guys,

Don't know if this is of any interest to you, but you can meet other like-minded people @ www.NorthAmericanTwoStrokes.com . If you are so inclined, give it a look.

Don

 

A piston for our 99 is around $40 each, a piston for the newer square bore engines are around $150 each. The 99 and older cases will last a long time if you take care of them. The newer square bore cases you replace after three cranks. There are no new bits for the older engines, while you can buy two piece heads and better ignitions for the newer bikes. I don't know anything about Honda's except that their prices went up on everything this year.

BTW, very clean 250 you sold Jon. Plenty of power when I took it for a spin.

 

I just joined up, thanks for the link
Ken