Jump to content

Taming A 2 Stroke!


bex
 Share

Recommended Posts

Ok maybe less about taming and more about 'understanding'!!

 

And hi all, I've just registered :)

 

I’ve been nosing around a bit seeing if I could find some answers before asking questions that have already been asked but I cant really find what I’m after, which is more specifically regarding 2 stroke riding.

 

So… basically I’m riding a 2 stroke Honda RS125GP. I’ve only ridden it once, on track @ CSS Level 1, and I highsided in the last session. Not entirely sure what happened, but one instructor who saw it believes I hit the powerband while cranked over on the edge of the tyre, rear wheel spun up, skidded, gripped, somersaulted etc… someone else noted my rear slick had a lot of oil on it as it turned out I'd sprung a bit of a leak, so I think it was a combination of both those things – though mostly the first.

 

Anyway, this is a very different animal to my road bike which is a grunty Ducati V twin with oodles of engine braking, so I’m trying very hard to understand the way I should be riding the 2 stroke and what keeps it happy. Its extremely light, and I'm barely 55kg myself. Its also just sheer bonkers by comparison, I do love it.

 

I was watching Simon Crafars motovudu film the other day and noted he said he always shuts of the throttle off going into a corner after working down through the gears at high revs and hard braking, and then very gradually rolling it on again as the bike has completed more of the turn and you're getting it more upright again. Since the 125 is happiest in high revs and inside the power band, is this irrelevant to me? Do I want to be in the high revs with a constant throttle on while cornering, as opposed to shutting off completely?

 

I guess I’m trying to understand this as its clearly where I went wrong last time, I came up behind a cluster of bikes as I was coming out of a corner outside the powerband; saw a gap, gave it some welly (probably abruptly as opposed to gradually, though I don’t remember)…and landed on my head. So I either want to be in the powerband and giving it the beans, or not in it and winding on very gently…. Is that correct?

 

One other thing I’d like to ask is about body positioning in corners – as I understand it the CSS method is to get your butt right back in the seat, while I’ve heard this contradicted and that you should have your nuts (if you have any), up against the tank and pivot off the seat. By default I seem to slide forward to the tank, but whats the correct way so at least I know what I should be trying to do? If its to stay back then I may get some grips for the tank to keep myself in the right place under heavy braking; usually I brake and slide forward and cant do much about it!

 

Advice appreciated, and any other tips for riding this bike would be great. I’m not planning on giving up… thanks in advance. :D

Link to comment
Share on other sites

Very welcome to the site, Bex !!!

 

I have been lucky enough to be riding 2-stroke bikes for many years.

 

If yours have a tuned pipe, then you have a lot of power in a narrow band of rpm's and very little out of there.

 

Fine throttle control is your friend and you need to learn to twist that wrist painfully slowly, opening and closing it.

 

The engine has much less rotational inertia and counter-compression than a 4-stroke when you close the throttle; hence, there is no much engine brake effect and changes in rpm's happen faster (the engine is more agile to gain or loose rpm's).

 

Those characteristics make any 2-stroke less flat than a 4-stroke, regarding torque versus rpm; more temperamental, if you wish.

 

Gears are also your friends, because they allow you to keep the crankshaft spinning within that range of rpm's that provide good torque; hence, surprising bursts of torque cannot catch you during critical situations, like extreme lean or coming out of a turn.

 

I would work hard with the gears to keep the engine at top performance at all times, regardless of the speed of the bike, using the throttle as CSS teaches: smoothly, progressively and timely, specially in turns that reduce your available traction.

Link to comment
Share on other sites

Welcome!

 

Best of luck on the the 2stroke, mine has only seen the trails.

 

As far as your seating position while cornering. I believe CSS trains the following; about a fist's width between the tank and your groin should give you plenty of pivot room, because if your right on the tank your outside leg may become disconnected from the tank. And you want to be locked on tight right? Do you grip the tank with your legs to support your body weight? Do you think that may help you keep from sliding forward?

Link to comment
Share on other sites

Hi there, thanks :)

 

Yes I generally try to grip the tank, though I admit I'm still trying to get into the habit as opposed to just doing it naturally. I'm speaking more from general riding experience, as I've only ridden the 125 on the track once, and that was my second track day. Maybe I've chucked myself in the deep end a little.

 

Anyway, I just tend to find that under braking force I tend to slide forwards. Maybe I'm not strong enough? Maybe those tank grip thingys would be helpful....

 

I'm heading off to Cartagena for a 3 day weekend with the 125 this week, a bit nervous since I crashed the first (and last) time I rode it, but pretty excited. Thought it would be a good idea to iron out some of these issues so that each day or half day on track I can set myself something in particular to work on, a bit like a day at CSS, and gradually try and put it all together, rather than go out hoofing around the place trying to concentrate on everything at once. So far the things that seem to be preoccupying my thoughts are what to do with the throttle in the corner, and my position on the bike as well. Maybe I'm over analysing it all since I binned it, then again, it almost feels like learning to ride all over again, so I'm trying to understand riding a 2 stroke as well as possible.

Link to comment
Share on other sites

Any additional grippy surface on the tank may help but don't let it be a crutch. It takes quite a bit of core strength to keep yourself from sliding forward at track speeds while hard on the brakes, especially on a thin profile bike. I think you have a wise idea there to work on one or two skills at a time to get handle on them before trying to flow them all together.

 

I wish I could advise more on the throttle control but my 2stroke track experience is not there for you.

 

Wish you the best at Cartagena, let us know how it goes and don't forget to have fun! :)

Link to comment
Share on other sites

Hi there, and thanks for the quick reply. Does that mean that its necessary to keep the throttle on when dropping into corners, to avoid a dramatic drop in rpms?

 

You are welcome.

 

Yes, you don't want a surprising burst of torque in the middle of a fast corner, while you are opening your throttle to keep the 40/60 weight distribution.

Consider that the engine's rpm will increase while you lean the bike and roll on a smaller diameter of the tire.

 

That could have been one of the reasons that led to your unfortunate high-side crash.

Your entry speed and gear keep your engine in the "weak" zone of the torque curve.

You quick flick and lean the bike and then crack the throttle open, the rpm's grow and suddenly enter the "strong" zone of the torque curve.

That way, you may overwhelm the traction of the rear tire by accident, just like you do in a 4-stroke by being greedy with the throttle.

In this case, a little twist of the throttle, done at the verge of the "weak" and the "strong" zones, may simply deliver too much torque onto the rear contact patch.

 

Others with more experience will post here soon; just hang in there. :)

Link to comment
Share on other sites

I ride a 4- stroke but it is a similar chassis - I have trouble with sliding forward on it, too, so one thing I did that helped was use some seat foam to make a pad on the back of the tank. It keeps me back a bit and I find it's nice to have a bit of padding on that tank when I DO get too far forward. I also have Stomp Grip on the sides of the tank to help hold on during braking.

 

For cornering, are you planning your lines so that you can start standing the bike UP on the exits of the turns, when you start your hard drive? Or do you end up still leaned WAY over or making steering adjustments at the end of the corner? If so, do you remember what causes that and what techniques you can use to fix it?

Link to comment
Share on other sites

Hi, thanks, that might be a good idea with the tank padding, I've seen it done before too, I may give that a go over the weekend.

 

I can't say I have enough track experience to answer your question really, as I've only been on track twice, one of which was CSS level 1 which didn't cover pushing the bike back up. I know I wasn't making a conscious effort to do it on the occasions I've been on track, though now that you've said it I think I can grasp the principle...

 

Is the purpose of doing so to shorten the corner ie. the time the bike is cranked over for, and make the straights/uprights as long as possible? So push the bike up while still hanging off so you can get back on the throttle sooner (or harder?)?

 

Hmmm, I guess having to make late adjustments in the corner, which i probably did, could mean wrong entry speed or wrong turning in point? Or both even?

 

...is this literally pushing the bike upwards into a more upright position? Must feel strange to start with!

Link to comment
Share on other sites

Hi, thanks, that might be a good idea with the tank padding, I've seen it done before too, I may give that a go over the weekend.

 

I can't say I have enough track experience to answer your question really, as I've only been on track twice, one of which was CSS level 1 which didn't cover pushing the bike back up. I know I wasn't making a conscious effort to do it on the occasions I've been on track, though now that you've said it I think I can grasp the principle...

 

Is the purpose of doing so to shorten the corner ie. the time the bike is cranked over for, and make the straights/uprights as long as possible? So push the bike up while still hanging off so you can get back on the throttle sooner (or harder?)?

 

Hmmm, I guess having to make late adjustments in the corner, which i probably did, could mean wrong entry speed or wrong turning in point? Or both even?

 

...is this literally pushing the bike upwards into a more upright position? Must feel strange to start with!

 

Well, the thing you DON'T want to be doing is leaning the bike over FARTHER at the END of the corner, when you are hitting your powerband and driving out, right? Your BEST rear tire grip is achieved with the bike more upright, so leaning the bike over farther at the same time you are screwing on the throttle can easily overload that rear tire and make it slide.

 

The drills from Level 1 will help prevent the tendency to run wide and have to make steering corrections - recall the Turn Points, Quick Turn, and Two-Step drills.

 

If you choose a turn point that is too EARLY, where do you end up at the exit of the corner?

Link to comment
Share on other sites

Exactly (run wide or make mid corner corrections, neither of which the bike wants).

 

First thing: oil on the tire, all bets are off. I wouldn't get too worried about what you did right or wrong, there was oil on the darn tire!

 

Next thing, what Hotfoot is talking about and Lnew, is the key to bringing the pace up, and not getting tossed on your head. This is throttle control AND what you are doing with your lean angle. Biggest source of crashes in turns we see is both being added at the same time. If you have very good technique on your throttle control and you don't add lean angle you won't get caught out. This is how the top guys get away with riding on the edge. Make sense?

 

CF

Link to comment
Share on other sites

Yeh, that makes sense. I'll do my best to practice over the next few days and report back, no doubt with more questions!

 

Thanks all for taking the time to read and give some really positive advice; really looking forward to getting out there :)

Link to comment
Share on other sites

Well, I'm delighted to report that I stayed shiny side up this time, which was quite a relief.

 

Had a wonderful time on track in Spain, took it easy enough to begin with as I was apprehensive, and of course didn't want to do anything silly. Built up my confidence a bit getting the lines right and took some instruction and found I was getting quicker and having a good old play with the big boys on larger bikes.

 

I think my gearing was slightly off and could have done with a larger rear sprocket for this circuit to help keep the revs up a bit; this didn't help when I was already finding this quite difficult. On chatting with someone else on the same bike we realised their's was geared a bit more favourably. I did struggle to keep it wound on in the corners and often dropped out of the powerband and lost momentum.

 

Still, I didn't take any other sprockets so I just got on with it and gradually built up entry speed as much as I felt comfortable with, practised feathering the clutch on corner exit to give her a little boost and began to get it right a bit more often. I really tried to push the bike up on corner exit while still hanging off, to get more tyre contact and onto the gas sooner, and managed to take the lead out of the corners quite a few times this way. I realise not carrying enough corner speed is where I'm loosing time; my instructor said I certainly wasn't afraid to go quick, but I needed to learn to keep it that way through the bends!

 

So all in all a really positive experience and I'm looking forward to the next outing on the little wasp so I can work on my technique a bit more.

 

Here's some pics from the weekend:

 

carta011-1.jpgcarta03-1.jpg

 

 

carta04-1.jpgcarta01-1.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...