Advise on restricting engine power please?

awyala said:
My understanding, now I could be wrong, is that the 2 stroke engine requires almost a constrant throttle to supply the fuel / oil mix to the pistons. If you throttle off and coast or engine brake too long, the engine continues to run on momentum alone while oil is not being supplied to the pistons / chamber. This can cause a gradual over heating and soft seize a lot faster than one would suspect! This is not from personal experience but from what I have been told by a couple people who owned the RS125.

It often happens when riding up near 120kph, then coasting on engine braking through an off ramp for example. Running the bike near its max range at 120kph provides sufficient near over heating, when coupled with lack of lubrication feed, lead to the soft seize.
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I’ve built, raced – and still do - and ridden 2 strokes on the road and dirt for over 30 years and lube/heat issues due to coasting will not cause a seizure. There are really 5 main ways a 2 stroke seizes and you need to be able to read the piston to find out why.

1) A piston can shatter the skirt because the piston to cylinder clearance was too great, either from bad workmanship or wear. When the piston is allowed to rattle in the cylinder bore, it develops stress cracks and eventually cracks or shatters. Forged pistons are a little more forgiving but at the end 3 or 4 races the skirts are already beginning to collapse on a set of Wiseco’s in my Yamaha’s

2) The piston may have a single point seizure. Single point’s occur on the center of the exhaust side of the piston when the bike has a bridged exhaust port. The causes for this are warming-up the bike too quickly and hammering a cold engine, running too lean which means the jetting is off or there is an air leak, or the sparkplug range is too hot.

3) The piston can have a four corner seizure when the piston has vertical seizure marks at four equally spaced points around the circumference. This normally caused the piston expands faster than the cylinder and the clearance between the piston and cylinder is reduced and is related to bad workmanship or the user hammering a cold engine.

4) The piston can have a multi point seizure when the piston has vertical seizure marks all around the piston skirt. This is normally caused when the bore has too little clearance for the piston. This is 100% down to bad workmanship. It also varies with use. I run my race bikes with a little more clearance than I would a street bike.

5) The piston can have an intake side seizure and this is the only thing that can really be attributed to lubrication failure and is very uncommon. In 30 years of racing everything from 125 – 500cc two strokes I have never had this type of seizure (fingers crossed). There are really only four causes for lubrication failure

– putting straight gas or wrongly mixed in the tank of a premix bike
– gas and oil separation in the gas tank
– water getting sucked through the air intake and causing problems with the oil film on the skirt
– or on a bike with an oil pump - a pump problem - could be a pump failure, broken pump cable or even something as stupid as forgetting to fill up the oil tank. Oil pumps are normally very reliable though

In general 2 strokes seize because they are running weak (wrong jetting, air leaks), the engine is running too hot (wrong jetting, air leaks, wrong plug heat range), too much or too little clearance between the piston and bore (bad workmanship or bad maintenance), warm up too quickly and hammering a cold engine. All this can all be attributed to the user, lack of maintenance or a shoddy mechanic

Lube failures are normally caused by the rider forgetting to lube or not lubing properly.

You will be fine coasting to a stop or down hill, trust me. If I can shut off a 30 year old TZ350 at 150 mph going into turn 8 at Mosport after hammering it down that straight without it seizing - then you will be fine on the exit ramp of the 401 :)
 
I tried, but I cannot bring myself to post anything useful in this thread. You lost me when you said the Ducati dealer told you that ABS was just to do with the rotors. Sorry, no comment.
 
ABS does have to do with the rotors... usually braking systems with ABS have ABS rings on the rotor.
 
I think I may have lost myself on the ABS issue. A search of other forums and after market "ABS" is turning up with dodgy or expensive alternatives.
 
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skapan said:
I tried, but I cannot bring myself to post anything useful in this thread. You lost me when you said the Ducati dealer told you that ABS was just to do with the rotors. Sorry, no comment.
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No no, the dealer didn't tell me that...you misquoted me, and I spoke out of ignorance.

The dealer said the ABS is a $1500 upgrade....not a retrofit. What I meant was, when purchasing a NEW Ducati, for an additional $1500, you can have the ABS. I then went on to hazard a guess at how much it may cost to retrofit any bike. But upon further investigation it seems there is no quoted price out on the market, suggestions of canibalizing ABS systems off similar models as one's own, or venturing into uncharted territory to modify it one's self.

But to be honest the point of this thread was to explore issues rather than claim authority on them...so by all means, comment, add to the discussion.
 
I didn't read the whole thread but to the OP when reading your initial post I got thinking about this and how it could be done.

When doing Formula 1 SAE in university, I believe we had an air intake restrictor of 20mm ... this means that the ENTIRE intake system had to pass thru a 20mm hole... with not a whole lot of work or money, you COULD use fibreglass INSIDE your RAM air tube to reduce its size to whatever you want ... say 10mm in the beginning for her. Then with a power commander attached you would need to remap your fuel curve to match the 10mm intake hole... The 10mm is something I pulled out of my butt so you'd need to think about what you wanted her to start with ... maybe something EVEN SMALLER ?

As she progresses in her learning curve, you could increase the size of the intake restrictor a little bit at a time and remap the power commander as needed. Obviously this isn't an exact science and you would need to have time spent for a proper dyno tune for these maps.

THEN when you want to do your track day on it ? you just go into the air intake system and remove your restrictor and using the power commander, return the map to something more free flowing. After the track day you put the restrictor back in and reset the power commander to the neutered version.

Amount of money spent ? probably not a whole lot if you know how to use fibreglass (guestimate 50 bucks).... power commander $300 ? and the dyno tune time ? probably 200 bucks... so guestimate 550 bucks

your ongoing costs would only be the dyno cost if you need a new map with a bigger restrictor ...

my 2 cents as an engineer


having said all that ... is it worth the 500 bucks ? only you can decide that one. I think if you just leave your bike in the garage uninsured it will only depreciate at the same rate as if you rode it (actually a bit less since no mileage being added). And you buy her a 125 Honda CBR and have her ride that for 1/2 a summer then you sell it at a $500 loss ... then you upgrade her to say a Ninja 250 and sell that a year later for another $500 loss then she can get on the litre bike you'd be fine.... total cost ? probably $1000 altogether... so comparing that to the making of the restrictor ? your 'losing' only a net of $450 ... is $450 worth your headache to go thru the other process? Again only you can decide...

and my 2 cents business person...
 
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Sorry - i'm bored but can't read through all that.

2 questions - what does the girlfriend want and why can't she control her own speed and braking?
 
chiller said:
I didn't read the whole thread but to the OP when reading your initial post I got thinking about this and how it could be done.

When doing Formula 1 SAE in university, I believe we had an air intake restrictor of 20mm ... this means that the ENTIRE intake system had to pass thru a 20mm hole... with not a whole lot of work or money, you COULD use fibreglass INSIDE your RAM air tube to reduce its size to whatever you want ... say 10mm in the beginning for her. Then with a power commander attached you would need to remap your fuel curve to match the 10mm intake hole... The 10mm is something I pulled out of my butt so you'd need to think about what you wanted her to start with ... maybe something EVEN SMALLER ?

As she progresses in her learning curve, you could increase the size of the intake restrictor a little bit at a time and remap the power commander as needed. Obviously this isn't an exact science and you would need to have time spent for a proper dyno tune for these maps.

THEN when you want to do your track day on it ? you just go into the air intake system and remove your restrictor and using the power commander, return the map to something more free flowing. After the track day you put the restrictor back in and reset the power commander to the neutered version.

Amount of money spent ? probably not a whole lot if you know how to use fibreglass (guestimate 50 bucks).... power commander $300 ? and the dyno tune time ? probably 200 bucks... so guestimate 550 bucks

your ongoing costs would only be the dyno cost if you need a new map with a bigger restrictor ...

my 2 cents as an engineer


having said all that ... is it worth the 500 bucks ? only you can decide that one. I think if you just leave your bike in the garage uninsured it will only depreciate at the same rate as if you rode it (actually a bit less since no mileage being added). And you buy her a 125 Honda CBR and have her ride that for 1/2 a summer then you sell it at a $500 loss ... then you upgrade her to say a Ninja 250 and sell that a year later for another $500 loss then she can get on the litre bike you'd be fine.... total cost ? probably $1000 altogether... so comparing that to the making of the restrictor ? your 'losing' only a net of $450 ... is $450 worth your headache to go thru the other process? Again only you can decide...

and my 2 cents business person...
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Good points. Insurance on the 125 and 250 will also likely be $1000 to $1500 per year savings on a 10R. I think convincing the insurer the 170ish HP is restricted to 30ish will be a hard sell. If it causes so much controversy here among riders, it wont fly with SF. In the UK the insurers are accustomed to it, but even a certificate of restriction here wont mean squat.

More and more it is looking like the 10R will be sold off or traded in.

Thanks for your input all. I think we can close this thread up, unless a revelation comes along.
 
If you are going to do this I would strongly suggest you stick with the throttle change covered earlier. The one where the throttle cable mounting point is changed at the throttle body so that full turn of the grip results in only a partial opening on the butterflies... If one is not available for the bike one could be easily made.

Using a restrictor plate may result in fuel mapping problems.

Leave the brakes as is.

A custom seat with a lower ride height (narrower and less padding) may already be available.

As others have noted you could also buy a small displacement bike used, have her ride it for a year or two and then flip it for little loss. If she is comfortable with the weight of the litre bike I also see the logic in her using it with a little less power until she is ready for the power.
 
I've been down the giving the wife my hand-me-downs route before and it never ever worked out in my benefit.

Get her a 250 cc cruiser that she can flat-foot to learn on and ride behind her for a couple of years.

You'll get to see the scenery, enjoy the view with/of her, and save on gas while she learns.

This will pay off in many ways. Oh and if it's a cruiser, she might be able to out brake you, as they tend to have more weight, low and to the back, so that they can apply a little more back brake.

If weight was any issue with vehicles for braking, then bicycles would out brake everything, and 125's would out brake all other motorcycles.
 
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