Honda NSR 125 engine braking

[Simon13245]

Hey guys,

so first of all sorry for the confusion about the black box under the seat.

Engine braking on a two-stroke. Yeah, I know it's been beaten to death, but I want to ask anyway. So my NSR has a working oil pump and the oil pump cable is adjusted as the manual says. So I've read a lot about engine braking on a two-stroke. Some say it's ok cause the pump regulates the flow, some say you should never do that because the pump is closed when the throttle is closed.
So my question is, if I engine brake from 5000rpm, is the pump working just like in idle, or is the shaft inside the bike spinning the pump faster so that the oil gets delivered into the engine?

I also have other problems with the bike like leaning left to right with no hands on the steering wheel, I can't full throttle the NSR under 3k rpm on 1st gear cause it dies, but I would have to spam all over the forum...

[jeffyjeff]

Your pump restricts oil flow at closed throttle because the engine produces no power at closed throttle; in fact, when engine braking, the engine is absorbing power (minimal heat generation in the combustion chamber). Flow from your oil pump is engineered to accommodate these variables. Don't worry about it and engine brake to your heart's content.

As far as stalling out below 3000 rpm, sounds to me like someone swapped out the carburetor with a larger (slide carburetor) in an effort to achieve more power. Whack open the throttle and the larger throat diameter does not provide sufficient air velocity to draw fuel through the venturi. Wrong move if smooth operation over the entire rpm range is important to you.
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History shows again and again how nature points out the folly of men - BOC

[MCN]

"No hands on the steering wheel"?

What sort of trollery is this?
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Robby]

You have probably opened a can of worms that has remained shut for many years on the debate about 2-stroke oiling on a closed throttle. My personal view - you may cause a bit more wear, but on a bike of that age the crank seals are going to dry out and fail before you wear out the crank. Just ride it how you want and don't worry too much about what is happening inside the engine. 2-stroke oiling is an ugly thing.

The full-throttle problem. Someone has probably fiddled with the carb, or fitted a different one. This is one of the few 125s that can be made faster, if you know what you're doing. You would need to know what jet sizes are fitted and what the current needle height is, and compare those against what are recommended for your current state of restriction. From memory the factory settings are for 12hp restricted bikes, with bigger jets used after derestriction.

Bike flopping around with your hands off the bars. The easiest solution is to keep your hands on the bars. After that, there are lot of things it could be, in vague order of cost/difficulty:
- Tyre pressures
- Wheel alignment
- Tyre wear
- Headstock bearings worn/notchy
- Swingarm, rear suspension linkage bearings worn
- Bent forks, frame

[Simon13245]

[jeffyjeff]

Your mechanic may have installed a new bearing but failed to set the preload correctly. Noises from the front end as you describe are not normal.
____________________
History shows again and again how nature points out the folly of men - BOC

[Simon13245]

[Nobby the Bastard]

What is this 'season' of which you speak?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Simon13245]

[stevo123]

Don't give it a second thought in normal riding conditions. Engine braking down a huge hill then yes give it a few blips, nothing more than that is needed (IMO)

[Simon13245]

[MCN]

There is still some residual 2t coating the upper cylinder/s after combustion. Not all of the 2t is burned or blown through.
As mentioned, the detriment to the engine on overrun is almost negligible as the load on the moving bits is low. Machines can run with no lubricant between moving parts. The need for lubrication is almost directly proportional to machine loading. Some machines rely on 'splash fed' lubrication where something that is in motion is submerged in lubricant and that throws lubricant all over the place.

I'd guess that unless you are engine braking from the tip of the North Face of the Eiger (13000' in Old Money) to the beach at Malaga, then it's nothing to worry much about.
If worried then move up to where the Men Live and buy a 4t



For piece of mind, make sure you use good quality 2t oil and mix properly, if no tank. Less ash and shite plus improved 'other additives' in it.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[stevo123]

Not an expert at all but I would start with basics re your bogging problem.
-Is your air filter in good condition, are there any splits in the system after the airfilter. Spray brake cleaner on any joints and listen to engine note changing.
-Do you have any water in your fuel?
-How is your HT lead and spark plug/plug cap?
-Might be worth removing the carb and taking it apart, checking as you go to be sure the right jets are in there and the float height is set right. (That sounds quite daunting but a local bike mech would do that easily for you).

[Simon13245]

[Robby]

Mixing oils will not be a problem (Except in a few very unusual circumstances, maybe, that are not going to apply in this situation)

The bogging problem is almost certain to be the wrong size small jet in the carb, or the needle at the wrong position. Possible that it's just a blockage in a jet, but this is only likely if the bike was sitting unused for ~12 months before you got it. If that is the case, running the bike fresh fuel may clear it out.

To test your own headstock bearings for notchiness:
1. Get the front wheel up in the air with no load on it. This is usually done by putting a bike on the centre stand (if it has one) or by putting a couple of car jacks under the footpeg mounts, and getting someone to push down on the back of the bike.
2. Very gently (fingertips) move the bars from side to side. If you feel a notch, roughness, or a click when the front wheel is pointing forwards, you have worn out bearings.

Changing them is one of those "simple" jobs that can be a pain in the arse. Certainly not something to attempt yourself if you're not comfortable working on bikes.

If they are not worn but just loose, get the person who changed them to tighten them up.

[Simon13245]

[buddy]

Allways did it on mine. Looked fine when i pulled it apart years later.
I think premixed 2 strokes are a different kettle of fish tho.
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When this baby hits 88 miles per hour... you're gonna see some serious shit.

[Pete.]

[Simon13245]