Mysterious two stroke engine failure

[Pixie]

The oil pumps (or at least anything made in the last 30 years) is motor driven, the oil metering is a function of engine RPM and thrrottle opening. As either one increases, so does the oil flow.
I have had more problems with my 4 strokes than any of the 2 strokes. Run good synthetic oil and they can take a mighy thrashing.
Geoff

If the thottle is closed ,the motor at say 3000 rpm on over run the oil supply will be less than ideal for that rpm.

[Motu]

You've obviously never seen a suzuki or yamaha oil pump .
Tell me why it's connected to the throttle cable???

Um....to give more fuel with wider throttle openings.

Why is it connected to the engine crankshaft? - to give more fuel as the engine speed increases.

As Geoff says it's a pretty good system and the only failures I have seen have been water damage.I still like to take them off if possible.

[Motu]

If the thottle is closed ,the motor at say 3000 rpm on over run the oil supply will be less than ideal for that rpm.

But more oil than premix,which will have no oil at all.Some is better than nothing.

[pete376403]

I've never locked the T500. But I think that is because Suzukis of that era didn't just inject the fuel into the inlet port, they actually piped it from the pump direct to the bearings, (and I think a jet onto the cylinder wall, not sure about that). So the bearings had oil come what may, just like a four stroke.

I always thought that was a really good lube system for a two smoker, was disappointed when they dropped it. Cost I suppose.

T500s still had a gotcha - the pump was driven from the gearbox, so running the engine for a long period with the clutch disengaged meant the oil pump wasn't in fact pumping. Was it also this model that had the tacho driven from the gearbox also, so when the clutch was pulled in the tacho dropped ( but very slowly, cos the instrument was so over-damped) to 0?

[Ixion]

T500s still had a gotcha - the pump was driven from the gearbox, so running the engine for a long period with the clutch disengaged meant the oil pump wasn't in fact pumping. Was it also this model that had the tacho driven from the gearbox also, so when the clutch was pulled in the tacho dropped ( but very slowly, cos the instrument was so over-damped) to 0?

Yes, that is a trap on the T500. Don't hold the clutch out for prolonged periods!. The later ones revised the tacho drive., but even the early ones, there was usually enough clutch drag for it to keep reading. Can't say I've noticed any great overdampening.

[Jantar]

I've never locked the T500. But I think that is because Suzukis of that era didn't just inject the fuel into the inlet port, they actually piped it from the pump direct to the bearings, (and I think a jet onto the cylinder wall, not sure about that). So the bearings had oil come what may, just like a four stroke.

I always thought that was a really good lube system for a two smoker, was disappointed when they dropped it. Cost I suppose.

Quite correct Ixion, The T series and the GTs had Suzuki's CCI (Cylinder and Crankshaft Injection). Each cylinder had an oil feed directly onto the cylinder wall and the amount of oil injected depended on both the engine revs and the throttle setting. Each Main bearin had a seperate oil feed where the amount of oil depended only on the engine revs. The big end bearings were a roller bearing and relied on oil vapourisation and condenstaion from the injected oil for their lubrication.

[MSTRS:Me]

Maybe Suzuki's were less prone to this but none of mine ever locked up.
This was most of the T series and a number of the GT's.
I did pop a neat hole in the piston of an A50 that I rode from AK to Hamilton,but I think that had more to do with long term abuse than anything else.
I really loved them old two strokes

IIRC the T series' oil pump was driven off the gearbox sdie of the clutch & stopped pumping if the clutch was (dis)engaged. I was told to always put the bike in neutral when engine was going but bike stationary such as at traffic lights.
Edit: just saw this was the case, don't mind me

[Motu]

On Suzuki singles (never had a multi apart) the left main was fed from the pump,a cup fitted on the flywheel collected the oil and centrifuged it to the big end.Right side bearing was lubed by the gearbox.Good bottom ends that could take abuse....if you kept them topped up with oil.

[Fluffy Cat]

You don't have to blip the throttle on over run etc because on a closed throttle the pilots let a bit of mixture through and there is a fair bit of overlap on the jetting.Bigger pilots when racing help.Do not be tempted to add more oil to pre-mix as you are in effect leaning off and more prone to heat seize.