2 cycle lubrication rumor BBC TOP Gear show

[tri again]

They were showing a saab 2 stroke and said that prolonged downhill engine braking could cause engine failure because engine lube comes with the fuel.

Downhill with no gas was the concept.

British mind control?

[dougspcs]

In theory it makes sense, but in the practical application its kinda thin...

1st, how much down hill engine braking you gonna do..really? Secondly there is minimal combustion and therefore little heat!!

If you're thinking you need to stop engine braking down the hills and use the brakes more..don't sweat it!

I think they are using this to promote their new oiling system technology..it's finding its way into other 2stroke engines such as snowmobiles..

It reduces oil consumption and smoke by focusing oil delivery into the areas that need it most like the crank bearings..let time tell the real story. Will these engines still be kicking in 25 years?

Environmental propaganda at its best!!

[NeverLift]

I watched an student at MMI seize a RM250 letting it engine brake on the Dyno. After seeing that I never engine brake 2 strokes. I'd rather replace brake pads than engine parts.

[tri again]

I know my 61 triumph will run cooler when I go down long grades
because of burning less gas.
Seems like if it's still running, it should have at least, some fuel going through it.

I also remember old timers saying to never let a 2 stroke idle for very long.
Not sure what that's about either.

[fabiodriven]

I seized up one side of a very fresh bore on my RD400 when doing a very long bit of braking with the engine. At that time I was mixing the oil with the gas instead of using the oil injection. I had always theorized that it wouldn't have happened if I were using the injection system because the oil injection delivers oil based on the engine speed, not fuel usage. That was about 16 or 17 years ago and this is the first I've ever heard of this theory outside of my own head. In this case yes, I will agree with the theory based on my own personal experience.

[El Camexican]

Where is barnett468 when we need him most?

[dougspcs]

I seized up one side of a very fresh bore on my RD400 when doing a very long bit of braking with the engine. At that time I was mixing the oil with the gas instead of using the oil injection. I had always theorized that it wouldn't have happened if I were using the injection system because the oil injection delivers oil based on the engine speed, not fuel usage. That was about 16 or 17 years ago and this is the first I've ever heard of this theory outside of my own head. In this case yes, I will agree with the theory based on my own personal experience.

What oil were you using Fabio?? Just so know which oil isn't best to use!!(Snicker snicker..)

[tanks350x]

Though I've never owned a 2 stroke, interesting topic to say the least

[El Camexican]

Found this on the net, seems it's a thing

All two-stroke engines running on a petroil mix will suffer oil-starvation if forced to turn at speed with the throttle closed, eg motorcycles descending long hills and perhaps when decelerating gradually from high-speed by changing down through the gears. Two-stroke cars (such as those popular in Eastern Europe) were in particular danger and were usually fitted with freewheel mechanisms in the powertrain, allowing the engine to idle when the throttle was closed, requiring the use of the brakes in all slowing down situations

Still, imagine a late 70's 125 GP bike chopping the throttle after a 17,000rpm blast and downshifting for a corner with the carb closed, that's got to be equivalent to a few hundred miles of engine braking on the trails for us mortals.

[just ben]

call mythbusters

[Billy Golightly]

Yes, very common way of seizing actually. When your drag racing or coming down from a long run, pull the clutch, don't chop the throttle and downshift like crazy

[RIDE-RED 250r]

It's funny this topic comes up...

When decelerating, I would always crack the throttle just a whisker, just enough to keep it popping like popcorn.. for lack of a better description.. For some reason I never liked the sound of letting it spool down from higher RPM without cracking the throttle just enough to keep it popping..

[JasonB]

i always coast over engine braking, theres no backpressure so engine braking is pretty useless on a 2stroke as it is. When i coast or am going down a hill with minimal throttle i always pull the clutch in, i heard this theory over on the trx forums somewhere and it made me super paranoid when i first started running my 310 bike.

[El Camexican]

This post really has me thinking now. I always open my throttle to try and match my RPM’s with what the next down shift will bring (2 or 4 stroke), I never just stomp down on the lever at idle, so I guess that helps lube the 2 strokes.

Somewhat related to this I have put off getting a Rekluse clutch because I am terrified of boiling the brakes on my endure bike while coming down steep mountains, so I always use engine breaking which I’m told is not available with the slipper clutches, but would solve this problem. Despite racing fluids, good pads, braided line and Brembo mechanicals I still manage to boil the fluid once in a while and it’s scary as heck to have that lever come to the bars with little or no effect on stopping while rolling towards a drop off. That said I did think my last piston was worn a little prematurely, especially since I was using a lot of oil, now I’m wondering if it wasn’t all the engine braking? Sometimes I’m rolling downhill against the engine for as much as 15 minutes or more at a time.

Thinking back I did drag race a 2 stroke for a year and always let it engine brake to a stop because pulling in the clutch at speed over heats the plates and warps them and searching for neutral at over 100mph is insane. I was using 20:1 premix and that engine looked fine when it came down.

This post is going to make me lose sleep!

[oscarmayer]

4-stroeks man! try them. ;) hehe a nice trx450 swap would be sweet!!

[RIDE-RED 250r]

I think the particulars of the riding situation has a big influence on whether this is true or not.

For example, riding the way I do, higher gears, on gravel, rolling into and out of the throttle with occasional WOT runs, I don't think it is big an issue. But still, I keep the throttle just cracked to keep it popping. And like you, I dont just slap the gearshift down and dump the clutch when downshifting. I blip the throttle and try to match RPM to ground speed for the gear I am heading into, just like down shifting my big rig..

But when coming down from extremely high RPM after a long WOT run, excessive engine braking may be an issue.

I agree with Jason, these 2-strokers really offer minimal power for holding things back and slowing down. My cracking the throttle has more or less been to make sure I am still getting fuel and air in the engine and because I don't like just pulling in the clutch and coasting. I have heard other machines that back fire pretty good when slowing down without cracking the throttle at all. I could be wrong, but I attributed this to the pipe getting loaded up with excess fuel and finally igniting when air is finally let in..

IDK, I could be way off in my inference though.

[El Camexican]

I think the particulars of the riding situation has a big influence on whether this is true or not.

For example, riding the way I do, higher gears, on gravel, rolling into and out of the throttle with occasional WOT runs, I don't think it is big an issue. But still, I keep the throttle just cracked to keep it popping. And like you, I dont just slap the gearshift down and dump the clutch when downshifting. I blip the throttle and try to match RPM to ground speed for the gear I am heading into, just like down shifting my big rig..

But when coming down from extremely high RPM after a long WOT run, excessive engine braking may be an issue.

I agree with Jason, these 2-strokers really offer minimal power for holding things back and slowing down. My cracking the throttle has more or less been to make sure I am still getting fuel and air in the engine and because I don't like just pulling in the clutch and coasting. I have heard other machines that back fire pretty good when slowing down without cracking the throttle at all. I could be wrong, but I attributed this to the pipe getting loaded up with excess fuel and finally igniting when air is finally let in..

IDK, I could be way off in my inference though.

I agree there isn't a lot of resistance in these 2 stroke engines (ever down shift a Ducati at speed?) but it's still something, especialy when you are in loose rocks and your stiff MX boot turns makes your rear brake more sensitive than a light switch.

[82 250r]

I ride trails exclusively and love to use the engine to brake until i heard of this theory a few years ago. Now I'm a bit paranoid about it.
To me, it's easier to use the engine brake on long descents but have since got in the habit of using the brakes more.
I agree with fabio that there's merit to the theory.

[barnett468]

Yes, very common way of seizing actually. When your drag racing or coming down from a long run, pull the clutch, don't chop the throttle and downshift like crazyyup, any experienced 2 stroke desert racer will tell you the same. this has been known since at least the 60's. some desert racers actually set their idle mix rich and set the idle a bit high to help compensate since some do not like pulling in the clutch during every turn in a desert race.

[atc007]

Good thread. Yes, when decelerating with a 2 cycle engine. The" cooling mist" of the intake charge is just as important as the oil mixture itself. The vapors of the cool gas and oil mixture keep things much cooler and happier in there. 100% true. Can't remember for the life of me which old timer taught me that...Pretty sure it was my old Arctic cat dealer after I had had a really spectacular run on pistons one winter,him or a Wiseco tech..

[Rigaman]

This thread just opened a can of worms for me. Now I'm gonna need to learn to ride all over again. I don't really ever engine brake though. It doesn't really do much. Not like a 4 stroke. The thought of blowing my top end on acceleration was always my concern. I never thought about deceleration.

[tri again]

I remember driving a 2 stroke car many years ago and after acceleration,
it would go to idle until you hit the gas to go faster again.
I thought it was either cool, odd or broken but it was the designed
freewheel clutch.
Apparently, the idea was to eliminate decel backpressure all together.

Kinda fun once you got used to it.

[fordnut79@hotma]

The polaris 2-stroke trike back in the 80's had an auto clutch (pvt) that would go back down to idle until you gave it more throttle too.

[Red Rider]

Come on guys, you shouldn't have needed this thread to bring this to your attention. Just the simple understanding of how a 2-stroke engine works should have been enough.

[Afrothunderkat]

2 stroke engine brake? HAH! None of my smokers have much of an engine brake so I always pull the clutch in when going down hill.

Plus, I give it a twist here and there when coming off a long hill climb or prolonged high RPM use. Gottah keep these thirsty bitches lubed!

[Afrothunderkat]

Good thread. Yes, when decelerating with a 2 cycle engine. The" cooling mist" of the intake charge is just as important as the oil mixture itself. The vapors of the cool gas and oil mixture keep things much cooler and happier in there. 100% true. Can't remember for the life of me which old timer taught me that...Pretty sure it was my old Arctic cat dealer after I had had a really spectacular run on pistons one winter,him or a Wiseco tech..

Learned that on a CR500 super moto thread 5 years ago on thumpertalk!

2 stroke computer sciences