Two-Stroke Mythbusters part I-SPOOGE

[Bruce CurtisMember]

Most longtime 2 stroke riders would at some stage become aware of a thick oily substance that exudes from their bike exhaust at times that has been nicknamed SPOOGE, until we are blessed with sme catchup technology for our Two-Cycle powerplants it will remain a part of our lives.
Well let us explore SPOOGE.
Common rumour has it that SPOOGE is the leftover 2T oil from mixing too much or a poor quality oil in your pre-mix, another common myth is that the rider hasn’t been on the gas enough to burn the oil.
Both theories have some foundations in truth, but are far from the truth at the same time. In truth the origins of most SPOOGE outbreaks is far more complicated than most would care to admit, in reality it is a mixture of unburnt hydrocarbons, semi solids, liquids and some oil, together they combine in your exhaust system to create the sticky gunky mess we know as SPOOGE.
The creation of SPOOGE begins as we start the bike, on full choke the A/F mixture is rich in hydrocarbons to overcome the urge that a too cold engine has to not leave the fuel in stasis, it reforms droplets on the inlet tracts and sticks to whatever surface it can, some of it burns in the combustion chamber, but a great deal of it escapes its intended fate and hangs around in the recesses of your exhaust waiting for more of its mates to show up to create a giant SPOOGE rave party in your silencer.
Now the Bike is warm off we go, winding our way through the tracks and trails of our day, all along opening and closing the throttle, all the time the SPOOGE is accumulating and waiting. SO where does the rest of this SPOOGE come from?
In some cases the jetting is rich in some or all portions of the carburettor circuits, this releases a constant flow of SPOOGE as the A/F ratio is wrong. In many cases it is a simple fact that the inlet tract is running too cool and droplets are still forming and clinging to the surface, which in turn means the jetting has been richened as all indications from riding the bike is it was running lean. In even more cases the combustion chamber has a poor design in some way with not enough heat being retained in the piston crown or head area and the mixture is not fully burnt and no amount of jetting will cure this. Some really old fashioned port configuration are another culprit, the port timing has too great of an overlap allowing too many unburnt gases to simply escape out the exhaust, and while the scavenging qualities of a 2 stroke pipe helps by recharging this mixture back in on the next stroke, too much will escape the pulse and again reside in the bowels of your stinger section and silencer.
Another area can be poor exhaust port or pipe design or incompatible design with the timing or configuration of the ports.

So how do we eliminate SPOOGE?

Sometimes it is as simple as a jetting and/or plug heat range change, ok you late model KTM & Suzuki RM lads can run off now, nothing more for you lot here.
Sometimes it is a change of piston surface, combustion chamber and the above two, with maybe a little case matching to the transfer ports, now you Yamaha 85, 125, Kawasaki, Husqvarna and GasGas laddies can leave the room, the rest is for the diehard SPOOGE addicts that own Honda CRs, Yamaha YZ250s, TMs and older Mxers to ponder. The rest of your problems me laddies lays within your casting finishes, they can be too smooth, too mismatched, too cold or most of the above. So you Gentlemen and Ladies need to really get dirty, you need to know the original engine blueprint specs to bring these up to scratch with good old fashioned grinding, filing and machining. You may even need to cut new holes in stuff, but if you do it right, not only will you minimise your SPOOGE output, you will have built a beautiful powerplant, with good power, better fuel economy and above all rideability.

So the next time some local Yokel is bagging you fuel mixing or riding prowess based on the black gunk dripping from your tailpipe enlighten the silly bugger with a few FACTS, cause the world is full of them, but often they are too boring or beyond the understanding of your average carpark hero and are replaced by rumours.

Stay tuned maybe if I can find my soapbox I will release more wonderful Two stroke facts and fallacies in the future.

Bruce Cee.

[dennis da menaceMember]

rhank you bruce. i was waiting for that :laugh:

“ok you late model KTM & Suzuki RM lads can run off now, nothing more for you lot here.”

reading into that bruce, one might be lead to believe that these are somewhat superior engines,
with cleaner burning, better engineered and designed porting and chamber surfaces out of the factory and reletively spooge free running, with better economy as well.

but is spooge good for anything though, except catching fire? :laugh:

[TrentMember]

Grrrrereeeeeeeeeeeeaaaaaaaaaaaatttttttttt post BRUCE! The TM has 2 crank case breather hoses and I keep asking people if the black oily muck they pump out each ride is normal and didn’t have an answer till now. I think it will be a while before I need to tune to head to get more power and I’m getting plenty of efficiency I think.

Cheers mate

[glennMember]

so thats why the IT crys them black tears ..

Thanks Bruce,I can die a happy man,,not just yet though

[Bruce CurtisMember]

menace wrote:

Quote:

rhank you bruce. i was waiting for that :laugh:

“ok you late model KTM & Suzuki RM lads can run off now, nothing more for you lot here.”

reading into that bruce, one might be lead to believe that these are somewhat superior engines,
with cleaner burning, better engineered and designed porting and chamber surfaces out of the factory and reletively spooge free running, with better economy as well.

but is spooge good for anything though, except catching fire? :laugh:

Hey Menace, the only thing you didn’t mention was POWER, it appears that the class leading engines in the POWER and delivery of this POWER are all heavy duty Spoogers, the TMs famous for their brutal delivery once unleashed, the CR250R honda second only 2T in the area of INSTANT boogie to the YZ250s, the KX500s and CR500s the same deal, it appears it has something to do with the port configuration, much like the timing overlap in a high-performance V8, their equivalent is flames on the overrun, ours is spooge almighty, it does burn well if you get it hot enough I know this for sure and you witnessed it after Mick brought mine back from his high speed shenanigans that day, smoking like a Winfield Ad.

BC

[dennis da menaceMember]

im not trying to be a smartarse here mate :laugh: honest :laugh:

but does that mean that spooge is produced by a lack of clean burning in general.

if i put my red spring in and wind up my PV will my bike spooge?

or is it all in design?

[MalMember]

Nice thread Mr Blue.

Does this ‘spooge’ biuld up to a point where it block the pipe or reduce performace? How often should I clean it out of the pipe?

I don’t see it dripping from my pipe but if I stick a rag in there I get the ‘spooge’ stuff on it.

[Bruce CurtisMember]

menace wrote:

Quote:

im not trying to be a smartarse here mate :laugh: honest :laugh:

but does that mean that spooge is produced by a lack of clean burning in general.

if i put my red spring in and wind up my PV will my bike spooge?

or is it all in design?

I know Menace, but I was… sorta, It depends, see the red spring does open the powervalve at a different rpm and this may coincide with a change in ignition advance and or a change in fuel circuit, but roughly I’d say it may get worse as it makes the overlap sooner in the RPMS, where the pulses of the pipe maynot be able to cope with the excess mixture being drawn back.

Yes Spooge is a lack of clean burn which is why bikes with smaller carbs and conservative porting get less, and why DFI should fix it up.

BC

[Bruce CurtisMember]

mal5.1 wrote:

Quote:

Nice thread Mr Blue.

Does this ‘spooge’ biuld up to a point where it block the pipe or reduce performace? How often should I clean it out of the pipe?

I don’t see it dripping from my pipe but if I stick a rag in there I get the ‘spooge’ stuff on it.

Heya Mal, it blocks your silencer packing up over a period, the time to clean and change is usually when it starts dripping out the tailpipe after the bike is stopped.

Heated up it creates Carbon that can and will eventually block the pipe, but only after many many hours usually, it’s mostly the silencer packing that it affects in the shorter term.

BC

[MalMember]

Thanks Blue.

Keep the 2 stoke info coming mate. It’s very interesting reading.

[Anonymous]

menace wrote:

Quote:

if i put my red spring in and wind up my PV will my bike spooge?

Mine doesn’t and neither does any of 3 or so other late model 300’s I’ve ridden with regularly.

I think spooge is more an issue on older bikes than the newer ones? That said the 200 doesn’t do it, it just pisses oil everywhere instead

Have you ever had it Mal? Champo? Austblue? Menace? And others.

[Bruce CurtisMember]

Moto wrote:

Quote:

menace wrote:

Quote:

if i put my red spring in and wind up my PV will my bike spooge?

Mine doesn’t and neither does any of 3 or so other late model 300’s I’ve ridden with regularly.

I think spooge is more an issue on older bikes than the newer ones? That said the 200 doesn’t do it, it just pisses oil everywhere instead

Have you ever had it Mal? Champo? Austblue? Menace? And others.

AB already answered in the affirmative, and Mal said he sees it in his pipe, Have a look inside your silencer Moto, wence it is absorbed as much as it can, then you will see it, although you did a rejet early on which may minimise it.

Bruce C

[dennis da menaceMember]

i get bugger all. even if i remove the silencer there is bugger all in the pipe, it is there, but it is bugger all.

the only time ive seen it on my bike is when i used some castrol oil or something at 40:1 (to be sure, as i was desperate), it didnt like it and spooged a little. it leaked out from the exhaust joint at the head too. hasnt done it since.

[DamoMember]

I have experienced spooge on my previous ride, the mighty 2002 KTM 300.

I beleive they were a different head design to later models (05 on).

I had it leaking from head to chamber joint (didn’t seal too well due to bent chamber several times), and also the join between chamber and silencer.

Also, after a very heavy throttled run I had a small fire and a lot of red glowing inside silencer. Pulled it down after I got home and found major carbon buildup. Every hole in the baffle tube was sealed off. I spent a long time clearing every hole and removing carbon. After repacking, the power and rideability improved a fair bit. Worth the effort.

[Bruce CurtisMember]

You Blokes with Late model KTMs are in a bit of a unique Boat, it is the only comtemporary 250+cc 2T that runs a little 36mm Carb, which is why your topend suffers in comparison to some others, flipside is it makes for a very high velocity intake which assists mixing and burn.

On the Spooge front, you will get it, not overnight but it will happen

BC

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