Are You Running Too Much Oil In Your 2T Mix?

[axulsuv]

Well to add to the mix ... In my trusty old Fantic 240 (and the ty80 , fantic 50 and my chainsaw and weedeater...) all use the same premix . Amsoil Dominator full synthetic and ave gas mixed at 70 :1.And I mix it in 5 gallon quantities and rinse the ratio-rite with fuel to get all the oil , so mixing a larger quantitie helps with the accuracy of the mix ... And I have had no fuel or lubrication issues since switching to this about 6 years ago . Everything starts and runs as designed (or better) every time ... And the long storage times my fuel see's sometimes , more than makes up for the price of the aviation fuel ... (110 octane to 30,000ft. ,whatever grade that is ?!) I've not had any fuel go bad and I've had some that didn't get used for over a year ..,

So I'll stick with it

Glenn

[dadof2]

A statement I definitely disagee with is 0007 "This will put carbon on the crown". Some modern oils meeting Jaso FD spec leave virtually no deposits whatever the combustion conditions. The jetting and conbustion temperature can be spot on and provided there is adequate oil film between the piston and barrel to conduct the heat away from the piston deposits will not form. (Suprising how many expensive oils don't meet FD spec)

Amsoil probably is a very good oil but I remember in about 1978 a friend put it in a 6 month old Mont 348 at 100:1 and within 10 minutes running the a main bearing seized. Bke had previously run fine from new on castrol TT at 24:1.

If you look at the mix ratios logically you have a range of ratio recommendations (with good fully syntheics) from 15:1 for kart engines to 75:1 trials bike manufacturers and 100:1 some riders and some oil suppliers.

As a general quide wear and stress in an engine increases at the 4th power of speed, ie doubling the engine speed results in 16 times stress and wear. Add to this the temperature increase effects and the actual increase is more than to the power4.

From this it follows that bikes trickling round 1 mile laps with tight nadgery sections will have significantly different oiling requirements from one doing 10 mile laps on boggy fells with big hills.

The worst that can happen with a rich ratio is a bit of fluffing on pick up after some nadgery slow going. The worst that can happen with a lean ratio is an blown motor, an long push and an expensive rebuild.

Its your choice as they say.

Cheers

Edited July 12, 2012 by dadof2

[0007]

http://www.freeengineinfo.com/two-stroke-carb-tuning.htm

http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

I could probably find a bunch of references to using the carbon on a piston as a tuning tool

It's got nothing to do with the oil, the fuel has more detergent to decrease gum and coke than the oil does and it makes up for pretty much 100% of what is burned in the combustion process

The temperatures involved on the piston crown are probably high enough to burn almost anything onto it and it's the underside that is the clearest indicator

Actually increasing the amount of oil will lean out jetting and cause slightly more carbon buildup

Anyway, back to oil ratios LOL

[0007]

And for the record I agree that a little more oil isn't going to cause an expensive failure so to err on the side of caution is not likely to cost you like doing it the other way

[breagh]

Just as a side issue I'm more than deeply suspicious about synthetic oil in 2 strokes.

Anything that doesn't break down naturally is bound to have an impact on the environment.

The quantities may be seem small but it soon adds up.

Don't know if any studies have been done?

[jse]

The temperatures involved on the piston crown are probably high enough to burn almost anything onto it and it's the underside that is the clearest indicator

This is true. In the "old days" I would "read" the color (and hopefully not the ash) of the piston under the crown to set the jetting on certain of the two-stroke

roadracers. It was a much better indicator of sustained chamber temps than the crown color. The crown edges and the outside of the squish band in the head

is where you looked for signs of detonation precursers.

Jon

ps. I run, full-synthetic 70/1 in my Pro and 50/1 in my air-cooled TYs, the TYs a little more prone to cylinder distortion and hot spots due to the lack of liquid cooling.

I've never had an oil-related engine failure with my Trials bikes in 41 years so my ratio guessing seems to work for my bikes and riding style (or lack thereof.....).

The ratios chosen on the basis of many hundreds of engine innards I've inspected and the advice of a bunch of chemical and mechanical engineers I've talked with

who replied to the question if those are good ratios to run, with "yep, sounds good to me"........

[pindie]

i think this is the whole point. Most jetting and set up guides for 2ts come from MX or road racing stables. No use at all for trials.

MX & RR create heat that trials bikes don't get near. This helps burn surplus oil off etc but leaves an indicator.

In a trials motor it tends to be relativley slow running and a lot of 1/8th throttle use so hardly ever into main jet or needle operating ranges.

My philosophy is think what you do and set up accordingly.

1. Only tight woods and sections. Lean out the pilot circuit bit by bit till you have clean running.

2. Sections with a bit of light trail. Lean out the pilot circuit a tad if needed but make sure its not lean once you start to open the needle/main jet circuits (but also not to rich).

3. Section with trail use and road work. Settle for a balance throughout the rev range. You need the oil in the motor on the road or sections or you'll get the eeeeeeeeeepppK! and seize. It'll smoke once hot but your only burning of the excess you have built up in slow bits.

4. If a clean pipe is your top agenda get a 4T.

Two strokes are all about compromise. this is why the old school road race bike had so many gears (and the expansion chamber was invented). They had to keep the revs in a very narrow rev band to keep it "on the boil". As soon as you change the revs or load the oil and heat range behaviour change a lot.

Above all I'd rather not scuff or wear pistons when I can clean a pipe in half the time to fix a knackered motor for a lot less cash. Pick your riding style and jet accordingly or ride accordingly to your jetting. If the pros have to "give her a handfull to clear it" then they are also using enough oil to create residue no matter what the ratio is.

Edited July 12, 2012 by pindie

[copemech]

I mentioned it before but may have been missed

If you don't have carbon forming on your piston crown you are too rich, it's simple

If you want to make power and run clean, you need correct or at least reasonable combustion temperature

This will put carbon on the crown

It's not an oil thing

But this might not be easy to do on a trial bike, it's probably an engine that needs to be jetted by feel rather than this way

Snowmobiles are the ideal example of 2 stroke jetting simply because of their CVT transmission

Once again, I would tend to agree with you on this, yet as you say it does seem to require the "feel"! Even trying to get some that are possibly running 30-50:1 ratios in a water cooled trials bike can be a chore, now try to get them to run near stoich!

[copemech]

Well to add to the mix ... In my trusty old Fantic 240 (and the ty80 , fantic 50 and my chainsaw and weedeater...) all use the same premix . Amsoil Dominator full synthetic and ave gas mixed at 70 :1.And I mix it in 5 gallon quantities and rinse the ratio-rite with fuel to get all the oil , so mixing a larger quantitie helps with the accuracy of the mix ... And I have had no fuel or lubrication issues since switching to this about 6 years ago . Everything starts and runs as designed (or better) every time ... And the long storage times my fuel see's sometimes , more than makes up for the price of the aviation fuel ... (110 octane to 30,000ft. ,whatever grade that is ?!) I've not had any fuel go bad and I've had some that didn't get used for over a year ..,

So I'll stick with it

Glenn

Now you see Glenn pop up with the 70:1 in an air cooled bike!

Now conservative as I am, I do not know that I would make that an absolute reccomendation for all, yet he knows well what he is doing and how to manage it. No roadracers here, yet a good blow on occasion!

Stoodly(JSE) is at the conservative 50:1mix on the old TY, which is fine as well(even if he never gets it hot).

There is one thing about air cooled trials bikes, they are not force fan cooled like a strimmer, which would possibly let them run a bit hotter at times, yet I doubt nowhere near critical levels just putting about.

[copemech]

One question comes to mind re the fuel supplied(by the fuelers) at SSDT! I am not sure the ratio as the lads are running a lot of roads at mid to high speeds., yet I would think 50:1 would suffice even for this running.

Possibly others may chime in here.

[jon v8]

Once again, I would tend to agree with you on this, yet as you say it does seem to require the "feel"! Even trying to get some that are possibly running 30-50:1 ratios in a water cooled trials bike can be a chore, now try to get them to run near stoich!

I wondered how long it would be before someone mentioned the Stoichiometric angle - The truth is its a complete waste of time for a trials bike,as the engines are virtually never used when it would be good to run at 14.7/1 air/fuel. Its only good for idle and cruise conditions.Clean pickup and mid range pull are much more useful where the ratio would be better back towards 12.5/1. I wonder if the top teams use wideband sensors to tune with ?

I guess HRC would with the efi 4RT motors,but I wonder about the two stroke motors from GG and Beta etc.

[0007]

I was going to mention Stoich but it is entirely a jetting thing and not a oil ratio thing

I think the engine would not suit a pyrometer but would certainly be easier to tune with an 02 sensor and a gauge on the bars, it would take a heated sender and all but....it wouldn't work in a section, you would have to check numbers at certain throttle openings, set and forget

I agree with wanting to keep the A/F ratio closer to12.5:1 as response is what we want, over 14 is really for fuel economy and clean emissions

As was mentioned before a lot can be learned from the factory's oil injection ratios, interesting that they go from practically no oil to 30 or 40:1 or maybe more but then again injection oils are somewhat diluted to reduce viscosity

Tells us that a straight ratio is really a compromise on both ends

Another note, Yamaha pre mix 2 stroke OB's run at a factory recommended and warrantied 100:1, these motors tolerate ridiculous loads and runn at WOT for extended periods, but max rpm is 5500, maybe ratio relates more to RPM than it does to load

I remember hearing about Jeremy Mcgraths last years at Honda on a 2 stroke and his bike was making something like 70 HP, they were running 25:1 and that bike didn't smoke even a little bit

I bet those engines were hand built masterpieces

[2stroke4stroke]

Do the additives replacing lead cause more harm than the lead? This was known at the time of the change with many deeming the Benzine to be far worse on several fronts.

Breathing in fumes that have not been through a catalytic convertor - it takes about eight miles, I am told, for a cat to reach operating temperature. Up to that point the emissions are apparently worse than with no convertor. The average car journey in the UK is less than 4 miles so most never reach temperature except perhaps the day they go for the MoT test. Moral of the story? Worry more about what you're breathing in when you go to the shops than in a section queue.

It seems fully synthetics are not well regarded by many tech types as suitable as they do not offer such good protection when the bike is lying up for extended periods - something many trials bikes do a fair bit of.

I bought a TY200 last year that ran 40:1 but did a good impression of the Red Arrows. For trials Silkolene recommended a variety of ratios in their Comp 2 Premix (which I can easily get) ranging from 40:1 for deep sand up to a rather lean ratio which I can't remember (I have a print out of the e-mail somewhere) for lighter use. I settled on 50:1 which seems reasonable as my Fantics ran fine on that with far inferior oils 30 years ago. The Beta seems to run OK on this at the Beta recommended 70:1.

[2stroke4stroke]

Do the additives replacing lead cause more harm than the lead? This was known at the time of the change with many deeming the Benzine to be far worse on several fronts.

Breathing in fumes that have not been through a catalytic convertor - it takes about eight miles, I am told, for a cat to reach operating temperature. Up to that point the emissions are apparently worse than with no convertor. The average car journey in the UK is less than 4 miles so most never reach temperature except perhaps the day they go for the MoT test. Moral of the story? Worry more about what you're breathing in when you go to the shops than in a section queue.

It seems fully synthetics are not well regarded by many tech types as suitable as they do not offer such good protection when the bike is lying up for extended periods - something many trials bikes do a fair bit of.

I bought a TY200 last year that ran 40:1 but did a good impression of the Red Arrows. For trials Silkolene recommended a variety of ratios in their Comp 2 Premix (which I can easily get) ranging from 40:1 for deep sand up to a rather lean ratio which I can't remember (I have a print out of the e-mail somewhere) for lighter use. I settled on 50:1 which seems reasonable as my Fantics ran fine on that with far inferior oils 30 years ago. The Beta seems to run OK on this at the Beta recommended 70:1.

As we can't seem to edit now I've used quote.

As regards petrol quality, a pal recently sold a TY 250 twinshock that had not run for eight years and last had petrol put in 10 years ago. It started second kick. Petrol was petrol in them days.

[copemech]

Unfortunatly, I do not believe the jetting will have much effect on a trials bike slogging about most the time at or near idle with an occasional blip or even a brief run between sections as far as the oil situation goes.

Only reason I even mentioned it was the fact that some bikes come jetted soo lean from new, in an effort to meet emissions I suppose, that they will barely run.

Seems to me that one first has to make a bit o' power to generate some heat, running fae lean will do niether.

2T4T did bring up a point reguarding runoff of the oils during periods of non use. I "think" the manufactures have added cling agents to address this in most cases. There was a big and expensive spat over this issue a number of years ago re Mobile 1 aviation synth and runoff destroying camshafts and lifters in very expensive motors. Many learned from that issue!

I have never neccessarily been a proponent of synthetic oils overall, and fact is it does seem there are a number of semi- blends out there that work quite well in all but the highest stress conditions .

As far as your car goes, my motto is simple. The best oil is clean oil! For the most there is no extended interval for expensive synthetics and it is likely not worth the extra in a low stress environment. A turbocharged and or high stressed motor is another story, yet still change it regularly like your underwear! Yhis does not mean every 3000 miles, either.