Hotelmoto, Do you recall when Castrol TTS was first launched in the early 80's in that beautiful 2 litre half rectangular tall metal can with the 1st class British green paint job on it and the red pull out easy pour spout? (If anyone still has one in their collection if they can post a photo of it)
It was the right technology, at the right time, in the right packaging, at a reasonable price by a brand name that already had credibility in the motorcycle market. It sold like crazy all over the world, and it was and still is a top product that in many cases is unequalled in its class. (About the same time it already bought out complimentary GPS 20W/50 and R-Synthetic 15W/50 for 4 strokes, and these products were locally blended with imported ingredients of course) And there was hardly any competition at the time with this product unlike today when the rider becomes mesmerised when he walks into a bike shop. In the 80's just the Castrol logo alone was worth A$350 Million in goodwill .
JiGantor (Adam Savage!) perhaps the "best" way I think is to conduct seat of the pants testing that translates to real world ridability. We can open our wallets, or sell our car, to pay for someone's rolling dyno (Like Jennings did with Jerry Branchs Dynoroom). I have used a Dyno years ago for roadrace bikes and they are not good for the engine, the crankshafts and pins suffer under prolonged use from the resistance and reverse torque from the dyno. I am not sure if you can use MX type tyres on a Dyno......I heard it will cause slippage from knob curl (I was going to say knob bend over) not allowing full HP to be applied to the dyno resulting in inaccurate readouts. They analyse your exhaust gas and allow jet changes and measure HP & torque and can have benefits but track testing was our best guage.
Conducting a compression test between oil ratios I am not sure will offer any figures that can be used conclusively. You are ineffect doubling the amount of oil by going to near 20:1. In theory you should show a greater cranking compression figure but not by too much. A hot engine with your throttle held wide open. It doesnt measure HP gains from reduced friction (see my extract below). More oil seals the engine up like you wouldnt believe. I was at my tuners shop today to inspect some racing outboards I am having built and we decided to run 20:1 in these after running 20:1 in the previous engine. Most racers traditionally run 30-40:1 in our class (F2 Tunnelboats) and some are starting to go richer from what US and UK winning teams are doing. We have EFI and O2 sensors so changes are made automatically to fuel delivery. The ECU and fuel can be changed further on the Mercury laptop. My tuner today said to me more oil will offer us a greater blast from out of the corners because the bores will be better sealed and offer snappier acceleration from reduced blowby. "20:1 is like an extra 20 thou off the barrel"
We suffered from a fall in power when running leaner oil ratios out of the turn. Even his other customers like the SLSC boats obtain better power running more oil (25:1) than the 50:1 recommended by Tohatsu (Most SLSC' s use this brand, they are the best engine under 30HP).
A10% compression increase is like going from a typical 185PSI to around 203PSI and any tuner will tell you that is significant and it is like taking perhaps 15-20 thou off the head.
What needs to be done is to mix a batch of 20:1 (10 litres + 500ml oil) and run it. You may find two things shortly after your engine gets its 20:1 tthroughout it. An increase in power and torque across the rev range, OR signs of leaness where you need to raise the needle by lowering the clip position. This helped me as I write below. You wont need to touch your pilot jet, perhaps fiddle with the air screw. I wouldnt worry about the main jet for now as you are testing the midrange, later maybe go a jet higher. You can test the main jet for correctness via the variuos methods of accelerating and closing the throttle to see if you get acceleration (run on) or deceleration. (Read the jetting guide offered by Lozza that should explain this)
Below is an extract from a ride report I put in the Vinduro section last year which discusses what proper jetting can do for you (Even by running 102 Octane race gas it did not stop the severe detonation till I fixed the jetting.......do not try to fix detonation by simply going to higher octane fuel!! :-
"The course wound over the undulating forested hills for a 16KM loop of single track. The day before I made the error of lowering my jet needle to the lowest point after reading one of the US mag articles in an attempt to fix the poor midrange and lack of power. The bike on the first lap detonated severely and of course the transition from different throttle openings was poor with the bike stuttering and breaking up when trying to wind it out. I was not very happy and thought something major is wrong with the engine or stators whatever. At one stage I thought the bike would quit as it sounded like little men in the head with tiny hammers smashing away.
I had one guy come up behind me and I let him pass me and he was on a 75'DT250 with trials tyres and he zigged zag fantastically through the forest as his centre of gravity was very low to the ground. I caught up to him on a greasy hill and overtook him again.
So, I came back to the pits after my first lap and was considering just throwing the bike back up onto the trailer and calling it quits for the day.
After Eugene (owns same model bike) came back I told him how bad my bike ran so he took it up the road for a spin and came back and said the bike doesnt go nowhere as crisp and nice as his. "Just totally different" shaking his head. "Must be all carboned up inside!"
Eugene and his workmates were camped next to me and Chris an expat New Zealander who came along to see what this Vinduro thing was all about (He is restoring a 81KDX175 (That lunched its bottom end as he ran 50:1 in it in another event 3 months later), said that my carb was running way too lean and that i shouldnt have lowered the needle so much. He said raise the needle to the second notch from the lowest postion and "also try winding out the idle screw even up to 3.5 turns from closed, the 1.5 turns is only the factory setting". So I pulled it apart and did that (I just turned the screw out 2 turns), started the bike and it was an entirley new machine from that moment onwards. It wound out crisply and buzzed all the way to the top end that it has never done before. No detonation, no running on after closing the throttle (reed flutter) and I came back and said it was a new bike. No more staggering, popping and crackling, just a smooth clean rise in revs. I was wrapt! I might take it to its highest setting and see if it gets better or worse (I have since done that it goes even better). I will also now reduce the main jet size from the 310 back to the stock 300 or even the 290 (which came with the bike when i got it) as recommended in one of the mag tests as i was enriching the wrong circuit. It should pull even cleaner. (now run a 280 but will also test a 290 at this weekends event)
I was now anxiuos to get back out onto the track for my 2nd run. I would go out with Chris on Eugenes 400 when Peter came back after going for a lap on it. (I will uploade some pics of Pete physically stuffed and bogged in the special test gully section)
At this point it started to rain again but neither of us cared (least the New Zealander from Dunedin who would mostly ride in the rain and snow) and we set off for the checkpoint and took off up the track and I just left it in 3rd gear (and as the Trail and Trail article once said, leave it in 3rd gear and use it like an automatic) and this is what i did. It just accelerated away from low revs and pulled like my old XR350's even better now that i look back! I was just so happy, with the engine zapping on with no issues. The corners came up far too quick and I had to really concentrate 100% with no mind wandering allowed or it was into a tree. With all the other mods I have done to the engine and exhaust the bike had way too much wasted power now I thought. I will never use it all unless I am out in a desert race. I never touched 4th and 5th as it was a moderate tight to open terrain and now top gear WOT would be frightening. Just twist the grip before the mudholes and ruts and through you go without any worry as before it would hesitate and you couldnt get power on in that instant when you came across an obstacle unexpectedly."
Going from the bottom setting of the needle to the top is a VERY big difference and my bike loved it, it was its ideal setting. The magazine article did not apply to my bike. And it did not take an hour of riding it was instantaneouos. I know when switching oil ratios will take a bit longer. I think the test bike back in 1980 ran MC-1 @ 50:1 .
As a result not only was the fuel/air mixture richer that produced great gobs of power and torque but it was being lubricated better with more oil going through. It also did not smoke any more than before. I would have loved the previous owner to have ridden the bike again.
The moral of this story is learn to jet your bike right. It may be the transformation your bike needs. Ask someone who knows bikes better than you ride it for you and take their advice as a guide.
Lozza, 710 @ 20:1 sounds good as long as the jetting is spot on regardless of the bike. As a few have said start rich and work down. I spoke to a desert racer who raced the Finke and Mt Ebenezer and due to the dryness of the West QLD desert air they jetted very rich to the point where the bike "blubbers" and then worked back.
From some other recent comments it is apparent that there is demand by other readers for information on oils and fuels, including the important task of jetting. Why have so many people been so shy and laidback to not ask for this information in the past.
I have my own questions like why do reeds "flutter" when the jetting is lean? It makes that "Ung Ung Ung" sounds when you back off the throttle and the engine runs on. It makes it then hard to corner properly. What causes that and what goes on in the crankcases to cause that?...........also what is the difference between your standard metal reeds, Boyeson reeds and the latest Carbon fibre reeds as to why one produces either better throttle response, power& torque or all 3 things?
