ESE's works engine tuner

[wobbly]

Re conrods, most Asian manufacturers use CRM415, there is no direct correlation in US types to this but its closer to 4140 than 4340.
Its called 15CrMo5 .The different spec gives a more ductile core when case hardened to 60-62RC as is needed to support needle rollers.
This gives a stronger forging able to withstand shock loading better.

[husaberg]

Where we are talking "normal " cranks and not idiot huge things like the KTM - or Triumph twins for that matter, axial end float on the crank
simply makes more power.
As the axial clearance of the stock bearings is taken up by differing expansion rates or crank flex, the normally fitted ball races see a huge increase in end wise friction.
Using C3 as you should ,does help, but when using balls you have to polish the crank axles to alow a slip fit with 0.3mm end float in a 125.
This ultimately causes wear on the slip fitted journals.
Using rollers means that the axial clearance can be arranged to be within the bearing end faces, and the inner race can still be a slight press fit.
As a side effect the rollers are capable of twice the radial load so last much longer - though they do have slightly higher rolling friction.
The only issue with the rollers is they dont like any axial angular misalignment, and in really dumb designs like a Triumph twin, where the axles of a 750 are the same size as that
we use in a 125, of course they bend like hell with 15Kg of pig iron flailing about.
So they developed a special line of rollers called " SuperBlend " that have a slight radius tapered end on the rollers to allow some axle flex.
Many designs have one bearing locked onto the crank - but floating the other end still works well to reduce axial friction.

I was looking at a pic the other day (a cutaway drawing of a RSW crankcase)I mused to myself... if one of the benefits of the roller bearing in this application was also a better smoother straighter inlet port due to a potentially smaller outer OD of the bearing.
Maybe I was overthinking it or its just a happy coincidence.
As a aside Burt Monroe much admired the radiused ends of the std Indian 1920's big end rollers that even when he finally sorted the bottom end (so it had a positive oil feed) he arranged the sizes so he could still use them.

[Frits Overmars]

I was looking at a pic the other day (a cutaway drawing of a RSW crankcase)I mused to myself... if one of the benefits of the roller bearing in this application was also a better smoother straighter inlet port due to a potentially smaller outer id of the bearing. Maybe I was overthinking it or its just a happy coincidence.

You weren't overthinking and is was not a happy coincidence either, but a necessity. When working at the first Rotax-256 tandem-twins in the winter of 1980,
I substituted the standard 34 mm carburettors with 38s. When adapting the rotary-side cases to the bigger carbs the outer ball bearing races started peeping through!

The later roller bearings allowed fitting 42 mm carbs. As an added benefit they made splitting and closing the cases a whole lot easier.
The first ball-bearing tandem-twins were real pigs, with both inner bearing races press-fitted to the crankshaft and both outer races shrunk into the cases.

[wobbly]

Thanks for reminding me Frits about how much we hated those early Rotaxes,I spent many cold nights at ZipKarts in England
grinding and dyno testing them.
Polishing the journals was the first thing I did and having slip fitted bearings was a godsend when pulling them apart all the time.
Hines 83 championship wining Superkart engine made 84Hp at the sprocket, and boy did we think we were clever - not.

[FastFred]

spark plug thread sizes and pitch http://www.mrcycles.com/page/sparkplugspecguide

[Martin1981]

84Hp at the sprocket, and boy did we think we were clever

come on wob.... 42 sprocket hp/125ccm in the early 80s..... this is not that bad!

[F5 Dave]

A mates one with std 82 barrels in a GP bike makes 60hp at the rear wheel. its got size smaller Mikunis & pipes for short ccts and a very nice curve at conservative revs (all the cranks could take with those size pins & without Wobs hand selected rollers). These were pre powervalve, so that's pretty impressive for the time.

[wobbly]

Ha, I had forgotten about the rollers - I spent a fortune back then buying a 4 digit micrometer and went thru boxes of big end bearings
to find enough to make sets of needles that were all the same within 0.001mm.
They varied up to 0.008mm in one cage set from the factory, and the rod bores varied 0.005,so if you were keen you could match them all together.
Hines championship year we were able for the first time to run the same cranks all season,previously we would be lucky if they lasted the first all gear run on the dyno even with 16:1 on 747.

[Frits Overmars]

Ha, I had forgotten about the rollers - Hines championship year we were able for the first time to run the same cranks all season,previously we would be lucky if they lasted the first all gear run on the dyno even with 16:1 on 747.

I did all my Rotax development work on the Rotax124 single (the one with the teflon inserts holding the crankshaft bearings in the magnesium cases).
The teflon had to go but after that I never experienced any crankshaft problems. I ran the engine to 14.500 rpm on 25:1 Castrol with 0,4 mm quish gap.

Hines 83 championship wining Superkart engine made 84Hp at the sprocket, and boy did we think we were clever - not.

In 1980 my single gave 34 HP at my Heenan & Froude brake. Meanwhile Jan Thiel was working at Reggianis Rotax tandem-twin in Italy and he too extracted 34 HP at his Borghi & Saveri brake from a 125 single. These Rotax tandem-twins would run circles around the Yamaha TZs until the primary coupling gears shed their teeth.
So you weren't doing all that bad, Wob.

[wobbly]

The 83 engine had special cylinders that Hines got the factory to cast with alot more material around the Aux ducts ( it was easy for them to scrape
material off the moulds prior to casting ) so I could make the Aux ports and ducts WAY bigger right down to the flange.
That is where I begun to learn about NOT making the exit size bigger as I ruined a perfectly good set of cylinders, and waisted JLs time building a special
set of pipes with 42mm headers.
This made a whole lot less power,so I wasnt too popular at the time, but if only I had done some testing with the stock small duct, and the big pipe.
In the end the new way fat belly JL pipes I did made big power gains,and they made a fortune selling these as you HAD to have them or simply got blown away.
The factory didnt believe what we were saying about the power numbers we got off our Borghi ( so basic I had to write down the numbers as the run progressed )
until we sent them one of the spare development sets.
Then it dawned on them why Hines had set new lap records at every track that year - near on a full week grinding one barrel.
But it was several years before we could replicate that power in production cylinders as the factory would not do " specials " for just anyone.

[husaberg]

You weren't overthinking and is was not a happy coincidence either, but a necessity. When working at the first Rotax-256 tandem-twins in the winter of 1980,
I substituted the standard 34 mm carburettors with 38s. When adapting the rotary-side cases to the bigger carbs the outer ball bearing races started peeping through!

The later roller bearings allowed fitting 42 mm carbs. As an added benefit they made splitting and closing the cases a whole lot easier.
The first ball-bearing tandem-twins were real pigs, with both inner bearing races press-fitted to the crankshaft and both outer races shrunk into the cases.

Seeing as I m now batting near one in 600.
The other thing that occurred to me was the other long rod advantage, in that there was a lot more room for a more gently radiuses more straight inlet as well as the many other advantages.


If I may ask does anyone know the dimensions of the rsw main bearings? I tried a quick google
They are only listed as a part number in the rws part manual that doesn't seem to cross reference.
but I think it maybe approximates this
http://www.kiwibiker.co.nz/forums/at...6&d=1413875767
25 x 52 x 15 mm

http://www.maranello-engineering.com...ml?language=en

[peewee]

wob i was thinking of something like this for carb angle. maybe i cant get a straight on shot into the cylinder but anything should be better than the large kink of the common aftermarket and oem manifolds. as the carb is tilted farther forward is it better to use a deep float bowl rather than a wide shallow one ? another question on crankshafts. been trying to locate a +4 set of new webs. only thing ive found is fully assembled +4 cranks, so ill have to pull them apart i guess. most are welded at the manufacturer so its going to be a pain. almost thinking of some billet webs from crankworks as theyre sold in unassembled sets but $1000. you got any ideas on this ?

[wobbly]

That carb angle is right at the limit, and is about what I end up with when machining 7* off the face of TZ350 cylinders.
The issue is the proximity of the fuel level to the pilot jet, you have to lower the floats at least 3mm or under brakes the slosh dumps
petrol straight thru the pilot drilling in front of the slide, and into the intake.
I have a few +4 cranks that are welded in the centre axle only, makes it easy to split the outside wheels off if needed.
Pm me re this.

[Grumph]

If the pilot jet is a plain orifice jet, like a dellorto for example,you can make up a male/female extension to lower the jet well down into the bowl. this removes most of the "slosh" effect.
If it's got an emulsion tube incorporated, you're on your own...But a piece of brass tubing slip fit over the jet, and long enough to be trapped against the bottom of the bowl will do much the same thing. Cut some slots in the bottom end of the tube of course for fuel entry.
If you think you've got a problem under braking, try speedway TQ's with bike carbs and Methanol. High sideways G's which the carbs were never intended for.

[wobbly]

Makes no difference whatever where the jet itself is situated, the rising fuel level at the front of the bowl simply runs up the drilling.
As soon as the bowls liquid level is higher than the pilot drilling into the carb bore, fuel will spill.
The only carbs that dont do this have the bowls sitting horizontal, and the bore downdraft, like FCRs,or the other is the Lectron that has
no pilot circuit at the front of the bowl.
Some Dellortos have the pilot behind the emulsion tube, so dont suffer from the level rising at the front of the bowl under brakes.