ESE's works engine tuner

[adegnes]

One you can undo the other you can't. I know which one I would be trying first. Well actually you could devcon the transfers if grinding them didn't work so well. There is of course a preferred taper and ratio between the bottom of the duct and the port at the cylinder.

That's a good point!

[Frits Overmars]

wobbly what do you think about roller bearings in this transmission ? one behind the front sprocket and one behind the clutch basket. i dont see any reason not to do it, although they would need a ring groove cut in them.

I don't see any basic problems for a roller bearing behind the sprocket, but it's a different kettle of fish behind the clutch basket. The remaining ball bearing on the clutch shaft will have to cope with the full force of all the clutch springs. Is it up to that?

EDIT: There are no big axial forces working on the secundary gearbox shaft (unless you have bevel gears driving a cardan shaft), but it still has to be kept in place.
So although you could use a roller bearing behind the front sprocket, it would require that the remaining ball bearing on this shaft is axially fixed in both directions, and in the cases as well as on the shaft. Could complicate things....

EDIT # 2 (it takes a while, but once I've got my brain in gear, it won't stop): unless you have a primary transmission with straight-cut gears, there will be axial forces acting on the clutch shaft in both directions, depending on whether the engine is driving or being driven. Violent up- and down-shifts, you know...

[peewee]

thnx for a response frits. the crank and clutch basket gears do have slanted cut teeth originally, i think theyre refered to as helical spur gears ? but im replacing those two primary gears with hinson straight cut spur gears.

as of now the clutch shaft has a ball bearing behind the basket and a needle bearing at the other end

the front sprocket shaft uses the same. a ball bearing behind the sprocket and a needle bearing on the other end

my plan was to keep the needle bearings but replace the ball bearings of both shafts with roller bearings.

i have done this same procedure on one of my ktm engines and its working well and the roller bearing usually has a far higher load rating than a similar sized ball bearing

[peewee]

That's a good point!

maybe my memory went bad or i simply misunderstood what he said, but i thought wobbly said several times that there wasnt much power difference between transer ducts that have high or low ratios between the entrance and exit ?

[TZ350]

what would yield the best results here? Case transfers are too wide - widen cylinder transfer duct entry 5mm on each side or epoxy the case to match?

Attachment 311314

From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.

[adegnes]

From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.

I thought it was short and fat is better than long and skinny? I'll do a search.
Kinda ironic - I fabricated this case partly because nothing with wide enough transfers for the cylinders I planned to run was available (mainly to use a rotary valve though), now this cylinder would actually fit a "stock" case with minor modications.

Maybe go for the malossi mhr team 50cc for derbi ebe050 instead, cheaper, the right width, and should be up there powerwise. It also shares stud pattern with the Emot cylinder.

[Frits Overmars]

.. the roller bearing usually has a far higher load rating than a similar sized ball bearing

Yeah, a far higher radial load rating; a roller bearing's axial load rating is about zero.

From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.

A gas column with a smaller cross section has to accelerate more rapidly in order to transfer the same amount of air/fuel mass as a column with a large cross area.
But the rate of acceleration depends on the pressure difference between crankcase and cylinder, which in turn depends on the blowdown time.area and the efficiency of the pipe. At high revs, when the available time for transfer becomes shorter and shorter, small transfer cross sections may be less than desirable.

[wobbly]

As always its impossible to say what would be a good mod if only half the info is available.
Grinding or epoxying would depend entirely on the case com ratio.
If its already way too small then grinding is needed as the case com ratio would have a way bigger positive effect than the cross sectional change may be a downside.
But that cylinder for sure needs a big radius on the duct/bore edge.

Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.
But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.

[Grumph]

Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.
But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.

What is not generally realised either is that most if not all of the double row races behind the clutch are actually angular contact bearings.
IMO there is probably a point below which it would be possible to use conventional ballraces but without actually measuring the side loads i'm not going to guess where that comes...

[peewee]

so keep the double row ballbearing behind the basket but use a roller behind the sprocket ?

[speedpro]

I'm asking myself why bother? Has something failed? Triple the horsepower? Measurably less losses with rollers?

[peewee]

hard to say how much power it will have but as far as im concearned you can never over build it.

anyone try a set of these reproductions ? i thought about resleeving some yamaha cylinders but for the same price i figured i would try some of these

[F5 Dave]

So no PV banshee copies? Not keen on CPI mono block? Many different types now.

[peewee]

i know theres better options but i wanted the challenge of working with a 30yo cylinder to see how much better i could make it run. it will be good tuning practice as theyre only $300. down the road i can simply drop a different cylinder on if i want

[seattle smitty]

i know theres better options but i wanted the challenge of working with a 30yo cylinder to see how much better i could make it run. it will be good tuning practice as theyre only $300. down the road i can simply drop a different cylinder on if i want

My kind of man!!

But Peewee, only 30yo, that's awfully recent, are you sure it will be a sufficient challenge for you?