ESE's works engine tuner

[chrisc]

Chris, in my humble opinion this is the way F5 should be heading, there are no, repeat no replacement bikes for F5 on the NZ market, I have a watch on all RS50 bikes that pop up on TM and there have been 0 in the past year. I have done my best to stir up enthusiasm for the class but it's tough when it's all built around antique mopeds. There are plenty of spare parts out there for the KTM 50, hell my ancient Honda uses KTM pistons which are an off the shelf item, KTM65 bottom end with a kTM50 top and you are away with a modern, cheap and reliable race bike.
I stand corrected there is one on TM for upwards of $3700

I will be asking for help on putting a submission to MNZ rules for a freetech rule change for F5 next merry go round.

Let's not discuss the rules for F5 in the ESE thread, rather the 50 thread, or the rule change submissions thread.

I partly agree with you on running freetech rules though but I'm on the fence considering the fun being had in F5 and growth seen at least in Auckland. The biggest challenge F5 faces is getting more riders keen to build a bike a ride it. Frankly, the rules are there right now for someone to build a F5 bike and run it if they want without needing a rule change. Yes a MX engine would make it slightly easier and potentially slightly less costly but it's definitely not the core reason why we don't have more F5 riders/bikes. Getting riders/builders keen is the part of this class that needs to improve because unfortunately there are only so many Dave Trustrum spec 50s for people to just buy and ride (lucky me).

I have worked on a few old 50cc Mopeds and allways was sad that there was not a single cylinder which fitted my needs - this is the first state of the art 50ccm cylinder ever made.
It has some issues (to big exhaust at the flange, auxilaries designed to suit the 65SX Rave) but I can't wait to work on it
Attachment 322757

Just to confirm, is this a mold of the KTM SX50 exhaust duct?

[karter444]

if a barrel has been raised to obtain the desired port timings and the bottom of the transfers end up above the piston at bdc by about 1 mm is there any benefit grinding the transfers down to match the piston height , does this increase the transfer sta
cheers

[lodgernz]

Chris, in my humble opinion this is the way F5 should be heading, there are no, repeat no replacement bikes for F5 on the NZ market, I have a watch on all RS50 bikes that pop up on TM and there have been 0 in the past year. I have done my best to stir up enthusiasm for the class but it's tough when it's all built around antique mopeds. There are plenty of spare parts out there for the KTM 50, hell my ancient Honda uses KTM pistons which are an off the shelf item, KTM65 bottom end with a kTM50 top and you are away with a modern, cheap and reliable race bike.
I stand corrected there is one on TM for upwards of $3700

I will be asking for help on putting a submission to MNZ rules for a freetech rule change for F5 next merry go round.

Tim, do I take it that you're planning to ask for factory race engines to be allowed in F5?

[wobbly]

Lowering the transfer bottom edge to BDC for sure increases the STA, but it also dramatically increases piston cooling
from the transfer streams attaching to it,right from the timing edge.

[peewee]

I think there might be a freetech 50 build in my future and the KTM SX 50 engine might be the way I go. The cylinders look pretty nicely made! Naturally, Rion Janssen's cylinder work caught my eye on Facebook. He's from Barcelona, Spain and works under JTMX Racing.
He gave me permission to post some photos of his work here and I've help him set up an account here so hopefully we can get some commentary on what he's been doing and his results.

could you ask him what he uses to get a fairly smooth surface on the tunnel walls ? ive tried a few things but nothing has worked good so far

[wobbly]

Rex-Cut cotton fiber mounted points are perfect for polishing plated port edges, and alloy ducts.

[peewee]

thanx mate ill order up a few

[Tim Ey]

Just to confirm, is this a mold of the KTM SX50 exhaust duct?

It is. These are some as well.



Also on pit-lane.biz there is a thread where Jan and Frits comment on the KTM 50SX.
Do not know whether it was in this area
http://www.pit-lane.biz/f31-50cc
or in the "All you wanted to know" Stuff...

By the way: Does anyone know the porting timings of a 300cc trial engine?

[wax]

Wobbly
The mismatch in the exhaust port duct to header pipe is not always there in all engines. Assuming I have an exhaust manifold I can grind one into, do you think it's worth while doing ??

[Frits Overmars]

Wobbly
The mismatch in the exhaust port duct to header pipe is not always there in all engines. Assuming I have an exhaust manifold I can grind one into, do you think it's worth while doing ??

You don't want a mismatch at all Wax. And if there is one, try to eliminate it by adding, not removing, material.

[jonny quest]

Most of the high performance 2 stroke dirt bikes case reed window is just square, and not flowed into the case transfer ducting. Some even with sharp corners that just end.

Is there really any power to be had by modifying this section?

[wax]

You don't want a mismatch at all Wax. And if there is one, try to eliminate it by adding, not removing, material.

Thanks Frits

[wobbly]

Frits is on the money as usual, the JTMX cylinder that is shown above is a classic case.
The steps into the duct are way better than it would be if the steps were ground away - but reversing the shape and
adding material to the manifold to adopt the oval exit shape of the cylinder, then transitioning out the the round
header will make more power.
Again just by eye i can see that the cylinder exit area is too big, and the Aux tunnels down the side should be way bigger and only blend into
the round header shape right at the end of the spigot.

Re the reed box shape into the case - a bit like the recent trend of reducing the Ex duct exit area, the exit of the reed tunnel is also being reduced in area
as it transitions as well.
This keeps the velocity of the streams exiting the reed tips higher thus aiding pressure recovery instead of it simply dumping into a big cavity.
In many cases ( literally ) what you would think ( by eye ) was a big flow discontinuity ie a corner near the entry to the transfer duct is in fact better than a nice radius as
the smaller exit area affects the velocity more than the flow direction improvement.

One area I want to look into is that after seeing Frits sketch of the flow from the reed ports spilling over the sides, guided in part by the big stuffer inserts - is to create side ducts
in the case to harness this side flow and direct it straight into the bottom of the transfer entry's.
And combining this with reducing the reed box vertical exit area as much as possible.

[jfn2]

Hello Wobbly;
Here are some pics of a reed intake port, one stock and one slightly modified.
http://www.kiwibiker.co.nz/forums/al...p?albumid=5033
Are you saying to leave the sharp edges and not to round the corners as in the modified pic?
Also I would like to see Frits' sketch of the flow from the reed cage, with his permission of course.
Also I would like to speak to you about a Yamaha YZ125 pipe but I don't have enough posts to PM you.
Thank you very much. jfn2

[wobbly]

I think Frits sketch is on here somewhere,showing the flow spill out sideways from the reedblock ports.
Yes grinding away the sides of the reed tunnel reduces the velocity,and does nothing to allow extra flow to be drawn into
the transfer duct entry - as you would think looking at it.
What you need to do now is reduce the vertical height of the reed box exit, and while you are at it weld in a couple of say 4mm strips right over
the tops of the flywheels to form a ramp - with just the width of the big end between them.
There is no need to have any more than the max reed tip lift height, where the reeds end, and the duct can get smaller in height further inward.
A nice radius on the boost port entry does help here.