ESE's works engine tuner

[TZ350]

Pictures of Bucket racing Team GPR's 125 2T cylinder build.



First, take a decent look at some good cylinders.



I am not sure the order Seymour did things in but here are some of the progress photos of his CNC work.



Cylinder block, I think it was machined from solid.



Cylinder Fins.



Barrel assembled with sleeve and fins.

[TZ350]

More pictures of Team GPR's 125 2T build.



Massive cylinder head carved out of a single block of alloy.



Its a team effort, and I think it is Reagan who does the fiberglass work.



Scott is the frame man and engine tuner.



Scott with the GPR125 at the Mt Wellington 2 hour.



12 photos is not enough to do this great bike justice.

But hopefully they show something of the dedicated engineering and development work that goes into some Buckets.

In case I have got some detail wrong the full GPR125 story can be found here as well as lots of great videos of Bucket racing:- http://www.kiwibiker.co.nz/forums/sh...am-GPR/page134

[wax]

Yes, 21mm is WAY too small even for the 250 engine..
And looking at the PV,it wont be working hardly at all with that big space down each side.
You need to add weld to the PV blade side walls and grind pockets further up in the duct to get alot better sealing.
Also looking at the dyno curve the overev thru the gears would be all done at 12500 - that isnt reving hard at all.
From memory the Tyga pipes have way steep rear cones, that wont be helping the dramatic drop off in power past peak.
So I would be getting the header and diffuser length % correct,then lengthen the rear cone to gain some upper mid,without loosing
any overev.
The rear cone is easy enough to replace as a single section.
The other big issue with the 150 cylinders is that they have no port stagger,and the roof angles are very flat.
Fix that and you will pump up power everywhere.

Wobbly can you please expand on port stagger.
I know what it is, I don't know why and I don't know what ports are higher

[peewee]

Pictures of Bucket racing Team GPR's 125 2T cylinder build.



First, take a decent look at some good cylinders.



I am not sure the order Seymour did things in but here are some of the progress photos of his CNC work.



Cylinder block, I think it was machined from solid.



Cylinder Fins.



Barrel assembled with sleeve and fins.

nice. definatly the coolest stuff on the intrnet around here. is there any money that can be won in that class or is it trophies only ?

[jonny quest]

Port stager is simply exactly the way it sounds. A transfers open sooner than B transfers, or vice versa. C typically always opens last.

[wax]

Thanks I know what it is. What Is the benefit and theory behind it

[TZ350]

Is there any money that can be won in that class or is it trophies only ?

No no money to be won, trophies only (if your lucky) but lots of good will and friendly fun.

You don't need to go to this effort to have a good ride, plenty of people have a great time competing on fairly basic bikes like the mighty FXR150 with just a few modifications for the track. But to be at the pointy end you pretty much have to have put some effort into developing a good race package.

Money would probably spoil it.

[jasonu]

nice. is there any money that can be won in that class ?

[wobbly]

Port stagger is a viable method of affecting the scavenging and trapping efficiency of a cylinder by using the fact that there is residual pressure above the transfers
as they open.
This residual blowdown pressure affects differently the flow regime of each transfer in turn.
The first port to open has flow reversal into the duct - as the case pressure is less than the blowdown pressure.

As a general rule normal stagger ie A port open first has a positive effect on the low to mid power,and thus is a good choice for situations where there is no PV.
Reverse stagger, with the B,C ports opening first, has a bias toward peak and overev power, loosing some bottom in the process.
This is due in part to the fact that alot more transfer area is gained with reverse stagger as the B port ( generally the biggest ) also has the highest timing and thus
increases the STA commensurately.

I have tried my hardest to run reverse stagger effectively in KZ2 engines, and did gain significant power past peak, but could never get back enough power at 9-10,000
that is the lowest rpm off slow corners for those karts.
Its all very well gaining 5 Hp at 14.000 that the driver hardly notices, but drop 2 Hp at 10,000 where it affects off corner acceleration - and the driver will bitch like hell even
if the outright lap time is 3/10s faster.

[jonny quest]

Sorry wax. To answer how they work best without typing a novel, what type of ex port do you have?

The basic idea is short circuiting into the ex port, and power band you're looking for

[wax]

Thanks wobbly. That's the answer I was looking for.
Johnny the cylinder is a twin reed cylinder, single exhaust port with 126 degree transfers and 198 degree exhaust ports, it's a performance jet ski cylinder for a 550. It's for the vintage class. It pulls about 8000 rpm and I'm primarily concerned about getting low end power for off the bouy turns.

[FastFred]

Bucket racing Face Book page.

https://www.facebook.com/groups/1623256484603284/

Video https://www.facebook.com/wil.killip/...1650092197724/

[chrisc]

More pictures of Team GPR's 125 2T build....

I can testify to the power of this bike, holy crap! Regan seemed to have a hard time getting on the throttle because it has so much of it (for a kart track). It picks the front up bloody everywhere, what a bull! At Edgecumbe we had some great battles and I often won out on my donkey 4 stroke FXR with a holey 19hp and about 35kg more. I think this was purely because I could rider smoother on a technical track with loads of tight corners. I followed him a bunch of laps, seeing him stand it up early just to get on the power as the front lifted. Lines similar to a 600/1000 on such a tight track. It definitely doesn't overly favor high powered bikes as you're on your knee the majority of it. Not to say that the bike isn't a total weapon with massive potential, more so that it looks like a bloody hard bike to ride to it's potential and therefore is very unforgiving... particularly in the wet, which half that Edgecumbe meeting was. Screw. That.

I think Rod's TZ125 chassis AM6 engine with 80cc cylinder is, for me, about right on with power and handling for the tight Mt Wellington, Taumaranui, Edgecumbe tracks. It has enough power to power wheelie if you're aggressive on the throttle and coming out of the infield going clockwise at Mt Welly, you get the front light as you're still on your knee. But, it doesn't have so much that you have to change your riding style and lines significantly just to get around the track, fighting the bike. Actually, the gearing (although I wouldn't highly rate the gearbox) is pretty good on Rod's bike. Love it.

Two more (from my perspective, in my opinion at least) examples:
- Kel's KE125 engined NF4 RS125 chassis beast which is no doubt a beautiful bike which looks like a total handful to ride and isn't necessarily always the fastest out there on the tight tracks
- Nathanael's Derbi EBE 80cc NF4 RS125 bike - A solid balance of pretty good power, light riding package, fast rider. Not the most powerful bike out there but the complete package which continuously wins championships.

Just wanted to point out that less is sometimes more, horses for courses and that having a F4 bike with over 30hp isn't always the fastest way to go around the track. It's that sexy, light weight and nimble chassis that really has my eyes

[TZ350]

Absolutely agree +1 ... a total focus on horse power can be a handicap. Fast light easy to ride and nimble is the way to go. There is probably nothing to fear from the horsepower arms race as its pretty much self limiting on a cart track, pity because engine tuning is the bit I like best.

[peewee]

guys has anybody tried or already determined with some certainty what range of crankshaft degrees the mixture is going forward through the reedvalve ? i want to get a idea where to place some piston windows