Bucket development: A few questions for the wise ones

[jasonu]

I have to disagree on that Speedpro.

The opposite is true for my experience. If you are developing one engine only, it is a good idea to find out what you are starting with, because sometimes you find that an engine that is designed for road use, has gains to be made, be they increasing or decreasing the volume.

Sorry Green, I agree with SS90. If you don't measure the comp ratio you have a huge unknown. Is it too low, too high or just right? Who knows. I used the pack the rings with vaseline pour h20 in and measure method. A Graham Bells Two Stroke Tuners Guide is a good place to find info about this.. TBH Mike, I am a little surprised at what you said, coming from the proud owner of a high performance T bike where the comp ratio is critical.
Just sayin' mate.

[bucketracer]

another Question

back to primary compression ratio, what is the best way of measuring this? (outside of sitting the motor flat and poring in fluid; measured); is there are trick to this?

does one have to measure the transfer& boost port volumes as part of this ?

I start to re-reading Jennings (but I'm a bit slow on the up take)..

The question was "how" not "why" we have our own ideas but would be interested in how others go about this.

[Bert]

Got that one figured out now, I think.
I'll post up some photos when its done to share...

[bucketracer]

.

Photos are always interesting, we eagerly await them, and looking forward to seeing it out on the track.........

[Buckets4Me]

Got that one figured out now, I think.
I'll post up some photos when its done to share...

why wait till it's done
half the fun is showing off what you are doing

[Bert]

why wait till it's done
half the fun is showing off what you are doing

Cause progress is very slow...
But yes, I'll post up a few soon now that things are starting to move along.

[Buckets4Me]

Cause progress is very slow...
But yes, I'll post up a few soon now that things are starting to move along.

progress is always slow unless you have gazillions $

this is what my bike has looked like for 3 months

and all I was doing is the frount engine mount and making the back mount stronger


will try and get it all back together for next week (making sure all bolts are done up . because i will have noone els to blame this time. It's my bike after all and not a borrowed one)

[Henk]

I can lend you some excuses if you feel you need them.

[Bert]

Yes Please....

[Buckets4Me]

Yes Please....

see if you can beat mine

as it looks like I'm going under the knife for a 2 year old sholder injury

but it will gove me time to do small things I have been putting off
like a new throtel cable and paint job (those FXR's are looking good so I need to clean the bike up a bit)

any idears what colour I should go for ?
it's going to be polished ally frame and tank

[Henk]

We now have

Orange - Connor
Yellow - Pumba
Green - Un stable
Blue - Me
Purple (call it indigo and Violet) - Michelle

So if you go for a solid red we can pretty much line up the whole rainbow

[Bert]

All this talk in the ESE tread (thanks Wobbly, TZ and others) around porting, pipes and crankcase volume has me a little scared that I've stuffed things up a little with my build...

So my little project started it life off as a TZR125 that we have sleeved down to a 50mm bore (stroke 50.7), we pretty much kept the same shape transfers and exhaust port (some modification to the transfers shape to deal with the smaller bore) but over all we were relativity conservative with the porting this time around. full six petal reed block and VM28 downdraft (or PK28-30 flatslide) carbs.

here's the rubbing


here's the port map with transfer angles into the bore. all ports are flat topped (except the the boost port which is about 60 degrees).


Crank case volumes:
50 bore 50.7 stroke is 99.94, so using the figures of ~305cc for the crankcase volume at TDC & ~205 at BDC, that would be 305/ 205 = ~1.48
some attempt has been made to clean up the ports and match everything up (http://www.kiwibiker.co.nz/forums/al...hmentid=228630)

So here is the full porting specs/figures:


So I calculated up the pipe and it looks something like this (with adjustable header), which has been built off a modified RS pipe:


Piston is a round top and I haven't started on the head design yet.

Wobbly has made the comment in the ESE tread that: (http://www.kiwibiker.co.nz/forums/sh...-tuner/page217)
In general, high bmep engines that by default will have good port/duct geometry, will like a case com down near 1.3:1, lower performance engines with crap transfer/duct geometry will perform best with the ratio higher, up near 1.4:1.

So rather than grinding to increase volume I should be filling to decrease...

Any thoughts on this?

[F5 Dave]

why does it look like left & right front transfers are different sizes?

Transfers seem quite low. hmm, 38 deg blowdown is quite excessive, that will be quite peaky despite a tame ex port height. I'd be aiming for say 34.

[Bert]

why does it look like left & right front transfers are different sizes?

Transfers seem quite low. hmm, 38 deg blowdown is quite excessive, that will be quite peaky despite a tame ex port height. I'd be aiming for say 34.

I think I distorted the rubbing a little, I'll give it another go once the barrel & Head are back from machining the o'rings. when i measured up the entry angles they were ~ equal size.

as for the transfers heights/blowdown, I wander if that was like that on the 125 barrel for the powervalve? as it shuts off about 6mm of the exhaust height.

[kel]

Hi Bert, buy yourself a copy of port map analyzer http://www.porting-programs.com/anal...lyzerV3.0.html ($23US from memory) it will allow you to compare your time areas form you rubbings plus it will calculate effective changes. Get a copy of Blairs software (pm me for a copy if you dont already have this) to set your motors target BMEP then go back to port map analyzer and work with your time areas until they match, (the biggest problem has proven to be blow down as this has a specific area which also needs to be met) as you know everything needs to work together. My revised timings have come in at 130deg transfers 195deg exhaust (212deg inlet but you dont have to worry about that one)to meet the BMEP and time area requirements.
From memory the TZR125 had a low case compression what with the reed inlet and that ugly crank, Im suprised its so close to 1.5:1.
ps looks like your a lot closer to finishing than I am!