ESE's works engine tuner

[F5 Dave]

groan, rings true and loud some of above. Was up late last night pulling my GasGas dirtbike down. To complicate matters, I can't help myself & while it was down being freshened up (& looing for an errant noise) I have to correct the squish clearance which is at 1.9mm. At least I think it is, my thickest solder is 2.0mm & I'm sure I can measure the flat.

either way I have to complicate the matter by measuring the comm & it is very easy to get lazy, but I pushed myself to measure it 3 times. Sure enough the 1st & 2nd measurements were miles apart. But then came them comedy of tired errors, measuring & then discovering the headbolts weren't done up, just resting on the o-rings as I had left them to tighten after letting the oil in the burette settle, but forgot. And the next time I got it all down & had forgotten to record what number I started out with. Sigh, take apart, clean out, reassemble repeat. Again & again. 3 times became about 7.

Heck & this is on a 300cc barrel, the margin of error is huge compared to my 50. - that takes some careful attn with only ~3cc head.

[husaberg]

I can, and I think I did. But I haven't discovered a forum yet where I could get along with the search function. Entering 'offset' just got back to me with 'Sorry - no matches. Please try some different terms.' So it will be up to you to (re)find what I wrote about it.

EDIT: found it after all: http://www.kiwibiker.co.nz/forums/sh...-tuner/page392 , 27th December 2011 04:04.

Sorry Frits here is your answer here

.....I would not bother with offsetting cylinders or piston pins to achieve asymmetrical timing. The effect is very small and who needs the complication.
The pic below shows a calculation I did on the Aprilia RSA125. I gave it an offset of no less than 10% of the stroke in order to enhance the effect.
It is obvious that the maximum conrod angles become asymmetric. What may be less obvious, is the increase in piston stroke for a given crankshaft stroke!
It is also remarkable that it takes more than 180 crank degrees from TDC to BDC, and less than 180° from BDC to TDC.

and it was much appreciated.

I should have been more specific re my latest question.
Were the Aprilia people asked to stop? and was it causing reliabilty issues?
As the info about whether the desaxle set up is hindering or helping potential reliability is quite contradictory.

Was it the increased vibes giving Aprilia problems or was there no problems? or no benefits was the reason testing was stopped.

This stuff from the Bantam thread

adding one point to the RSA 125 point trevor noted, an aquantance of mine said they only dropped it because they were told to! and it was somthing to do with the increased friction at higher RPM apparently needed to much cost /time - and the potential that it cancells out the advantages at higher rpm because of the extra friction.
! But he who should be listened to, said there are possibilities for engines only running to 10,000 and with a low number of gears. !

As you can see, the design locates the piston to the side of the crank centerline, creating a straighter path for the connecting rod during the power stroke and reducing its sideways force on the piston as it slides up and down in the cylinder. This means less frictional losses and an easier life for the pistons and rods, which can be made lighter, thereby reducing reciprocating mass. That helps the Ninja make a record 197bhp, but bikes like the Honda CBR250R and even the Horex VR6 benefit too.

This stuff other sources

désaxé engines aim at giving the pistons an easier life.
During the power stroke, the cylinder pressure is forcing the piston down the bore, but the conrod is at an angle to it. This means the piston is being forced hard against the side of the bore, which every engine builder will know about as there’s always a lot more wear on one side of the bore and piston than the other. By shifting the cylinder to one side relative to the crank, the conrod’s angle with the piston is reduced during the downward power stroke, and the sidethrust is reduced with it.
This has two useful effects: one is a reduction in friction, improving the efficiency of the motor. The second is that because the peak forces on the pistons are smaller, they can be lighter, which in turn allows for lighter conrods and smaller bearings, also reducing internal friction.

[Gigglebutton]

Husaberg, Giggles does actually have a dentist drill, not sure if it came from the back of a German car though[/QUOTE]

I got it off Trademe from a bloke that made Grandfather clocks. You can still get the carbide burs for it from a croud that sell dentist bits over the shore. Made porting the RG50 so much easier.

[2T Institute]

My understanding is desaxation is a de facto long rod.
Funny the Mark Jordan pic as Mark sent me over a couple of those long series double cut burrs, very often used. Cheap diamond bits work OK and you can buy 1/8th end mills cheap off ebay.

[F5 Dave]

Sadly my father was a dentist (no German cars, we had a Monaro) but I never got cast off drills in time. Actually that isn't true, I had an old style handpiece as a toy when I was a nipper. Not sure where it went but a mate has one I borrow from time to time. Good for the 50 barrels.

[dinamik2t]

mr Frits, I was thinking of the piston pin plugs.
You think it would a succesful idea to use light, button-headed allen bolts on a inner threaded pin?



Insert about 10mm (E/F) into each side, using thread locker and shape the head accordingly (which is easy and bolts are cheap to screw with).
A small, swallow 6mm hex hole (K) would still cause short-circuiting?



--------

Also, would anyone know why port floors (or ceilings, if looked from below) sometimes extend further than the stroke height? Wouldn't that create turbulent flow on the spot?
What I mean can be seen in the rsa's (bleached) blue-prints here:

[wobbly]

Re the port floor positions - you are wrongly making the assumption that the cylinder deck is TDC.

[dinamik2t]

It crossed my mind at first, but to be honest I thought of a non-zero deck height to be more bizzare. I don't know why it shouldn't be.
It is common with the C tfrs/boost ports, like here:

[Frits Overmars]

mr Frits, I was thinking of the piston pin plugs. You think it would a succesful idea to use light, button-headed allen bolts on a inner threaded pin?

Insert about 10mm (E/F) into each side, using thread locker and shape the head accordingly (which is easy and bolts are cheap to screw with). A small, swallow 6mm hex hole (K) would still cause short-circuiting?

Also, would anyone know why port floors (or ceilings, if looked from below) sometimes extend further than the stroke height? Wouldn't that create turbulent flow on the spot?

What I mean can be seen in the rsa's (bleached) blue-prints here:

Light is the keyword, dinamik. I do not think it would be a successful idea to use any type of bolt there; in fact I know it would be a disaster. I did a lot of calculating and testing before eventually coming up with my 'plastic' (terribly expensive space-age stuff; it makes teflon look old-fashioned) end caps.
An RSA at maximum revs (14,500) generates quite some g's in its reciprocating parts: 48,700 m/s² at BDC and 77,160 m/s² at TDC. In case it escaped your mind: earth gravitation is 9.8 m/s²... So take a minute to calculate the forces that work on your light bolts, also take into consideration that these forces alternate at a rate of 242 times per second, and then take some aspirin and a stiff drink to calm your nerves.
By the way, you can do me a favour: drop the Mister. Just Frits will do fine; Mister makes me feel old (yes, I know, I am old).
Regarding your port floor question: not only is TCD below top deck like Wobbly pointed out, but there is another give-away in the drawing you used: Prelavorato means that the final dimensions have yet to be applied. The 53.1 mm bore dimension (for a 53.94 mm piston) might have been an indication, even if your Italian is not perfetto.
But you are right about the turbulent flow: the port floors should under no circumstances lie beneath BDC. Your picture of the two piston-fed C-grooves (I wouldn't call them ports) is hardly a good example; just consider the specific power that such kind of scavenging produces, compared to an RSA...

[dinamik2t]

Howdy Frits! Wanna go grab a beer and talk about motor stuff? I'll call the girls too..
-hope no wives reading-

Anyway, thanks for the answers!
In your files by the way, there is a 'prelavorato' with 53.1 bore and a 'prelavorazione' with 53.8 and some hand-written corrections (?).

[F5 Dave]

yes I've been thinking about pin plugs esp after my recent & knumbskulled experiment using spring steel as a shim in the end of a sleeved piston pin. The sleeves in the piston were fine, but the 0.5mm spring steel washer used as a (as it turns out unnecessary) shim lasted practice & one decent race start before disintegrating. There's obviously quite a harsh environment in there that one can forget about when handling the pieces & slo-mo head animation of the flow etc.

I'll pay some more attn before making up plugs.

[TZ350]

yes I've been thinking about pin plugs ....

We have been experimenting with pin plugs too....



Plug is a close fit in the pin and retained by the circlip.



Last night on the dyno one side came loose, there were aluminium shavings all through the motor.



The engine was making good power even after one side had come out and was taking a bit of a battering, the motor kept running, it was not until we stopped that it locked up and wouldn't re-start.



Luckily there was no damage to the piston or cylinder.

I guess the plug was being batted back into the pin while the motor was running and it was able to drop into the transfer port when we stopped and jammed the piston when we tried to re-start it.

[2T Institute]

Made many cheap and cheerful pin plugs from balsa and JB Weld, much to Frits' dismay Worst that can happen is it falls out and gets burnt and disappears into the exhaust. A kart motor that got a slight bit of deto showed no residual traces of the plugs.

[2T Institute]

TZ have you had a look at the kart shop for yamaha KT100 S gudgeons for comparision they are much thinner taper wall design than your gudgeon

[dinamik2t]

I am troubled by the flat surface of the plug . Generally, how much area must there be in the spot, to determine whether the plug work as TFR/AUX.EX sealant or just a plain pin plug?

Institute, do you happen to have any photos? Balsa is the light wood material used in modeling planes, isn't it?