ESE's works engine tuner

[Kickaha]

and preheated the piston in the oven.

The engineer who did one for me preheated it and then cooled it in an oven, this was in a 125 National Kart running to 12,000, lasted all season but when we stripped it there was a crack by the edge of the weld

[Ocean1]

The engineer who did one for me preheated it and then cooled it in an oven, this was in a 125 National Kart running to 12,000, lasted all season but when we stripped it there was a crack by the edge of the weld

I've not done a 2T piston, but the ones I have done have been done like that. In the more modern pistons I found it almost impossible not to blow through into the top ring groove, in which case I just welded that up too and recut it later. Another thing I think helped is a plug, to keep the skirt shape true. They're not round, but the machined surface inside the skirt usually are, so I made up a heavy wall tubular plug to fit. It stayed in there through the heating and welding cycles and seemed to do the trick. Might have worked OK without it, who knows, but I also used the plug to hold the piston in the lathe.

Oh, and as Wobbly said, 10 to 15% silicon rods flow much better, easier to control.

[RAW]

I've not done a 2T piston, but the ones I have done have been done like that. In the more modern pistons I found it almost impossible not to blow through into the top ring groove, in which case I just welded that up too and recut it later. Another thing I think helped is a plug, to keep the skirt shape true. They're not round, but the machined surface inside the skirt usually are, so I made up a heavy wall tubular plug to fit. It stayed in there through the heating and welding cycles and seemed to do the trick. Might have worked OK without it, who knows, but I also used the plug to hold the piston in the lathe.

Oh, and as Wobbly said, 10 to 15% silicon rods flow much better, easier to control.

Firstly what is the piston ? Cast or forged ,
silicon is a grain refiner, it's assists with edge wetting ( fluidity along the edges of the welds ) it also assists with the cleaning, if the piston is high in silicon content then a high silicon filler metal is desirable
The added benefit of the available high silicon Alluminium filler wires are that they have a large mangenise content, this is particularly desirable as this is the element that supplies the toughness to material ( not hardness, but toughness ) therefore it's ability to withstand sustained cyclic loading.
Final note, small weld beads, a large weld requires large heat inputs, this inturn leaves the component with large grains, ( for a given area the grains will be flowing accordingly as per the manufacturing process, if we super heat this area as applying a large weld we will have an item with large grains for a given area ) if we apply small weld beads we do not require the high heat inputs therefore the grain growth is minimised, Yes you will need to have more weld beads to comlete the same buildup, but the greater benefit to this is that each subsequent weld applied along the edge of the previous weld has the ability to refine the grains of the preceding weld if done correctly, this in turn has a direct effect upon the toughness of the finished item,

[Gazzza]

Thanks for the advice re the piston, I have to admit I knew the right people to ask are on this forum, in all fairness the pistons and bike in question is a restro project of mine... The problem is its a 1962 Honda CB92, as you can imagine parts for these are fairly scarce. The bore and stroke are 44 x 41, and I'm guessing cast for that era??? With out taking the head off I think we had it rebored .50 over but could only source C92 pistons, thus the lower crown height. Going from what I'm reading yes it can be done, but I need to find some one who knows the business, so would any one who has replied be willing to tackle the job or recommend some one? It's not something that is needed to be done for a bit as its still a way off being finished.
I have tried to attach a pic, but this isn't mine, mine as is all complete but looking a bit sad awaiting its resto.

[RAW]

Thanks for the advice re the piston, I have to admit I knew the right people to ask are on this forum, in all fairness the pistons and bike in question is a restro project of mine... The problem is its a 1962 Honda CB92, as you can imagine parts for these are fairly scarce. The bore and stroke are 44 x 41, and I'm guessing cast for that era??? With out taking the head off I think we had it rebored .50 over but could only source C92 pistons, thus the lower crown height. Going from what I'm reading yes it can be done, but I need to find some one who knows the business, so would any one who has replied be willing to tackle the job or recommend some one? It's not something that is needed to be done for a bit as its still a way off being finished.
I have tried to attach a pic, but this isn't mine, mine as is all complete but looking a bit sad awaiting its resto.

If you want to send it to Australia & you are prepared to wait , PM me

[husaberg]

Thanks for the advice re the piston, I have to admit I knew the right people to ask are on this forum, in all fairness the pistons and bike in question is a restro project of mine... The problem is its a 1962 Honda CB92, as you can imagine parts for these are fairly scarce. The bore and stroke are 44 x 41, and I'm guessing cast for that era??? With out taking the head off I think we had it rebored .50 over but could only source C92 pistons, thus the lower crown height. Going from what I'm reading yes it can be done, but I need to find some one who knows the business, so would any one who has replied be willing to tackle the job or recommend some one? It's not something that is needed to be done for a bit as its still a way off being finished.
I have tried to attach a pic, but this isn't mine, mine as is all complete but looking a bit sad awaiting its resto.

Send me the measurements that you want Honda will have something to suit.

OEM Ref No	Model	HP	No Cyl	Cyl Dia	Piston			Ring		Pin
Head Type	Length	Comp Dist	Comp	Oil Comp	Dia	Length
13101-230-040	CB125 CD125	125cc	2	44	85	53.1	21+5.6	1.2-2	2.5-1	13	35
13101-303-000	CD125K3	125cc	2	44	85	53.5	21.7+5.3	1.2-2	2.5-1	13	35
13101-200-020	C92 C90	125cc	2	44	130	52.9	23+6.9	1.2-2	2.5-1	14	35
13101-216-000	CB93	125cc	2	44	18	55.3	21.2+8.1	1.2-2	2.5-1	14	35
3101-KCI-003	CB-125T RM-125	125cc	2	44	18	48.5	21.5+3.5	1.0-2	2.5-1	13	34

IF these figures are close you may be better off skimming the C92 pistons around the squish band, to suit rather than welding the dome?

---

"Chimney effect" i 'd never heard of it?
http://www.raerdesign.com/article_1.html

The page designer has heard of Jan and Frits though



cough cough......

Mr Waynewright, the question for you and Mr Frits it was about air cooled cylinders with rear facing ex port.
I didn't word it that clear though, so my fault.
With air cooled (or water cooled for that mater)I can see how the straighter ex would be beneficial the weight distribution can be improved the sheilding of the exhaust pipe can be beneficial.

But i have often seen it written that the cooling of the cylinders is better and more uniform with the rear facing exhaust on a air cooled cylinder

Which is counter intuitive to me as the hotter part of the cylinder around the ex port would receive preheated air, so intuitively it seems that the cooling would be less uniform. With the cooler part of the cylinder getting better cooler airflow with this set up

But this isn't the case..... or is it?

[Frits Overmars]

"Chimney effect" i 'd never heard of it?
http://www.raerdesign.com/article_1.html
The page designer has heard of Jan and Frits though

...But apparently he has never heard of the Aprilia RSA250:

The Bimota V Due broke the first rule of two-stroke engine design by having a downward pointing front cylinder.

Nevertheless he goes on about " the only successful version of the world’s most advanced production engine, the Bimota ‘V-Due".
There is a reason this Bimota is usually called the V-Didn't ....
Now I am going to read everything else on this RaerDesign Website. I wonder what other brilliant ideas are in there, waiting to be discovered.
Maybe I will even change my job description from engine designer to chimney sweep .

Later:
It cost me an hour, but at least now I am sure I did not miss a single piece of valuable information. I also discovered that the web designer "borrowed" several engine sketches from my friend Martijn Stehouwer ( www.emot.nl ). I very much doubt whether Martijn was even informed...

[husaberg]

...But apparently he has never heard of the Aprilia RSA250.

Or the YZR500 either. Honda also have some explaining to do.

Someone else would do too... LOL.

[speedpro]

It reminded me of the marketing for the Yamaha 750 when they first came out with the downdraught intakes and the forward sloping cylinders. Gravity was supposed to be helping fill the cylinders, It would have been of course but I'd like to see someone measure it.

[senso]

Good night folks, hope you don't mind I ask my first question.
I hope to one day(hopefully still this year) to have a running two stroke engine with injection, and I want to start measuring a good engine running on a carb, and I would like to measure crankcase pressure(before and after reeds), can someone tell me what are the ball-park/expected maximum and minimum pressure values, so that I can narrow the sensor selection?

Best regards.

[wobbly]

Here is the intake pressure traces of RZ400 at 10,000 rpm.
The case goes to approx 0.6 Bar, the intake +/- 0.25 Bar if my reading of pressure ratio is correct.

[TZ350]

Fuel injected twostroke second in national MX series. EFI performed seamlessly through out the whole series.

It will be interesting to see how TZ's EFI works out.

There should be a brass band playing and ticker tape parade up main street for Flettner. As a fuel injected racing air cooled EFI 2-Stroke that has been competitive and reliable over a whole race series, is a very, very good effort.

I too think Flettners EFI 2-Stroke is a very remarkable effort that hasn't received the positive recognition it deserves.

I have heard that the other 2T EFI project Wob and Flettner have been working on is up and running and I would love to hear from anyone else, who have had success with raceable 2-Strokes running EFI. Like Flettner's project, it would be good to see how others have gone about it or even to hear of any other privateer who has managed to build a successful racing EFI 2T.

I have now sorted some base maps to get started with for my own EFI project using simulated dyno graphs generated using EngMod2T. And now feel comfortable with how the EFI programming software works so the next step is to start fitting the EFI hardware to the Beast and then its dyno and track time.

[gamma500]

I have built several inertial dynos for 40 Hp engines ( engine dyno, not roller for a bike ) and the steel wheel were all sort of around the same dimensions.
Depending on what scrap I could beg ,borrow or steal.
Last one was 525 by 60 thick, new one is 450 by 80 thick.
Depending upon what gear you use you can vary the spin up time, thus the acceleration rate very easily to get the test length in the ballpark.
One thing not mentioned in many build descriptions is that you must use an overun clutch to prevent the inertia wheel from driving the test motor forward, after a test or
more importantly, if it fails on the dyno.
Imagine the mess if it siezes, and it is forced to keep running whilst you are frantically jumping on the brake.
Im just about to assemble my new setup, so will take some pics when its up and running.

I've been reading some old posts, and found wobblys post about engine dynos.
Wob, could you post some pics(and maybe specs?) of your engine dyno setup?

[wobbly]

Here are some engine dyno shots.
SportDevices software is very easy to setup and use, so is 3rd dyno I have built using it.
Gives appox 10 second run time from 8,000 to 15,000 in 4th gear with 46Hp.
Had everything from 50cc scooter to 100Hp RZ500 on it, repeatable to 1/10ths of Hp easily.
And the engine is at my easily accessed level of crippledom.

[TZ350]

OK?but why change it?(the shaft)
The basket will likely have a press-in steel female spline in the alloy Clutch hub
Just a thought?
If it is anything like Honda's the drum/hub will be fairly generic casting with a different primary gear riveted on and steel spline adapter pressed in for different models.
You will likely need to rivet on the correct gear but it may be easier. Worth a crack anyway?
Some Hondas have rather wide shoulder behind the drum in the casting to accommodate different shaft lengths with the same basic hub casting shared between models.
Could also be an opportunity to get rid of those funny clutch springs pressure plate at the same time.
Have a look for cross over clutch plates from a aftermarket cattledog to see what drums are likely to be very similar say Dr125 etc.
Rob was going to get one off Kicka at one stage to see how they match up i recall.

These all share similar plates
GP 100 C/UC 78 CK3319
RM 100 A 76 CK3319
RM 100 N/T/X 79-81 CK3319
GP 125 C/N 78-79 CK3319
RG 125 CG/CH/J (NF12A) (Gamma/Rear Drum Brake Model) 86-90 CK3319
RG 125 UCG/UCH/UCJ/J/BUJ (NF12B) (Gamma/Rear Drum Model) 86-90 CK3319
RG 125 FN/FP/FR Gamma (NF13A / Rear Disc Model) 92-94 CK3319
RG 125 FUN/FUP/FUR Gamma (NF13B/Rear Disc Model) 92-94 CK3319
RG 125 UN - Wolf (NF13E / Naked) 92-94 CK3319
RM 125 N/T 79-80 CK3319
RM 125 G/H 86-87 CK3319
TS 125 XUE/XUF/XUG/XUH/XUJ 84-90 CK3319
TS 125 RK/RL/RM/RN/RP/RR 90-94 CK3319
GT 185 K/L/M/A/B/C/EC 73-79 CK3319
TS 185 K/L/M 73-75 CK3319
TS 185 B/C 77-78 CK3319
TS 185 ERN/ERT/ERX 79-81 CK3319
DF 200 EV/EW/EY (SH42A) 98-99 CK3319
DR 200 G/H/J 86-89 CK3319
DR 200 SEP/SER/SES/SEV/SEW/SEX/SEY (SH42A) Djebel 93-00 CK3319
DR 200 SE Trojan CK3319
DR 200 SEK1-SEK9 01-09 CK3319
GT 200 EN/EX X5 79-80 CK3319
RV 200 K2/K3 02-03 CK3319
SB 200 N/X 79-80 CK3319
SX 200 R/R-Z/RJ/RM 90-91 CK3319
GSF 250 N/ZM/P/NP/ZP/R/NR (GJ74A) 92-96 CK3319
GSX 250 RCH/RH (GJ72A) CK3319
GSXR 250 CJ (GJ72A) CK3319
GSXR 250 CK (GJ72A) CK3319
TS 250 XE/XG/XH/XJ/XK 85-89 CK3319

Scraped of another thread (Thanks Husa) as its a good list of clutch plate possibilities. I am not sure about the 250's as I haven't thought to look at them before, but the others look like they will fit the GP. Kevlar clutch plates can be purchased of Ebay for a reasonable price, its usually just the number of friction plates that varies between the smaller Suzuki models.