Piston clean up
 

Has any one ever poslished the buildup out the top of they piston before. I thinking that by doing a poslish I might get better glow plug life plus keep the Temp down. The Motor is a TMaxx 2.5...

:)

Is it possible to convert a Ns12s3 to a turbo head?
- Dust

impossible to convert a standard head button to a turbo head button, but you can always pop a S5 head button on the S3.

hello Ed

My sleeve is distorted a little bit and I took it to a local mechanical place where they do the grinding. Does the sleeve has to be re-chromed? How oo I get the roundness of the sleeve back to the original shape?
The guy said I need to pay for a set of holder/clamp to do the grinding?
Which method do you use, honing or grinding?

Engines sleeves and pistons will always be distorted. They wear more in one axis than on the other, therefore when measured one side will be smaller than the other. In full size racing sometimes they make the pistons allready with the shape to whish they will wear.

UH OHHHHHHHHHHH!
 

If you did any serious grinding on the inside of the sleeve you better replace it!!!!!!!!!!!:eek:

It is very complecate process-grinding the sleeve and if you want to do only one-it will probably costs for you the same if you buy at list 3-4 for new sets. It can be done by hand laping, but it is realy time consumption process to and if it is totaly destorted-ther eis no way you will be able to fix it cheap way. All tooling to griding sleeve costs aproximately $ 5-7 K.
Just get another set out of realy good material and it will last double what you have expirienced.
We use grinding and final polishing, honning doesn't give very good surface and it is working as griding tool for piston when we are run in engines. So only grinding and polishing. People who saw my P/S sets can tell you how it looks. BTW, pistons are ground too, individualy fit.
Paul I need your adress urgent, can you please send it to me, I got something for you.

On my engine ( PS12) induction is 230 degree, open at 25 ABDC and close at 75 ATDC, but it will not work on conventional design due to the great crancase volume. The best opening so far I found for MR12 is 215-218 degree, but the is great chace that shaft will simply broken-not a realy good materials are used for mas production engines. I heard a lot of modfyers are faced this problem.

Does anybody know the stock port timings on a Novarossi NS12S3.

thanks for the reply about duration TG......

I know some of you guys modify carbs....has anyone ever enlarged the venturi(sp?) on the carb to like 7.5mm and just used carb inserts to adjust to different sizes like 6.5, 5.5, 5.4 and so on

just mod my first engine WOW i didnt know i could do that with a dermel. can anyone help me mod the carb, i herd of something about drilling, and polishing.

Man that was a long time ago when they interviewed me for that article.

An its still a great article ;)

Dennis, How was the new motor? When will it hit the shelves?

hey folks.....


do the piston surface finish have anything to do with exhaust gas flow????

IMO, it's a myth, but I'd like to get some fedback from the experts......


thanks!!!

Nope. I guess you are talking about top of piston-this is only one place where exhaust gases meeting the piston. We are talking in reasonable limits. Build up on top of piston makes difference, finish on walls makes big difference, but not in relation with exhaust gases
Edward.

yes, I referred to the top of piston....

i was told that polishing the top of piston (the part closer to the exhaus port), gives a better flow to the exhaust gases, but I didnt believe.......

thanks edward....

Polishing makes your engine easy to clean and build up resistance ( from fuel deposits ).

Head clearance
 

Hi all.

This is not really a modding question but it seems to be the right place to get a sensible answer.

I am helping someone to tune a Rossi 173R12 X3 and am having some difficulty.

So I started checking through the basics and discovered that the head clearance would not compress a piece of 1mm solder.

Removed all the shims and the clearance is 0.7mm.

Can this be right. If not, what should the clearance or compression ratio be for 16% nitro?

Thanks

somethings that we all can do is polish the sleeve and the crank...

some people say dont polish it coz the fuel/oil wont stick... or something...

i see jp engines dont have polished crank or sleeve....

what are your opionons on polishing the sleeve and crank?

I wouldn't bother touching these components other than regular cleaning if you arent familiar with them. If you polish the wrong area you could cause wear (crank pin, inside of sleeve, etc..).

NEVER touch the inside of the sleeve where the piston goes...EVER!! Do this and you might as well throw away your engine..

John

Never touch the sleeve.

I wouldn't go messing with port polishing either. The fuel/air needs to mix around together and if your ports are smooth surfaced then there is less chance of the fuel and air mixing together if you had rougher ports.

So basically, your engine would perform better without the port polish because of the fuel/air mixing together.

Sean

Question for modders : Sleeve Porting but not crankshaft

What mod that increase maximum rpm ? shall I mod ( porting ) the front ? The side ?

I don't want to mod all ports for fuel economy reason.

Increase exhaust timing by .3 mm (aprx 6 degrees) and don't polish anything in the motor.
Edward

side porting 4 more power..

When you said increase timing by .3mm : Should I dremel upper or lower lip of exhaust port ? I guess is lower side right ?

Upper line of exhaust window. Don't use dremel, use needle file, daimond kind.

Thanks..... TopGun 777

It's LL5 engine I recently bought from Daniz24,

deleted

So what is the advantages of modding besides its disadvantages? Does it acts the life of the engine?
And can you classify the type of moddings, how is it done simply and why is it done for?

When measuring the induction duration, I put the piston at BDC. After that I rotate the crank CCW until it opens. Degs measured may be for example 35*. Then I rotate it CW until it opens from the other side( it is actually the closing side). Degs measured may be 232*.

232*-35*=197* duration. Is a proper method of measuring the induction duration?

I can't get ATDC measurements because the piston gets stuck.

Any one have an answer to the above question

.

Yep if piston still tight in the sleeve this is right method to mesure. In your case induction is open @ 35 ABDC and close @ 52 ATDC with total duration of 197 deg of opening.
As a sugestion-opening is OK, but closing is too early (for on road engine) at list by 5 degrees.
Edward

Thanks guys, I'd been crashing my brain trying to make sure that was right.

How to modifiy intake and exhaust timing
 

Can anyone tell me step by step how to get degree of the intake and exhaust. I have a 360 protractor but trying to get the method down pack. Trying to modifiy my rb v12 :weird:

First, you need to attach the degree wheel to the engine. I take a broken prop, and cut both blades off. This allows you to use it as a spacer, and mount the degree wheel on the crankshaft. Tighten your prop nut tight enough that the wheel won't slip unless you want it to. You also need a reference pointer. I used a large metal paperclip--the kind with handles, sort of like a clothespin--and soldered a stiff wire to it. You can clip the paperclip to a cooling fin, and bend the pointer so it's pointing towards the center of the degree wheel. The whole idea is to be able to accurately and repeatable measure the rotational position of the engine. The more accurate your clip is, the better your numbers will be.

It's time to measure now! Take the glow plug out, so the engine turns easier. A flashlight will make measuring slightly easier--if you shine it in the spark plug hole, you'll be able to see the ports better.

Exhaust port first. Turn the engine counterclockwise until the piston top is going down, and just opens up at the top of the exhaust port. Write down or memorize the number on the degree wheel, or turn the degree wheel (but not the engine) so the pointer is at zero. You want this point to be the point at which the gases will just be able to flow through, with the piston top at the top of the port. Now, turn the engine to move the piston down, and keep turning until the piston has gone back up, and stop just as it reaches the top of the exhaust port. If you set your pointer at zero, you now have the exhaust port timing. Typically, lower timing numbers are for lower rpm. The higher numbers, are typically for higher rpm.

Repeat this step for the intake port (crankshaft window), which is in effect a rotary valve. You will measure from the instant the port opens until it's fully closed. Rotary valve engines have longer timing because they don't open until the piston is moving up at BDC--creating a vacuum in the crankcase--and they close just after the piston reaches TDC.

Now, do it again for the transfer ports. Usually, there are two mirror image ports, one on each side of the exhaust port, then there is a third transfer port that's opposite of the exhaust port. This third transfer port is called the boost port, and it's common to have different timing than the other two transfer ports.

Now you've measured the port timing on your two stroke model engine.

AFM

counting the degree
 

How do you count the degree on the protractor when it goes over 90 degree is my setup:

Any Special Techniques for tightening the Flywheel
 

Do any of you employ anthing special for tightening the flywheel? The collet and flywheel will move towards the front bearing when the nut is tightened. This will pull the 2 insides of the crankshaft ballraces towards each other. This will surely tend to bind them up. The situation will get even worse under temperature, because aluminum expands faster than the steel crank.
This must rob power from the motor?